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Solid waste management 10CV757

SOLID WASTE MANAGEMENT

Sub code : 10CV757 IA Marks : 25 No. of Lecture Hrs/Week : 04 Exam Hrs : 03 Total no. of Lecture hrs : 52 Exam Marks : 100

PART - A UNIT – 1 INTRODUCTION: Definition, Land pollution – scope and importance of solid waste management, functional elements of solid waste management

SOURCES: Classification and characteristics – municipal, commercial & industrial. Methods of quantification.

08 Hours UNIT -2COLLECTION AND TRANSPORTATION: Systems of collection,collection equipment, garbage chutes, transfer stations – bailing andcompacting, route optimization techniques and problems.

06 Hours UNIT -3TREATMENT / PROCESSING TECHNIQUES: Components separation,volume reduction, size reduction, chemical reduction and biologicalprocessing problems.

6 Hours UNIT -4INCINERATION: Process – 3 T‟s, factors affecting incineration process,incinerators – types, prevention of air pollution, pyrolsis, design criteria forincineration.

7 Hours PART -B

UNIT -5 COMPOSTING: Aerobic and anaerobic composting, factors affecting composting, Indore and Bangalore processes, mechanical and semi mechanical composting processes. Vermicomposting.

6 Hours UNIT -6 SANITARY LAND FILLING: Different types, trench area, Ramp and pit method, site selection, basic steps involved, cell design, prevention of site pollution, leachate & gas collection and control methods, geosynthetic fabrics in sanitary land fills.

8 Hours UNIT -7DISPOSAL METHODS: Open dumping – selection of site, ocean disposal,feeding to hogs, incineration, pyrolsis, composting, sanitary land filling,merits and demerits, biomedical wastes and disposal.

6 Hours UNIT -8 RECYCLE AND REUSE: Material and energy recovery operations, reuse in other industries, plastic wastes, environmental significance and reuse.

5 Hours

Department of Civil Engineering, ACE


TABLE OF CONTENT

Unit No. Topic Page No.

I Introduction 3

II Collection and 12

Transportation

III Treatment / Processing 24

Techniques

IV Incineration 35

V Composting 51

VI Sanitary Land Filling 58

VII Disposal Methods 63

VIII Recycle and Reuse 73



UNIT – I INTRODUCTION Solid waste

Solid wastes are the wastes arising from human activities and are normally solid as opposed to liquid or gaseous and are discarded as useless or unwanted. Focused on urban waste (MSW) as opposed to agricultural, mining and industrial wastes.

Integrated Solid Waste Management (ISWM) is the term applied to all the activities associated with the management of society's wastes. In medieval times, wastes discarded in the streets led to the breeding of rats and the associated fleas which carried the bubonic plague. The lack of management of solid wastes thus led to the Black Plague which killed half of 14th century Europe. USPHS has traced 22 human diseases to improper solid waste management.

Solid wastes also have a great potential to pollute the air and water. Mining tailings from Colorado gold and silver mines will probably being spilling arsenic into the water supply forever. Just finished toxic metal treatment facility in Park City, Utah. Materials Flow - The best way to reduce solid wastes is not to create them in the first place. Others methods include: decrease consumption of raw material and increase the rate of recovery of waste materials. Technological advances - Increased use of plastics and fast, pre-prepared foods.

Solid Waste Management Solid waste management is the control of :

- generation, materials are identified as being no longer value - storage, management of wastes until they are put into a container - Collection, gathering of solid wastes and recyclable materials and the transport of these

materials where the collection vehicle is emptied. 50% or higher of the total cost. - Processing, source separated (at the home) vs. commingled (everything together) is a

big issue. Includes: physical processes such as shredding and screening, removal of bulky material, and chemical and biological processes such as incineration and composting.

- transfer and transport, small trucks to the biggest trucks allowable - Disposal of solid waste, landfilling with or without attempting to recover resources. In a manner that is in accord with: - public health - economics - engineering - conservation - aesthetics - public attitudes

Final disposal at the turn of the century included: - dumping on land in - dumping water - plowing into soil - feeding to hogs - incineration



Waste Generation

Waste handling, separation, storage and processing at the source

Collection

Transfer and Separation and processing

and transformation of

Transport

solid waste

Disposal

Integrated Solid Waste Management (ISWM)

ISWM - defines as the selection and application of suitable techniques, technologies and management programs to achieve specific waste management objectives and goals. AB939 in California: 25% reduction by 1995, 50% reduction by 2000. Hierarchy - adopted by EPA to rank actions:

- source reduction, most useful, may involve design of packaging with minimum toxic

content, minimum volume or a longer useful life. - recycling - waste combustion (transformation), physical, chemical and biological alteration of the

waste for the purposes of: - improving efficiency

- recover reusable material, glass - recover conversion products, compost

- landfilling, material that: - cannot be recycles - has no further use - residual matter attendant to another process, ash left over after combustion

Legislative Trends and Impacts

Rivers and Harbors Act, 1899, regulated the dumping of debris in navigable waters and adjacent land. The idea was to protect navigation. Solid Waste Disposal Act, 1965, PL89-272,

- The intent was: - Promote solid waste management and resource recovery.



- Promote technical and financial aid - Promote national research. - Provide for guidelines. - Provide for training grants.

- Enforcement was by USPHS.

National Environmental Policy Act (NEPA), 1969, Required Environmental Impact Statement (EIS). Resource Recovery Act, 1970, PL95-512, amended the SW Disposal Act of 1965. Directed that the emphasis should be shifted from disposal as its primary objective to recycling and reuse. Management activities were transferred the US EPA which was formed by presidential order under Reorganizational Plan No. 3 of 1970. Resource Conservation and Recovery Act (RCRA), 1976, PL94-580. Legal basis for implementation of guidelines and standards for solid waste storage, treatment and disposal. RCRA was amended in 1978, 1980, 1982, 1983, 1984, 1986 and 1988. The 1980 and 1984 versions emphasized concern with hazardous waste. Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), 1980, (Superfund), PL96-510. Response to uncontrolled hazardous waste disposal sites.

- Ancillary laws:

Public Utility Regulation and Policy Act (PURPA), 1981. Directs public and private utilities to purchase power from waste-to-energy facilities. Noise Pollution and Abatement Act, 1970. Limits noise.

Clean Air Act, 1970, PL91-604, (reauthorized in 1990), pertains where dust, smoke and gases discharged from solid waste operations are involved. AB939, 25% reduction by 1995, 50% reduction by 2000. Local agency in LA is the LA County Sanitation Districts.

Sources, Composition, and Properties of Solid Waste

1. Sources of Solid Waste

MSW, Municipal Solid Waste, is the primary focus of this course, which excludes industrial, mining and agricultural wastes.

A. Residential and Commercial

Residential: Generated by me and you: Organic (combustible) and inorganic (non-combustible), food, paper, garden trimmings, glass, white goods, waste oil, spent cans of insecticide. Commercial: stores, restaurants, hotels, car repair: paper, plastic. Commingled. Mixed wastes, not separated at the source. Putrescible, wastes that will decompose rapidly primarily food.

Plastics, contain a numerical code, 1 through 7, which is stamped on the bottom of the container inside a small triangle.



- Polyethylene terephthalate (PETE/1), 2-liter soda bottle - High-density polyethylene (HDPE/2), milk bottles

Special Wastes: - Bulky items: furniture, lamps. - Electronics

- Major appliances (white goods) - Batteries, oil and tires

Household hazardous wastes: - paint - cleaners - bug and garden sprays B. Institutional and others

Generated by government buildings, schools, prisons and hospitals.

Does not include medical wastes which are typically incinerated and manufacturing wastes from prisons. Construction and Demolition. Road repair, sewer jobs, renovations: wood, concrete, steel, shingles, electrical parts. Municipal Services. Street cleaning, parks, catch basins: trimmings, food, paper, sweepings, dead animals, abandoned vehicles. Treatment Plant Sludges.

C. Industrial Wastes

SIC (Standard Industrial Classification) codes. Excludes process and hazardous wastes. SIC 32 - Stone, clay and glass products from the manufacture of flat glass etc., yielding glass, gypsum (sulfur source) abrasives, etc.

D. Agricultural Wastes

Enormous quantities from planting, harvesting from row, field, tree and vine crops and animal husbandry, feedlots.

2. Composition of Solid Waste

Composition describes the individual components that make up solid waste and the distribution of these components by weight. Example Given: Scales indicate that a landfill is collecting about 800 ton/day of MSW, 5 days per week. Find: The weight of material collected from the catch basins in a year.



Weight MSW generated per week = 800 tons/day x 5 days/week Weight MSW generated per week = 4000tons/week

Weight in catch basins = 4000tons/week x .007 x 52 weeks/year Weight in catch basins = 1456 tons/year

3. Variation in Distribution

Highly variable, local studies should be considered, collected data is expensive and of limited value; make sure that collected data is useful before collecting. Location, warmer more affluent communities generate more wastes.

Season, More yard and food wastes in the summer; more glass and metals in the winter. Example

Given: A recycling company is expecting about 1500 tons/year of glass and they did some field testing during the winter to verify this number. They chose winter to get a low end of the range assuming that less beverages would be consumed in the winter.

Find: The percentage decrease in revenues when the glass is actually counted. Assume that the real glass production will be based on the average of winter and summer months.

Glass in winter 3.5%, glass in summer 2.5%

Total tonnage = 1500 tons/year .035 Total tonnage = 42,857 tons/year

Actual glass percentage = (3.5 + 2.5)/2 Actual glass percentage = 3.0%

Real tonnage of glass = 42,857 tons/year x .03 Real tonnage of glass = 1286 tons/year

% decrease = (1500 - 1286)/1500 % decrease = 14.3% reduction in revenues Note: They made an incorrect assumption by assuming that there would be more glass in the summer.

Economics and others.

Physical, Chemical and Biological Properties of MSW 1. Physical Properties of MSW A. Specific Weight



lb/yd3

, a volume measure and, therefore, subject to interpretation and variable. Beware of reporting: loose, as found in containers, uncompacted, compacted. Use:

- 220 lb/yd3

for residential - 270 lb/yd

3 for commercial

- 500 lb/yd3

in the compactor truck

- 760 lb/yd3

in the landfill

Example Given: MSW Find: What's the decrease in volume for MSW from the house to the landfill.

1 -

1

Density Density

Volume = original new

Densityoriginal

Volume = (1/220 - 1/760) / 1/220 = (.004545 - .001316)/.004545 Volume = 71.0% decrease

Example B. Moisture Content

Wet-weight relationship: w-d

M = w 100

Varies from 15-40%, use 21%, food and yard wastes very high-70%; paper, plastics and inorganics very low-3%.

Important consideration for transformation processes: energy recovery (incineration) and composting. Rain soaked trash will way more than its dry counterpart, a consideration at the weighing scales. Example

C. Particle Size and Distribution

Imprint consideration in the recovery of materials, pre-processing antecedent to a classification or sorting process. Eqs. 4-2 to 4-6, based on a single linear measurement, the average size is 7-8".

D. Field Capacity (FC)

The amount of moisture that can be retained in a waste sample subject to the downward pull of gravity. Water in excess of FC will flow out of the waste as leachate.

50-60% for uncompacted, commingled waste from residential and commercial sources.

E. Permeability (hydraulic conductivity) of Compacted MSW Department of Civil Engineering, ACE


Measures the movement of gasses and liquids in landfills.

K = Cd2

= k eq. 4-7, p.76

k= 10-11

to 10-12

m2

in the vertical and 10-10

in the horizontal. Example

Given: The horizontal direction Find: Calculate the coefficient for permeability at 60 F.

K = Cd2

= k = 10-10

m2

x (ft/.3048m)2

x 62.37 lb/ft3

/ 2.359x10-5

K = .02845 ft/s 2. Chemical Properties of MSW A. Proximate Analysis

Includes the following tests: - Moisture - Volatile combustible matter - Fixed carbon (combustible residue after volatile matter is removed) - Ash (weight of residue after combustion in an open crucible

Fusing point of ash - temperature at which the ash forms a solid (clinker) by fusion and agglomeration. 2000-2200 F. Magazines are:

- 4.1% moisture - 66.4% volatile matter - 7.0% fixed carbon - 22.5% non-combustible - energy content, 4600 Btu/lb as collected. - Note: rubber as in tires and plastics have a very high energy content.

Example

Given: The Town of Waytogo, population 56,789, has decided to burn its as collected MSW which amounts to about 6 lb/capita.day Find: How many barrels of oil do they save on a daily basis. 1bbl

oil = 5.8x106

BTU Energy in the MSW = 4600 Btu/lb x 56,789 cap x 6 lb/capita.day Energy in the MSW = 1.57 x 10

9 Btu

Oil = 1.57 x 109

Btu / 5.8x106

BTU

Oil = 270 barrels/day B. Ultimate Analysis of SW Components

Determination of the percent C, H, O, N, S, and ash.

Opportunity to calculate chemical formula, which then can be used in various chemical and biological reactions. Magazines are:

- 32.9 % C - 5.0 % H - 38.6 % O



- .1 % N - .1 % S - 23.3 % ash C. Energy Content of SW Components

Potentially critical element in incineration. Can be measured or calculated. DuLong Formula:

Btu/lb = 145C +610(H2 - O2/8) + 40S +10N

Constituents are % by weight Plastics have:

- An inert residue of 10.0% - An energy value of 14,000 Btu/lb D. Essential Nutrients

Potentially critical element in composting. 3. Biological Properties of MSW

VS, volatile solids, ignition at 550 C is often used as a measure of the biodegradability of the organic fraction. An alternative is the lignin content can be used to determine biodegradability:

BF = 0.83 - 0.028 LC BF is the biodegradable fraction and LC is the lignin content

Odors typically result from the anaerobic decomposition of the organic fraction.

- Sulfate is reduced to sulfides and the to H2S. - Organic compounds containing a sulfur radical can lead to the formation of methyl

mercaptan and aminobutyric acid. Breeding of flies takes 9-11 days.

4. Physical, Chemical and Biological Transformations A. Physical Transformations

Component separation

- Separating identifiable matter from the commingled MSW. - Used to:

- Recover usable material - Remove contaminants - Improve specifications for the separated material - Remove hazardous waste - Recover energy and conversion products Mechanical Volume Reduction (Densification)

- The initial volume is reduced usually by force or pressure.



- Compaction, baling. Mechanical size reduction

- Purpose: - reduce size - create a more uniform product

- Size reduction does not necessarily mean volume reduction, shredded paper occupies

more volume than the parent material - Shredding, grinding, milling

B. Chemical Transformations

1.) Combustion (Incineration)

Combustion is the chemical reaction of oxygen with organic materials, to produce oxidized compounds with the emission of light and heat. Results in gasses, ashes and heat, highly exothermic.

2.) Pyrolysis (Destructive Distillation)

The splitting or organics by thermal cracking and condensation in an oxygen-free atmosphere into gaseous, liquid and solid fractions. Highly endothermic. Equation

3(C6H10O5) 8H2O + C6H8O + 2CO +CH4 + H2 + 7C In which:

- C6H10O5 is cellulose

- the gases are CO +CH4 + H2

- the tar and/or oil stream is C6H8O

- and the char is C

3.) Gasification

Partial combustion of a carbonaceous fuel to generate a combustible fuel gas rich in carbon monoxide, hydrogen and methane. The fuel gas can then be combusted. Results in low-BTU gas, char and oil.



UNIT – II COLLECTIION AND TRANSPORTATION

Waste Generation


Collection



Transport

solid waste

Disposal

Issues in this topic:

Types of services

Types of collection systems

Detailed analysis of collection systems

Setting up collection routes

1. Waste Collection A. General

Major cost element of solid waste disposal - typically 50-70% of the total and therefore, demands major attention especially with final disposal getting so much press. Collection includes:

- picking up MSW from sources - hauling to the emptying location - emptying of the truck or container B. Collection of Commingled Wastes, Low Rise, Detached:

The waste is commingled or heaped together as opposed to source separation e.g. picking out class, cardboard Collection services:

- curb - (manual or mechanical) most common, homeowner moves the container back and forth between the curb from the storage location. Larger 90 gallon containers require placement in the street, perhaps at a precise angle in cul-de-sacs.

- alley - Narrow utility thoroughfare in the rear of residences; not uncommon in older communities, Claremont, Pomona.



- backyard carry - collectors retrieve the container from the storage location, empty it and return the container to the storage location. Manual methods of collection: - direct lifting and carrying - rim roll - small lifting devices - satellite vehicles, Cushmans

C. Collection of Commingled Wastes, Others.

Low and medium rise apartments, high rise apartments, commercial industrial facilities. Smaller containers handled by maintenance personal for curb side collection, larger containers done mechanically. Much collection is done at night and very early morning to avoid the traffic.

D. Collection of Waste at the Source

The generator separates the waste as opposed to commingled wastes. Methods include:

- Curbside collection using standard or specially designed vehicles. - Standard vehicles can be used to pick up just newspaper or just can on some kind of

appropriate time cycle; perhaps every other week or the third Thursday of the month for glass.

- Specially designed vehicles include: - closed body recycling trucks - recycling trailers - modified flatbed trucks - open-bin recycling trucks - compartmentalized trailers Example

Given: You are a community activist and believe in recycling. It has been decided to make two categories: the first for paper and cardboard and the second for everything else. You think that you can get 50% of the 458 homes to participate. You have actually counted the residents and there are 1338 of them. You have made a mini-survey of the paper wastes such as wrappers, packaging and determined that newspapers are about 1/3 of the total paper; the rest you hope will be separated to the tune of 75%. Find: The big meeting is Tuesday night and the neighbors want some hard numbers on how you are going to accomplish the recycling. 1. Computation table to calculate volumes. Department of Civil Engineering, ACE


Component Total Solid Waste Specific Volume, Wastes, Materials Weight, yd

3

lb Separated, lb/yd3 (col. 3/4)

lb

(col. 2x75%)

Organic

Food wastes 8.0 not-recycled 490

Paper 35.8x1/3 8.9 150 .0593 Cardboard 6.4 4.8 85 .0565

Plastics 6.9 5.2 110 .0520 Textiles 1.8 not-recycled 110

Rubber 0.4 not-recycled 220

Leather 0.4 not-recycled 270

Garden 17.3 not-recycled 170

Wood 1.8 not-recycled 400

Inorganic

Glass 9.1 6.8 330 .0206 Tin cans 5.8 4.3 150 .0287

Aluminum .6 .4 270 .0148 Other metal 3.0 not-recycled 540

Dirt Ashes, 2.7 not-recycled 810

etc.

Total 100.0 .2319

2. Determine the relative volumes newspaper + cardboard = .0593 + .0565 newspaper + cardboard = .1158yd3 others, plastics, glass, tin cans, aluminum = .0520+.0206+.0287+.0148 others, plastics, glass, tin cans, aluminum = .1161 Note: .1158+.1161=.2319,OK The relative volume is useful for calculating the relative size of the bins. .1158/.2319=.50 .1161/.2319=.50 In this case, the split is 50/50 which is ideal. The meaning is the collection containers would be of equal size.

3. Determine a pickup ACEnario Assume: 3.82 lb/cap.day, 1338 residents x 3.82 lb/cap.day x .50(participation rate) = 2556lbs/day vol. of news and cb = 2556lbs/day x .1158yd

3/100lbs

vol. of news and cb = 2.96yd3

/day vol. of others = 2556lbs/day x .1161yd3/100lbs vol.

of others = 2.97yd3

/day Possibilities: You are getting about 3x7days/week=21 yards/week 1. 2-25 yard trucks that each operate the route: one trip for each truck, once/week 2. 2-bifurcated trucks that collect both materials at one time, the route is traveled once/week. 4. The next step should be of primary interest: Cost Analysis What are the revenues earned: - Earnings from recycled material



- Costs avoided by not paying for the materials being landfilled vs. Costs - Equipment - Labor Ancillary issues - Meeting AB939 - Do the right thing because you believe it.

2. Types of Collection Systems

The major dichotomy is between HCS and SCS. In HCS the container is carried to and from the disposal area. With SCS, the container is emptied into a truck and the truck travels to and from the disposal area.

A. Hauled Container Systems

The container is sited at a location. In accordance with some cycle, the container is picked up and hauled off to the disposal area where the container is emptied and returned to the original location. The truck had no container, per se; the container is carried by the truck. A variation is start with an empty container. Advantages:

- Useful when the generation rate is high and the containers are large. - May eliminate spillage associated with multiple smaller containers. - Flexible. Need more capacity, use a larger container.

Disadvantage: - If the containers are not filled, low utilization

rate. Types: - Hoist truck - similar to an AAA emergency truck, but dumsters are picked up or hoisted

instead of cars, smaller volumes, bulky items. - Tilt-frame - assembly on truck allows sliding of large containers on and off the truck. - Trash-trailer The slider assembly is not part of the truck, but part of the trailer.

Example Given: A new sub-division with a single, central park serves about 500 homes. The average occupancy is 2.8 cap/residence. Find: The director of public works wants to know if he can service the park, once per week collection with a single hoist truck.

T6-3, p.138: "Parks and recreational areas".12lbs/cap.day T4-1, p.70: assume rubbish, 220 lbs/yd

3

T8-3, p.205: 6-12yd3

capacity for a hoist truck

1. weight of park material weight = 500 residences x 2.8 cap /residence x .12lbs/cap.day x 7 days/week weight = 1176 lbs/week

2. Volume of park material volume = 1176 lbs/week / 220 lbs/yd

3 volume =

5.3 lbs/yd3

vs. 6-12 yd3

capacity Therefore, a hoist system can be used.

B. Stationary Container System



The waste container remains in the vicinity of where the waste is generated. The waste is unloaded into a bigger truck. A large container is an integral part of the truck. When fully loaded from multiple waste containers, the truck travels to and from the landfill as opposed to the waste container. Types:

- Manually loaded. Small containers. Residential pickup. - Mechanically loaded. Larger containers. Wheeled residential pickup and

commercial pickup - Almost all contain internal compaction equipment

The major advantage is that the vehicle does not travel to the disposal area until it is full yielding higher utilization rates. The major disadvantages include:

- The system is not flexible in terms of picking up bulky goods. - Wastes e.g. demolition, that make damage the relatively delicate mechanisms. - Large volume generations may not have room for storing large containers 3. Analysis of Collection Systems A. Definition of Terms

1.) Pickup (Phcs or scs)

Phcs: The time spent: - driving to the next container after an empty container has been deposited. - the time spent pickup the loaded container. - the time required to redeposit the container after it has been emptied.

Pscs: Refers to the time spent loading the vehicle, beginning with the stop to load the first container and ending when the last container has been loaded. 2.) Haul (h)

Does not include actually picking up the loaded container or redepositing the empty container nor the time spent at the location where the waste is unloaded.

HCS- The time required to reach the location where the waste will be emptied, starting

when the container has been loaded on the truck and continuing through unloading until the

truck arrives at the location where the empty container is to be redeposited. SCS - The time required to reach the location where the full vehicle will be emptied

and continuing until the truck arrives at the location where the first container will be emptied for the next route. 3.) At-Site

The time spent at the site (landfill, MRF, transfer station) where the system is unloaded including waiting time.

4.) Off-Route (W) Non-productive activities

- Necessary - Check in, check out, meeting, breaks. - Unnecessary - Personal errands, extended coffee breaks

Typically 15%

B. Hauled Container System Department of Civil Engineering, ACE


Thcs = (Phcs + s + h)

The time required for a trip is the sum of the pickup time, the time on site and the haul time. The haul time may be expressed as:

h = a + bx (Fig. 8-16, p.214) and is essentially a function of the distance traveled. The pickup time may be expressed as follows:

Phcs = pc + uc + dbc (Fig. 8-16, p.214) In plain English, the pickup time is the sum required to pickup the container,

to unload the container and drive between containers (p+u+d). C. Stationary Container System

Tscs = (Pscs + s + h)

Pscs = Ct(uc) + (np-1)(dbc)

The pickup time depends upon the number of containers multiplied by the unit loading time plus the number of locations times the driving time between the locations. example

Given: A stationary container system (mechanically loaded), 3.5 collection trips/wk, 8hrs/day, 3.22 h/trip (pick up time), at site time .1h/trip, round trip = 10miles, a=.018 h/trip. b= .020h/trip, productive time = 85%

Note: Even though a partial trip (3.5 collection trips), a full trip (4) will have to be made to the disposal area. Find: Time required per week

days/week = no. of trips/week x time/trip

time/day

Tw = [NwPscs + tw(s + a + bx)]

= [3.5x3.22 + 4(.1 + .018 + .020(10))]

(1-W)H (.85)8

Tw = 1.84 days/week 4. Collection Routes A. General

Use a heuristic (common sense), trial and error approach consistent with the philosophy of collecting the most waste with least resources in the context of constraints such as equipment breakdowns, holidays and vacations, good labor practices and the following guidelines:

- Crew size and vehicles must be known and coordinated. - Routes should begin and end near arteries - Topographic and physical boundaries should be route boundaries. - Start at the top of a hill and work downward. - Last collection point should be near disposal site.



- Traffic problems should be dealt with early in the morning. - Extremely large load should be dealt with early in the morning. B. Layout of Collection Routes

Location maps showing data concerning the sources including location, collection frequency, number of containers Data analysis, try to balance the routes in accordance with pickups and time.

Preliminary layout of routes, start at the depot and do a route. An idea of truck capacity vs. loads is in order. Fine tune the preliminary design.

Types of Transfer Stations

Three types: direct-load, storage-load, combined direct-load and discharge load. A. Direct-Load Transfer System

The wastes in the collection vehicles are emptied directly into: - the vehicle that will transport the wastes to the final disposal side - into facilities to compact the wastes into transport vehicles or - into waste bales.

Surge - volume of waste that can be stored temporarily on the loading platform Large capacity - Direct from collection to transport vehicle typically employing a two level operation. Compaction and moving the waste within the transfer vehicle is using done by some kind of back hoe with clamshell tip stationed on the top ramp. An alternative is to direct load into a compactor which in turn moves the waste directly into the haul trailer. Medium and small capacity - Generally small with less equipment and concrete to the

point where Demsey Dumsters are placed on a patch of ground. Alternately, a dual level

system can be made by raising the dumpers or lowering the dumsters, such that the waste

is thrown down into the containers. Individuals seem to like this system. B. Storage-Load Transfer System

Wastes are dumped into a pit or unloading area as opposed to the transfer vehicle.

The pit is typically a larger area and thus facilitates unloading of collection vehicles

and shortens waiting time. Auxiliary equipment such as payloaders move the material

from the storage area into the transfer vehicle. The storage time is typically 1-3 days.

Large capacity - A large pit at a lower level is surrounded by unloading collection

vehicles. Two bull dozers break up the wastes and push the wastes into hoppers

which discharge into the transfer vehicles. C. Combined Direct-Load and Discharge Load Transfer Stations.

Usually a multipurpose facility: perhaps a transfer station and a MRF. Department of Civil Engineering, ACE


Solid waste and Collection Rates

Waste Generation


Collection



Transport

solid waste

Disposal

In this topic:

Importance of waste quantities

Measures and methods used to quantify waste

Waste generation rates

Factors that affect waste generation rates

Types and quantities of recovered materials

Household hazardous wastes

Waste characterization rules

1. Importance of Waste Quantities

Compliance with law such as AB939 which mandates 25% reduction by 1995 and 50% reduction by 2000 Equipment selections.

2. Measures and Methods Used to Assess Quantities

MSW should be measured as a weight as opposed to a volume because the weight measurements are consistent and reproducible while the volume can vary considerably attendant to compaction. Ultimately, however, the capacity of a landfill is a volume consideration.

Units - lb/capita.day for residential and commercial, a repeatable measure of

production for industry and agriculture e.g. lb of manure/chicken. Estimation of Waste Quantities -



- Load-count analysis - A landfill without scales may estimate the vehicular capacity

and the number of vehicles of that capacity.

Example Given: On a single day you observe the following at a landfill: 10-16 yd

3

compactor trucks 18-3

yd3 pickup trucks hauling loose and dry leaves 56-1 yd

3

private cars 2-45 yd

3 trucks with broken concrete

Find: If there are 3.82 lb/cap.day with 2.7 cap/home and all the waste comes from the town, estimate the number of homes in the town. What's wrong with the answer? 1. Compute the total weight

Item Number of Avg. Volume Specific

a Total Weight

loads yd3 Weight lb

lb/yd3 col.2x3x4

Compactor 10 16 500 80,000

truck

Pickup trucks 18 3 100 5,400

with

leaves

loose and

dry

private cars 56 1 220 12,320

broken 2 45 2595 233,550

concrete

Total 331,270

lb/day

a From T4-1, p70

2. Determine the number of homes

number of residence = 331,270 lb

x capita.day

x residence

day 3.82lb 2.7cap

number of residence = 32,118 3. What's wrong with the answer? The demolition load, broken concrete may not be representative; calculate the number of houses with the concrete.

lb capita.day residence number

of residence = (331,270-233,550) day x 3.82lb x 2.7cap number of residence = 9,475 vs. 32,118 with the broken concrete

- Material Balance (eq. 6-1, 6-2, 6-3)

Accumulation = inflow - outflow + generation dM

dt = M

in - M

out + r

w

Note: Always write rw as positive in the parent equation and make a negative substitution as required in the final analysis.



exampleGiven: Paper is 32% of the waste produced and all of it goes to the fireplace

except magazines. Find: Materials flow diagram and amount of solid waste disposed

of during the day. 1. Material Flow Diagram

2. Amount of solid waste disposed of during the day. a. Waste produced = 20lb in the door -7lb food consumed -5lb food stored

Waste produced = 8 lb/day b. Bottles and Cans recycled = 8lb/day x .20

Bottles and Cans recycled = 1.6lb/day

c. Paper goods = 8lb/day x .32 Paper goods = 2.56lb/day

d. Magazines stored = 2.56lb/day x .05 Magazines stored = .13lb/day

e. Paper good combusted = 2.56lb/day x .20 (20% burned) Paper good combusted = .51lb/day

f. solid waste disposed of = 8 lb/day - 1.6lb/day -.51lb/day -0.13lb/day solid waste disposed of = 5.76 lb/day

Statistical Analysis - First determine (p.929) if the data are normally distributed or

skewed by plotting on log normal, probability paper. Arithmetic probability paper is

arithmetic on the ordinate axis, logarithmic probability paper is logarithmic on the

ordinate axis. If the data plots as a straight line on arithmetic paper , it is normal;

departure from a straight line is an indication of skewness. If it is skewed, plot the data

on logarithmic paper; the implication being that the log of the values is normally

distributed which may or may not be the case. If the data is distributed normally, normal

statistics such as mean, standard deviation, variance can be applied.

example Given: The weekly volume of MSW from the local Von's is: 10, 6, 7, 3, 15,10,18,5 yd

3.

Find: Mean, standard deviation coefficient of variation p. 921 1. Mean xbar = x/N = (10+6+7+3+15+10+18+5)/8 = 74/8 xbar = 9.25 2. Standard Deviation

(10-9.25)2

+(6-9.25)2

+...+(5-9.25)2

s = (x-xbar)

2 =

N-1 7



s = 5.11 Note: Using N in the denominator gives 4.79

3. Coefficient of Variation (relative measure of dispersion, typically 10-60% in solid waste) CV = 100s/xbar = 100(5.11)/9.25 CV = 55.24

3. Generation and Collection Rates

Most studies prior to 1990 reflect the amount of waste collected as opposed to the amount of waste generated. The difference may be in recycling, garbage disposal, composting, fireplaces, donations to the Salvation Army etc. The variation may be from 4-15%.

One ton/capita.year 2000 lb/365days/year = 5.48 lb/capita

.day. More precisely, 3.82

lb/capita.day for residential and commercial and 6.16 lb/capita

.day total. The total is

augmented by hazardous, institutional, construction and demolition, municipal services wastes and treatment plant sludges. Residential and commercial is typically 60% of the total. example

Given: The Simi Valley Landfill services app. 50,000 homes. Find: What is the weekly output of hazardous waste to the landfill? Assume: 2.35 capita/residence, T6-3, p138 hazardous waste=.0063lb/capita.day

HW = 50,000 residence x 2.35 capita/residence x .0063lb/capita.day HW = 740.25 lb/day x 7 days/wk HW = 5181.75 lbs/wk

Special Wastes - batteries - 10household batteries/capita.year - used oil - .80 gal/capita.year

example Given: A tire recycler has costed out his capital investment and he needs 1000 tires/day, 5 days/week in order to meet his goal of 8% return on investment. Find: How big of a town does he need? 1. Tire needed Tires needed = 1000tires/day x 5days/week Tires needed = 5000 tires/week

capita.year

People required = 5000 tires/week x .80tire x 52weeks/year People required = 325,000capita

Rate Variation - The larger the data base, the less the variation. - For a residence, peak day factor of 3.0, minimum day factor of .20

example Given: The projected volume at the transfer station was 325tons/day on St. Patrick's Day which was identified and projected as a peak day. You subsequently discovered that holidays are, in fact, not peak days but minimum days. Find: The normal tonnage Assume that the transfer station approximates a small community. From T6-6, for a small community, peak day 2.0, minimum day = .5



Actual tonnage = 325tons/day x 1/2.0(Peak day) Actual tonnage = 162.5 tons/day Normal day tonnage = 162.5 tons/day x 1/.5(minimum day) Normal day tonnage = 325tons/day Note: The peak would be 650.

4. Factor that Effect Generation Rates Source Reduction and Recycling. Design with disposal in mind.

Public Attitudes and Legislation. If not reimbursed, the public must be recruited to a "tree saving" mentality. Legislation includes bottle laws, AB939, green waste pick-ups.

Geographic and Physical Factors. The bigger the yard and the longer the growing season, the more the waste. Seasonal, fall leaves, Christmas gifts, spring cleanup. Kitchen grinders contribute a minimal reduction. Frequency. More waste is collected if the frequency is increased. Note that more wastes are not generated.



UNIT – III TREATMENT AND PROCESSING TECHNIQUES

Separation and Processing and Transformation of Solid Waste

Waste Generation


Collection



Transport

solid waste

Disposal

Issues in this topic:

Recovery of separated materials. Separation and processing of solid waste components Transformation processes

1. General

Methods used to recover source separated material: - Curbside collection - Homeowner delivery to drop-off centers

Further separation of source separated material as well as separation of commingled waste

- MRF's Material Recovery Facilities - MR/TFs Material Recovery/Transfer Facilities, a facility of the future which

may include: -drop-off center -materials separation facility - composting - bioconversion - production of refuse derived fuel (DRF) - transfer and transport facility

2. Reuse and Recycling Opportunities A. Opportunities for reuse include:

Direct reuse as a raw material, 55 gal. drums, furniture, bicycles. Thrift shops.

Raw material for re manufacturing. Must meet material specifications, e.g.



- glass: color, no label or metal, degree of cleanliness - plastics: type (PETE/1, HDPE/2 etc.) moisture content

Feed stock for the production of compost and other processes. If used as an intermediate cover the compost can be fairly contaminated. However, compost for sale must be free of contaminants.

Fuel Source: (perhaps the greatest value of MSW) - Direct burn of the organic fraction. Dirt, ashes, metal, refrigerators will not burn and

perhaps other constituents such as plastics and tires should not be burned. - Converting MSW to fuel.

Land reclamation. Enormous opportunity to reclaim land such as strip-mines or areas below sea level as in the Netherlands, or create new green areas such as golf courses, ball fields, equestrian centers.

B. Drop-off, Buy-back Centers

Drop-off centers may be a wooden bin for newspapers to a thrift shop. Participation can be low because the material must be stored by the homeowner and there is not an economic incentive. Convenience, next to a supermarket, may be critical.

Buy-back centers may be a vending type machine in front of Lucky's to a large commercial venture, such as the Holt Boulevard operation.

3. Unit Operations for Separation and Processing A. Purpose

Modify the physical characteristics to facilitate removal of desired component. Remove specific components or contaminants. Prepare the material for subsequent uses.

B. Size Reduction

Size reduction is the process by which as collected materials are mechanically reduced in size. Object is to obtain a uniform final product that is reduced in size potentially reducing storage and shipping course. Size reduction does not necessarily mean volume reduction. Shredded paper occupies more space than the parent stock. Shredders include hammer mill, flail mill and shear shredder and usually involve metal parts revolving against one another. Glass crushers.

Wood grinders include chippers, such as local tree cutters use, to reduce the branches to chips and tub grinders. Once the wood is broken up, the finer pieces can be used as raw material for composting and the larger pieces can be used as a fuel.

C. Screening

Screening is a unit operation used to separate mixtures of materials of different sizes into two or more size fractions by means of screen surfaces. Object is to:

- Remove oversized material - Remove undersized material - Separate into light (combustible, paper) and heavy (non-combustible, glass) fractions. - Screening devices include: (Fig. 9-8, p. 260) Department of Civil Engineering, ACE


- Vibrating screens - Rotary screens - Disc screens

D. Other Processes

- Density Separation (Air Classification) is the unit process used to separate light materials such as paper and plastic from heavy materials such as metals based on weight difference in the air stream. In solid waste the light fraction is typically organic while the heavy fraction is typically inorganic. Used to separate glass from plastic in a commingled situation. - Magnetic Separation is the operation by which ferrous metals are separated from the waste stream utilizing magnetic principals. Used to separate tin cans from aluminum in a commingled situation. - Densification (compaction) is a unit operation used to increase the density of the material so that it can be stored and transported more cheaply and as a means of preparing densified refuse-derived fuels (dRDR) and include balers and can crushers.

4. Facilities for Handling, Moving and Storing MSW Conveyors Transfer wastes from one location to another and include hinge, belt drag and pneumatic. Conveyors are used in the manual sorting of MSW. Belt is 4' wide and move at 15-90 ft./min. with a thickness of waste of 6". Example

Given: A recycling operation of commingled wastes. Find: The Chief of Public Works of Pomona wants to know how many sorters, jobs, will be needed on the sorting conveyor line. You know the population is 120,000. From T6-3, p.138 3.82 lb./capita.day Weekly tonnage = 120,000 residents x 3.82 lb./capita.day x days/week x 1 ton/2000 lb. Weekly tonnage = 16,044 tons/week 2.5 ton/person.hour, Assume a work week of 40 hours

person.hour

Persons required = 16,044 tons/week x 2.5ton

Persons required = 160 people not including augmentation because of sickness, vacation, holidays, absenteeism etc. An analysis of the economic advantages of the recycling operation seems in order.

Movable Equipment - front end loaders, fork lifts Weighing facilities Storage facilities

5. Development and Implementation of MRF's A. Engineering Considerations

Function of MRF. Depends on role of MRF, type of materials, how the material will be delivered and how it will be presented to the buyer. Selection of materials to be separated. Depends on the program set up in the community, e.g. commingled, 3 recycle containers and 1 for waste. Material specifications. Flow diagrams


x 1 week/40 hours


- Characteristics of the waste material to be processed. - Material specifications. - Available equipment. - Example: Refrigerators must be removed, plastic bags must be burst open, brown bags

are moved from the paper to the cardboard section where they command a higher price. Paper may be baled which weigh 1400 lb. and are 30x40x60 inches.

Estimate Quantities and Loading rates. Mass balance. Usually expressed in tons/hour. Based on 1820 operating hours year.

Number of ton/yr (or ton/d) Loading rate, ton/h =

1820 processing h/yr (or h/d)

Layout and design. Would consider: - Waste deliveries, ingress. - Material delivery rates. - Loading rates including storage for peak times. - Material flow and handling patterns - Performance criteria for equipment selection

Equipment Environmental controls Aesthetics

B. Planning and Design Process for MRF's

Feasibility analysis. Technical and economic merits.

- The coordination of the MRF into the overall IWM (integrate waste management) plan. - What kind of MRF and what kind of materials will it process. - Economics, capital and operating costs. A sensitivity analysis of the effects of

fluctuating prices is particularly important. - Ownership and Operation. Public, private, combination.

Preliminary design. Final design.

C. Issues for MRFs

Siting. Remote locations, as much buffer as possible, NIMBY inevitable. Environmental issues. Traffic, noise, dust, odor, vector control, airborne litter, looks terrible.

Public health and safety. General public and employees. For the employees, protective clothing, puncture-proof gloves, air filters, showers, perhaps a radio.



Economics. Sensitive to market prices. Must be environmentally correct or be shut down.

6. Combustion A. General

Object: - Reduce the volume (85-95% reduction) and weight of wastes. - Recover conversion products and energy.

Major concerns: - Air pollution. - Siting, NIMBY. B. Description of Combustion Process - Unload into a storage pit, usually a 2 day volume. The tipping area should

minimize unloading waiting time with reason. - An overhead crane drops material into a charging chute which directs the wastes to the furnace. The operator tries to get an even mix and remove non-combustible items such as mattresses or engine blocks. - The waste falls on grates and is mass fired. Air is typically introduced. - Gases and small particles rise to the combustion chamber and burn at 1600 F. - Heat is recovered from the gases using water-filled tubes in the combustion chamber and a boiler that produces steam which is converted to electricity in a generator. - Air pollution is controlled including NOx, SO2 and particulates. - Clean gases are discharged to the stack. - Ash and unburned material are quenched (cooled with water). The water and residue must be properly disposed of. See p.641 for an excellent discussion of air pollution systems. C. Types of Combustors

Mass fired. Use unseparated, commingled MSW. Predominate in US, 68%. Pick out the bicycles and refrigerators, burn the rest. The energy content is probably extremely variable.

RDF (Refuse Derived Fuel) fired. 23%. Produced from the organic fraction and can be made with consistency to meet energy, moisture, ash content specifications. Forms include: shredded, fluff, pellets or cubes. Also, since metals, plastics etc. are not burned, air emissions are cleaner.

D. Volume Reduction

Typically 90% volume reduction of the materials that were combusted. Demolition wastes, white goods, cars etc. were never considered. Always a residue and ash left over after combustion consisting of glass, tin cans, iron and steel.

E. Issues With Combustion Facilities

Siting. As with MRF's, a remote location with plenty of buffer zone. Department of Civil Engineering, ACE


Air Emissions. May exceed the cost of the combustion facilities. Most pressing issue in the LA area. Important consideration in the decision between mass-fired and RDF systems. Disposal of residues, bottom ash, fly ash, scrubber product. Typically disposed of in land fill. Liquid Emissions. Sources: ash removal, wet scrubbers. Economics. Standardized life cycle costing

7. Composting A. General

The organic fraction of MSW (less plastic, rubber and leather) is converted into an earthy, humus-like, material by the action of bacteria and other microbes.

Proteins

Amino acids

Lipids

Compost + New Cells + Dead Cel

Carbos + O2 +Nutrients+MOs

Cellulose

Lignin CO2 + H20 + NO3 + SO4 +heat

Ash

Objectives: - Convert the MSW into a biologically stable material which is reduced in volume. - Destroy unwanted biologicals: pathogens, weeds, insect eggs. - Retain the maximum nutrient (N, K, pH). - To produce a valuable, soil amendment product. Not a fertilizer. Lousy C:N ratio. B. Process Description

Howard et al in India in 1930. Three basic steps:

- Preprocessing MSW - Segregating degradable matter, removing engine blocks, tin cans. - moisture content. - fertilizer content perhaps by adding sewer sludge

- Decomposition - windrow - static pile - in-vessel

- Preparation for market. - grinding - screening - blending - additives



- bagging C. Design and Control

- Particle size - Seeding, mixing and turning - Oxygen requirement (aerobic process) - Moisture content - C:N ratio D. Composting Techniques

Agitated and Static. With agitated, the material is turned; with static, air is blown through the material. Windrow composting.

- Most common agitated method. - The material to be composted is shredded into 1-3" pieces and the moisture is adjusted

between 50-60%. -The material is formed into triangular shapes called windrows which may be 6-7'

high and 1`4-16' at the base. - The windrows are tuned twice a week to maintain aerobic decomposition and

the temperature is maintained at 131 F (55 C). - Takes 3-4 weeks and cured for an additional 3-4 weeks without turning.

Aerated Static Pile (Fig. 9-40, p. 307) (also Beltville or ARS process) - MSW is placeed on top of exhaust piping in mounds 7'-8' high. - Each pile has its own blower to deliver air, oxygen. - 3-4 weeks of processing with an equal period for curing.

In-Vessel. Inside an enclosed vessel. Proprietary.(Fig. 9-41, p. 309) - Plug flow and dynamic systems. - Takes 1-2 weeks and 4-12 weeks of curing. E. What Can Be Composted (Applications)

Yard wastes - Ranges from minimal which may take 3 years to high level in container which can be done in several weeks. MSW (organic fraction). Metals or household hazardous waste can easily contaminate the compost. If a high quality product is desired, source separation is a must. MSW (commingled, partially processed). Not suitable as a gardener's compost; use as an intermediate cover if allowed. MSW (with sewer sludge). May avoid sludge dewatering. Increases the nutrient and moisture contents of the mix; may also contain heavy metals. A 2:1, MSW: sludge is recommended as a starting point.

F. Issues With Composting Facilities

Odors. Usually caused by:

- Low C:N ratios - Poor temperature control - Excessive moisture - Poor mixing Department of Civil Engineering, ACE


- Can be controlled with various towers and facilities and odor-masking agents and enzymes.

Pathogens. Usually destroyed by normal composting parameters of 55 C for 15-20 days Heavy metals. Particles are created when the waste is shredded and these particles may become attached to the lighter fractions. Definition of acceptable compost

Waste Handling and Separation

Storage and Processing at the Source

Waste Generation


Collection



Transport

solid waste

Disposal

1. Handling and Separation at the Source Handling refers to activities associated with MSW before they are placed in a collection container May also include handling the collection container to and from the collection point

Source recovery is one of the most effective ways to recycle: aluminum cans, newspaper, plastic soda and milk bottles.

2. Handling Low rise < stories; medium rise 4-7 stories; high rise > 7 stories typical size and dimensions of containers. A. Low Rise

Single family detached and attached Department of Civil Engineering, ACE


Single family detached - separate recyclables at the MRF, not at the home - variety of storage containers and mixed waste: plastic bags, 32 gallon galvanized or

plastic, cardboard boxes -90 gallons containers equipped with wheels, mixed waste

example: Given: In the town of Prolific, the average family size is 6.7. It has been decided to use a standard container which will be provided by the town. Find: Size the container From T6-3, p.138 3.82lbs/capita.day

From T4-1, p.70 220lbs/yd3

yd3

Residential weekly volume = 6.7capita x 3.82lbs/capita.day x 220lbs x 7days/week

Residential weekly volume = .814yd3

x 27ft3

/yd3

= 22.0ft3 x 7.48gal/ft3

= 164.5gallons Use 2-90gallon containers

B. Low and Medium Rise

Basement storage by residents and moving of the container by maintenance personnel.

Large outdoor containers, located in special areas that are emptied mechanically by the collection truck. example

Given: The Wooki Wooki Garden apartments consisting of 50 units with an average of 1.9 persons/unit. The manager has decided to provide one disposal unit for mixed waste and a single unit for all recycled material. Use 2lbs/capita.day,total waste. Find: Size the two containers for weekly pickup. (Quick, first cut estimate)

Total weight = 2lbs/capita.day x 1.9 persons/unit x 50 units x 7days/wk Total weight = 1330lbs/week

T6-7, p.147 %recovered for recycling 12-16% by weight

Total weight of recycled mat'l = 1330lbs/week x .16(use max to give largest recycle container) Total weight of recycled mat'l = 213 lbs/week

Total weight of waste = 1330lbs/week x (1-.12)(use min to give largest waste container) Total weight of waste = 1170 lbs/week

yd3

Volume of recycle container = 213lbs/week x 150lbs yd

3

150lbs is a guess from T4-1, p.70 based on plastics at 110 and aluminum at 270 and glass at

330. A more detailed analysis would not be difficult. In any case, the best information may be forthcoming from actual operating data. Volume of recycle container = 1.42 yards Any container larger than this number will do the trick. Since there should not be putrescible in the recycling bin, a larger container with more infrequent collections e.g. may be suitable.

yd

3

Volume of waste container = 1170 lbs/week x 220lbs

Volume of waste container = 5.3 yd3

/week Department of Civil Engineering, ACE


C. High Rise Apartments Porters pick up the waste at the apartment door. Wastes are taken to the SW area by tenants Chutes on each floor (12-36")

yd3

Use

175lbs 1-2lbs/tenant.day Vacuum transport systems have been used most notably at Disney World

D. Commercial and Industrial Facilities

Commercial - removed from work area by wheeled containers or blanket wrapped and transported via the service area to a disposal/processing area. Compaction would not be unusual. Industrial area - May be more suACEptible to the profit motive e.g. can order employees to recycle cans.

3. Storage of SW at the Source A. Effects of Storage

Putrefaction - Microbial decomposition via bacteria and fungi leading to vermin and odors. Adsorption of Fluids - If more than a week, the water will become equally distributed, primarily moisture from food and garden material moving into the paper. Contamination - A small volume of paint had great potential to contaminate a great deal of plastic, an argument for source separation of recyclables.

B. Types of Storage Containers

For residential containers, manually collected, the max. weight should be 40-65lbs as not injure the collector. 32 gallons galvanized or plastic is the most common.

Temporary and disposable containers such as cardboard boxes, plastic bags and paper bags are common. A problem with these is that animals are attracted by the food and tear them open and spread the material around.

Low rise - trend towards 1 man collection crews with vehicles with mechanical, articulated arms and 90 gallon containers, (75-120) Low and medium rise - Demsey dumsters, portable or not, galvanized or plastic

High rise - more proned to have processing equipment: compaction, shredding, baling and in the old days incineration. Container Locations: side or rear of house, alleys, common location identified for that purpose. Public health and aesthetics - Potential for odors and vermin. Randy and his maggots....

4. Processing at Dwellings

Insinkeration of food - No significant decrease in the weight or volume of the MSW. Separation - very effective if you can engender meaningful participation.



Compaction - individual units under the counter, collection and processing by large units. Potentially counterproductive if the wastes are to sorted at a MRF; also, compaction may foster contamination.

5. Composting The biological conversion of the biodegradable organic fraction of the MSW resulting in a volume reduction and producing a useful by-product Isolate a 3ft square area with chicken wire and dump the yard wastes. Food wastes may be stirred into the mix if odor and vermin problems can be obviated. Water and turn occasionally, once/week. Perhaps ready to use after 1 year, put in at top, take out at bottom. Produces a humus-like material which is a soil conditioner, not a fertilizer.



UNIT – IV INCINERATION Incineration is a waste treatment process, the combustion of organic substances

contained in waste materials. Incineration and other high temperature waste treatment

systems are described as "thermal treatment". Incineration of waste materials converts the

waste into ash, flue gas, and heat. The ash is mostly formed by the inorganicconstituents

of the waste, and may take the form of solid lumps or particulates carried by the flue gas.

The flue gases must be cleaned of gaseous and particulate pollutants before they are

dispersed into the atmosphere. In some cases, the heat generated by incineration can be

used to generate electric power. Incineration with energy recovery is one of several waste-to-energy (WtE) technologies

such as gasification, Plasma arc gasification, pyrolysis and anaerobic digestion.

Incineration may also be implemented without energy and materials recovery.

In several countries, there are still concerns from experts and local communities about the

environmental impact of incinerators (see arguments against incineration).

In some countries, incinerators built just a few decades ago often did not include

a materials separation to remove hazardous, bulky or recyclable materials before combustion. These facilities tended to risk the health of the plant workers and the local

environment due to inadequate levels of gas cleaning and combustion process control.

Most of these facilities did not generate electricity.

Incinerators reduce the solid mass of the original waste by 80–85% and the volume

(already compressed somewhat ingarbage trucks) by 95-96 %, depending on composition

and degree of recovery of materials such as metals from the ash for recycling.[2]

This

means that while incineration does not completely replace landfilling, it significantly

reduces the necessary volume for disposal. Garbage trucks often reduce the volume of

waste in a built-in compressor before delivery to the incinerator. Alternatively, at

landfills, the volume of the uncompressed garbage can be reduced by approximately

70%[citation needed]

by using a stationary steel compressor, albeit with a significant

energy cost. In many countries, simplerwaste compaction is a common practice for

compaction at landfills.

Incineration has particularly strong benefits for the treatment of certain waste

types in niche areas such as clinical wastesand certain hazardous

wastes where pathogens and toxins can be destroyed by high temperatures. Examples



include chemical multi-product plants with diverse toxic or very toxic wastewater

streams, which cannot be routed to a conventional wastewater treatment plant.

Waste combustion is particularly popular in countries such as Japan where land is a

scarce resource. Denmark and Sweden have been leaders in using the energy generated

from incineration for more than a century, in localised combined heat and power facilities

supporting district heating schemes.[3]

In 2005, waste incineration produced 4.8 % of the

electricity consumption and 13.7 % of the total domestic heat consumption

The first incinerators for waste disposal were built in Nottingham by Manlove, Alliott &

Co. Ltd. in 1874 to a design patented by Albert Fryer. They were originally known as

destructors.

An incinerator is a furnace for burning waste. Modern incinerators include pollution

mitigation equipment such as flue gas cleaning. There are various types of incinerator

plant design: moving grate, fixed grate, rotary-kiln, and fluidised bed.

The burn pile, or burn pit is one of the simplest and earliest forms of waste disposal,

essentially consisting of a mound of combustible materials piled on bare ground and set

on fire. Indiscriminate piles of household waste are strongly discouraged and may be

illegal in urban areas, but are permitted in certain rural situations such as clearing

forested land for farming, where the stumps are uprooted and burned.[6]

Rural burn piles

of organic yard waste are also sometimes permitted, though not asphalt shingles, plastics,

or otherpetroleum products.

Burn piles can and have spread uncontrolled fires, for example if wind blows burning

material off the pile into surrounding combustible grasses or onto buildings. As interior

structures of the pile are consumed, the pile can shift and collapse, spreading the burn

area. Even in a situation of no wind, small lightweight ignited embers can lift off the pile

viaconvection, and waft through the air into grasses or onto buildings, igniting them. Burn barrel

The burn barrel is a somewhat more controlled form of private waste incineration,

containing the burning material inside a metal barrel, with a metal grating over the

exhaust. The barrel prevents the spread of burning material in windy conditions, and as

the combustibles are reduced they can only settle down into the barrel. The exhaust

grating helps to prevent the spread of burning embers. Typically steel 55-US-gallon (210

L) drums are used as burn barrels, with air vent holes cut or drilled around the base Department of Civil Engineering, ACE


for air intake.[7]

Over time the very high heat of incineration causes the metal to oxidize

and rust, and eventually the barrel itself is consumed by the heat and must be replaced.

Private burning of dry cellulosic/paper products is generally clean-burning, producing no

visible smoke, but the large amount of plastics in household waste can cause private

burning to create a public nuisance and health hazard, generating acrid odors and fumes

that make eyes burn and water. The temperatures in a burn barrel are not regulated, and

usually do not reach high enough or for enough time to completely break down chemicals

such as dioxin in plastics and other waste chemicals. Therefore plastics and other

petroleum products must be separated and sent to commercial waste disposal facilities.

In the United States, private rural incineration is typically permitted so long as it is not a

nuisance to others, does not pose a risk of fire such as in dry conditions, and the fire is

clean-burning, producing no visible smoke. However, many states, such as New York,

Minnesota, and Wisconsin, have laws against private burn barrels due to EPA findings

that one household burning their own waste can release more dioxins and furans annually

than a modern incinerator processing 200 tons per day.[8]

People intending to burn waste

may be required to contact a state agency in advance to check current fire risk and

conditions, and to alert officials of the controlled fire that will occur.[9]

Moving grate The typical incineration plant for municipal solid waste is a moving grate incinerator. The

moving grate enables the movement of waste through the combustion chamber to be

optimised to allow a more efficient and complete combustion. A single moving grate

boiler can handle up to 35 metric tons (39 short tons) of waste per hour, and can operate

8,000 hours per year with only one scheduled stop for inspection and maintenance of

about one month's duration.[10]

Moving grate incinerators are sometimes referred to as

Municipal Solid Waste Incinerators (MSWIs).

The waste is introduced by a waste crane through the "throat" at one end of the grate,

from where it moves down over the deACEnding grate to the ash pit in the other end.

Here the ash is removed through a water lock.

Part of the combustion air (primary combustion air) is supplied through the grate from

below. This air flow also has the purpose of cooling the grate itself. Cooling is important

for the mechanical strength of the grate, and many moving grates are also water-cooled

internally.



Secondary combustion air is supplied into the boiler at high speed through nozzles over

the grate. It facilitates complete combustion of the flue gases by introducing turbulence

for better mixing and by ensuring a surplus of oxygen. In multiple/stepped hearth

incinerators, the secondary combustion air is introduced in a separate chamber

downstream the primary combustion chamber.

According to the European Waste Incineration Directive, incineration plants must be

designed to ensure that the flue gases reach a temperature of at least 850 °C (1,560 °F)

for 2 seconds in order to ensure proper breakdown of toxic organic substances. In order to

comply with this at all times, it is required to install backup auxiliary burners (often

fueled by oil), which are fired into the boiler in case the heating valueof the waste

becomes too low to reach this temperature alone.

The flue gases are then cooled in the superheaters, where the heat is transferred to steam,

heating the steam to typically 400 °C (752 °F) at a pressure of 40 bars (580 psi) for the

electricity generation in theturbine. At this point, the flue gas has a temperature of around

200 °C (392 °F), and is passed to the flue gas cleaning system.

In Scandinavia scheduled maintenance is always performed during summer, where the

demand for district heating is low. Often incineration plants consist of several separate



'boiler lines' (boilers and flue gas treatment plants), so that waste can continue to be

received at one boiler line while the others are subject to revision. Fixed grate

The older and simpler kind of incinerator was a brick-lined cell with a fixed metal grate

over a lower ash pit, with one opening in the top or side for loading and another opening

in the side for removing incombustible solids called clinkers. Many small incinerators

formerly found in apartment houses have now been replaced by waste compactors. Rotary-kiln

The rotary-kiln incinerator[11]

is used by municipalities and by large industrial plants.

This design of incinerator has 2 chambers: a primary chamber and secondary chamber.

The primary chamber in a rotary kiln incinerator consist of an inclined refractory lined

cylindrical tube. Movement of the cylinder on its axis facilitates movement of waste. In

the primary chamber, there is conversion of solid fraction to gases, through volatilization,

destructive distillation and partial combustion reactions. The secondary chamber is

necessary to complete gas phase combustion reactions.

The clinkers spill out at the end of the cylinder. A tall flue-gas stack, fan, or steam jet

supplies the needed draft. Ash drops through the grate, but many particles are carried

along with the hot gases. The particles and any combustible gases may be combusted in

an "afterburner" Fluidized bed

A strong airflow is forced through a sandbed. The air seeps through the sand until a point

is reached where the sand particles separate to let the air through and mixing and

churning occurs, thus a fluidized bed is created and fuel and waste can now be

introduced.

The sand with the pre-treated waste and/or fuel is kept suspended on pumped air currents

and takes on a fluid-like character. The bed is thereby violently mixed and agitated

keeping small inert particles and air in a fluid-like state. This allows all of the mass of

waste, fuel and sand to be fully circulated through the furnace. Specialized incineration

Furniture factory sawdust incinerators need much attention as these have to handle resin

powder and many flammable substances. Controlled combustion, burn back prevention



systems are essential as dust when suspended resembles the fire catch phenomenon of

any liquid petroleum gas. Use of heat

The heat produced by an incinerator can be used to generate steam which may then be

used to drive a turbine in order to produce electricity. The typical amount of net energy

that can be produced per tonne municipal waste is about 2/3 MWh of electricity and 2

MWh of district heating.[2]

Thus, incinerating about 600 metric tons (660 short tons) per

day of waste will produce about 400 MWh of electrical energy per day (17 MW of

electrical power continuously for 24 hours) and 1200 MWh of district heating energy

each day. Pollution

Incineration has a number of outputs such as the ash and the emission to the atmosphere

of flue gas. Before the flue gas cleaning system, the flue gases may contain significant

amounts of particulate matter, heavy metals, dioxins, furans, sulfur dioxide, and

hydrochloric acid.

In a study from 1994, Delaware Solid Waste Authority found that, for same amount of

produced energy, incineration plants emitted fewer particles, hydrocarbons and less SO2,

HCl, CO and NOx than coal-fired power plants, but more than natural gas fired power

plants.[13]

According to Germany's Ministry of the Environment, waste incinerators

reduce the amount of some atmospheric pollutants by substituting power produced by

coal-fired plants with power from waste-fired plants.[14]

Gaseous emissions Dioxin and furans

The most publicized concerns from environmentalists about the incineration of municipal

solid wastes (MSW) involve the fear that it produces significant amounts of dioxin and

furanemissions.[15]

Dioxins and furans are considered by many to be serious health

hazards.

In 2005, The Ministry of the Environment of Germany, where there were 66 incinerators

at that time, estimated that "...whereas in 1990 one third of all dioxin emissions in

Germany came from incineration plants, for the year 2000 the figure was less than 1 %.

Chimneys and tiled stoves in private households alone discharge approximately 20 times

more dioxin into the environment than incineration plants."[14]



According to the United States Environmental Protection Agency, incineration plants are

no longer significant sources of dioxins and furans. In 1987, before the governmental

regulations required the use of emission controls, there was a total of 10,000 grams (350

oz) of dioxin emissions from US incinerators. Today, the total emissions from the 87

plants are 10 grams (0.35 oz) annually, a reduction of 99.9 %.

Backyard barrel burning of household and garden wastes, still allowed in some rural

areas, generates 580 grams (20 oz) of dioxins annually. Studies conducted by the US-

EPA[16]

demonstrate that the emissions from just one family using a burn barrel produced

more emissions than an incineration plant disposing of 200 metric tons (220 short tons) of

waste per day by 1997 and five times that by 2007 due to increased chemicals in

household trash and decreased emissions by municipal incinerators using better

technology Dioxin cracking methods and limitations

Generally, the breakdown of dioxin requires exposure of the molecular ring to a

sufficiently high temperature so as to trigger thermal breakdown of the strong molecular

bonds holding it together. Small pieces of fly ash may be somewhat thick, and too brief

an exposure to high temperature may only degrade dioxin on the surface of the ash. For a

large volume air chamber, too brief an exposure may also result in only some of the

exhaust gases reaching the full breakdown temperature. For this reason there is also a

time element to the temperature exposure to ensure heating completely through the

thickness of the fly ash and the volume of waste gases.

There are trade-offs between increasing either the temperature or exposure time.

Generally where the molecular breakdown temperature is higher, the exposure time for

heating can be shorter, but excessively high temperatures can also cause wear and

damage to other parts of the incineration equipment. Likewise the breakdown

temperature can be lowered to some degree but then the exhaust gases would require a

greater lingering period of perhaps several minutes, which would require large/long

treatment chambers that take up a great deal of treatment plant space.

A side effect of breaking the strong molecular bonds of dioxin is the potential for breaking

the bonds of nitrogen gas (N2) and oxygen gas (O2) in the supply air. As the exhaust flow

cools, these highly reactive detached atoms spontaneously reform bonds into reactive oxides

such as NOx in the flue gas, which can result in smog formation and acid rain if they were

released directly into the local environment. These reactive oxides must



be further neutralized with selective catalytic reduction (SCR) or selective non-catalytic

reduction (see below). Dioxin cracking in practice

The temperatures needed to break down dioxin are typically not reached when burning of

plastics outdoors in a burn barrel or garbage pit, causing high dioxin emissions as

mentioned above. While plastic does usually burn in an open-air fire, the dioxins remain

after combustion and either float off into the atmosphere, or may remain in the ash where

it can be leached down into groundwater when rain falls on the ash pile. Fortunately,

dioxin and furan compounds very strongly bond to solid surfaces and are not solvated by

water so leaching processes are limited to the first few milimeters below the ash pile. The

gas-phase dioxins can be substantially destroyed using catalysts, some of which can be

present as part of the fabric filter bag structure.

Modern municipal incinerator designs include a high temperature zone, where the flue

gas is ensured to sustain a temperature above 850 °C (1,560 °F) for at least 2 seconds

before it is cooled down. They are equipped with auxiliary heaters to ensure this at all

times. These are often fueled by oil, and normally only active for a very small fraction of

the time. Further, most modern incinerators utilize fabric filters (often with Teflon

membranes to enhance collection of sub-micron particles) which can capture dioxins

present in or on solid particles.

For very small municipal incinerators, the required temperature for thermal breakdown of

dioxin may be reached using a high-temperature electrical heating element, plus a

selective catalytic reduction stage.

CO2

As for other complete combustion processes, nearly all of the carbon content in the waste

is emitted as CO2 to the atmosphere. MSW contains approximately the same mass

fraction of carbon as CO2 itself (27%), so incineration of 1 ton of MSW produces

approximately 1 ton of CO2.

If the waste was landfilled, 1 ton of MSW would produce approximately 62 cubic metres

(2,200 cu ft) methane via the anaerobic decomposition of the biodegradable part of the waste.

Since the global warming potential of methane is 21 and the weight of 62 cubic meters of

methane at 25 degrees Celsius is 40.7 kg, this is equivalent to 0.854 ton of CO2, which is less

than the 1 ton of CO2 which would have been produced by incineration. In



some countries, large amounts of landfill gas are collected, but still the global warming

potential of the landfill gas emitted to atmosphere in the US in 1999 was approximately

32 % higher than the amount of CO2 that would have been emitted by incineration.[18]

In addition, nearly all biodegradable waste has biological origin. This material has been

formed by plants using atmospheric CO2 typically within the last growing season. If

these plants are regrown the CO2 emitted from their combustion will be taken out from

the atmosphere once more.

Such considerations are the main reason why several countries administrate incineration

of the biodegradable part of waste as renewable energy.[19]

The rest – mainly plastics and

other oil and gas derived products – is generally treated as non-renewables.

Different results for the CO2 footprint of incineration can be reached with different

assumptions. Local conditions (such as limited local district heating demand, no fossil

fuel generated electricity to replace or high levels of aluminium in the waste stream) can

decrease the CO2 benefits of incineration. The methodology and other assumptions may

also influence the results significantly. For example the methane emissions from landfills

occurring at a later date may be neglected or given less weight, or biodegradable waste

may not be considered CO2 neutral. A study by Eunomia Research and Consulting in

2008 on potential waste treatment technologies in London demonstrated that by applying

several of these (according to the authors) unusual assumptions the average existing

incineration plants performed poorly for CO2 balance compared to the theoretical

potential of other emerging waste treatment technologies.[20]

Other emissions

Other gaseous emissions in the flue gas from incinerator furnaces include sulfur dioxide,

hydrochloric acid, heavy metals and fine particles.

The steam content in the flue may produce visible fume from the stack, which can be

perceived as a visual pollution. It may be avoided by decreasing the steam content by

flue-gas condensation and reheating, or by increasing the flue gas exit temperature well

above its dew point. Flue-gas condensation allows the latent heat of vaporization of the

water to be recovered, subsequently increasing the thermal efficiency of the plant. Flue-gas cleaning

The quantity of pollutants in the flue gas from incineration plants is reduced by several

processes. Department of Civil Engineering, ACE


Particulate is collected by particle filtration, most often electrostatic precipitators (ESP)

and/or baghouse filters. The latter are generally very efficient for collecting fine particles.

In an investigation by the Ministry of the Environment of Denmark in 2006, the average

particulate emissions per energy content of incinerated waste from 16 Danish incinerators

were below 2.02 g/GJ (grams per energy content of the incinerated waste). Detailed

measurements of fine particles with sizes below 2.5 micrometres (PM2.5) were performed

on three of the incinerators: One incinerator equipped with an ESP for particle filtration

emitted 5.3 g/GJ fine particles, while two incinerators equipped with baghouse filters

emitted 0.002 and 0.013 g/GJ PM2.5. For ultra fine particles (PM1.0), the numbers were

4.889 g/GJ PM1.0 from the ESP plant, while emissions of 0.000 and 0.008 g/GJ PM1.0

were measured from the plants equipped with baghouse filters.[21][22]

Acid gas scrubbers are used to remove hydrochloric acid, nitric acid, hydrofluoric

acid, mercury, lead and other heavy metals. Basic scrubbers remove sulfur dioxide,

forminggypsum by reaction with lime.[23]

Waste water from scrubbers must subsequently pass through a waste water treatment

plant.

Sulfur dioxide may also be removed by dry desulfurisation by

injection limestone slurry into the flue gas before the particle filtration.

NOx is either reduced by catalytic reduction with ammonia in a catalytic converter (selective catalytic reduction, SCR) or by a high temperature reaction with

ammonia in the furnace (selective non-catalytic reduction, SNCR). Urea may be

substituted for ammonia as the reducing reagent but must be supplied earlier in the

process so that it can hydrolyze into ammonia. Substitution of urea can reduce costs and

potential hazards associated with storage of anhydrous ammonia.

Heavy metals are often adsorbed on injected active carbon powder, which is collected by

the particle filtration. Solid outputs

Incineration produces fly ash and bottom ash just as is the case when coal is combusted. The

total amount of ash produced by municipal solid waste incineration ranges from 4 to 10 % by

volume and 15-20 % by weight of the original quantity of waste,[2][24]

and the fly ash

amounts to about 10-20 % of the total ash.[citation needed]

The fly ash, by far, constitutes more

of a potential health hazard than does the bottom ash because the fly ash often Department of Civil Engineering, ACE


contain high concentrations of heavy metals such as lead, cadmium,copper and zinc as well

as small amounts of dioxins and furans.[25]

The bottom ash seldom contain significant levels

of heavy metals. In testing over the past decade, no ash from an incineration plant in the USA

has ever been determined to be a hazardous waste.[citation

needed]

At present although some

historic samples tested by the incinerator operators' group would meet the being ecotoxic

criteria at present the EA say "we have agreed" to regard incinerator bottom ash as "non-

hazardous" until the testing programme is complete.[citation

needed]

Other pollution issues

Odor pollution can be a problem with old-style incinerators, but odors and dust are

extremely well controlled in newer incineration plants. They receive and store the waste

in an enclosed area with a negative pressure with the airflow being routed through the

boiler which prevents unpleasant odors from escaping into the atmosphere. However, not

all plants are implemented this way, resulting in inconveniences in the locality.

An issue that affects community relationships is the increased road traffic of waste

collection vehicles to transport municipal waste to the incinerator. Due to this reason,

most incinerators are located in industrial areas. This problem can be avoided to an extent

through the transport of waste by rail from transfer stations.

Agency's (ESPA) comprehensive health effects research concluded "inconclusively"

on health effects in October, 2009. The authors stress, that even though no conclusive

evidence of non-occupational health effects from incinerators were found in the

existing literature, "small but important effects might be virtually impossible to

detect". The report highlights epidemiological deficiencies in previous UK health

studies and suggests areas for future studies.[33]

The U.K. Health Protection Agency

produced a lesser summary in September 2009.[26]

Many toxiocologists criticise and

dispute this report as not being comprehensive epidemiologically, thin on peer review

and the effects of fine particle effects on health

The highly toxic fly ash must be safely disposed of. This usually involves additional

waste miles and the need for specialist toxic waste landfill elsewhere. If not done properly, it may cause concerns for local residents.



Some people are still concerned about the health effects

of dioxin and furan emissions into the atmosphere from old incinerators; especially

during start up and shut down, or where filter bypass is required.

Incinerators emit varying levels of heavy metals such

as vanadium, manganese, chromium, nickel, arsenic, mercury,lead, and cadmium,

which can be toxic at very minute levels.

Incinerator Bottom Ash (IBA) has elevated levels of heavy metals with

ecotoxicity concerns if not reused properly. Some people have the opinion that IBA

reuse is still in its infancy and is still not considered to be a mature or desirable

product, despite additional engineering treatments. Concerns of IBA use in foam

concrete have been expressed by the UK Health and Safety Executive in 2010

following several construction and demolition explosions. In its guidance document,

IBA is currently banned from use by the UK Highway Authority in concrete work

until these incidents have been investigated

Alternative technologies are available or in development such as Mechanical

Biological Treatment, Anaerobic Digestion(MBT/AD), Autoclaving or Mechanical

Heat Treatment (MHT) using steam or plasma arc gasification (PGP), which is

incineration using electrically produced extreme high temperatures, or combinations

of these treatments. Erection of incinerators compete with the development and

introduction of other emerging technologies. A UK government WRAP report,

August 2008 found that in the UK median incinerator costs per ton were generally

higher than those for MBT treatments by £18 per metric ton; and £27 per metric ton

for most modern (post 2000) incinerators.

Building and operating waste processing plants such as incinerators requires long

contract periods to recover initial investment costs, causing a long term lock-in.

Incinerator lifetimes normally range 25–30 years. This was highlighted by Peter

Jones, OBE, the Mayor of London's waste representative in April 2009

Incinerators produce fine particles in the furnace. Even with modern particle

filtering of the flue gases, a small part of these is emitted to the atmosphere. PM2.5 is

not separately regulated in the European Waste Incineration Directive, even though they are repeatedly correlated spatially to infant mortality in the UK (M.Ryan's ONS

data based maps around the EfW/CHP waste incinerators at Edmonton, Coventry,

Chineham, Kirklees and Sheffield). Under WID there is no requirement to monitor

stack top or downwind incinerator PM2.5 levels.[43]

Several European doctors Department of Civil Engineering, ACE


associations (including cross discipline experts such as physicians, environmental

chemists and toxicologists) in June 2008 representing over 33,000 doctors wrote a

keynote statement directly to the European Parliament citing widespread concerns on

incinerator particle emissions and the absence of specific fine and ultrafine particle

size monitoring or in depth industry/government epidemiological studies of these

minute and invisible incinerator particle size emissions.

Local communities are often opposed to the idea of locating waste processing

plants such as incinerators in their vicinity (the Not In My Back Yard phenomenon).

Studies inAndover, Massachusetts strongly correlated 10% property devaluations

with close incinerator proximity.

Prevention, waste minimisation, reuse and recycling of waste should all be

preferred to incineration according to the waste hierarchy. Supporters of zero

waste consider incinerators and other waste treatment technologies as barriers

to recycling and separation beyond particular levels, and that waste resources are

sacrificed for energy production.

A 2008 Eunomia report found that under some circumstances and assumptions,

incineration causes less CO2 reduction than other emerging EfW and CHP

technology combinations for treating residual mixed waste.[20]

The authors found

that CHP incinerator technology without waste recycling ranked 19 out of 24

combinations (where all alternatives to incineration were combined with advanced

waste recycling plants); being 228% less efficient than the ranked 1 Advanced MBT

maturation technology; or 211% less efficient than plasma gasification/autoclaving

combination ranked 2.

Some incinerators are visually undesirable. In many countries they require a visually intrusive chimney stack.

If reusable waste fractions are handled in waste processing plants such as

incinerators in developing nations, it would cut out viable work for local economies.

It is estimated that there are 1 million people making a livelihood off collecting

waste.

The history of municipal solid waste (MSW) incineration is linked intimately to the

history of landfills and other waste treatment technology. The merits of incineration are

inevitably judged in relation to the alternatives available. Since the 1970s, recycling and



other prevention measures have changed the context for such judgements. Since the

1990s alternative waste treatment technologies have been maturing and becoming viable.

Incineration is a key process in the treatment of hazardous wastes and clinical wastes. It

is often imperative that medical waste be subjected to the high temperatures of

incineration to destroy pathogens and toxic contamination it contains.

The first incinerator in the U.S. was built in 1885 on Governors Island in New York.[50]

In

1949, Robert C. Ross founded one of the first hazardous waste management companies in the

U.S. He began Robert Ross Industrial Disposal because he saw an opportunity to meet the

hazardous waste management needs of companies in northern Ohio. In 1958, the company

built one of the first hazardous waste incinerators in the U.S.[51]

The first full-scale,

municipally operated incineration facility in the U.S. was the Arnold O. Chantland Resource

Recovery Plant, built in 1975 and located in Ames, Iowa. This plant is still in operation and produces refuse-derived fuel that is sent to local power plants for

fuel.[52]

The first commercially successful incineration plant in the U.S. was built in Saugus, Massachusetts in October 1975 by Wheelabrator Technologies, and is still in

operation today.

There are several environmental or waste management corporations that transport

ultimately to an incinerator or cement kiln treatment center. Currently (2009), there are

three main businesses that incinerate waste: Clean Harbours, WTI-Heritage, and Ross

Incineration Services. Clean Harbours has acquired many of the smaller, independently

run facilities, accumulating 5–7 incinerators in the process across the U.S. WTI-Heritage

has one incinerator, located in the southeastern corner of Ohio (across the Ohio River

from West Virginia).

Several old generation incinerators have been closed; of the 186 MSW incinerators in

1990, only 89 remained by 2007, and of the 6200 medical waste incinerators in 1988,

only 115 remained in 2003.[53]

No new incinerators were built between 1996 and 2007.

The main reasons for lack of activity have been:

Economics. With the increase in the number of large inexpensive regional

landfills and, up until recently, the relatively low price of electricity, incinerators were not able to compete for the 'fuel', i.e., waste in the U.S.

Tax policies. Tax credits for plants producing electricity from waste were rescinded in the U.S. between 1990 and 2004.



There has been renewed interest in incineration and other waste-to-energy technologies in

the U.S. and Canada. In the U.S., incineration was granted qualification for renewable

energy production tax credits in 2004.[54]

Projects to add capacity to existing plants are

underway, and municipalities are once again evaluating the option of building

incineration plants rather than continue landfilling municipal wastes. However, many of

these projects have faced continued political opposition in spite of renewed arguments for

the greenhouse gas benefits of incineration and improved air pollution control and ash

recycling.

In Europe, with the ban on landfilling untreated waste, scores of incinerators have been

built in the last decade, with more under construction. Recently, a number of municipal

governments have begun the process of contracting for the construction and operation of

incinerators. In Europe, some of the electricity generated from waste is deemed to be

from a 'Renewable Energy Source (RES) and is thus eligible for tax credits if privately

operated. Also, some incinerators in Europe are equipped with waste recovery, allowing

the reuse of ferrous and non-ferrous materials found in landfills. A prominent example is

the AEB Waste Fired Power Plant.

The technology employed in the UK waste management industry has been greatly

lagging behind that of Europe due to the wide availability of landfills. The Landfill

Directive set down by the European Union led to the Government of the United Kingdom

imposing waste legislation including the landfill tax and Landfill Allowance Trading

Scheme. This legislation is designed to reduce the release of greenhouse gases produced

by landfills through the use of alternative methods of waste treatment. It is the UK

Government's position that incineration will play an increasingly large role in the

treatment of municipal waste and supply of energy in the UK.

Emergency incineration systems exist for the urgent and biosecure disposal of animals

and their by-products following a mass mortality or disease outbreak. An increase in

regulation and enforcement from governments and institutions worldwide has been

forced through public pressure and significant economic exposure.

Contagious animal disease has cost governments and industry $200 billion over 20 years

to 2012 and is responsible for over 65% of infectious disease outbreaks worldwide in the

past sixty years. One-third of global meat exports (approx 6 million tonnes) is affected by

trade restrictions at any time and as such the focus of Governments, public bodies and

commercial operators is on cleaner, safer and more robust methods of animal carcass

disposal to contain and control disease. Department of Civil Engineering, ACE


Large scale incineration systems are available from niche suppliers and are often bought

by Governments as a safety net in case of contagious outbreak. Many are mobile and can

be quickly deployed to locations requiring biosecure disposal.

Pyrolysis

• It is defined as heating the solid waste at very high temperature in absence of air.

• Pyrolysis is carried out at a temperature between 500 0 C to 1000

0C to

produce three component streams.

• Gas: It is a mixture of combustible gases such as hydrogen, carbon

dioxide, methane, carbon mono-oxide and some hydrocarbons.

• Liquid: It contains tar, pitch, light oil, and low boiling organic chemicals

like acetic acid, acetone, methanol etc.

• Char: It consists of elemental carbon along with inert material in the waste feed.

• The char liquid and gases have high calorific values.

• It has been observed that even after supplying the heat necessary for pyrolysis,

certain amount of excess heat still remains which can be commercially exploited.



UNIT – V COMPOSTING Composting Composting is an excellent method of recycling biodegradable waste from an ecological

point of view. Composting is in fact the controlled biological decomposition of organic matter, such as food and yard wastes, into humus, a soil-like material. Composting is nature‟s way of recycling organic waste into new soil, which can be used in vegetable and flower gardens, landscaping and the like. However, many large and small composting schemes have failed because composting is regarded as a disposal process, and not a production process. Environmental problems may arise when waste is composted without noncompostible matter like metals and plastics being removed. Hazardous substances like heavy metals may then be found in the compost, which in turn may be taken up in the food chain when compost is used on agricultural land. To prevent this situation, sorting at the composting plant or even at the household level might be called for.

Benefits of Composting-

Keeps organic wastes out of landfills.

Provides nutrients to the soil.

Increases beneficial soil organisms (e.g., worms and centipedes).

Suppresses certain plant diseases.

Reduces the need for fertilizers and pesticides.

Protects soils from erosion.

Assists pollution remediation Composting is also defined as process in which organic matter of the solid waste is

decomposed and converted to humus and stable mineral compounds. The end product

of composting process is called compost which is rich fertilizer.

There are three methods of composting:

(1) Composting by Trenching

(2) Open window composting

(3) Mechanical Composting Department of Civil Engineering, ACE


Composting by Trenching:

In this method trenches 3 to 12 m long, 2 to 3 m wide and 1 to 2 m deep are excavated with

clear spacing of 2 m. The trenches are then filled up with dry solid waste in layers of 15 cm.

On top of each layer 5 cm thick sandwiching layer of night soil animal dung is spread in

semi liquid form. On the top layer of night soil animal dung is spread in semi liquid form. On

the top layer protruding about 30 cm above the surrounding ground layer, a layer of earth

having thickness of around 10 cm is laid so that there is no problem of flies. Intensive

biological action starts in 2 to 3 days and organic matter decomposition starts. In this process

considerable heat is generated and temperature of the composting mass rises upto 75 0 C.

Due to this fly breeding does not take place. The solid waste stabilizes in 4 to 6 months and

gets changed in to a brown coloured, odourless, innocuous powdery form known as humus

having high manure value because of nitrogen content.

The stabilized mass is then removed from trenches screened to remove coarse

inert materials like stones brick bats, glass pieces plastic articles etc.

Indore Method of Composting:

In this method solid waste night soil and animal dung etc. are placed in brick lined pits 3 m x

3 m x 1 m deep in alternate layers of 7.5 to 10 cm height, till the total height becomes Department of Civil Engineering, ACE


1.5 m. Chemical insecticides are added to prevent fly breeding. The material is turned

regularly for a period of about 8 to 12 weeks and then stored on ground for 4 to 6 weeks. In

about 6 to 8 turnings and period of 4 months time compost becomes ready for use as

manure. Insecticide used in Indore method was DDT but now because of very high half life

of DDT in nature other suitable insecticide is recommended, e.g. Gamaxine.

Bangalore Method

The solid waste is stabilized anaerobically. Earthen trenches of size 10 x 1.5 x 1.5 m

deep are filled up in alternate layers of solid waste and night soil/cow dung. The material

is converse with 15 cm earthen layer and left for biodegradation. In about 4-5 months the

compost becomes ready to use, normally a city produces 200 to 250 kg/capita/year of

refuse and 8 to 10 kg / capita/year of night soil. Composting will produce about 5600 to

6750 of compost annually from above waste.



Open Window Composting:

• In This method large materials like broken glass pieces, stone, plastic articles

etc. are first removed are first removed and remaining solid waste is dumped on

ground in form of piles of 0.6 to 1 m height the width and length of pile are kept

as 60%. The piles are then covered with night soil, animal dung to supply

necessary organisms for biodegradation.

• The temperature rises because of biological activities in the waste piles and

microbial action shift to misophilic to thermophilic stage. After this pile is turned

up for cooling and aeration to avoid anaerobic decomposition. The temperature of

pile again rises to 75 0 C and process of turning cooling and aeration are repeated.

The complete process may taker 4 to 6 weeks and finally compost is ready to use.

As fertilizers



• Mechanical Composting

• The composting by trenching and open window composting methods require

very large area. The process ire laborious and time consuming. In large cities the

larger area may not be available and therefore mechanical composting is adopted

which is very fast mechanical devices are employed in turning the solid waste

undergoing composting. The stabilization of the wastes takes only about 3 to 6 m

days.

• The operation involves

(1) Reception and refuse

(2) segregation

(3) Shredding

(4) Stabilization

(5) Marketing the humus.



Aerobic composting It is the aerobic, or oxygen-requiring, decomposition of organic materials by microorganisms under controlled conditions. During composting, the microorganisms consume oxygen (O2) while feeding on organic matter. Active composting generates

considerable heat, and large quantities of carbon dioxide (CO2) and water vapor are

released into the air.The CO2 and water losses can amount to half the weight of theinitial materials, thereby reducing the volume and mass ofthe final product

Vermicomposting

It is the product of composting utilizing various species of worms, usually red wigglers,

white worms, and earthworms to create a heterogeneous mixture of decomposing

vegetable or food waste (excluding meat, dairy, fats, or oils), bedding materials, and

vermicast. Vermicast, also known as worm castings, worm humus or worm manure, is

the end-product of the breakdown of organic matter by species of

earthworm.Vermicomposting is widely used in North America for on-site institutional

processing of food waste, such as in hospitals and shopping malls.This type of

composting is sometimes suggested as a feasible indoor home composting method.

Vermicomposting has gained popularity in both these industrial and domestic settings

because, as compared to conventional composting, it provides a way to compost organic

materials more quickly (as defined by a higher rate of carbon-to-nitrogen ratio increase)

and to attain products that have lower salinity levels that are therefore more beneficial to

plant mediums.



The earthworm species (or composting worms) most often used are red wigglers (Eisenia fetida or Eisenia andrei), though European nightcrawlers (Eisenia hortensis or Dendrobaena Veneta) could also be used. Red wigglers are recommended by most vermiculture experts, as they have some of the best appetites and breed very quickly. Users refer to European nightcrawlers by a variety of other names, including dendrobaenas, dendras, Dutch Nightcrawlers, and Belgian nightcrawlers.

Containing water-soluble nutrients, vermicompost is a nutrient-rich organic fertilizer and soil conditioner in a form that is relatively easy for plants to absorb.Worm castings are sometimes used as an organic fertilizer. Because the earthworms grind and uniformly mix minerals in simple forms, plants need only minimal effort to obtain them. The worms' digestive systems also add beneficial microbes to help create a "living" soil environment for plants



UNIT VI - SANITARY LAND FILLING The term „landfill‟ is used herein to describe a unit operation for final disposal of „Municipal Solid Waste‟ on land, designed and constructed with the objective of minimum impact to the envi ronment by incorporating eight essential components described. This term encompasses other terms such as „secured landfill‟ and „engineered landfills‟ which are also sometimes applied to municipal solid waste (MSW) disposal units. The term „landfill‟ can be treated as synonymous to „sanitary landfill‟ of Municipal Solid Waste, only if the latter is designed on the principle of waste containment

and is characterised by the presence of a liner and leachate collection system to

prevent ground water contamination. The term „sanitary‟ landfill has been

extensively used in the past to describe MSW disposal units constructed on the

basis of „dump and cover‟ but with no protection against ground water pollution.

Such landfills do not fall under the term „municipal solid waste landfills‟ as used

in this chapter. Land filling involves the controlled disposal of solid waste on or in the upper layer of

the earth‟s mantle.

• Landfilling Methods and Operations

The principal methods used for landfilling dry area may be classified as

(1) Area

(2) Trench

(3) Depression.

Site selection Selection of a landfill site usually comprises of the following steps, when a large number landfill sites are available:

(i) setting up of a locational criteria; (ii) identification of search area; (iii) drawing up a list of potential sites; (iv) data collection; (v) selection of few best-ranked sites; (vi) environmental impact assessment and (vii) final site selection and land acquisition.



The Area Method

The Area Method is used when the terrain is unsuitable for the excavation of

trenches in which to place the solid wastes. The filling operation usually is started by

building an earthen against which wastes are placed in thin layers and compacted as the

fill progresses untill the thickness of the compacted wastes reaches a height of 2 to 3 m at

the end of day‟s operation a 150 mm to 300 mm layer of cover material is placed over the

compacted fill. The cover material must be hauled in by truck or earth-moving equipment

from adjacent land or from borrow-pit areas. A final layer of cover material is used when

the fill reaches the final design height.

The Trench Method

The trench method is suited to areas where an adequate depth of cover material

is available at the site and where the water table is well below the surface. To start the

process To start the process, a portion of the trench is dug with a bulldozer and the dirt

is stockpiled to form an embankment behind the first trench. Wastes are then placed in

the trench, spread into thin layers and compacted. The operation continues untill the

desired height is reached. Cover material is obtained by excavating an adjacent trench or

continuing the trench that is being filled. Department of Civil Engineering, ACE


Depression Landfills

At locations where natural or artificial depression exist, it is often possible to use

them effectively for landfilling operations. Canyons, ravines, fry borrow pits and

quarries have all used for this purpose. The technique to place and compact solid waste

in depression landfills vary with the geometry of the site, the characteristics of the cover

material, the hydrology and geology of the site, and the access to the site



Leachate control Leachate is a liquid generated as a result ofpercolation of water or other liquid through

landfilled waste, and compression of the waste as the weight of overlying materials

increases. Leachate is considered to be a contaminated liquid, since it contains many

dissolved and suspended materials. Good management techniques that can limit adverse

impact of leachate on ground and surface waters include control of leachate production

and discharge from a landfill, and collection of the leachate with final treatment and/or

disposal.

The minimization and containment of leachate within a landfill ultimately depends on the design of the landfill. Providing an impervious cover, minimizing the working face of the landfill, and limiting liquids to household containers and normal moisture found in refuse, are all methods that will minimize leachate production.



Gas control Production. Although gas generated within some types of landfills may be negligible, most landfills are expected to generate a significant quantity of gas. The quality of gas depends mainly on the type of solid waste. As with leachate, the quality and quantity of landfill gas both vary with time. The following discussion on gas quality and quantity pertains mainly to landfills with municipal type wastes, which would be expected at most installations. Quality. Landfill gases, specifically methane gas, are natural by-products of anaerobic microbial activity in the landfill. The anaerobic process requires water and the proper mix of nutrients to maintain optimal conditions. The quality of gas varies with time, and may be characterized by four distinct phases. Quantity The quantity of gas generated depends on waste volume, waste composition, and time since deposition of waste in the landfill, as summarized above. Methane production ranges from 0.04-0.24 cubic feet per pound of waste per year. Gas production may be increased by adding nutrients, such as sewage sludge or agricultural waste, the removal of bulky metallic goods, and the use of less daily and intermediate cover soil.

UNIT – VII DISPOSAL METHODS



Until relatively recently, solid waste was dumped, buried, or burned, and some of the

garbage was fed to animals. The public was not aware of the links of refuse to rats, flies,

roaches, mosquitoes, fleas, land pollution, and water pollution. People did not know that

solid waste in open dumps and backyard incinerators support breeding of diseases

vectors including typhoid fever, endemic typhus fever, yellow fever, dengue fever,

malaria, cholera, and others. Thus, the cheapest, quickest, and most convenient means of

disposing of the waste were used. Rural areas and small towns utilized the open dump or

backyard incinerator. Larger towns and cities used municipal incinerators. Later, land filling became the method of choice for disposing of solid waste. In solid waste management disposal is one of basic programs that has to be done with maximum precautions. If it is not done effectively and efficiently, the whole program will not be satisfactory. Strictly speaking the task of solid wastes disposal is normally handled by a municipal, city or town authorities, if such service exists. Disposal of solid waste has to be accomplished without the creation of nuisance and health hazards in order to fill full the objectives of solid waste management program. These are: • improvement of esthetic appearance of the environment • avoidance of smells and unsightliness. • reduction of disease by curtailing fly and rodent breeding • prevention of human and stray dogs from scavenging In disposal of solids wastes, it is recommended that the following will be done to avoid any risks: the disposal site to be 30 meters from water sources in order to prevent possible contamination prevention of underground waster pollution should be taken into account radioactive materials and explosives should not be together. site should be fenced to keep way scavengers.

all surface of dump should be covered with materials all wastes should be dumped in layers and compacted. disposal site should be about 500 meters from residential areas Solid waste disposal methods

Generally there are several methods of solid waste disposal that can be utilized. These methods are: 1. Ordinary open dumping 2. controlled tipping/burial 3. Hog feeding 4. Incineration 5. Sanitary landfill 6. Composting 7. Grinding and discharge in to sewer 8. Dumping into water bodies 9. Disposal of corpus 1. Open dumping



Some components of solid waste such as street sweepings, ashes and non combustible

rubbish are suitable for open dumping. Garbage and any other mixed solid wastes are

not fit or suitable because of nuisance and health hazard creation. Generally, solid waste

is spread over a large area, providing sources of food and harborage for flies, rats and

other vermin. It causes unsightly odor and smoke nuisance and hazards. Carefully

selected rubbish must be disposed in order to prevent fire accidents that might occur.

The location of open dumping must be carefully chosen so that there will be a minimum

chance of complaints from near by residents. Advantage of open dumping

Can take care of all types of solid wastes except garbage It causes less health problem if proper site is selected. Needs less labor and supervision

Disadvantage of open dumping Attraction of flies, mosquitoes and other insects as well as stray dogs, rats,

and other animals. Creation of breeding sites for rodents, arthropods and other vermin Creation of smoke, odor and nuisance It makes the lands and other surrounding areas useless. It leads to cuts and wounds.

It attracts scavengers, both humans and animals. The following points should be kept in mind and must be considered before selection and locating sites for open dumping.

Sources of water supply and distance from it Direction of wind

Distance from nearest residents near by farm areas and main land Distance that flies can travel from disposal site to the living quarter as well as

the distance that the rodents can travel from disposal areas and living quarters. Negligence to these and some other factors would lead unforeseen health problems; if at all this method is selected.

2. Controlled tipping/burial Indiscriminate dumping of garbage and rubbish create favorable conditions for fly-breeding, harborage and food for rodents, nuisances etc. In order to avoid such problems, garbage and rubbish should be disposed of under sanitary conditions. One of the simpler and cheaper methods is burning garbage and rubbish under controlled

conditions. Controlled or engineered burial is known as Controlled Tipping or Sanitary

Land Fill System. In places where there is no organized service, this system can be done

by digging shallow 2 trenches, laying down the generated waste in an orderly manner,

compacting the waste manually or mechanically and covering with adequate depth of

earth or ash at the end of each day‟s work. The process is repeated each day

systematically at appropriate locations. If properly done this system can prevent fly-

breeding, rodent harborage, mosquito-breeding and nuisances. It can be applied in areas

where appropriate land is available for such practice. This system can be considered an

adaptation of what is technically called the SANITARY LAND FILL system in

municipal solid wastes management service. Principally it consists of the



following steps. • Choosing suitable site, usually waste land to be reclaimed within reasonable distance from habitation. • Transporting the generated wastes to the site by appropriately designed vehicles. • Laying the wastes in appropriate heap to a pre-determined height. • Compacting the layer mechanically • Covering the compacted layer with a thin layer of earth 22 cm depth at the end of each work day. The same steps are repeated for each work period. 3. Hog feeding The feeding of garbage to hogs has been practiced for many years in different parts of the world. But there is surprising high incidence of trichinosis among hogs which are fed with uncooked garbage. Consumption of insufficiently cooked meat from hogs is believed to be the main source of trichinosis. Hogs which are fed on garbage containing hogs scraps and slaughter house offal are very likely to be infected. Also rats living around the slaughter house are infected and there is possibility that hog eats dead rats. Trichinosis worm is easily killed only at a temperature of 58 0 C. So the pork should be

cooked until this temperature is obtained. Refrigeration at -35 O C for a period of 30

days will also kill the larva. Pickling, salting and smoking also kill the larva when done

thoroughly. Garbage feeding is profitable if properly handled by farmers and if they are

willing to use them by collecting it them selves. They should collect it daily and furnish

clean cans while garbage is the most potential valuable element or component of solid

waste. It is the most difficult to handle in a sanitary manner and is responsible for the

majority of nuisances and health hazards associated with the disease. To use garbage for

hog feeding it has to be cooked at temperature of 100 C for 30 minutes just to be on safe

side. Cooking the garbage before Hog feeding will not reduce the food value. 4. Incineration Incineration is a process of burning the combustible components of garbage and refuse. Disposal of solid waste by incineration can be effectively carried out in small scale in food service establishments as well as in institutions such as hospitals, schools etc. The disadvantage of this method is that only combustible materials are incinerated, hence

there is a need for separation of the waste into combustible and non-combustible. The

noncombustible needs separate disposal. Generally there are two types of incinerators,

the open and the closed systems. In the open system the refuse is incinerated in a

chamber open to the air; while the closed system contains a special chamber designed

with various parts to facilitate incineration. It requires a chimney of appropriate height to

provide a good flow of air thorough the combustion chamber. There are varieties of

designs for small scale incinerators. A typical example of design. The size can be varied

depending on the volume of the refuse to be incinerated. The combustion chamber laid with iron grids, at the bottom of which are air inlets in front and at the back. • The front and back walls with provision for installing chimney.



• The feeding door with baffle wall to facilitate refuse feeding. • The base below the combustion chamber for collecting.

On-site Incineration This term applies to incineration of refuse at home, office, apartment house, commercial building, hospital or industrial site. Refuse collection and disposal could be much reduced satisfactory by using on-site incineration. Generally, air-pollution can be expected. Advantages of an incinerator 1. Less land is required than for landfills 2. A central location is possible - allow short hauling for the collection service. 3. Ash and other residue produced are free of organic matter, nuisance- free, and acceptable as fill material. 4. Many kinds of refuse can be burned. Even non-combustible materials will be reduced in bulk. 5. Climate or unusual weather does not affect it. 6. Flexibility is possible - no restriction for its operation 7. Getting income through the sale of waste heat for steam or power is possible. Disadvantages of an incinerator 1. Initial cost is high - during construction 2. Operating cost is relatively high 3. Skilled employees are required for operation and maintenance 4. There may be difficulty in getting a site.

An example of this type is commonly seen in some institutions in Ethiopia. A typical design consists of the following dimensions: width = 110 cm; length =110cm; height in front = 135cm; height at back =150cm. Concrete base (chamber)= 60cm by 75cm by 10cm top fueling door = 60cm by 60cm square, with thickness 5cm.With proper

management and little fueling the incinerator can effectively burn dry as well as wet materials.

5. Sanitary landfill Landfill design, construction, and operation The problem of managing the increased volume of solid waste is compounded by rising public resistance to siting new landfills. There are five general phases of landfill

construction: site selection; site investigation; design; daily operation; and, landfill completion or closure.

These stages are discussed in further detail below. Site selection criteria include items such as availability of land, good drainage, availability of suitable soil for daily and final cover, visually isolated, access to major



transportation routes, certain distance away from airport, not located in wetlands, and out of a floodplain. The engineer should also consider what the final use of the site will be and how long-term management of the site will impact this final use. After a suitable site is identified, a site investigation is then performed. The site investigation includes items such as performing: 1) a topographic survey for surface contours and features (used also to estimate amount of available soil), 2) a hydrologic survey that looks at how the local hydrology will impact drainage requirements, and 3) a hydrogeology survey that will determine underlying geological formations and soil types, the depth to the groundwater table, the direction of groundwater flow, and the current quality of the groundwater (so one can determine whether the landfill is adversely impacting groundwater quality). Landfill design and operation is the next step in the engineering process. Engineers have to consider the method of land filling and design the landfill interface (soil foundation, liners), leachate collection and treatment systems, and gas collection and venting system. The engineer also has to consider the selection of equipment that is used for hauling, excavating, and compaction; access to haul roads, fencing, and the storage and use of soil that is used for daily and final cover. During daily operation, topsoil is removed and stored; refuse is transported into the site, dumped, and compacted; daily soil cover is placed over the refuse; groundwater is monitored; and, leachate is collected and treated.

The primary methods used for landfill are called: 1) the area method; 2) the trench method; and, 3) the depression method. The area method is used when the site conditions do not allow the excavation of a trench.

Typically an earthen levy is constructed and refuse is placed in thing layers against this levy

and compacted. In a day, the compacted waste will reach a height of approximately 200

to300 meters and at the end of the day, a minimum of 15 centimeters inches of daily soil

cover is applied as a barrier to disease vectors (e.g., it prevents the hatching of flies and the

burrowing of rodents) and also prevents fires, odors, scavenging, and blowing litter. When

the final design height is reached, a final soil cover is placed on top of the material. Each of

the day‟s work of refuse is entombed in a “cell.” The trench method is most suitable in locations where the depth to the groundwater table

does not prevent one from digging a trench in the ground. In this method, a trench is

excavated with a bulldozer. Refuse is then placed in the trench and placed in thin layers that

are compacted. The operation continues for the day until the desired daily height is reached.

Again, daily cover is placed over the refuse to produce a “cell.” The depression method

occurs at sites where natural features such as canyons, ravines, dry borrow pits, and quarries

are available that can be filled in. Care is given to the hydrology of the site. For example,

canyons are filled from the inlet to the outlet to prevent backing up of



water behind the deposited refuse. When the landfill has exhausted its life, a final cover

is placed on top of the landfill; topsoil is replaced on the site and the site is landscaped;

groundwater is continuously monitored; leachate is continuously collected and treated;

and, gases are continuously collected and vented. Leachate production and groundwater

monitoring. Leachate is the liquid that percolates through a landfill. It is very high in

concentration of water quality parameters. An engineer designs a landfill to minimize

movement of water into the mass of refuse and thus attempts to minimize the production

of leachate. The leachate collection system must be designed to keep the depth of the

leachate over the liner to less than 30 cm. Landfills are lined with either compacted clay

or some type of geosynthetic liner. The purpose of these systems is to greatly reduce the

hydraulic conductivity in the liner that minimizes the flow of leachate through the liner.

If compacted clay is used, it is typically 15 t0 120 centimeters thick and it is very

important that the clay liner be compacted properly and not be allowed to dry out or

crack. Geosynthetic liners are gaining widespread popularity and their installation is

extremely important so that seams are sealed properly. Lying on top of this liner system

is a leachate collection system, and on top of this is the compacted solid waste. Generally, ground-water monitoring is conducted at all landfills. In fact, Environmental

Protection Agency (EPA) requires that owners/operators install enough ground-water

monitoring wells in the appropriate places to accurately assess the quality of the uppermost

aquifer 1) beneath the landfill before it has passed the landfill boundary (to determine

background quality) and 2) at a relevant point of compliance (down gradient).

Owners/operators should consider the specific characteristics of the sites when establishing

their monitoring systems, but the systems must be certified as adequate by a qualified

groundwater scientist or the director of an EPA-approved state/tribal program. Composting Composting is an excellent method of recycling biodegradable waste from an ecological point of view. Composting is in fact the controlled biological decomposition of organic matter, such as food and yard wastes, into humus, a soil-like material. Composting is nature‟s way of recycling organic waste into new soil, which can be used in vegetable and flower gardens, landscaping and the like. However, many large and small

composting schemes have failed because composting is regarded as a disposal process, and not a production process. Environmental problems may arise when waste is composted without noncompostible matter like metals and plastics being removed. Hazardous substances like heavy metals may then be found in the compost, which in turn may be taken up in the food chain when compost is used on agricultural land. To prevent this situation, sorting at the composting plant or even at the household level might be called for.

Benefits of Composting-

Keeps organic wastes out of landfills.

Provides nutrients to the soil.

Increases beneficial soil organisms (e.g., worms and centipedes).



Suppresses certain plant diseases.

Reduces the need for fertilizers and pesticides.

Protects soils from erosion.

Assists pollution remediation Composting is also defined as process in which organic matter of the solid waste is

decomposed and converted to humus and stable mineral compounds. The end product

of composting process is called compost which is rich fertilizer.

There are three methods of composting:

(1) Composting by Trenching

(2) Open window composting

(3) Mechanical Composting

Composting by Trenching:

In this method trenches 3 to 12 m long, 2 to 3 m wide and 1 to 2 m deep are excavated with

clear spacing of 2 m. The trenches are then filled up with dry solid waste in layers of 15 cm.

On top of each layer 5 cm thick sandwiching layer of night soil animal dung is spread in

semi liquid form. On the top layer of night soil animal dung is spread in semi liquid form. On

the top layer protruding about 30 cm above the surrounding ground layer, a layer of earth

having thickness of around 10 cm is laid so that there is no problem of flies. Intensive

biological action starts in 2 to 3 days and organic matter decomposition starts. In this process

considerable heat is generated and temperature of the composting mass rises upto 75 0 C.

Due to this fly breeding does not take place. The solid waste stabilizes in 4 to 6 months and

gets changed in to a brown coloured, odourless, innocuous powdery form known as humus

having high manure value because of nitrogen content.

The stabilized mass is then removed from trenches screened to remove coarse

inert materials like stones brick bats, glass pieces plastic articles etc.



Indore Method of Composting:

In this method solid waste night soil and animal dung etc. are placed in brick lined pits 3

m x 3 m x 1 m deep in alternate layers of 7.5 to 10 cm height, till the total height

becomes 1.5 m. Chemical insecticides are added to prevent fly breeding. The material is

turned regularly for a period of about 8 to 12 weeks and then stored on ground for 4 to 6

weeks. In about 6 to 8 turnings and period of 4 months time compost becomes ready for

use as manure. Insecticide used in Indore method was DDT but now because of very high

half life of DDT in nature other suitable insecticide is recommended, e.g. Gamaxine.



Bangalore Method

The solid waste is stabilized anaerobically. Earthen trenches of size 10 x 1.5 x 1.5 m

deep are filled up in alternate layers of solid waste and night soil/cow dung. The material

is converse with 15 cm earthen layer and left for biodegradation. In about 4-5 months the

compost becomes ready to use, normally a city produces 200 to 250 kg/capita/year of

refuse and 8 to 10 kg / capita/year of night soil. Composting will produce about 5600 to

6750 of compost annually from above waste.



UNIT – VIII RECYCLE AND REUSE

Reduction: Reduction in generation, reduction in amount of material, increase

lifetime, or eliminate the need

Recycle - used, reused, or reclaimed, use of the material as a source raw material, involves physical transformation

– Reused: The direct use or reuse of a secondary material without prior

reclamation

– Reclaimed: regeneration of wastes or recovery of usable materials from

wastes (e.g., regenerating spent solvents in a solvent still). Wastes are

regenerated when they are processed to remove contaminants in a way that

restores them to their usable condition materials that must be

reclaimed/recycled prior to use or reuse

Recovery - Process to recover useful material from mixed waste (energy is an example)

Materials are solid wastes (and potentially hazardous waste) if they are recycled in the

following ways:

Used in a manner constituting disposal - Directly placing wastes or products

containing wastes on the land is considered to be use constituting disposal.

– If, however, direct placement on the land is consistent with its normal use

(e.g., pesticides), then the material is not regulated as a solid waste.

– For example, heptachlor can potentially be a P-listed waste. This pesticide is

not regulated as a solid waste, however, when it isused as a pesticide.

Burned for energy recovery

Reclaimed (with some exceptions) - materials that must be reclaimed/ recycled prior to use or reuse

Accumulated speculatively

Materials that are not solid waste (and therefore not hazardous wastes) when recycled:



(i) Used or reused as ingredients in an industrial process to make a product, provided the materials are not being reclaimed; or

(ii) Used or reused as effective substitutes for commercial products; or

(ii) Returned to the original process from which they are generated, without first

being reclaimed or land disposed

Recycling Advantages

Prevents the emission of many greenhouse gases and water pollutants,

Saves energy,

Supplies valuable raw materials to industry,

Creates jobs,

Stimulates the development of greener technologies,

Conserves resources for our children‟s future, and

Reduces the need for new landfills and combustors.

Paper Recycling ~ 50% of consumed material and growing

Goal 55% by 2012

Strong markets for old corrugated cardboard (OCC) and newsprint (ONP)

Expanding domestic and international demand

Office paper lower demand

Expanding economy – increased steel demands; China and India biggest markets

36.4% of steel is recycled

Use of plastic for automobiles is a problem



One ton steel recycled saves 2500 lb of iron ore, 1000 lb of coal, 40 lb of limestone, and significant energy savings

Steel Recycling Expanding economy – increased steel demands; China and India biggest markets

36.4% of steel is recycled

Use of plastic for automobiles is a problem

One ton steel recycled saves 2500 lb of iron ore, 1000 lb of coal, 40 lb of limestone, and significant energy savings

Aluminum Recycling About 51 percent of aluminum cans is being recycled

Twenty years ago it took 19 aluminum cans to make one pound, but today, aluminum beverage cans are lighter and it takes 29 cans to make a pound.

Americans throw away enough aluminum every three months to rebuild our entire commercial air fleet.

Making new aluminum cans from used cans takes 95 percent less energy and 20 recycled cans can be made with the energy needed to produce one can using virgin ore.

Domestic recycling has declined recently, collection is expensive

Glass Recycling Glass always lags other recyclables

Alternative markets needed – grind for construction fill, “glassphalt,” fiberglass

Transportation of heavy glass is expensive

Raw materials are inexpensive

Contamination is an issue



Reuse used to be common practice; however as manufacturing plants became larger and decreased in number, bottles had to be carried further for refilling.

More colored glass is imported than used domestically

Plastic Recycling

– Light weight, bulky, low density

– Wide variety of polymers

– Concerns over contamination for reuse

– Difficult to differentiate among types

– PET and HDPE have high prices due to domestic and international demand

– Curbside recycling is down, driving prices up

More expensive oil prices makes virgin plastic more expensive Department of Civil Engineering, ACE

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