solid waste generation and handling

CHAPTER 2

SOLID WASTE GENERATION

WSEE 4192

Hawassa University

Institute of Technology

School of Bio-Systems & Environment Engineering

Course contents2

Chapter 1: Solid Waste Management

Chapter 2:Solid Waste Generation

Chapter 3:Solid Waste Handling, Storage and Processing at the

Source

Chapter 4:Collection Methods of Solid Waste

Chapter 5:Solid Waste Separation, Processing and

Transformation

Chapter 6: Solid Waste Transport and Transfer and Disposal

Chapter 7:Hazardous Solid Wastes Management

Chapter 8:Urban And Rural Sanitation

Chapter 2:Solid Waste Generation2.1 Introduction

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The characteristics, quantities, volume and composition of solid waste generated may differ from one country to another and between urban and rural areas.

It depends mainly upon the customs, climate, living conditions and economic standard of the area.

As a consequence, if solid waste management is to be accomplished in an efficient and orderly manner, the fundamental aspects and relationships involved must be identified, adjusted for uniformity of data, and understood clearly.

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Aesthetic, land use, health, water pollution, air pollution, and economic considerations make proper storage, collection and disposal of solid wastes municipal and individual functions that must be taken seriously.

Indiscriminate dumping of solid waste and failure of the collection system in a populated community would soon cause many health problems.

Introduction…

Solid Wastes Polluting a River

2.2 Functional elements of solid waste management

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The activities involved with the management of solid wastes from the point of generation to final disposal have been grouped into six functional elements:

1. Waste generation

2. On-site handling, storage, and processing

3. Collection

4.Transfer and transport

5. Processing and recovery and

6.Disposal. By considering each functional element separately it is possible to

identify the fundamental aspects and relationships involved in each element and to develop where possible, quantifiable relationships for the purposes of making engineering comparisons analyses, and evaluations.

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2.2 Functional elements of solid waste management…

Interrelationship of functional elements comprising a solid waste management System

2.2 Functional elements of solid waste management… 7

Waste generation: Those activities in which materials are identified as no longer being of value and are either thrown away or gathered together for disposal.

On- site handling, Storage, and processing: Those activities associated with the handling, storage, and processing of solid wastes at or near the point of generation.

Collection: Those activities associated with the gathering of solid wastes and the hauling of wastes after collection to the location where the collection vehicle is emptied.

Transfer and transport: Those activates associated with the transfer of wastes from the smaller collection vehicle to the larger transport equipment and the subsequent transport of the wastes, usually over long distance to the disposal site.

Processing and recovery: Those techniques, equipment and facilities used both to improve the efficiency of the other functional elements and to recover usable materials, conversion products, or energy from solid wastes.

Disposal: Those activities associated with ultimate disposal of solid wastes including those wastes collected and transported directly to a landfill site, semisolid wastes (sludge) from wastewater treatment plants incinerator residue compost, or other substances from the wires solid waste processing plants that are of no further use.

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2.2 Functional elements of solid waste management…

2.3. Generation Rate of Municipal Solid Waste

Determination of the generation rate of solid waste is important to obtain data in order to determine waste volume and for subsequent solid waste management.

In addition to knowing the source and composition of solid waste, it is equally important to have uniform units of expression.

• Household waste (kg/capita/day) • Commercial waste (kg/x/day where x can be m2 of floor area

of commercial establishment, unit volume or dollar in sales, the number of employees, etc.)

• Institutional waste (kg/x/day where x can be the number of students, m2 of the area of park or public place, number of visitors, etc.)

• Industrial waste (kg/x/day where x can be unit volume or dollar of production output, m2 of floor area, the number of employees, etc.)

• total waste (kg/capita/day)

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2.3. Generation Rate of Municipal Solid Waste....

Waste quantities are usually estimated on the basis of data gathered by conducting a waste characterization study, using previous waste generation data or some combination of the two approaches.

Load-Count Analysis: In this method, the number of individual loads and the corresponding waste characteristics (types of waste, estimate volume) are noted over a specified time period. If scales are available, weight data are also recorded.

Weight -volume analysis: measuring the volume of the truck and weight of each load will give sample data.

Materials Mass Balance Analysis: The only way to determine the generation and movement of solid wastes with any degree of reliability for each generation source, such as an individual home or a commercial or industrial activity. In some cases, the materials balance method of analysis will be required to obtain the data needed to verify compliance with state-mandated recycling programs.

10Methods of Estimate MSW Quantities

Methods of Estimate MSW Quantities…Preparation of Materials Mass Balances: Draw a system boundary around the unit to be studied. It will be

possible to simplify the mass balance computations. Identify all the activities that cross or occur within the boundary and

affect the generation of wastes. Identify the rate of waste generation associated with each of these

activities. Using appropriate mathematical relationships, determine the

distribution which is about 40 to 50 percent rubbish , 20 to 30 percent wood and related products, and 20 to 30 percent miscellaneous wastes (painted or contaminated lumber, metals tar-based products, plaster, glass, white goods, asbestos and other insulation material, and plumbing, heating and electrical parts).

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2.3. Generation Rate of Municipal Solid Waste....

2.3. Generation Rate of Municipal Solid Waste…

Solid waste generation rates estimate the amount of waste created by residences or businesses over a certain amount of time (day, year, etc.).

Waste generation includes all materials discarded, whether or not they are later recycled or disposed in a landfill.

Waste generation rates for residential and commercial activities can be used to estimate the impact of new developments on the local waste stream.

They may be useful in providing a general level of information for planning purposes.

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2.4. Factors affecting MSW Generation Rates

1. Effect of source reduction , Reuse and Recycling Activities on Waste Generation

Source Reduction: Waste reduction may occur through the design, manufacture, and packaging of products with minimum toxic content, minimum volume of material, and longer useful life.- Reduce office paper waste by implementing a formal policy to duplex all draft reports and by making training manuals and personnel information available electronically.

- Improve product design to use less materials.-Redesign packaging to eliminate excess material while maintaining strength.

-Work with customers to design and implement a packaging return program.

- Switch to reusable transport containers.

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2.4. Factors affect MSW Generation Rates…14

Waste management aims to: Minimize the amount of

waste generated (source reduction)

Recover waste materials and recycle them

Dispose of waste safely and effectively

So urc e re duc tio n is the p re fe rre d a p p ro a ch

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2.4. Factors affect MSW Generation Rates…

Reuse:

Cleaning and using the material over and over again

Increasing the lifespan of the product.

2.4. Factors affect MSW Generation Rates…16

Reuse…

Recycling is collecting materials that can be broken down and reprocessed to manufacture new items.

Household Recycling products are: Paper Products, Glass, Aluminum, Steel and Some plastics

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Benefits of Recycling


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Recycling…

2. Effect of public Attitudes and legislation on waste generation Public Attitudes - significant reduction in the quantities of solid

wastes generated occur when and if people are willing to change of their own volition- their habits and lifestyles to conserve natural resources and to reduce the economic burdens associated with the management of solid wastes.

A program of continuing education is essential in bringing about a change in public attitudes.

Legislation Perhaps the most important factor affecting the generation of certain type of wastes is the existence of local, state, and federal regulations concerning the use of specific materials.

Encouraging the purchase and use of recycled materials by allowing a price differential (typically 5 to 10 percent) for recycled materials is another method.

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3. Effect of Geographic and physical factors on waste Generation Geographic and physical factors that affect the quantities of

waste generated and collected include:a. geographical location – related primarily to the different climate

that can influence both the amount generated and collection operation.

b. season of the yearc. frequency of collectiond. characteristics of populatione. extent of salvage and recycling.f. legislationg. public attitude

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CHAPTER 3

SOLID WASTE HANDLING, STORAGE AND

PROCESSING AT THE SOURCE

3.1. Introduction

The handling, storage and processing of solid wastes at the source before they are collected is the second of the six functional elements in the sold waste management system.

Waste handling and sorting involves the activities associated with management of wastes until they are placed in storage containers for collection.

Handling also encompasses the movement of loaded containers to the point of collection.

Sorting of waste components is an important step in the handling and storage of solid waste at the source. For example, the best place to separate waste materials for reuse and recycling is at the source of generation.

Households are becoming more aware of the importance of separating newspaper and cardboard, bottles/glass, kitchen wastes and ferrous and non-ferrous materials.

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Introduction… 24

Segregation at source MSW Waste minimization

Waste collection from source to segregation centers

Waste segregation into degradable to non- degradable

Non degradable wastes Organic waste size reduction

Recycling plant aerobic composting

Agricultural land, gardens etc

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3.2. On Site Handling of Solid Waste

On-site handling methods and principles involve public attitude, individual belief and ultimately affects the public health.

It is an activity associated with the handling of solid waste until they are placed in the containers used for their storage before collection. This may take place at any time before, during or after storage.

Importance of on-site handling of solid waste: - reduce volume of waste generated - alter physical form - recover usable materials On- site handling methods: Segregation, shredding, grinding and

composting.

Segregation of wastes into degradable and non-degradable wastes is to be done to recover or divert non-degradable wastes (electric items, plastics, tyres etc.) and degradable items (wood, textiles etc.) to its recycling plant and if possible, it can be reused.

It is a tedious process which therefore needs labor. Magnets can also be used to segregate ferrous metals.

This process will help in reducing the amounts of waste going for composting and also earns money through selling wastes to recycling plant.

Shredding or Pulverizing: this process involves in size reduction of organic wastes before it goes for composting. This process reduces the overall volume by 40%.

It will increase surface area availability for bacterial activity for decomposition and facilitates easy handling of moisture content and aeration.

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3.2. On Site Handling of Solid Waste…


Composting: Solid waste composting for use as a soil amendment, fertilizer or growth medium.

Aerobic composting is one of the cheapest and easiest methods that are being available for MSW.

There are two fundamental types of composting techniques:

1. Open or windrow composting: a slower process conducted outdoors with simple equipment.

2. Enclosed system composting: where composting is performed in a building, tank, box, container or vessel.

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Composting…


Duration of composting Composting is completed when the compostable materials have

entirely turned into humus. Compost stability can be tested by re-wetting the material to see

whether it heats up again, thus revealing still un-composted materials in the pile.

Most aerobic composting systems include a period of active composting, generally from 21 to 60 days, and a period of curing, generally from 6 to 24 months.

Composting can be accelerated by intensive aeration and inoculation of the piles with suitable bacteria. More land is required when the period of composting is longer, as the throughput of waste is slower. In places where land for sitting is scarce, sound practice may entail selection of more intensive management practices instead of more extensive land use.

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Major composting factors to be considered: Sitting: Compost facilities must be reasonably close to the input stream

and potential users should meet the needs of the nearby community. Input stream: Source-separated organics are best. However, in most

developing countries, this is not always possible. Mixed waste can be processed to yield acceptable compost.

Selection of appropriate technology: The technology chosen must be adequate for the input stream and level of economic development of the country.

Scale: A smaller-scale facility often facilitates careful composting and formation of a good product.

Market development: Governments generally need to stimulate the compost market. Quality standards are an important marketing element.

Existing compost practices using compost from dumps and garbage dump farming: These traditional activities, while often dangerous could, in some instances, be safe if they include an adequate testing program.

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3.3. On Site Storage of Solid Waste

The first phase to manage solid waste is at home level. It requires facilities for temporarily storing of refuse on the premises. Individual house holder or business owner has responsibility for onsite storage of solid waste.

For individual homes, industries, and other commercial centers proper onsite storage of solid waste is the beginning of disposal. Because un-kept or simple dumps are sources of nuisance, flies, smells and other hazards.

Factors that should be considered in the on-site storage of solid waste are:

1. the type of container to be used, 2. the location where the containers to be kept,3. public health, 4. the collection method and time.

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1. Storage container Garbage and refuse generated in kitchens and other work areas

should be collected and stored in properly designed and constructed water-proof garbage cans (waste bins).

The cans or receptacles can be constructed from galvanized iron sheet or plastic materials. They should have tightly fitting covers.

They must be of such size that, when full, they can be lifted easily by one man. They should be located in a cool place on platforms at least 30 centimeters above ground level.

After putting in garbage, they should be kept covered. The bins must be emptied at least daily and maintained in clean conditions.

An adequate number of suitable containers should be provided with proper platforms with receptacles stand. The number may depend on the amount, type and establishments where the need arises.

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3.3. On Site Storage of Solid Waste…

Storage container…..33

public garbage binsWaste container attached to wall

Waste container in the shape of a dolphin.

Bins in fast food restaurants are marked to thank the customers for disposing of their own garbage A typical office trash can

Containers

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Storage container…

High capacity trash bin for solid waste collection

Storage container…..

Certain public areas have waste bins which are placed alongside paths frequently walked by visitors.

This encourages people to avoid littering, as littering creates an unhealthy and aesthetically unpleasant Social environment.

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Bins in public areas

Waste containers

2. Container size (capacity) Consideration should be given for the size of the loaded

container that must be hauled the collection vehicle or to the disposal site. Therefore, container size for:

• ash up to 80 to 128 litter• mixed refuse should not exceed 120 to 128 litter• rubbish up to 200 liter• office waste is 10-20 liter• kitchen waste is 40 liter• garbage is 48 to 80 liter Plastic liners for cans and wrapping for garbage reduce the need

for cleaning of cans and bulk containers, keep down odors, rat and fly breeding.

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Galvanized metal is preferable for garbage storage because it is resistant to corrosion.

Plastic cans are light in weight but are easily gnawed by rats.

Bulk containers are recommended where large volumes of refuse are generated, such as at hotels, restaurants, apartment houses, shopping centers.

A concrete plat form provided with a drain to an approved sewer with a water faucet at the site to facilitate cleaning.

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Containers for recycling

Garbage containers

3.4. On Site Processing of Solid Waste

On-site processing is intended to improve disposal options, recover valuable resources, and prepare materials for recovery as new products or energy.

Factors that should be considered in evaluating on-site processing are capabilities, reliability, environmental effects, ease of operation, safety to workers and the local community, efficiency, economics, and, aesthetics (noise, odors, litter, increased traffic).

A number of processing technologies have been developed for solid waste management and one of the jobs of the engineer is to select and design the most sustainable and cost effective for a given community.

Some of the objectives of solid waste processing include:• Component separation (hand sorting, screening, magnetic separation, air

classification for lighter materials such as paper and plastic). Volume reduction (baling, shredding, incineration) Size reduction (Shredding, grinding) Resource recovery (composting, energy recovery, material recovery)

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