environmental engineering

WASTEWATER TREATMENTGROUP 4

Leader: Arvin Salinas

Members: Yvonne Japin

Mirafe Orlanes

John Arlo Real

1. Wastewater

2. Pollution of Receiving Water

3. Wastewater Collection

SUBTOPICS:

Reporter: Salinas

1. Principles of Wastewater Treatment

2. Land-Based Treatment

SUBTOPICS:

Reporter: Japin

1. Wastewater Treatment Plants

SUBTOPICS:

Reporter: Orlanes

1. On-Site Treatment Facilities

2. Government / Public Role in Pollution Control

SUBTOPICS:

Reporter: Real

What is Wastewater Treatment?Wastewater treatment is the process of taking

wastewater and making it suitable for discharge back into the environment. Wastewater treatment reduces the contaminants to acceptable levels so as to be safe for discharge into the environment.

12.2 WASTEWATER

Wastewater can be formed by a variety of activities, including washing, bathing, and using the toilet. Rainwater runoff is also considered wastewater. No matter where it comes from, this water is full of bacteria, chemicals, and other contaminants.

12.2.1 CONSTITUENTS1. Microorganism2. Solids - Total Solids - Inorganic Constituents - Organic Matter

Inorganic constituents of wastewater includes:1. Chlorides & Sulfates2. Nitrogen & Phosphorus3. Carbonates & Bicarbonates4. Toxic Substances

Organic Matter includes:1. Protein2. Carbohydrates

The sources of these biodegradable contaminants include excreta and urine from humans: food wastes from sinks: soil and dirt from bathing, washing, laundering: plus various soaps, detergents, and other cleaning products.

12.2.2 BOD MEASUREMENT

The amount of organic matter in water or wastewater can be measured directly (as TOC),but this doesn’t tell us whether the organics are biodegradable or not. TOC is determined by measuring the amount of CO2 produced when the produced when the organic carbon in the sample is oxidized by a strong oxidizer and comparing it with the amount in a standard of known TOC.

Figure 12-1 Total Organic Carbon Analyzer

Current model of an automatic analyzer in w/c chemical oxidation is used to determine the TOC in water and wastewater.

12.2.2 BOD MEASUREMENT

)(100

kt

LL and )1( 1000

kt

LL L

Where:L = carbonaceous BOD remaining at time t = t (O2 needed to oxidize carbonaceous organic matter remaining).L0 = ultimate carbonaceous oxygen demand (i.e. ultimate BOD; O2 needed to oxidize carbonaceous organic matter initially present).L0 – L = carbonaceous oxygen demand (i.e. BOD satisfied; O2 used to oxidize carbonaceous organic matter at time t = t.t = time (days)k = rate constant (base 10) (day -1)

12.2.3 Municipal WastewaterThe excreted waste from humans

is called sanitary sewage. Wastewater form residential areas, referred to as domestic sewage, includes kitchen, bath, laundry, and floor drain wastes. These, together with the liquid wastes from commercial and industrial establishments, are termed municipal wastewater.

12.2.3 Industrial WastewaterWastewater from industries include

employees’ sanitary wastes, process wastes from manufacturing, wash waters, and relatively uncontaminated water from heating and cooling operations.

12.2.3 StormwaterThe runoff from rainfall, snowmelt,

and street washing. It is less contaminated than municipal wastewater.

12.3 POLLUTION OF RECEIVING WATERS12.3.1 Effects of Pollutants

Water pollution occurs when the discharge of wastes impairs water quality or disturbs the natural ecological balance.

The contaminants that cause problems includes:1. Pathogens2. Organic Matter3. Solids4. Nutrients 5. Toxic & Hazardous Substances6. Other Pollutants (color, foam, heat, &

radioactive materials.

12.4 WASTEWATER COLLECTION1. Early Systems2. Present Systems

Present Systems Sewage collection systems today

normally consist of separate storm and sanitary sewers in the newer areas and combined sewers in the older sections of cities.

3 Types of Sewers1. Sanitary Sewers

Sanitary sewers carry domestic sewage, liquid commercial and industrial wastes, and undesirable contributions from infiltration and storm water.

2. Storm SewersStorm sewers receive storm water runoff

from roads, roofs, lawns, & other surfaces.3. Combined Sewers

Combined sewers perform the functions of sanitary and storm sewers and are common in the older section of most municipalities because these sewers carry sanitary wastes and are connected to basement floor drains, any surcharging could cause a backup of untreated sanitary sewage into basements.

There are two types of wastewater treatment systems:1.Biological treatment plant , &2.Physical/Chemical treatment plant

1. Biological Treatment Plant

A biological wastewater treatment plant, such as a municipal treatment plant, uses several tanks to treat the wastewater that comes into it. First, wastewater is screened to eliminate easily removed objects. Next the wastewater is taken to a primary settling basin where matter can float or sink in the tank. The remaining water is then sent to the secondary treatment tank where biological matter, such as bacteria, removes much of the remaining suspended matter.

2. Physical/Chemical Treatment Plant

this treatment starts with removing suspended solids from the wastewater. The water is pumped into large tanks where matter settles or sinks. Just like in a biological treatment plant, this process may be aided by stirrers that mix the water up causing small particles to join into bigger particles. In a physical/chemical plant, this process can also be further aided by the addition of flocculants, a chemical that forms larger particles.

Commonly used chemical processes for industrial wastewater treatment:1.Oxidation2.Reduction3.Precipitation4.Neutralization

Commonly used chemical processes for municipal wastewater treatment:1.Disinfection2.Precipitation

Physical processes of wastewater treatment:1.Removing grit2.Clarifyinhg raw sewage & concentrating

the settled solids4.Clarifying biological suspensions &

concentrating the settled floc5.Gravity thickening of primary or

secondary sludges

Advantages of Land based Treatment Methods Over Wastewater Treatment Plants:1.Characterized Simplicity2.Lower Operating Cost3.Lower Capital Cost

Impounded System:1.Wetlands2.Aerated Lagoons3.Anaerobic Lagoons4.Aerated Ponds5.Facultative Ponds

Regarded as Practical Cutlets for the Disposal of Treated or Untreated Wastewater:1.Streams2.Lakes3.Rivers4.Oceans

Factors that Influence the Decision in Choosing a Suitable Wastewater Treatment Method:1.Local Preference2.Experience of the consultant based on engineering methods3.Wastewater process/track record of the process

Options in Dealing with the Organic & Inorganic Contaminants:1.Removed physically2.Converted biologically3.Changed chemically

Objective of Land Application SystemThe objective of the land based

treatment was to reduce waste discharged to surface waters while utilizing the nutrient content for crops and encourage the used of effluent for irrigation and ground water recharge.

Permeable Soil – a type soil having pores or openings that permits liquids or gases to pass through.Impervious soil – an impenetrable soil.Sludge – the substances that are removed during water treatment.

Permeable Soil – a type soil having pores or openings that permits liquids or gases to pass through.Impervious soil – an impenetrable soil.Sludge – the substances that are removed during water treatment.