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Introduction to WastewaterENV 501

Chapter 1

Chapter Overview

1 |I n t r o d u c ti o n

Introduction to Wastewater1

INTRODUCTION TO WASTEWATER

Definition of Wastewater

Wastewater and it sources

Reason to treat wastewater

Infiltration and Inflow

Common wastewater terms

Chapter 1 Introduction to WastewaterENV 501

1.1 DEFINITION OF WASTEWATER

Wastewater is sewage, stormwater and water that have been used for various

purposes (e.g. washing, flushing or in a manufacturing process and so contains waste

products) around the community.Wastewater is any water that has been adversely affect in

quality by antrophogenic influence. It comprised liquid waste discharged by domestic

residences, commercial properties, industry and agriculture. In relatively simplistic terms, the

composition of wastewater can be expressed as:

2 | i n t r o d u c ti o n t o w a s t e w a t e r

LEARNING OBJECTIVES:After studying this chapter, you should be able to:

1. Understand the basic terms in wastewater management

2. Discuss the principles of wastewater sources

3. Describe the wastewater composition

4. Discuss the types, sources and effect of microbial and chemical pollutants.

Water Solids

Organic Inorganic

Proteins Carbohydrates Fats Grit Salts Metals

99% 1%

0.30.7

Composition of Wastewater


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Unless properly treated, wastewater can be harmful to the public health and the

environment. Domestic household produce an average of 200 – 300L of wastewater per

person every day. Ninety percent of this wastewater is water, the other one percent is the

contaminating waste. Much of the wastewater we produce has been changed in a way that

means it cannot be used again unless it is treated. Changes made to water that turn it into

wastewater include:

Fertilizer ( nutrient –NPK ( Nitrate, phosphate, Kalium)

Warming or cooling it

Adding human wastes

Adding oit, grease or fat

Adding organic matter such as food wastes

Adding poison such as pesticides, some organic compound, synthetic

chemicals and heavy metals

Wastewater from the sewerage system is sent to sewage treatment plant for treatment

before it is released back into the environment.

Adapted from Kwazulu 2006



1.2 WASTEWATER AND IT SOURCES

Wastewater is used water that contains dissolved or suspended matter. Kinds of

wastewater: Spent water is water that has been used and can no longer serve the purpose

for which it was used because of contamination. Domestic wastewater is the wastewater

produced by humans in their daily lives (gray water is the water produced by bathing,

cooking, and washing dishes and clothes, gray water may be high in detergent pollutants)

Sewage is the wastewater produced by residential and commercial sources, it is the water

that is discharged into sanitary sewers or treated in septic systems (sanitary sewers are

systems of pipes or conduits that carry off sewage)

WHERE DOES WASTEWATER COME FROM?

The principles sources of domestic wastewater in a community are the residential area and

commercial district. Other important sources include institutional and recreational facilities

and storm water (runoff) and groundwater (infiltration). Each sources produce wastewater

with specific characteristic.

Sources of wastewater include homes, shops, offices and factories, farms, transport and fuel

depots, vessel, quarries and mines. Water used in toilet, shower, baths, kitchen sink and

laundries in homes and offices is domestic wastewater.Wastewater from manufacturing and

industrial operations such as food processing or metal refining is industrial or trade waste.

This includes liquid waste from any process (e.g. water used to cool machinery or clean

plant and equipment.). Most communities generate wastewater from both residential and

nonresidential sources.

a. Residential wastewater

Although the word sewage usually brings toilets to mind, it actually is used to describe

all types of wastewater generated from every room in a house.There are two types of

domestic sewage: blackwater, or wastewater from toilets and grey water which is

wastewater from all sources except toilets. Blackwater and graywater have different

characteristic, but both contain pollutant and disease causing agents that required treatment.



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b. Nonresidential wastewater

Nonresidential wastewater in small communities is generated by such diverse sources

as offices, business, department stores, restaurant, schools, hospitals, farms, manufacturers

and other commercial, industrial and institutional entities. Because of the variety of

nonresidential wastewater characteristic, communities need to assess each source

individually or compare similar types of nonresidential sources to ensure that adequate

treatment is provided.

Laundries differ from many other nonresidential sources because they produce high volumes

of wastewater containing lint fibers. Restaurant typically generates a lot of oil and grease. It

may be necessary to provide pretreatment of oil and grease from restaurant or to collect it

prior to treatment for example by adding grease traps to septic tanks. Wastewater from

some nonresidential sources also may require additional treatment steps. For example,

storm water should be collected separately to prevent the flooding of treatment plants during

wet weather.

Storm water is runoff that flows from agriculture and urban areas such as roofs, parks,

gardens, roads, paths and gutters into storm water drains, after rain. Stormwater is a

nonresidential source and carries trash and other pollutant from street, as well as pesticides

and fertilizers from yards and field. Stormwater flows untreated directly to local creeks or

rivers eventually reaching the ocean, can harm our rivers and lakes.



1.3 REASON TO TREAT WASTEWATER

We need to remove the wastewater pollutants to protect the environment and protect

public health. When water is used by our society, the water becomes contaminated with

pollutants. If left untreated, these pollutants would negatively affect our water environment.

For example, organic matter can cause oxygen depletion in lakes, rivers, and streams.

This biological decomposition of organics could result in fish kills and/or foul odors.

Waterborne diseases are also eliminated through proper wastewater treatment. Additionally,

there are many pollutants that could exhibit toxic effects on aquatic life and the public.

Major contaminants of wastewater that is potentially dangerous to human health or the

environment.

o Infectious Agent

A waste water infectious agent is any organism that can cause disease in humans

and other living organisms. The most common infectious agent are:

Bacteria (fecal coliform bacteria are the bacteria found in the intestines

(colon) of mammals)

Viruses (hepatitis, meningitis, diarrhea, and respiratory disease)

Protozoa (amoebic dysentery, diarrhea, and ulcers)

Worms (tapeworm, roundworms, and whipworms)

o Toxic waste substances

Toxic waste is any materials capable of causing injury to humans and other

organisms. The materials can enter the body by inhalation, swallowing, or being

absorbed through the skin. Pesticides, detergents, bleach, and heavy metal residues

are commonly found in wastewater.

o Organic matter

Most organic matter in domestic wastewater is easily biodegraded. The main

constituents are undigested food, raw food fragments, uneaten cooked food, and

paper. Organic materials provide a good place for the growth of infectious agents



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Others major contaminants of concern in wastewater.

GENERATION OF WASTEWATER

Wastewater is generated by five major sources: human and animal waste, household waste,

industrial waste, stormwater runoff and groundwater infiltration.

o Human and animal waste :

Contain the solid and liquid discharged of humans and animals and is considered by

many to be the most dangerous from a human health viewpoint. The primary health

hazard is presented by the millions of bacteria, viruses and other microorganism (some

of which may be pathogenic) present in the waste stream.

o Household waste :

Consists of waste other than animal and human waste, discharged from the home.

Household wastes usually contain paper, household cleaner, detergent, trash, garbage

and other substances the homeowner discharge into the sewer system.



o Industrial waste :

Includes industry specific materials that can be discharge from the industrial processes

into the collection system. Typically contain chemicals, dyes, acids, alkalis, grit,

detergent and highly toxic materials.

o Storm water runoff:

Many collection system are designed to carry both the waste of the community and

storm water runoff. In this types of system when a storm even occur, the wastestream

may contain large amount of sand, gravel and other grit as well as excessive amount of

water.

o Groundwater infiltration :

Groundwater will enter older improperly sealed collection system through cracks or

unsealed pipe joint. Not only cn this add large amount of water to wastewater flows but

also additional grit.

HOW DO WE COLECT THE WASTEWATER?

The sewer or collection system is designed so that it flows to a centralized treatment

location. The collection system is comprised of smaller sewers with a diameter of about four

inches. As more homes and companies are connected along the system, the pipes become

larger in diameter. Where gravity systems are not practical, pumping stations are often

included to lift the wastewater.

In Malaysia and in many other states, there are some very old collection systems. Materials

of construction and methods of construction have changed significantly over the years. Many

systems experience problems during wet weather periods with inflow and infiltration. This is

commonly referred to as “I&I.” Wet weather operating periods typically occur during heavy

rainstorms. Water resulting from storms should flow into a storm water system and not into

the sanitary sewer system. Unfortunately, this isn’t always the case.



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1.4 INFILTRATION AND INFLOW

Infiltration is groundwater that is influenced by surface or sea water, that enters

sewer pipes (interceptors, collectors, manholes or side sewers) through holes, breaks, joint

failure, connection failures and other openings.Infiltration quantities often exhibit seasonal

variation in response to groundwater levels. Storm events can trigger a rise in groundwater

level and increase infiltration flows.

The highest infiltration flows are observed following significant storm event or following

prolonged periods of precipitation. Since infiltration is related to the amount of piping and

appurtenances in the ground and not to anyspecified water use component, it is usually

expressed in term of the total land area being served or in term of the length and diameters

of sewer pipe.

Inflow is surface water that enters the wastewater system from yard, roof and footing drains

from cross connection with storm drains, downspout and through holes in manholes covers.

Inflow occurs as a result of storm events such as rainfall, spring or snow melt that contribute

to excessive sewer flow. Inflow can also occur in sewer pipes or facilities that are subject to

excessive sewage flow due to direct or indirect connections to a water body or operational

inflow such as water system connections for sewer cleaning. Peak inflow can occur during

heavy storm events when storm sewer system are surcharged resulting in hydraulic backups

and local ponding. The impact of inflow and infiltration on our network is represented in the

following diagram.

Why is infiltration and inflow a problem?

Sewer system (sewer pipes and pumping station) are designed to handle sewage flows from

houses and busineses plus some additional flow from infiltration and inflow. Sewage flow

rates used to design sewers have been developed over the years based on information

obtained from water usage within the household and workplace.

The exact volume of groundwater and rainwater (infiltration and inflow) entering the system,

however varies with location and is virtually impossible to predict. Infiltration and inflow

entering the system can be much higher than the system capacity when there is too much

leakage due to infiltration from deteriorated sewer pipes or significant sources of rainwater

inflow.



Once it enters the sewer system, infiltration and inflow must be moved and treated in the

same manner as sewage. When too much excess water enters our sewers as infiltration or

inflow the following problems may occur: (1) Sewage may backup into residents homes

creating a health hazard and an expensive cleanup of their property. (2) Sewage may spill /

overflow from manholes or bypass treatment facilities contaminating properties as well as

rivers, lakes and harbor. The extra flow from infiltration and inflow simply causes the sewer

system capacity to be exceeded. Sewage spill pose a public health risk due to increased

probability of human contact with harmful pathogen as the sewage runs down the street to

the storm drains, the stream and eventually our recreational waters. (3) Sewer systems will

required upgrades (larger sewers and treatment plants) sooner than designed resulting in

increased utility bill to residents. (4) Infiltration and inflow will use up existing hydraulic

capacity in our sewers which will restrict the opportunity for growth.

This is an example of questions that you typically find in a questionnaire where predetermined set of responses is given.

1. Differentiate between the following pairs:

i) Sewer and sewage

ii) Infiltration and inflow

2. Differentiate between sanitary sewers and combined sewers.


EXAMPLES


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1.5 WHAT ARE COMMON WASTEWATER TERMS?

In wastewater vernacular, there are acronyms for many processes. Some of the most

common terms are listed below with a brief description.

Terms Description

Activated sludge

Sludge particles produced by the growth of microorganisms in

aerated tanks as a part of the activated sludge process to treat

wastewater.

Aeration

exposing to circulating air; adds oxygen to the wastewater and

allows other gases trapped in the wastewater to escape (the first

step in secondary treatment via activated sludge process)

Biochemical

oxygen demand

(BOD)

a laboratory measurement of wastewater that is one of the main

indicators of the quantity of pollutants present; a parameter used

to measure the amount of oxygen that will be consumed by

microorganisms during the biological reaction of oxygen with

organic material

Biosolids

sludge that is intended for beneficial use. Biosolids must meet

certain government specified criteria depending on its use (e.g.,

fertilizer or soil amendment).

Decomposition the process of breaking down into constituent parts or elements

Domestic

wastewater

wastewater that comes primarily from individuals, and does not

generally include industrial or agricultural wastewater

Effluenttreated wastewater, flowing from a lagoon, tank, treatment

process, or treatment plant

Grit chamber

a chamber or tank used in primary treatment where wastewater

slows down and heavy, large solids (grit) settle out and are

removed



Terms Description

Influent wastewater flowing into a treatment plant

Lagoons

(oxidation ponds

or stabilization

ponds)

a wastewater treatment method that uses ponds to treat

wastewater. Algae grow within the lagoons and utilize sunlight to

produce oxygen, which is in turn used by microorganisms in the

lagoon to break down organic material in the wastewater.

Wastewater solids settle in the lagoon, resulting in effluent that is

relatively well treated, although it does contain algae.

Municipalof or relating to a municipality (city, town, etc.). Municipal

wastewater is primarily domestic wastewater

Primary treatment

the first stage of wastewater treatment that removes settleable

or floating solids only; generally removes 40% of the suspended

solids and 30-40% of the BOD in the wastewater

Secondary

treatment

a type of wastewater treatment used to convert dissolved and

suspended pollutants into a form that can be removed,

producing a relatively highly treated effluent.

Secondary treatment normally utilizes biological treatment

processes (activated sludge, trickling filters, etc.) followed by

settling tanks and will remove approximately 85% of the BOD

and TSS in wastewater. Secondary treatment for municipal

wastewater is the minimum level of treatment required by the

Environmental Quality Act 1974.

Sedimentation

the process used in both primary and secondary wastewater

treatment, that takes place when gravity pulls particles to the

bottom of a tank (also called settling).

settling tank

(sedimentation

tank or clarifier)a vessel in which solids settle out of water by gravity during

wastewater or drinking water treatment processes.



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Terms Description

Sludge

any solid, semisolid, or liquid waste that settles to the bottom of

sedimentation tanks (in wastewater treatment plants or drinking

water treatment plants) or septic tanks

Tertiary treatment

any level of treatment beyond secondary treatment, which could

include filtration, nutrient removal (removal of nitrogen and

phosphorus) and removal of toxic chemicals or metals; also

called “advanced treatment” when nutrient removal is included

Total suspended

solids (TSS)

a laboratory measurement of the quantity of suspended solids

present

in wastewater that is one of the main indicators of the quantity of

pollutants present

Trickling filter

process:

a biological treatment process that uses coarse media (usually

rock or plastic) contained in a tank that serves as a surface on

which microbiological growth occurs.

Wastewater trickles over the media and microorganisms remove

the pollutants (BOD and TSS). Trickling filters are followed by

settling tanks to remove microorganisms that wash off or pass

through the trickling filter media.

Turbiditythe cloudy or muddy appearance of a naturally clear liquid

caused by the suspension of particulate matter

Wastewater water that has been used for domestic or industrial purposes



At this point you should be able to:

Discuss the principles of wastewater sources

Discuss the types, sources and effect of microbial and chemical pollutants.

You have now reached the stage where you should be able to identify the problem in

wastewater management. Try the following exercise so that you will become much clearer

based on the problem given.

Factory Z involved in food processing wishes to discharge liquid wastes into a nearby river.

The water in this river is to be used as a town water supply downstream. The untreated

wastes from the factory contain high amount of dissolved and suspended food matter in the

water. Occasionally, pathogenic bacteria are also detected.What problems would this type of

waste cause to the river?

PART A: DEFINITIONPlease define the following terms:

1. Effluent

2. Influent

3. Wastewater


Understand the basic terms in wastewater management

Describe the wastewater composition


Chapter 1

PART B: SHORT ANSWERAnswer the following questions:

1. Suggest four changes made to water that turn it into wastewater.

2. List the four main sources of wastewater and give example of its component.




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