Introduction to Wastewater
ENV 501
1
Chapter 1
Introduction to Wastewater
Chapter Overview
INTRODUCTION TO WASTEWATER
Definition of Wastewater
Wastewater and it sources
Reason to treat wastewater
Infiltration and Inflow
Common wastewater terms
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Chapter 1
Introduction to Wastewater
ENV 501
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.
1.
DEFINITION OF WASTEWATER
2.
Wastewater is sewage, stormwater and water that have been used for various
3.
purposes (e.g. washing, flushing or in a manufacturing process and so contains waste
4.
products) around the community.Wastewater is any water that has been adversely affect in
1.1
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:
Composition of Wastewater
99%
1%
Water
Solids
0.7
0.3
Organic
Proteins
Carbohydrates
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Inorganic
Fats
Grit
Salts
Metals
Introduction to Wastewater
ENV 501
Chapter 1
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
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Introduction to Wastewater
ENV 501
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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Introduction to Wastewater
ENV 501
b.
Chapter 1
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.
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Introduction to Wastewater
ENV 501
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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Chapter 1
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.
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Introduction to Wastewater
ENV 501
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
Chapter 1
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.
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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.
EXAMPLES
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.
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Introduction to Wastewater
ENV 501
1.5
Chapter 1
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
Sludge particles produced by the growth of microorganisms in
Activated sludge
aerated tanks as a part of the activated sludge process to treat
wastewater.
exposing to circulating air; adds oxygen to the wastewater and
Aeration
allows other gases trapped in the wastewater to escape (the first
step in secondary treatment via activated sludge process)
a laboratory measurement of wastewater that is one of the main
Biochemical
indicators of the quantity of pollutants present; a parameter used
oxygen demand
to measure the amount of oxygen that will be consumed by
(BOD)
microorganisms during the biological reaction of oxygen with
organic material
sludge that is intended for beneficial use. Biosolids must meet
Biosolids
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 that comes primarily from individuals, and does not
wastewater
generally include industrial or agricultural wastewater
Effluent
treated wastewater, flowing from a lagoon, tank, treatment
process, or treatment plant
a chamber or tank used in primary treatment where wastewater
Grit chamber
slows down and heavy, large solids (grit) settle out and are
removed
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Introduction to Wastewater
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Terms
Description
Influent
wastewater flowing into a treatment plant
a wastewater treatment method that uses ponds to treat
Lagoons
wastewater. Algae grow within the lagoons and utilize sunlight to
(oxidation ponds
produce oxygen, which is in turn used by microorganisms in the
or stabilization
lagoon to break down organic material in the wastewater.
ponds)
Wastewater solids settle in the lagoon, resulting in effluent that is
relatively well treated, although it does contain algae.
Municipal
of or relating to a municipality (city, town, etc.). Municipal
wastewater is primarily domestic wastewater
the first stage of wastewater treatment that removes settleable
Primary treatment
or floating solids only; generally removes 40% of the suspended
solids and 30-40% of the BOD in the wastewater
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
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.
the process used in both primary and secondary wastewater
Sedimentation
treatment, that takes place when gravity pulls particles to the
bottom of a tank (also called settling).
settling tank
(sedimentation
a vessel in which solids settle out of water by gravity during
tank or clarifier)
wastewater or drinking water treatment processes.
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Introduction to Wastewater
ENV 501
Terms
Chapter 1
Description
any solid, semisolid, or liquid waste that settles to the bottom of
Sludge
sedimentation tanks (in wastewater treatment plants or drinking
water treatment plants) or septic tanks
any level of treatment beyond secondary treatment, which could
Tertiary treatment
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
a laboratory measurement of the quantity of suspended solids
Total suspended
present
solids (TSS)
in wastewater that is one of the main indicators of the quantity of
pollutants present
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.
Trickling filter
process:
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.
Turbidity
Wastewater
the cloudy or muddy appearance of a naturally clear liquid
caused by the suspension of particulate matter
water that has been used for domestic or industrial purposes
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Chapter 1
Introduction to Wastewater
ENV 501
At this point you should be able to:

Understand the basic terms in wastewater management

Discuss the principles of wastewater sources

Describe the wastewater composition

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: DEFINITION
Please define the following terms:
1.
Effluent
2.
Influent
3.
Wastewater
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ENV 501
Chapter 1
PART B: SHORT ANSWER
Answer 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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ENV 501
STUDY NOTES:
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