CHAPTER 2 2.

3 Socioeconomic Impact Assessment

2.1 Environmental Impact A systematic analysis used during EIA to identify and evaluate the
potential socio-economic and cultural impacts of a proposed development on the
Essentially, environmental impact assessment (EIA) is an lives and circumstances of people, their families and their communities.
environmental decision support tool, which provides information on the likely
impacts of development projects to those who take the decision as to whether the Six Steps of SEIA
project should be authorized.
Scoping
The purpose of an EIA is to determine the potential environmental, social,
and health effects of a proposed development, so that those who take the decisions in A preliminary analysis that identifies and prioritizes SEIA considerations and
developing the project and in authorizing the project are informed about the likely required information. Early and effective scoping narrows the focus of SEIA onto
consequences of their decisions before they take those decisions and are thereby issues of potential significance.
more accountable.
Profiling Baseline Conditions

Focuses on gathering information about the socio-economic environment and

Environmental Impact Assessment (EIA) is a systematic and integrative process context of the proposed development. This can include defining measurable
for considering possible impacts prior to a decision being taken on whether or not a indicators of valued socio-economic components.
proposal should be given approval to proceed (Wood 2003)
Predicting Impacts
Strategic Environmental Assessment (SEA) is a process of prior examination and
appraisal of policies, plans, and programs and other higher level or pre-project Based on the analysis of information gathered from issues scoping, saline profiling
initiatives and past experiences to predict possible socio- economic impacts. Identifying trade-
offs between the adverse and beneficial impacts of a proposed development is part
of this analysis.
2.2 Use of Risk Analysis in Environmental Assessment Identifying mitigation

In many regions of the world the threat of natural events such as volcanic Predicted adverse impacts require mitigation. Mitigation includes strategies, plans
eruptions, earthquakes and tsunamis, hurricanes and tornadoes extreme rainfall, and programs to reduce, avoid or manage impacts.
droughts or forest fires are permanently present. People living in these regions are
exposed to these natural hazards, but they may be able to prevent them having grave Evaluating Significance
consequences (e.g. earthquake-resistant building, a dyke or a good insurance policy). Involves determining whether a proposed development is likely to cause significant
People who are unable to protect themselves sufficiently against the adverse effects adverse impacts on valued socio-economic components. If appropriate mitigation
of a natural event are particularly 'vulnerable' to disaster. The disaster risk (of a measures cannot be identified, a proposed development may not be approved.
region, a family, or a person) is therefore made up of two elements: hazard and
vulnerability. Applying Mitigation & Monitoring

Good mitigation for socio-economic impacts requires good monitoring programs

Disaster Risk =Hazard x Vulnerability
(also known as “follow up”) to ensure the mitigation is working effectively, and,
when necessary, the mitigation is adapted as required.
CHAPTER 2: WATER POLLUTION
SOURCES OF WATER POLLUTION

•SEWAGE (WATER WASTE)

•AGRICULTURAL POLLUTION
•OIL POLLUTION
•RADIOACTIVE SUBSTANCES
•RIVER DUMPING

SEWAGE (WATER WASTE)

SEWAGE IS ANOTHER NAME FOR WASTE WATER FROM DOMESTIC AND INDUSTRIAL PROCESSES. DESPITE STRICT
REGULATORY CONTROL, THE ENVIRONMENT AGENCY DATA SHOWS THAT THE WATER AND SEWAGE INDUSTRY ACCOUNTED FOR
ALMOST A QUARTER OF THE SERIOUS WATER INCIDENTS IN ENGLAND AND WALES IN 2006.

AGRICULTURAL POLLUTION
THE AGRICULTURE INDUSTRY COVERS 76% OF THE LAND AREA OF ENGLAND AND WALES. AGRICULTURAL PROCESSES SUCH
AS UNCONTROLLED SPREADING OF SLURRIES AND MANURE, DISPOSAL OF SHEEP DIP, TILLAGE, PLOUGHING OF THE LAND, USE
OF PESTICIDES AND FERTILISERS CAN CAUSE WATER POLLUTION. ACCIDENTAL SPILLS FROM MILK DAIRIES CAN ALSO AFFECT
THE QUALITY OF WATER.

OIL POLLUTION
EVERY YEAR THERE ARE ABOUT 3,000 POLLUTION INCIDENTS INVOLVING OIL AND FUELS IN ENGLAND AND WALES. OIL
SPILLAGES AFFECT WATER QUALITY IN A NUMBER OF WAYS. OIL CAN MAKE DRINKING WATER UNSAFE TO DRINK. A
SUBSTANTIAL AMOUNT OF OIL RELEASED INTO OCEANS AND SEAS WILL DESTROY WILDLIFE AND THE ECOSYSTEMS THAT
SUSTAIN THEM. OIL SPILLS ALSO REDUCE OXYGEN SUPPLIES WITHIN THE WATER ENVIRONMENT

RADIOACTIVE SUBSTANCES
RADIOACTIVE WASTE IS ANOTHER SOURCE OF WATER POLLUTION. RADIOACTIVE SUBSTANCES ARE USED IN NUCLEAR
POWER PLANTS, INDUSTRIAL, MEDICAL AND OTHER SCIENTIFIC PROCESSES. THEY CAN BE FOUND IN WATCHES, LUMINOUS
CLOCKS, TELEVISION SETS AND X-RAY MACHINERY. THERE ARE ALSO NATURALLY OCCURRING RADIOISOTOPES FROM
ORGANISMS AND WITHIN THE ENVIRONMENT. IF NOT PROPERLY DISPOSED OF, RADIOACTIVE WASTE CAN RESULT IN SERIOUS
WATER POLLUTION INCIDENTS.

RIVER DUMPING
LOTS OF PEOPLE DUMP SUPERMARKET TROLLEYS, BICYCLES, GARDEN CUTTINGS AND ELECTRONIC WASTE INTO RIVERS OR
RIVER BANKS. THIS IS ILLEGAL AND OFFENDERS MAY BE CHARGED FOR FLY- TIPPING IF CAUGHT.

AQUATIC ECOLOGY
AQUATIC ECOLOGY INCLUDES THE STUDY OF THESE RELATIONSHIPS IN ALL AQUATIC ENVIRONMENTS, INCLUDING OCEANS,
ESTUARIES, LAKES, PONDS, WETLANDS, RIVERS, AND STREAMS.

ELEMENTS OF AQUATIC ECOLOGY

MARINES
MARINE ECOSYSTEMS, THE LARGEST OF ALL ECOSYSTEMS COVER APPROXIMATELY 71% OF THE EARTH'S SURFACE AND CONTAIN
APPROXIMATELY 97% OF THE PLANET'S WATER. THEY GENERATE 32% OF THE WORLD'S NET PRIMARY PRODUCTION.

FRESH WATER

FRESHWATER ECOSYSTEMS COVER 0.78% OF THE EARTH'S SURFACE AND INHABIT 0.009% OF ITS TOTAL WATER. THEY GENERATE
NEARLY 3% OF ITS NET PRIMARY PRODUCTION. FRESHWATER ECOSYSTEMS CONTAIN 41% OF THE WORLD'S KNOWN FISH SPECIES..

FRESH WATER

•LENTIC: SLOW MOVING WATER, INCLUDING POOLS,

•PONDS, AND LAKES.
•LOTIC: FASTER MOVING WATER, FOR EXAMPLE STREAMS AND RIVERS.
•W ETLANDS: AREAS WHERE THE SOIL IS SATURATED OR INUNDATED FOR AT LEAST PART OF THE TIME
 LAKE ECOSYSTEM
LAKE ECOSYSTEMS ARE A PRIME EXAMPLE OF LENTIC ECOSYSTEMS. LENTIC REFERS TO STATIONARY OR RELATIVELY STILL
WATER, FROM THE LATIN LENTUS, WHICH MEANS SLUGGISH. LENTIC WATERS RANGE FROM PONDS TO LAKES TO WETLANDS,
AND MUCH OF THIS ARTICLE APPLIES TO LENTIC ECOSYSTEMS IN GENERAL.

BIODEGRATION
BIODEGRADATION IS THE DECOMPOSITION OF ORGANIC MATERIAL BY MICROORGANISMS. THE TERM BIODEGRADATION IS
OFTEN USED IN RELATION TO SEWAGE TREATMENT, ENVIRONMENTAL REMEDIATION (BIOREMEDIATION) AND TO PLASTIC
MATERIALS.

TWO TYPES OF BIODEGRATION

AEROBIC BIODEGRATION
IT IS THE BREAKDOWN OF ORGANIC CONTAMINANTS BY MICRO ORGANISM WHEN OXYGEN IS PRESENT. ORGANIC
CONTAMINANTS ARE RAPIDLY DEGRADED UNDER AEROBIC CONDITIONS
BY AEROBIC BACTERIA CALLED AEROBES.

ANAEROBIC BIODEGRATION
THE DEGRADATION OF COMPOUNDS BY MICROORGANISMS IN THE ABSENCE OF OXYGEN IS TERMED AS ANAEROBIC
BIODEGRADATION. THE PROCESS WHEREBY MICROORGANISMS USE A CHEMICAL OTHER THAN OXYGEN AS AN ELECTRON
ACCEPTOR.

STREAMS
IS A BIG CAUSE OF POLLUTION IN OUR RIVERS AND STREAMS. RAIN WASHES DIRT INTO STREAMS AND RIVERS. DIRT CAN
SMOTHER FISH AND OTHER ANIMALS THAT LIVE IN THE WATER. IF PLANTS CAN'T GET ENOUGH SUNLIGHT BECAUSE THE WATER
IS MURKY, THEY DIE

LAKES
LAKES OFTEN CONTAIN HIGH POLLUTION LEVELS RELATIVE TO THE SURROUNDING LANDSCAPES AND ENVIRONMENT.
RIVERS AND STREAMS DRAIN POLLUTANTS FROM THE LANDSCAPE WHERE THEY CONCENTRATE IN LAKES AND OTHER WATER
BODIES. AQUATIC SPECIES SUCH AS FISH CAN BE EXTREMELY HIGH IN CONTAMINANTS AS SOME POLLUTANTS DON’T READILY
DISSOLVE AND DILUTE IN WATER AND ARE INSTEAD TAKEN UP INTO ORGANISM.
GROUNDWATER
GROUNDWATER IS ALSO ONE OF OUR MOST IMPORTANT SOURCES OF WATER FOR IRRIGATION. UNFORTUNATELY,
GROUNDWATER IS SUSCEPTIBLE
TO POLLUTANTS. GROUNDWATER CONTAMINATIONOCCURS WHEN MAN-MADE PRODUCTS SUCH AS GASOLINE, OIL, ROAD SALTS AND
CHEMICALS GET INTO THE GROUNDWATER AND CAUSE IT TO BECOME UNSAFE AND UNFIT FOR HUMAN USE.

OCEANS
LOADS OF OIL DUMPED INTO THE OCEANS ON YEARLY BASIS SERIOUSLY AFFECTS THE OCEAN CREATURES.
OCEAN POLLUTANTS CONTAIN A VARIETY OF TOXIC SUBSTANCES ESPECIALLY HEAVY METALS LIKE LEAD AND MERCURY
THE CORAL REEFS ARE DESTROYED AT AN ALARMING RATE OWING TO OIL SPILLS AND OTHER CHEMICAL NUTRIENTS.

HEAVY METALS AND TOXIC SUBSTANCES

HEAVY METALS ARE DANGEROUS BECAUSE THEY TEND TO BIOACCUMULATE. BIOACCUMULATION MEANS AN INCREASE IN
THE CONCENTRATION OF A CHEMICAL IN A BIOLOGICAL ORGANISM OVER TIME, COMPARED TO THE CHEMICAL'S
CONCENTRATION IN THE ENVIRONMENT.

HEAVY METALS AND TOXIC SUBSTANCES

HEAVY METALS CAN ENTER A WATER SUPPLY BY INDUSTRIAL AND CONSUMER WASTE, OR EVEN FROM ACIDIC RAIN
BREAKING DOWN SOILS AND RELEASING HEAVY METALS INTO STREAMS, LAKES, RIVERS, AND GROUNDWATER. HEAVY METAL
TOXICITY CAN RESULT IN DAMAGED OR REDUCED MENTAL AND CENTRAL NERVOUS FUNCTION, LOWER ENERGY LEVELS, AND
DAMAGE TO BLOOD COMPOSITION, LUNGS, KIDNEYS, LIVER, AND OTHER VITAL ORGANS.
to the requirements of one or more biotic species and or
to any human need or purpose.

CHAPTER 5: MEASUREMENT
OF WATER QUALITY 5.1 Sampling

Water quality Sampling is a process used in statistical analysis

in which a predetermined number of observations are
Refers to the chemical, taken from a larger population. The methodology used to
physical, biological, and radiological characteristics of sample from a larger population depends on the type of
water. It is a measure of the condition of water relative analysis being performed but may include simple random
sampling or systematic sampling. 5.3 Biochemical Oxygen Demand
The amount of dissolve oxygen needed by
5.2 Dissolve Oxygen aerobic biological organisms to break down organic
material present in a given water sample at certain
Dissolved oxygen refers to the level of free, temperature over a specific time period.
non- compound oxygen present in water or other liquids.
It is an important parameter in assessing water quality
because of its influence on the organisms living within a 5.4 Total Organic Carbon
body of water. In limnology (the study of lakes),
dissolved oxygen is an essential factor second only to Total organic carbon (TOC) is the
water itself. amount of carbon found in an organic carbon and is
often used as a non-specific indicator of water quality or
cleanliness of pharmaceutical manufacturing equipment.
TOC may also refer to the amount of organic carbon in
soil, or in a geological formation, particularly the source
rock for a petroleum play; 2% is a rough minimum.

5.5 Turbidity
Turbidity is a measure of the degree to which
the water loses its transparency due to the presence of
suspended particulates.

5.6 Color, Taste, and Odor

It was already mentioned that iron and
manganese will produce reddish brown stains. However,
the color in water is most often caused by dissolved
matter from decaying organic materials. Some color is
almost always present in surface water, but it can occur
in well water also. Color makes water unpleasant for
drinking and cooking and, like iron and manganese,
causes staining
5.7 pH not be confused with basicity which is an absolute
measurement on the pH scale.) Alkalinity is the strength
pH is a scale used to specify how acidic or basic a of a buffer solution composed of weak acids and their
water- based solution is. Acidic solutions have a lower conjugate bases.
pH, while basic solutions have a higher pH. At room
temperature (25 °C), pure water is neither acidic nor 5.9 Solids
basic and has a pH of 7.
A solid is a sample of matter that retains its shape
and density when not confined. The adjective solid
5.8 Alkalinity describes the state, or condition, of matter having this
property.
Alkalinity is the capacity of water to resist changes
in pH that would make the water more acidic. (It should
5.10 Nitrogen and phosphorus
Nitrogen and phosphorus are nutrients that are 5.12 Heavy Metals
natural parts of aquatic ecosystems. Nitrogen is also the
most abundant element in the air we breathe. Nitrogen The term heavy metal refers to any metallic
and phosphorus support the growth of algae and aquatic chemical element that has a relatively high density and
plants, which provide food and habitat for fish, shellfish is toxic or poisonous at low concentrations. Examples of
and smaller organisms that live in water. heavy metals include mercury(Hg), cadmium(Cd),
arsenic
(As), chromium (Cr), thallium (Tl),and lead (Pb).

5.11 Pathogens 5.13 Other Organic Compound

Pathogens can infect unicellular organisms Organic compound is generally any chemical
from all of the biological kingdoms. There are compound that contains carbon. Due to carbon's
several substrates and pathways whereby pathogens ability to catenae (form chains with other carbon atoms),
can invade a host millions of organic compounds are known. The study of
the properties, reactions, and syntheses of organic
compounds comprises the discipline known as organic
chemistry.

CHAPTER 6:
Water supply
The provision of water by public utilities,
commercial organizations, community endeavors or
by individuals, usually via a system of pumps and
pipes. Water supply systems get water from a
variety of locations after appropriate treatment,
including groundwater (aquifers), surface water
(lakes and rivers), and the sea through desalination.

Hydrologic Cycle

It begins with the evaporation of water from the

surface of the ocean. As moist air is lifted, it cools and
water vapor condenses to form clouds. Moisture is
transported around the
globe until it returns to the surface as precipitation. Once 2) the water may penetrate the surface and
the water reaches the ground, one of two processes may become groundwater.
occur;
1) some of the water may evaporate
Transpiration
back into the atmosphere or
The evaporation of water into the atmosphere from
the leaves and stems of plants. Plants absorb soil water materials because they have large connected
through their roots and this water can originate from spaces that make them permeable.
deep in the soil. Plants pump the water up from the soil
to deliver nutrients to their leaves.
Water treatment

Runoff Any process that improves the quality of water

to make it more acceptable for a specific end-use.
The movement of land water to the oceans, chiefly The end use may be drinking, industrial water supply,
in the form of rivers, lakes, and streams. Runoff consists irrigation, river flow maintenance, water recreation or
of precipitation that neither evaporates, transpires nor many other uses, including being safely returned to
penetrates the surface to become groundwater. the environment.

Any process that improves the quality of water

Groundwater to make it more acceptable for a specific end-use.
The end use may be drinking, industrial water supply,
The water present beneath Earth's surface in soil irrigation, river flow maintenance, water recreation or
pore spaces and in the fractures of rock formations. A many other uses, including being safely returned to
unit of rock or an unconsolidated deposit is called an the environment.
aquifer when it can yield a usable quantity of water.
It removes contaminants and undesirable
components, or reduces their concentration so that the
Aquifers water becomes fit for its desired end-use.

Are typically made up of gravel, sand,

sandstone, or fractured rock, like limestone. Water
can move through these
CHAPTER 7: WATER
TREATMENT
7.1 COAGULATION AND FLOCCULATION

Chemical coagulation and flocculation is

used to promote the removal of finely divided solids
by forming more readily settleable flocs, prior to
filtration or sedimentation.

Common Chemicals that are used:

• LIME (Ca(OH))2, most commonly used for

drinking water treatment), through subsequent addition
of water, into the less caustic (but still strongly alkaline)
slaked lime or hydrated
lime (calcium hydroxide, Ca(OH)2), the process
of which is called slaking of lime.
• SODA ASH (Na2CO3) All forms have a polyelectrolytes) are used in drinking water processing
strongly alkaline taste and give moderately alkaline to produce quick-forming, dense and rapid-settling flocs
solutions in water, and in order to enhance the removal efficiency of suspended
solids.
• ORGANIC POLYELECTROLYTES
(starch, polysaccharide gums or synthetic
7.2 SETTLING/SEDIMENTATION • Alkaline/Water Ionizers

A physical water treatment process using gravity to These filters use a process known as
remove suspended solids from water. Solid particles
electrolysis. What this means is the water is passed over
entrained by the turbulence of moving water may be
removed naturally by sedimentation in the still water of
plates which are electrically charged, and it’s separated
lakes and oceans. into two streams.
7.3 FILTRATION
is any of various mechanical, physical or • UV Filters
biological operations that separates solids from fluids
(liquids or gases) by adding a medium through which These types of filters are possibly one of the
only the fluid can pass. newest technologies on the market. When ultraviolet
radiation is used to treat water, it has the ability to
Types of filtration: destroy various bacteria that can be damaging to your
health.
• Activated Carbon Filters If you want a more environmentally friendly way of
purifying
These are also known as carbon filters or your water, this filter may well be the answer because it
pre-filters and are generally responsible for removing doesn’t
larger particles like sediment and silt from your need any chemicals or additional heat to be effective.
water.
• Infrared Filters
• Reverse Osmosis
As with alkaline filters, this technology is used
This type of filter is incredibly popular mainly
to help soften your water, so if you live in a hard water
because it has the ability to remove all sorts of
area infrared technology will help. Much like alkaline
contaminants that can be a danger to your health, as well
filters, infrared uses heat and light to negatively charge
as making sure the end result is clear and odor free.
the water, and give it a softer feel.

7.4 DISINFECTION:
The disinfection of potable water and
wastewater provides a degree of protection from
contact with pathogenic organisms including those
causing cholera, polio, typhoid, hepatitis and a number
of other bacterial, viral and parasitic diseases.

• bactericidal effect:

This is the disinfectant’s capacity

for destroying
microorganisms during a specific stage of the treatment;
• remnant effect:

This is the disinfectant’s capacity to persist in CHAPTER 8:

the water in the mains distribution network and its
ability to maintain the water’s biological quality at the
consumer’s tap. 8.1 WASTEWATER COLLECTION SYSTEMS
Types of sewer systems: equipment that they serve. A drain is the
primary vessel or conduit for unwanted water or
1. Sanitary sewer - (or wastewater collection waste liquids to be flumed away, either to a
system) carries domestic, industrial, and more useful area, funneled into a receptacle, or
infiltration/inflow. run into sewers or storm water mains as waste
discharge to be released or processed.
 Manholes into sewer lines permit service,
2. Storm sewer - (or storm water collection inspection, and cleaning of a line. They may be
system) conveys water resulting from runoff of located where sewer lines intersect or where
rain and snow from buildings and paved and there is a significant change in direction, grade,
unpaved areas to a natural watercourse or body or sewer line diameter.
of water, usually without treatment.  Trenches can be used to transport industrial
waste water from point of generation to
collection units such as junction boxes and lift
3. Combined sewer - combination of sanitary and station, from one process area of an industrial
storm sewer. facility to another, or from one treatment unit to
another.
 Junction boxes typically serve several process
Wastewater Collection System sewer lines, which meet at the junction box to
combine multiple waste water streams into one.
-are systems that gather the used water from our
Junction boxes normally are sized to suit the
homes, businesses and industries and convey it to a
total flow rate of the entering streams.
wastewater treatment plant. Wastewater collection
 Sumps are used typically for collection and
systems face more challenges than water distribution
equalization of waste water flow from trenches
system due to the following factors:
or sewer lines before treatment or storage. They
 Wastewater must be transported from the point are usually quiescent and open to the
of collection to the treatment plant as quickly as atmosphere.
possible to prevent septic conditions.  Lift stations are usually the last collection unit
 Waste flows are highly variable before the treatment system, accepting waste
 Waste flows contain cores solids water from one or several sewer lines. Their
 System may carry storm runoff main function is to lift the collected waste water
to a treatment and/or storage system, usually by
Most common types of wastewater pumping or by use of a hydraulic lift, such as a
collection system components screw.
 Weirs can act as open channel dams, or they
can be used to discharge cleaner effluent from a
 Area drains will serve several sources and are settling basin, such as a clarifier.
located centrally among the sources or pieces of
8.2 ESTIMATING WASTE WATER  Inflow: water that enters through drains which is
QUANTITIES relatively unpolluted source of water.
 Storm water: runoff from rain.
Sources (components) of wastewater flow

 Domestic: discharges from residential,

commercial, and institutional facilities. ESTIMATE OF WASTEWATER QUANTITIES
 Industrial: discharges from different industries.
 Infiltration: groundwater seepage that enters
sanitary sewer through cracks in pipe joints and  Quantity of wastewater is related to water
manholes. consumption
 Wastewater flow is usually from 50 to 100% of 8.3 SYSTEM LAYOUT
the water demand
 Theoretically, the quantity of sewage that is Types of Collection Systems
likely to enter the sewerage system should be
equal to certain proportionate quantity of water  Gravity - The primary type of public sanitary
supplied to the contributing area. The net sewer collection system is a gravity system. A
quantity of sewage generated will be about 80% gravity system is so named because the
of the water supply. But in actual practice, apart wastewater flows down gradient in the sewer,
from certain portion of the quantity of water driven by forces of gravity.
supply, certain additions and subtractions do  Low Pressure - Low pressure sewer systems
take place from it: are used in areas where the use of gravity sewers
is impractical due to topography or economic
 Addition due to private water supplies reasons. Low pressure systems are often found
 Addition due to infiltration around lakes and in rolling terrain.
 Subtraction due to water losses  Vacuum - Vacuum collection systems are used
for the same reason as low pressure systems.
 Subtraction from water supply not
However, it is rare to find a vacuum collection
entering the sewerage system
system in use and operation and maintenance is
more difficult than a low-pressure system.

APPURTENANCES

Appurtenances are machinery, appliances,

structures and other parts of the main structure
necessary to allow it to operate as intended, but are not
considered to be a part of the main structure.

 Manholes -Manholes are the key appurtenance

included in a sanitary sewer system. The
manholes are typically a round concrete
structure, 4- to 5-feet in diameter. Older systems
often contain brick manholes that can be a
source of groundwater infiltration.
 Backflow Preventers - Backflow preventers are
used in a sanitary sewer lateral to prevent the
accidental backflow of wastewater into
buildings.
 Cleanouts - Cleanouts are used in a sanitary
sewer lateral to permit access for the removal of
solids that result in blockages. At least two
cleanouts should be provided; one
approximately 3 feet from the building
foundation, and one at the property line.
 Lateral - The lateral is the piping that connects in the path of the gravity sewer. Wastewater is
the public sewer to the building. The size of the pushed up the downstream end of the siphon by
lateral is typically 4 to 6 inches in diameter. the velocity of the wastewater. Additional
 Inverted Siphon - An inverted siphon is maintenance is typically required to remove
generally used in situations where there is a solids.
depressed obstruction, typically a watercourse,  Flow Regulators - Flow regulators are used to
 divert flow from one sewer line to another to 8.4
prevent overloading the system. An example of
a flow regulator is a weir in a manhole. S
System Layout E
• The first step in designing a sewerage system is to W
establish an overall system layout that includes a plan of
the area to be sewered, showing roads, streets, buildings, E
other utilities, topography, soil type, etc…
R
• Care should be taken to include undeveloped areas.
L
• A tentative layout of collecting sewers and intercepting
sewer A
should be made.
Y
• The sewer location should minimize the length
required while providing service to the entire area. O

• Normally, the sewer slope should follow the ground U

surface so that flows can follow the approximate path of T
the area’s surface drainage.
Se
• In some instances, it may be necessary to lay the
sewer slope in opposition to the surface slope, or to w
pump the wastes across a drainage divide.
er
ag
e
sy
st
e
m
s
T
yp
es
of
se
w
er
s:
  Building sewer/Building connections: Activated sludge generally has a brown flocculants
Connected to the building and used for
conveyance of wastewater from building to appearance. If the color is quite dark, it may be approaching a
lateral/branch sewer. septic condition. If the color is lighter than usual, there may
 Lateral or branch: Usually laid out on streets have been under-aeration with a tendency for the solids to
and used to collect the wastewater from one or
more buildings. settle slowly. Sludge in good condition has an inoffensive
 Main: Convey wastewater from one of more characteristic odor.
lateral sewers to trunk sewers or to intercepting (iv) Trickling Filter Sludge:
sewer. Trickling filter sludge also called humus is brownish,
 Trunk: Large sewers used to convey flocculants, and relatively inoffensive when fresh. It generally
wastewater from main sewer to treatment or undergoes decomposition more slowly than other undigested
other disposal facilities or to large intercepting sludges.
sewers 10.3 Sludge Treatment
Treatment of sewage sludge may include a
 Intercepting: Large sewers that are used to
combination of thickening, digestion, and dewatering
intercept a number of main or trunk sewer and processes.
convey wastewater to treatment or other
disposal facilities. Thickening

Thickening is usually the first step in sludge

CHAPTER 10: SLUDGE TREATMENT treatment because it is impractical to handle thin sludge, a
AND DISPOSAL slurry of solids suspended in water. . A thickener can reduce
the total volume of sludge to less than half the original
SLUDGE volume.
The residue that accumulates in sewage treatment
plants is called sludge (or biosolids). Sewage sludge is the
solid, semisolid, or slurry residual material that is produced Digestion
as a by-product of wastewater treatment processes. Digestion reduces the total mass of solids, destroys
10.1 Sources of Sludge pathogens, and makes it easier to dewater or dry the sludge.
Produced from a range of industrial processes, Digested sludge is inoffensive, having the appearance and
from water treatment, wastewater treatment or on- characteristics of a rich potting soil.
site sanitation systems. Dewatering
10.2 Characteristics of Sludgers Digested sewage sludge is usually dewatered before disposal.
Sludge consists of organic and inorganic solids Sludge-drying beds provide the simplest method of
present in the raw sewage and removed in the primary dewatering. A digested sludge slurry is spread on an open bed
settling tanks plus organic solids produced during secondary of sand and allowed to remain until dry. Drying takes place
treatment of sewage and removed in the secondary settling by a combination of evaporation and gravity drainage through
tanks. the sand.
10.4 Ultimate Disposal
(i) Sludge from Primary Settling Tanks: The final destination of treated sewage sludge usually is the
Sludge from primary settling tanks is usually gray- land. Dewatered sludge can be buried underground in
colored, slimy (or sticky) slurry of settleable solids a sanitary landfill. It also may be spread on agricultural land
accounting for about 50 to 60% of the applied suspended in order to make use of its value as a soil conditioner
solids and tank skimming. This sludge has an extremely and fertilizer. Since sludge may contain toxic industrial
offensive odor and it does not drain easily. chemicals, it is not spread on land where crops are grown for
(ii) Chemical-Precipitation Sludge: human consumption.
Sludge from chemical precipitation tanks is usually
dark in color, though its surface may be red if it contains
much iron. Its odor may be objectionable, but not as bad as CHAPTER 11: NON-POINT
odor from sludge obtained from primary settling tanks.
(iii) Activated Sludge: SOURCE WATER POLLUTION
  Remove obstructions from stream channels and
revegetate stream banks.
11.1 Sediment Brosion and the Pollutant
 Don’t mow all the way to the edge of a lake or
Transport Process pond. Leave a buffer of tall grasses or shrubs to
The transport of pollutants in water can occur filter pollutants.
under particulate or dissolved forms, either in surface  Landscape yards to minimize rainwater runoff.
or groundwaters. In surface waters, soil particles can be  Preserve neighborhood trees that help minimize
introduced in streams and move under particulate form the damage caused by surface runoff.
downstream (bed-load transport) by rolling, sliding, and  Place retaining walls or diversions on steeply
saltation and further deposited downstream. This transport sloping ground to reduce the rate of water flow
depends on flow velocity, turbulence, and grain size, and erosion.
shape, and density. In groundwaters, particulate transport  Make sure septic tanks work properly.
is not so expressive and occurs for very small grain size  Dispose of litter in garbage cans or in recycling
particles. bins. Recycle glass, aluminum, plastic, paper,
motor oil, and newspapers.
There are four main forms of nonpoint source pollution:  Compost yard and garden waste.
sediments, nutrients, toxic substances and pathogens.  Pick up pet waste and bag it with regular
household trash or flush it in the toilet.
 Sediments are soil particles carried by rainwater
 And, never ever intentionally dump anything into
into streams, lakes, rivers and bays. By volume,
a storm drain!
sediment is the greatest pollutant of all. It is caused
mainly by erosion resulting from bare land, some
farming practices, and construction and development.
 Nutrients are substances that help plants and
animals live and grow. The main concern is excessive
amounts of two nutrients: nitrogen and phosphorus. 
 Toxic substances are chemicals that may cause
human and wildlife health concerns. They include
organic and inorganic chemicals, metals, pesticides,
household chemicals, gasoline, motor oil, battery acid,
roadway salt and other pollutants.
 Pathogens are disease-causing microorganisms
present in human and animal waste. Most pathogens
are bacteria.

11.2 Prevention and Mitigation of Non-point

Source of Pollution

WHAT CAN CITIZENS DO TO REDUCE

NONPOINT SOURCE POLLUTION?

 Limit use of pesticides and fertilizer and use them

at appropriate times of the year in recommended
amounts. Introduce natural predators to your
garden, and use pest resistant plants. Remove
eggs, larvae, cocoons, and adults from plants by
hand.
 Prevent property erosion by covering bare soil
with vegetation and mulch.
 Participate in a stream cleanup program.