This document discusses wastewater and its treatment. It defines wastewater as used water from domestic, industrial, commercial or agricultural activities. It describes the types of pollutants found in wastewater, including chemical, physical and biological pollutants. The document then discusses the objectives and various stages of wastewater treatment processes, including primary treatment techniques like screening and sedimentation, as well as secondary treatment processes like activated sludge, trickling filters and aerated lagoons. Finally, it notes that wastewater treatment aims to reduce pollutants and allow water to be safely discharged or reused.

1. Submitted to- Dr. Suman Upadhyay
Submitted by- Suchita Verma
M.Sc 3rd semester
roll no- 110082

2.  What is waste water?
 Wastewater is used water from any combination of
domestic, industrial, commercial or agricultural
activities, surface runoff and any sewer inflow or
sewer infiltration.
 Types of wastewater include:
a) domestic wastewater from households.
b) municipal wastewater from communities (also
called sewage).
c) industrial wastewater from industrial activities.

3.  Wastewater can contain physical,
chemical and biological pollutants.
a) Chemical and physical pollutant
 Heavy metals including mercury, lead, and chromium
 Organic particles such as feces, hairs, food, paper fibers,
plant material, etc.;
 Soluble organic material such as urea, fruit sugar,
soluble proteins, drugs, etc.
 Inorganic particles such as sand, grit, metal
particles, ceramics, etc.;
 Soluble inorganic material such as ammonia, road-salt, sea-
salt, cyanide, hydrogen sulfide, et
 Macro-solid such as household items.
 Emulsions such
as paints, adhesives, mayonnaise, hair colorants, emulsified
oils.
 Toxins such as pesticides, poisons, herbicides, etc.

4. b) Biological pollutants
Bacteria (for
example Salmonella, Shigella, Campylobacter, Vibrio
cholerae)
Viruses (for example hepatitis A, rotavirus, enteroviruses),
Protozoa (for example Entamoeba histolytica, Giardia)
Parasites such as helminths and their eggs
(e.g. Ascaris (roundworm), Ancylostoma (hookworm), Trichu
ris (whipworm));
It can also contain non-pathogenic bacteria and animals
such as insects, arthropods, small fish.

5. Why to Treat Wastewater?
 It's a matter of caring for our environment and for our own
health. There are a lot of good reasons why keeping our water
clean is an important priority:
a) Fisheries
Clean water is critical to plants and animals that live in water. This
is important to the fishing industry and future generations.
b)Wildlife Habitats
Our rivers and ocean waters teem with life that depends on
shoreline, beaches and marshes. They are critical habitats for
hundreds of species of fish and other aquatic life. Migratory
water birds use the areas for resting and feeding.
c)Health Concerns
If it is not properly cleaned, water can carry disease. Since we live,
work and play so close to water, harmful bacteria have to be
removed to make water safe.

6. Objective of Waste Water Treatment:
 The objective of municipal and industrial waste water
treatment:-
a)extract pollutants
b)remove toxicants
c)Neutralize coarse particles
d)kill pathogens so that quality of discharged water is
improved to reach the permissible level of water to be
discharged into water bodies or for agricultural land.
 Treatment of water thus aims at reduction of BOD,
COD, eutrophication etc. of receiving water bodies
and prevention of bio-magnification of toxic
substances in food chain.

7.  The waste water treatment is carried out in three
stages:-
a)Primary treatment
b)Secondary treatment
c)Tertiary treatment

9. The primary treatment is used for removing the
following :-
a) Large settable solid
b) Fat, oil and greases
c) Sand , gravel and rocks
d) Floating materials
 Primary treatment of sewage removes 60%
suspended solids, 30% COD, 35% BOD, 10% P
and 20% total nitrogen.

10.  Primary treatment Process involved:-
I. Screening
II. Comminuting
III. Grit removal
IV. Skimming tank
V. sedimentation
VI. Floatation
VII. neutralization

11.  Screening is the first operation at any wastewater treatment
works.
 This process essentially involves the removal of large non-
biodegradable and floating solids that frequently enter a
wastewater works, such as rags, papers, plastics, tins, containers
and wood.
 Wastewater screening is generally classified into
a) coarse screening- Coarse screens are typically used as primary
protection devices, and usually have openings of 10mm or
larger.
b) Fine screens - are used to remove material that may cause
operation & maintenance problems in downstream processes,
particularly in systems that lack primary treatment.

12.  Typical opening sizes for fine screens are 3 to 10mm.
 With advances in screening technology, fine screens with
openings of less than 3mm are now utilized to reduce suspended solids
to levels near those achieved by primary clarification.
Most modern wastewater treatment plants will utilize a combination
of coarse and fine screening (i.e. upstream coarse screens providing
protection to downstream fine screens)
SCREEN USED IN TREATMENT PROCESS

13.  Comminuting devices are
shredders which
incorporate mechanisms
that cut the retained
material without
removing it from the
sewage flow.
 However; solids from a
Comminutors produce
more scum at the
digesters.
 Comminutors are
generally located between
grit chambers and the
primary settling tanks

14.  Grit includes sand, gravel, cinder, or other heavy
solid materials that are “heavier” (higher specific
gravity) than the organic biodegradable solids in
the wastewater. Grit also includes eggshells, bone
chips, seeds, coffee grounds, and large organic
particles, such as food waste.
 Removal of grit prevents unnecessary abrasion and
wear of mechanical equipment, grit deposition in
pipelines and channels, and accumulation of grit in
anaerobic digesters and aeration basins.
 Many types of grit removal systems exist,
including aerated grit chambers, vortex-type , grit
removal systems, detritus tanks , horizontal flow
grit chambers and hydrocyclones.

15.  Air is introduced in the
grit chamber along one
side, causing a
perpendicular spiral
velocity pattern to flow
through the tank.
Heavier particles are
accelerated and diverge
from the streamlines,
dropping to the bottom
of the tank, while
lighter organic particles
are suspended and
eventually carried out
of the tank

16.  A skimming tank is a chamber so arranged that the floating
matter like oil, fat, grease etc., rise and remain on the
surface of the waste water (Sewage) until removed, while
the liquid flows out continuously under partitions or
baffles.
 It is necessary to remove the floating matter from sewage
otherwise it may appear in the form of unsightly scum on
the surface of the settling tanks or interfere with the
activated sludge process of sewage treatment.
 It is mostly present in the industrial sewage. In ordinary
sanitary sewage, its amount is usually too small.
 The chamber is a long trough shaped structure divided up
into two or three lateral compartments by vertical baffle
walls having slots for a short distance below the sewage
surface and permitting oil and grease to escape into stilling
compartments.

17.  The rise of floating matter is brought
about the blowing air into the
sewage from diffusers placed in the
bottom. Sewage enters the tank from
one end, flows longitudinally and
leaves out through a narrow inclined
duct. A theoretical detention period
of 3 minutes is enough. The floating
matter can be either hand or
mechanically removed.
 Grease traps are in reality small
skimming tanks designed with
submerged inlet and bottom outlet .
The traps must have sufficient
capacity to permit the sewage to cool
and grease to separate.

18.  Sedimentation is a physical water
treatment process using gravity to
remove suspended solids from water.
 Solid particles entrained by the turbulence of
moving water may be removed naturally by
sedimentation in the still water of lakes and
oceans. Settling basins are ponds constructed for
the purpose of removing entrained solids by
sedimentation.
 Clarifiers are tanks built with mechanical means
for continuous removal of solids being deposited
by sedimentation.

20.  Dissolved air flotation (DAF) is a water treatment process that
clarifies wastewaters by the removal of suspended matter such
as oil or solids.
 The removal is achieved by dissolving air in the water under
pressure and then releasing the air at atmospheric pressure in a
flotation tank basin.
 The released air forms tiny bubbles which adhere to the
suspended matter causing the suspended matter to float to the
surface of the water where it may then be removed by a
skimming device.
 Dissolved air flotation is very widely used in treating the
industrial wastewater effluents from oil
refineries, petrochemical and chemical plants.
 In the oil industry, dissolved gas flotation (DGF) units do not
use air as the flotation medium due to the explosion risk.
 Nitrogen gas is used instead to create the bubbles.

21. A typical dissolved air flotation unit (DAF)
 Modern DAF units using parallel plate
technology are quite compact.
 The feed water to the DAF float tank is dosed
with a coagulant (such as ferric chloride or
aluminum sulfate) to coagulate the colloidal
particles and/or a flocculants to
conglomerate the particles into bigger
clusters.
 A portion of the clarified effluent water
leaving the DAF tank is pumped into a small
pressure vessel (called the air drum) into
which compressed air is also introduced.
 Bubbles form at nucleation sites on the
surface of the suspended particles, adhering
to the particles. As more bubbles form, the
lift from the bubbles eventually overcomes
the force of gravity. This causes the
suspended matter to float to the surface
where it forms a froth layer which is then
removed by a skimmer. The froth-free water
exits the float tank as the clarified effluent
from the DAF unit.

22.  When pH of the industrial waste is too high or too low
then it should be neutralized by acid or alkali and only
neutral effluent should be discharged into drain.
 For neutralization of the acidic effluent, follow
techniques are used:-
a) Lime stone treatment
b) Caustic soda treatment
For neutralization of the alkaline effluent, following
techniques are used:-
a) Carbon dioxide treatment
b) Sulphuric acid treatment
c) Utilizing waste boiler- flue gas

24.  Secondary treatment is the portion of a sewage treatment
sequence removing dissolved and colloidal compounds
measured as biochemical oxygen demand (BOD).
 Secondary treatment is traditionally applied to the liquid portion
of sewage after primary treatment has removed settleable solids
and floating material.
 Secondary treatment is typically performed by indigenous,
aquatic microorganisms in a managed aerobic habitat.
 Bacteria and protozoa consume biodegradable soluble organic
contaminants (e.g. sugars, fats, and organic short-
chain carbon molecules from human waste, food waste, soaps
and detergent) .
 Biological oxidation processes are sensitive to temperature and,
between 0 °C and 40 °C, the rate of biological reactions increase
with temperature. Most surface aerated vessels operate at
between 4 °C and 32 °C.

25.  Activated sludge process
 Trickling filters
 Surface aerated lagoons

26.  The activated sludge process is a type
of wastewater treatment process for
treating sewage or industrial wastewaters
using aeration and a biological floc composed of
bacteria and protozoa.
 The process takes advantage of aerobic micro-
organisms that can digest organic matter in
sewage, and clump together (by flocculation) as
they do so.
 It thereby produces a liquid that is relatively free
from suspended solids and organic material, and
flocculated particles that will readily settle out and
can be removed.

27. Purpose of activated sludge process
 In a sewage (or industrial wastewater) treatment
plant, the activated sludge process can be used for
one or several of the following purposes:
a) oxidizing carbonaceous matter: biological matter.
b) oxidizing nitrogenous matter: mainly ammonium
and nitrogen in biological materials.
c) removing phosphate.
d) driving off entrained gases carbon dioxide,
ammonia, nitrogen, etc.
e) generating a biological floc that is easy to settle.

28.  The general arrangement of an
activated sludge process for removing
carbonaceous pollution includes the
following items:
 Aeration tank where air (or
oxygen) is injected in the mixed
liquor.
 Settling tank (usually referred to as
"final clarifier" or "secondary
settling tank") to allow the
biological flocs (the sludge blanket)
to settle, thus separating the
biological sludge from the clear
treated water.
 Treatment of nitrogenous matter or
phosphate involves additional
steps where the mixed liquor is left
in anoxic condition (meaning that
there is no residual dissolved
oxygen).

29.  Sewage sludge treatment describes the
processes used to manage and dispose
of sewage sludge produced during sewage
treatment.
 Sludge is mostly water with lesser amounts of
solid material removed from liquid sewage.
Primary sludge includes settleable solids
removed during primary treatment in
primary clarifiers. Secondary sludge separated
in secondary clarifiers includes treated sewage
sludge from secondary treatment bioreactors
 Sludge treatment is focused on reducing sludge
weight and volume to reduce disposal costs,
and on reducing potential health risks of
disposal options. Water removal is the primary
means of weight and volume reduction,
while pathogen destruction is frequently
accomplished through heating during
thermophilic digestion, composting,
or incineration.

30.  A trickling filter is a type of wastewater treatment
system. It consists of a fixed bed
of rocks, lava, coke, gravel, slag, polyurethane foam,
sphagnum peat moss, ceramic, or plastic media over
which sewage or other wastewater flows downward
and causes a layer of microbial slime (biofilm) to grow,
covering the bed of media.
 Aerobic conditions are maintained by splashing,
diffusion, and either by forced-air flowing through the
bed or natural convection of air if the filter medium is
porous.
 The terms trickle filter, trickling
biofilter, biofilter, biological filter and biological
trickling filter are often used to refer to a trickling
filter.

31.  Typically, sewage flow enters at a high level and flows through the
primary settlement tank.
 The supernatant from the tank flows into a dosing device, often a
tipping bucket which delivers flow to the arms of the filter. The
flush of water flows through the arms and exits through a series of
holes pointing at an angle downwards. This propels the arms
around distributing the liquid evenly over the surface of the filter
media. Most are uncovered and are freely ventilated to the
atmosphere.
 The removal of pollutants from the waste water stream involves
both absorption and adsorption of organic compounds and some
inorganic species such as nitrite and nitrate ions by the layer of
microbial bio film. The filter media is typically chosen to provide a
very high surface area to volume. Typical materials are often
porous and have considerable internal surface area in addition to
the external surface of the medium. Passage of the waste water over
the media provides dissolved oxygen which the bio-film layer
requires for the biochemical oxidation of the organic compounds
and releases carbon dioxide gas, water and other oxidized end
products. As the bio film layer thickens, it eventually sloughs off
into the liquid flow and subsequently forms part of the secondary
sludge.

32.  The bio-film that develops in a
trickling filter may become several
millimeters thick and is typically a
gelatinous matrix that contains
many species
of bacteria, cilliates and amoeboid
protozoa, annelids, round
worms and insect larvae and many
other micro fauna.
 This is very different from many
other bio-films which may be less
than 1 mm thick. Within the
thickness of the biofilm both
aerobic and anaerobic zones can
exist supporting both oxidative and
reductive biological processes. At
certain times of year, especially in
the spring, rapid growth of
organisms in the film may cause the
film to be too thick and it may
slough off in patches leading to the
"spring slough

33.  An aerated lagoon (or aerated pond) is a
simple wastewater treatment system consisting of
a pond with artificial aeration to promote the
biological oxidation of wastewaters.
 There are many other aerobic biological processes
for treatment of wastewaters, for example activated
sludge, trickling filters, rotating biological
contactors . They all have in common the use
of oxygen and microbial action to reduce the
pollutants in wastewaters.

34.  Suspension mixed lagoons,
where there is less energy
provided by the aeration
equipment to keep the sludge
in suspension.
 Facultative lagoons, where
there is insufficient energy
provided by the aeration
equipment to keep the sludge
in suspension and solids settle
to the lagoon floor. The
biodegradable solids in the
settled sludge then degrade as
in an anaerobic lagoon.

35.  Tertiary treatment, also referred to as effluent
polishing, is carried out to improve water quality.
 Tertiary processes include
A) filtration
B) lagooning
C) nutrient removal
D) disinfection

36. A) FILTRATION
 Filtration is a common method of tertiary treatment, with
either sand or activated carbon used to filter wastewater.
 The water is passed through a bed of sand or charcoal,
allowing particulate matter in the water to adhere to the
filter medium, removing it from the water.
B)LAGOONING
 It is a method in which water is stored for some time in
man-made ponds.
 During this process, plants and invertebrate animals
which live in the water improve water quality by
ingesting remaining particulate matter.

37. C)NUTRIENT REMOVAL
 In some locations, high levels of nutrients such as
phosphorous and nitrogen must be removed from the
wastewater before it can be released into the environment.
 This is important because if these nutrients are not removed
from the water, they can provoke large-scale outgrowth
of algae, causing ecosystem imbalance.
 Nutrient removal is performed by bacteria present in the
wastewater, which convert the nutrients into forms that can
be removed from the water.
D) DISINFECTION
 The final tertiary process to be performed is disinfection,
which is typically carried out with the addition of chlorine to
wastewater.
 This process is used to kill microorganisms present in the
water, to reduce the environmental impact of the waste.
 Water chlorination is one of the most common forms of
disinfection, as it is an inexpensive and relatively simple
process.