20CE501PE – INDUSTRIAL WASTE MANAGEMENT.ppt

20CE501PE
INDUSTRIAL
WASTE
MANAGEMENT
by
S.MOHANKUMAR
AP/MECH/KNCET

UNIT I INTRODUCTION
Undesirable waste water
characteristics – Characteristics of
industrial waste waters – Waste
water characteristics – Estimating
the organic content – Measuring the
efficiency toxicity – In plant waste
control and waste reuse – Storm
water control.

INTRODUCTION
Industrial waste is the waste produced by industrial
activity which includes any materials that is rendered
useless during a manufacturing process.
The waste materials generated by industries or
industrial processes, is called industrial waste. It
includes chemicals, trash, oils, solvents, dirt and
gravel, many harmful gases etc. These are dumped in
seas, rivers or land without adequate treatment.
Thus, become a large source of environmental
pollution.

Types or Classification of Industries
• Industries can be classified into the
following four groups,
• (i) Primary Industry
• (ii) Secondary Industry
• (iii) Tertiary Industry
• (iv) Quaternary Industry

PRIMARY INDUSTRY
They are further classified into the following
types, such as
• Genetic Industry
• Extractive Industry
• Manufacturing Industry
• Construction Industry
• Service Industry

Causes of Industrial waste
• a. Lack of policies to control waste
• b. Unplanned industrial waste
• c. Presence of large number of small
scale industries
• d. Inefficient waste disposal
• e. Leaching or resources from out
natural world.

Types of industrial wastes
• Industrial waste can be divided into
following two types –
• Biodegradable industrial waste
• Non – biodegradable industrial waste

Biodegradable wastes
• Those waste materials which can be
decomposed into simpler unharmful
substances by the action of microorganisms
are called biodegradable wastes.
• Some industries such as the paper industry,
food industry, sugar industry, wool industry
etc. mostly produce biodegradable industrial
wastes.
• Management of these wastes can be done at
low cost and easily.

Non-biodegradable wastes
• Non-biodegradable waste cannot be further
decomposed via the action of the microorganisms.
• Such waste is the major source of toxins in the
landfills. Chemicals, metals, plastics, paints, rubber
etc. are examples of non-biodegradable wastes.
• These materials can remain as landfills for thousands of
years without any damage.
• Toxins from metals and plastics get soaked into the
earth and pollute the soil and water sources.
• Cleaning materials such detergent, phenols etc.
producing industries, coal industries, dying
industries etc.
• produce a large amount of non-biodegradable
industrial waste. These types of wastes are difficult to
manage and very toxic in nature.

Effects of Industrial Waste
• Liquid industrial waste which is thrown
into the sea is at an alarmingly dangerous
level for marine ecosystems.
• Industries release many harmful gases
such as carbon dioxide, sulfur dioxide,
nitrogen oxides etc. which cause air
pollution.

• In industrial wastewater nitrates and
phosphates are there which often cause
eutrophication.
• Generally, air around industries is highly
polluted and causes skin, eyes, throat, nose
and lungs diseases

• It is one of the main causes of global
warming.
• Industrial wastewater destroys useful
bacteria and other microorganisms present
in soil.
• Some industries cause sound pollution as
well.
• Industrial wastes and industries are
destroying natural habitat of many species
and responsible for wildlife extinction.

INDUSTRIAL WASTEWATER
• Industrial wastewater is not just a by-
product of oil and gas or mining and
chemical manufacturing companies,
but also a by-product of food and
beverage processing industries,
essential in the making of the clothes
on your back, the shoes on your feet,
the computer at your fingertips, and
the car your drive.

•Organic matter, metals,
and the like found in the
wastewater must be
removed before the
water can be safely
discharged back to land,

Categories of pollutants
Industrial water contains a large variety of
pollutants which as categorized as follows:
• Organic Pollutants
• Inorganic Pollutants

ORGANIC POLLUTANTS
• Sugars
• Oils and fats
• Proteins
• Hydrocarbons
• Phenols
• Detergents
• Organic acids

INORGANIC POLLUTANTS
 • Alkalis
 • Mineral acids
 • Inorganic Salts
 Free Chlorine
 • Ammonia
 • Hydrogen Sulphide
 • Salts of Chromium
 • Nickel
 Zinc
 • Cadmium
 • Copper
 • Silver
 • Phosphates
• Sulphates
• Chlorides
• Nitrates
• Cyanides
• Calcium
• Magnesium
• Sodium
• Potassium
• Iron
• Manganese
• Arsenic etc.

Industries Produce Industrial
Wastewater
a) Metal Finishers
b) Industrial laundries
c) Chemical Manufacturing
d) Mining
e) Steel/Iron Production
f) Oil and Gas Fracking
g) Power Plants
h) Waste water treatment plants
i) Food Processing

UNDESIRABLE WASTE WATER
CHARACTERISTICS

CHARACTERISTICS OF
INDUSTRIAL WASTE WATER
✓ A colloidal type of turbidity
✓ A typical Colour(Grey – yellowish)
✓ A low alkalinity(pH around 7.5)
✓ Large amount of Nitrogen,
entirely of organic origin
✓ They have an unpleasant odour

EFFECTS OF WASTEWATER
• Oxygen depletion on the body of water
• Presence of undesirable colour, odour and taste
in the water
• Reduced photosysnthesis
• Formation of blanket of suspended solids settling
at the bottom of the receiving body of the water
• The death of fish
• Toxicity added to the adequate life due to the
formation of mercaptans (mercaptan acts as an
odorant to make it easier to detect). ,
pentachlorophenol, sodium pentachlorophenate.

Physical Characteristics of
Wastewater
Following are important physical characteristics
of wastewater
(i) Colour
(ii) Odour
(iii) Temperature
(iv) Turbidity
(v) Solid contents (Total solids).

Colour
• Fresh domestic sewage is grey, somewhat
resembling a weak solution of soap.
• The colour of septic sewage is more or less
black or dark in colour.
• The colour of industrial wastewater depends
upon the chemical process used in the
industries.
• Industrial waste water, when mixed with
domestic sewage, may also add colour to it.

Odour
• Normal fresh sewage has a musty odour which is
normally not offensive, but as it starts to get
stale, it begins to give offensive odour.
• Within 3 or 4 hours, all the oxygen present in the
sewage gets exhausted and it starts emitting
offensive odour of hydrogen sulphide, gas and
other sulphur compounds produced by anaerobic
micro-organisms.
• Industrial wastewater may contain either process
of wastewater treatment.

Turbidity
• The turbidity of wastewater depends on the
quantity of solid matters present in the
suspension state.
• Turbidity is a measure of light-emitting
properties of wastewater, and turbidity test is
used to indicate the quality of waste
discharges with respect to colloidal matter.
• The turbidity depends upon the strength of
sewage or waste water. The stronger or more
concentrated the sewage, the higher is its
turbidity. Turbidity can be determined either
by turbidity rod or by Jackson’s turbidimeter.

Total Solids
• Sewage normally contains 99.9 per cent
of water and 0.1 per cent of solids.
Analytically, the total solids content (ST)
of a wastewater is defined as all the
matter that remains as residue upon
evaporation to 103 to 105°C.
• Total solids in wastewater exist in three
different forms (a) suspended solids (b)
colloidal solids and (c) dissolved solids.

CHEMICAL CHARACTERISTICS OF
WASTEWATER AND THEIR
DETERMINATION
(i) pH value
(ii) Chloride content
(iii) Nitrogen content
(iv) Fats, grease and oil content
(v) Sulphides, sulphates and H2S gas
(vi) Dissolved oxygen (DO)
(vii) Chemical oxygen demand (COD)
(viii) Bio-chemical oxygen demand (BOD)
(ix) Stability and relative stability.

pH VALUE
The test for pH value of wastewater is
carried out to determine whether it- is
acidic or alkaline in nature.
Fresh sewage is generally alkaline in
nature, (its pH value between 7.3 to 7.5).
A high concentration of either an acid (pH
≪ 7) or alkali (pH ≫ 7) in wastewater is
indicative of industrial wastes.

CHLORIDES CONTENT
• Chlorides are mineral salts and, therefore, are
not affected by biological action of sewage.
• Chlorides in natural water result from the
leaching of chloride-containing rocks and soils
with which the water comes in contact.
• Water softeners also add large quantities of
chlorides. Large amounts of chlorides may also
enter in wastewaters from industries like ice
cream plants, meat salting etc.
• Chlorides found in domestic sewage are derived
from kitchen wastes, human faeces and urinary
discharges etc.
• Human excreta, for example, contain about 6 g of
chlorides per person per day.

NITROGEN CONTENTS
• The presence of nitrogen in waste-
water indicates the presence of
organic matter in it.
• Nitrogen is essential to the growth of
Protista and plants and as such is
known as nutrient or bio-stimulant.

Nitrogen appears in the following five
different forms in waste-water
Ammonia nitrogen or free ammonia
Organic nitrogen
Albuminoid nitrogen
Nitrites nitrogen and
Nitrates nitrogen.
Fats, Grease and Oils
Surfactants
Phenols, Pesticides and Agricultural Chemicals
Toxic Compounds
Sulphates, Sulphides and H2S Gas

FATS, GREASE AND OILS
• Fats and oils are mainly contributed from kitchen
wastes, because they are major components of
food stuffs such as butter , vegetable oils and
fats.
• Fats are also commonly found in meats, seeds,
nuts and some fruits.
• Grease and oils are also discharged from
industries like garages, workshops, factories etc.
Fats and oils are compounds (esters) of alcohol or
glycerol (glycerine) with fatty acids.
• Such matters float on the top of sedimentation
tanks, often choke pipes in the winter, and clog
filters.

Surfactants (surface-active agents)
 Surfactants come primarily from synthetic
detergents.
 These are discharged from bathrooms, kitchens,
washing machines etc.
 Surfactants (or surface-active agents) are large
organic molecules which cause foaming in
wastewater treatment.
 Due to this, aeration of wastewater is hindered.
Alkyl-benzene-sulphonate (ABS), a type of surfactant
commonly used in synthetic detergents, is more
troublesome since it is not biodegradable.

Phenols, Pesticides and Agricultural
Chemicals
• Phenols are mostly found in industrial
wastewater.
• If such wastewaters are directly discharged
into receiving streams, they cause serious
taste problems in drinking water, specially
when water is disinfected by chlorination.
• However, phenols can be biologically
oxidized if the concentrations are upto 500
mg/l.

Toxic Compounds
• Copper, lead, silver, chromium, arsenic and
boron are some of the cations which are toxic to
micro-organisms resulting in the malfunctioning
of the biological treatment plants.
• These results from industrial wastewaters. Some
toxic anions, including cyanides and
chromates, present in some industrial wastes
also hinder the wastewater treatment facilities.
• Hence their presence should be taken into
consideration in the design of biological treatment
plants.

Sulphates, Sulphides and H2S Gas
• Sulphates and sulphides are formed due to
decomposition of various sulphur containing
substances present in wastewater.
• The sulphate ions (SO4) occur naturally in
most water supplies and hence they are also
present in wastewater
• Sulphur, required in the synthesis of proteins is
released in the degradation.

Following are the gases that are
commonly found in untreated
wastewater
(i) Nitrogen (N2)
(ii) Oxygen (O2)
(iii) Carbon-dioxide (CO2)
(iv) Hydrogen sulphide (H2S)
(v) Ammonia (NH3)
(vi) Methane (CH4).

Oxygen in a sample of wastewater is
reported in the following three ways
(a) Oxygen consumed
(b) Dissolved oxygen and
(c) Oxygen demand.

The demand of oxygen may be
expressed in the following ways
(i) Biochemical oxygen demand (BOD)
(ii) Chemical oxygen demand (COD)
(iii) Total oxygen demand (TOD)
(iv) Theoretical oxygen demand (Th. OD).
In addition to these, the amount of organic
matter present may also be determined by
the total organic carbon (TOC) test.

Biochemical Oxygen Demand (BOD)
• The BOD may be defined as the oxygen
required for the micro-organisms to carry
out biological decomposition of dissolved
solids or organic matter in the
wastewater under aerobic conditions at
standard temperature.
• It is the most widely used parameter of
organic pollution applied to both
wastewater as well as surface water

Chemical Oxygen Demand (COD)
• The BOD test takes a minimum of 5 days’
time, and due to this, it is not useful in
the control of treatment processes.
• An alternative test is the COD test, which
can be used to measure content of
organic matter of both wastewater as
well as natural waters.
• COD can be determined only in 3 hours
in contrast to 5 days of BOD test.

Total Oxygen Demand (TOD)
• The TOD method is based on the
quantitative measurement of the
amount of oxygen used to bum the
organic substances and to a minor extent,
inorganic substances.
• It is thus a direct measure of the oxygen
demand of the sample.
• The test is conducted in a platinum-catalysed
combustion chamber.

Theoretical Oxygen Demand (ThOD)
• This is a theoretical method of computing the
oxygen demand of various constituents of the
organic matter present in wastewater.
• The organic matter present in the wastewater
may be of animal or vegetable origin,
consisting of principal groups such as
carbohydrates, protein, fats and products of
their decomposition.
• Each one of these is a typical combination of
carbon, hydrogen, oxygen and nitrogen, based
on its chemical formula.

BIOLOGICAL CHARACTERISTICS OF
WASTEWATER
Domestic sewage, by its nature, contains
enormous quantities of micro-organisms.
The biological characteristics of sewage are
related to the presence of these microorganisms.
The sanitary engineer must have considerable
knowledge of
(i) principal groups of microorganisms found in
water and wastewater
(ii) pathogenic organisms in wastewater, and
(iii) organisms used as indicators of pollution.

The various micro-organisms found in water or
wastewater may be broadly classified under
three categories
(i) Aquatic plants
(ii) Aquatic animals
(iii) Aquatic moulds, bacteria and
viruses.

(i) Aquatic Plants:
Under this category, the following are included
(a) Spermophyta – Water weeds.
(b) Bryophyta – Mosses and lever words.
(c) Pteridophyta – Ferns and horsetails.
(d) Thallophyta – Algae.

(ii) Aquatic Animals
They include the following
(a) Vertebrate – Fish and amphibians.
(b) Mollusca – Mussels, snails, slugs,
limplets, cocklets
(c) Arthopoda – Crustacea, insects, spiders,
mites.
(d) Worms – Aquatic earthworms, thread
worms, rotifera.
(e) Metazoa –Hydra, polyzoa.
(f) Protozoa – Endameba histolytica etc.

(iii) Aquatic Moulds, Bacteria and
Viruses
• Strictly speaking, moulds (or fungi),
bacteria and viruses come under the
category of aquatic plant, but because of
their special importance, they are
generally kept in a separate category.

AEROBIC PROCESSES
The work of the aerobic bacteria, i.e.
combination with oxygen is called oxidation.
Aerobic bacteria utilise free oxygen as an
electron acceptor.
The end products of aerobic activity are CO2,
H2O, SO4, NO3, NH3 and more bacteria.
The bulk of the available energy finds its way
into cell mass or heat, yielding a stable
effluent which will not undergo further
decomposition

ANAEROBIC PROCESSES
The work done by anaerobic bacteria, viz.
decomposition of organic matter is called
putrefaction and the result is called
liquefaction, as the solid organic matter is
dissolved by enzymes.
Anaerobic bacteria oxidise organic matter
utilising electron acceptors other than
oxygen.
In carrying out their metabolic processes, they
produce CO2, H2O, H2S, CH4, NH3, N2,
reduced organics and more bacteria

The end products of an anaerobic
fermentation are likely to be odourous.
The production of a stable effluent is
unlikely since wastes do not usually contain
sufficient electron acceptors to permit
complete oxidation.
In the first stage, the anaerobic bacteria
decompose complex organic matter into
simple organic compounds while in the
second stage, the aerobic bacteria oxidise
them to form stable compounds

ESTIMATING THE ORGANIC
CONTENT
• The organic matter present in the water
body can be analyzed in laboratory by
determining Biochemical Oxygen
Demand (BOD), Chemical Oxygen
Demand (COD), and by determination of
Total Organic Carbon (TOC).

Biochemical Oxygen Demand (BOD)
• The BOD can be defined as the oxygen
required for biochemical oxidation of organic
matter present in the water under aerobic
conditions

BOD Test
• Biochemical oxidation is slow process and
theoretically takes an infinite time to go to
completion i.e. complete oxidation of
organic matter. During the first few days the
rate of oxygen depletion is rapid because of
the high concentration of organic matter
present.
• As the concentration of organic matter
decreases, so does the rate of oxygen
consumption.

Chemical Oxygen Demand (COD)
• During COD determination total organic
content of the waste is oxidized by dichromate
in acid solution.
• In this test to determine the oxygen
requirement of the wastewater, strong oxidizing
agent ‘potassium dichromate’ is used.
• Acidic environment is provided to accelerate
the reactions by addition of sulphuric acid.

COD test measures virtually all oxidizable organic
compounds whether biodegradable or not,
except some aromatic compounds which resists
dichromate oxidation.
The COD is proportional to BOD only for readily
soluble organic matter in dissolved form e.g.
sugars.
No correlation between BOD and COD exists
when:
Organic matter is present in suspended form;
under such situation filtered samples should be
used.
Complex wastewater containing refractory
substances.

Relationship between the organic
carbon fractions in wastewater

MEASURING THE EFFICIENCY
TOXICITY
Acute toxicity
Chronic toxicity

Acute toxicity
Acute toxicity is the kind of harm which
describes classical poisoning effects.
People often compare measures of acute
toxicity expressed as LD50, which measures
lethal effects from a large one-time dose,
when trying to place these exposures in
context. As the famous quote goes, “the dose
makes the poison” characteristics as shown in
fig

CHRONIC TOXICITY
• Outside of cases of acute poisoning, most of
the time we are interested in finding the
lowest level of daily exposure that causes
harm.
• As mentioned above, LD50 values give us very
little information about these long-term
effects. Instead, chronic toxicity metrics are
based on the “Lowest Observable Adverse
Effects Level” (LOAEL) and the “No
Observable Adverse Effects Level” (NOAEL)
characteristics as shown in fig

IN PLANT WASTE CONTROL
AND WASTE REUSE
Waste Management
• Waste management is a process that
combines all the activities necessary for
managing waste – collection of garbage,
transportation, and disposal of the trash.
• Its primary purpose is to lessen the waste of
unusable materials and avoid potential
environmental and health risks.

• The waste can be in any form – liquid,
solid, gas – but with the help of waste
management processes, each state has its
own disposal methods.
• It offers a variety of solutions to recycle
the waste, which ultimately leads down to
finding ways to recycle it as a valuable
resource.

One of the ways to put that plan into action is through
the 3 Rs of waste management — Reduce, Reuse,
Recycle.
1. Reduce means to cut back on the amount of
trash we generate.
2. Reuse means to find new ways to use things
that otherwise would have been thrown out.
3. Recycle means to turn something old and
useless (like plastic milk jugs) into something
new and useful (like picnic benches, playground
equipment and recycling bins).

WASTE REDUCTION
Waste reduction or source reduction is the
practice of preventing waste by decreasing or
eliminating the amount of materials initially used.
Some examples of waste reduction include
purchasing products in bulk quantities rather than
single servings, like cereal or potato chips.
Another example is to use reusable serving
utensils and trays instead of disposable items; or
to manage grass clippings by using a mulching
lawn mower and leaving clippings on the lawn.

Effective solid waste disposal
and management methods
1. Preventing or Reducing Waste
Generation
2. Recycling
3. Incineration
4. Composting
5. Sanitary Landfill
6. Disposal in Ocean/Sea
7. Plasma Gasification

Benefits of Waste Management
1. Better Environment
2. Reduced Pollution
3. Energy Conservation
4. Increases Employment Opportunities
5. Helps Create a Change

STORM WATER CONTROL
Storm water management means to
manage surface runoff.
It can be applied in rural areas (e.g. to
harvest precipitation water), but is
essential in urban areas where run-off
cannot infiltrate because the surfaces are
impermeable

Stormwater management is essential to
prevent erosion of agricultural land and
flooding of inhabited urban or rural
areas.
Both cases can cause severe damages and
contamination of the environment if
sanitation facilities are flooded.
This results in high costs and notably
massive suffering for the local
communities

UNIT-II
WASTE WATER
TREATMENT PROCESSES

INTRODUCTION
• Wastewater treatment is the process of
improving the quality of wastewater and
converting it into an effluent that can be either
returned to the nature or incorporated to the
water cycle with minimum environmental issues
or that can be reused.
• The end user may be drinking, industrial water
supply, irrigation, river flow maintenance, water
recreation or many other uses, including being
safely returned to the environment.

INDUSTRIAL WASTEWATER
PRETREATMENT WORKS
Waste water Pretreatment
The term “pretreatment” means the treatment of
wastewater by commercial and industrial facilities
to remove harmful materials before being
discharged to a sewer system under the control
of a publicly owned wastewater treatment plant.
If you fail to properly treat your water or
improperly manage your discharge, you could
incur fines and possible legal action.

PRIMARY TREATMENT OF INDUSTRIAL
EFFLUENTS
• It is of general nature and is used for removing
suspended solids, odour, colour and to
neutralizethe high or low pH.
It involves methods of:
(i) Screening
(ii) Neutralization
(iii) Equalization
(iv) Sedimentation
(v) Coagulation

SCREENING
• It is a process through which large materials
like wooden pieces, metal pieces, paper, rags,
pebbles, fibers etc. are removed.
TYPES OF WASTEWATER SCREENS
Coarse screens
fine screens
micro screens

COARSE OF SCREENING IN
WASTEWATER TREATMENT
Coarse screens have clear openings ranging
from 6 to 150 mm (0.25 to 6 in).
Coarse screens consist of parallel bars, rods or
wires, wire mesh or perforated plates with
openings generally of circular or rectangular
shapes.

COARSE OF SCREENING IN
WASTEWATER TREATMENT

Based on the wastewater screening
method used to clean them, coarse
screens are classified into two types
1. Hand cleaned coarse screens
• Used in the screening process in wastewater
treatment at small facilities, hand cleaned coarse
screens are hand raked. They are ideal to use as a
standby during periods of high flow, or when
more modern mechanical screening methods are
under repair or maintenance.
2. Mechanically cleaned screens
• Mechanically cleaned coarse screens increase
efficiency and reduce problems in the wastewater
treatment process.

Mechanically cleaned screens can be
classified into the following four main
categories
1. Chain Driven Screens
• These front and back chain driven screens can
rake from upstream or downstream. An
automatic chain cleans the stream, increasing the
functionality of the entire wastewater treatment
solution.
2. Catenaries Screens
• These front return, front cleaned chain driven
screens use impressive, yet straight forward
internal mechanics to prevent further jamming in
the presence of large or heavy objects.

3. Reciprocating Rakes:
• Also known as a climber screen, these
wastewater treatment screening solutions use
one rake rather than multiple, making them less
efficient when facing heavy loads during the
screening process in water treatment.
4. Continuous belt screen:
• Ultra-high tech, functional and efficient, this type
of screening has many rakes and is continuous
and self-cleaning, whether facing fine or coarse
solid loads.

MICROSCREENS FOR WASTEWATER
SCREENING

MICROSCREENS FOR WASTEWATER
SCREENING
The smallest type of screening in wastewater
treatment is micro screening shown in fig .
These screens are typically low-speed drum
screens
The drums are lined with filtering fabrics with
openings of 10 to 35μm.
Wastewater enters the drum, and the
retained solid waste is collected and disposed
of waste.

FINE SCREENING IN WASTEWATER
TREATMENT PLANTS
The screening process in water treatment
plants employs screens that have clear
openings less than 6mm called fine screens.
They are made of wire cloth, wedge wire or
perforated plates.
Like micro screens, they are tools for
screening in wastewater treatment that are
used to remove fine solids.

Three common types of fine screening in
wastewater treatment are
• Drum Screens (rotating cylinders in the
flow channel)
• Step Screens (fixed and movable plates
across the width of the channel)
• Static Wedge Wire Screens (used by
large treatment plants with ample floor
space)

NEUTRALIZATION
• 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 the public sewer.
(a) Lime stone treatment
• For acidic effluent, lime stone should be used
as it will form calcium compounds [CaCl2,
CaBr2, Ca (NO3) or CaSO4] depending upon
the presence and amount of acid.

(b) Caustic soda treatment
• Although it is costly method but it is also
utilized for neutralizing the acid.
• Here caustic soda is added in the effluent to
make the pH neutral. Only small amount of
caustic soda is needed for this work.

For neutralization of alkaline effluent
the following techniques are used
(a) Carbon dioxide treatment
• If factory is producing carbon dioxide then only this
method should be utilized for neutralizing the pH
otherwise it would be costlier affair. Here CO2 is
passed in alkaline effluent to make its pH almost 7.
(b) Sulphuric acid treatment
• This is a common method of neutralizing alkaline
effluent. Here sulphuric acid is added in the effluent till
pH becomes almost 7.
(c) Utilizing waste boiler – Flue gas
• The stack gas which contains about 12% carbon dioxide
is utilized to react alkaline effluent to make it neutral.

EQUALIZATION
• When effluent is discharged from factory then
its pH along with the quantity of suspended
solids, dissolved solids etc. vary from the
beginning to the last depending upon the
dilution, velocity and the amount of reactants
etc.

Equalization Tanks
The equalization tanks are provided
(i) to balance fluctuating flows or
concentrations
(ii) to assist self neutralization, or
(iii) to even out the effect of a periodic "slug"
discharge from a batch process.
Types of Equalization Tanks
Equalization tanks are generally of three types:
• Flow through type
• Intermittent flow type
• Variable inflow/constant discharge type

SEDIMENTATION
This treatment is only employed for the
settlement of suspended particles by gravity.
This technique is only used in the beginning to
settle down the solid particles in a high
suspension effluent
When a thick layer of sediment continues to
settle, this is known as consolidation.
When consolidation of sediment, or sludge, is
assisted by mechanical means then this is
known as thickening.

There is a variety of methods for applying
sedimentation and include:
Horizontal flow
Radial flow
Inclined plate
Ballasted flocculation and flocculation blanket
sedimentation.

OIL SEPARATION
An oil water separator is a piece of
equipment used to treat wastewater,
making it safe to discharge into an
approved discharge point, such as a
sewer.
It removes oils, grease and
hydrocarbons, leaving only the non-
hazardous water.
The wastewater can then dispose of
safely drainage.

The four common types of oil water
separators are
Coalescing plate separators -remove oils,
grease, and hydrocarbons from wastewater
Vertical gravity separators -Vertical gravity
separators operate by controlling both fluid
velocity and pressure.
Hydro cyclone separators -Hydro cyclone oil
separators work by sending wastewater through
a 'cyclone chamber', which applies extreme
centrifugal forces.
Petrol and oil interceptor pits -These systems
typically feature two to three compartment gravity
flow systems which work on the premise that
hydrocarbons, petrol, and diesel float above water

Sour water strippers
• The sour water stripper removes
hydrogen sulfide and ammonia from the
sour water generated in the refinery.
• The sour water is received from the
refinery in the flash drum, where light
hydrocarbons are flashed off.
• The sour water is then fed to the feed
prep tank, where the feed is mixed and
stabilized

Process of Sour water
strippers

• The sour water is then heated in the
feed/bottoms exchanger and fed to the stripper
column.
• Steam, generated in the re-boiler, heats the
water and strips the hydrogen sulfide (H2S) and
ammonia (NH3) from the water.
• The stripped water from the column is cooled in
the feed/bottoms exchanger and in the stripped
water cooler, and returned to the refinery.
• The H2S and NH3 removed from the sour water
is cooled in the pump-around cooler system or
in an overhead condenser system and sent to
the sulfur recovery unit for further processing

FLOATATION
• Flotation is a separation technique that
employs the use of gas bubbles as a transport
medium.
• Suspended particulate matter that is
hydrophobic or has been conditioned to be
hydrophobic attaches to the bubbles and flows
in the opposite direction of gravity towards the
aqueous solution surface

Removal of micro plastics
• Micro plastics (plastic particles less than 5
mm) are removed from effluent in four municipal
wastewater treatment plants using various
modern final stage treatment technologies,
including flotation.
• For the fast removal of antibiotics from water, a
coagulation-flotation approach (containing an
anionic surfactant and a cationic polyelectrolyte)
can be used.
• A common application for flotation is oily
wastewater (perhaps for density reasons).

Flotation of Metal Ions
• Ion flotation is the act of eliminating surface-
inactive ions from aqueous solutions using
surfactants or collectors, usually an ion with
the same charge as the metal ion to be
eliminated.
• Ion flotation is used to extract metal ions
from solutions containing low concentrations
of heavy metal, which can be produced by
any industrial process, including metal
working, semiconductor, and metal industries,
as well as mine water

Types of flotation
• Flotation can be divided into three categories: natural,
aided and induced flotation.
1. Natural Flotation
• Natural flotation is valid if the density has difference
which is naturally sufficient for separation.
2. Aided Flotation
• Aided flotation takes place when external means are
used to promote the separation of particles that are
naturally floatable
3. Induced Flotation
• Induced Flotation takes place when the density of
particles is artificially reduced to allow particles to
float. This flotation is based on the capacity for certain
solid and

• 4. Dissolved Air Flotation (DAF)
It is a method of induced flotation with very fine
air bubble or micro bubbles which are up to 40
to 70 microns.

COAGULATION
• Coagulation is the chemical water
treatment process used to remove solids
from water, by manipulating electrostatic
charges of particles suspended in water.
• This process introduces small, highly
charged molecules into water to
destabilize the charges on particles,
colloids, or oily materials in suspension

• For dealing waters with such impurities a
chemical process was evolved.
• This process removes all these impurities
within reasonable period of 3 — 4 hours.
• This chemical process is called coagulation
and the chemical used in the process is called
coagulant.

Principle of Coagulation
a. Floe formation
b. Electrical charges
a. Floe formation
When coagulant is added to the water and
thoroughly mixed, it produces a thick insoluble
gelatinous precipitate.
This precipitate is called floe.
The floe has the property of arresting the
suspended impurities in water during its
downward settlement towards the bottom of the
tank.

b) Electrical charges
• The flock ions are electrically charged
(positive) while all the colloidal particles have
negative charge.
• Therefore floes attract the colloidal particles
and cause their removal easily by settlement
at bottom of the vessel in which it is used.

Coagulants
The chemicals given below can be used as coagulants either alone or in combination
1. Sodium aluminates.
2. Sodium aluminates +
Aluminium sulphate.
3. Aluminium sulphate.
4. Sodium aluminate + Ferric
chloride.
5. Aluminium chloride (but used
under exceptional circumstances
only).
6. Aluminium sulphate + caustic
soda.
7. Ferric chloride alone.
8. Aluminium sulphate + hydrated
lime.
9. Polyelectrolyte.
10. Ferrous sulphate.
11. Copper sulphate.
12. Sodium aluminate + Magnesium
chloride.
13. Copper sulphate + hydrated lime.
14. Ferric sulphate.
15. Aluminium sulphate + Sodium
carbonate.
16. Ferric sulphate + hydrated lime.
17. Ferrous sulphate + hydraed lime.
18. Ferrous sulphate + chlorine.
19. Potassium permanganate +
ferrous sulphate.
20. Magnesium carbonate.

In water treatment plants following are the usual
coagulants most commonly used
1. Ferrous sulphate and lime.
2. Magnesium carbonate.
3. Polyelectrolyte.
4. Aluminium sulphate.
5. Sodium aluminate.
6. Chlorinated copper

Dry powder of coagulant is filled in the conical
hopper.
The hoppers are fitted with agitating plates which
prevent the chemical from being stabilized.
At the bottom of the hopper a revolving helical
screw or the toothed wheel is fixed.
The rotation of the helical screw or the toothed
wheel is regulated through a venturi device in the
raw water pipe.
When more discharge is passed through the
venturi device, the rotation of the screw or
toothed wheel gets increased and more
coagulant is thrown in the water

Mixing Channel of dry fed device

HEAVY METAL REMOVAL
• The presence of heavy metals in wastewater has
been increasing with the growth of industry and
human activities,
• e.g., plating and electroplating industry,
batteries, pesticides, mining industry, rayon
industry, metal rinse processes, tanning
industry, fluidized bed bioreactors, textile
industry, metal smelting, petrochemicals,
paper manufacturing, and electrolysis
applications.
• The heavy metal contaminated wastewater finds
its way into the environment, threatening human
health and the ecosystem.

Heavy metals are non-biodegradable and
could be carcinogenic thus, the presence of
these metals in water by improper amounts
could result in critical health issues to living
organisms.
The most popular heavy metals are lead (Pb),
zinc (Zn), mercury (Hg), nickel (Ni), cadmium
(Cd), copper (Cu), chromium (Cr), and arsenic
(As).
Although these heavy metals can be detected
in traces; however, they are still hazardous.

AERATION
Aeration brings water and air in close contact
in order to remove dissolved gases (such as
carbon dioxide) and oxidizes dissolved metals
such as iron, hydrogen sulfide, and volatile
organic chemicals (VOCs).
Aeration is often the first major process at the
treatment plant.
During aeration, constituents are removed or
modified before they can interfere with the
treatment processes.

• Aeration also helps remove dissolved metals
through oxidation, the chemical combination
of oxygen from the air with certain
undesirable metals in the water
• The efficiency of aeration depends on the
amount of surface contact between air and
water, which is controlled primarily by the size
of the water drop or air bubble

Chemicals Removed or Oxidized by
Aeration
Constituents commonly affected by aeration are
• Volatile organic chemicals, such as benzene (found
in gasoline), or trichloroethylene, dichloroethylene
(used in dry-cleaning or industrial processes)
• Ammonia
• Chlorine
• Carbon dioxide
• Hydrogen sulfide
• Methane
• Iron and Manganese

AERATION EQUIPMENTS
Aerators fall into two categories. They either
introduce air to water, or water to air.
The water-in-air method is designed to produce
small drops of water that fall through the air.
The air-in-water method creates small bubbles of
air that are injected into the water stream.
All aerators are designed to create a greater
amount of contact between air and water to
enhance the transfer of gases and increase
oxidation.

Water-Into-Air Aerators
Cascade Aerators
Cone Aerators
Slat and Coke Aerators
Draft Aerators
Spray Aerators

Air-Into-Water Aerators
a. Pressure Aerators
b. Centrifugal Aerators

AIR STRIPPING
Air stripping is a process by which a liquid, usually
wastewater, is brought into intimate contact with
a gas, usually air, so that some undesirable
volatile substances present in the liquid phase
can be released and carried away by the gas.
Processes such as mechanical surface aeration,
diffused aeration, spray fountains, spray or tray
towers, and countercurrent packed towers are
encompassed by the term air stripping.

A certain amount of dissolved oxygen is present
in raw and treated waters.
However, dissolved oxygen can cause corrosion.
Corrosion can occur whenever water and oxygen
come into contact with metallic surfaces.
Generally the higher the dissolved oxygen
concentration, the more rapid the corrosion
The solution to this problem is to not over-aerate.
This may be difficult because no definite rule
exists as to what constitutes over-aeration.
The amount of aeration needed will vary from
plant to plant and will also vary with the season.

False Clogging of Filters (Air Binding)
• Filters in water containing a high amount of
dissolved oxygen will have a tendency to
release the oxygen in the filter as it passes
through.
• The process can continue until the spaces
between the filter media particles begin to fill
with bubbles Called air binding, this causes
the filter to behave as though it is plugged and
in need of backwashing.

Slow Removal of Hydrogen Sulfide
Hydrogen sulfide is most efficiently removed,
not by oxidation, but by the physical scrubbing
action of aeration.
This removal is dependent on the pH of the
water. At a pH of 6 or less, the hydrogen
sulfide is easily removed.
If the water has a high pH, the hydrogen
sulfide will ionize, precluding removal by
aeration.

Three basic control tests are required
for aeration
1. Dissolved oxygen - The concentration of
dissolved oxygen can be used to determine if the
water is over or under-aerated. The pH test will give
an indication of the amount of carbon dioxide
removed.
2. pH - pH increases as carbon dioxide is removed.
pH can also be used to monitor the effective range
for hydrogen sulfide, iron, and manganese removal.
3. Temperature - The saturation point of oxygen
increases as the temperature decreases. As water
temperature drops, the operation.

Unit-III
POLLUTION
FROM MAJOR
INDUSTRIES

SOURCES, CHARACTERISTICS, WASTE
TREATMENT FLOW FROM TEXTILES
TEXTILES MILLS WASTE
• The Fibers used in the Textile Industry may be
broadly classified into four groups:
• cotton, wool, regenerated and synthetics.

Cotton textile mill waste
• Carding:- It is a process in the manufacture of
spun yarns whereby the staple is opened,
cleaned, aligned and formed into a continuous
untwisted strand called sliver.
• Drawing:- It is the process of increasing the
length per unit weight of sliver.
• Combing:- A method to remove short fibers,
foreign matter from cotton stock by pressing it
through a series of needles or combs
• Spinning:- It is a process by which a long strand of
fibers is drawn out to a short strand and
converted into a yarn. After drawing out, it is
subjected to twisting and the resulting yarn is
wound into a bobbin.

• Winding:- It is the process of transfer of a yarn
or thread from one type of package to
another.
• Weaving:- It is the process of interlocking two
yarns of similar materials so that they cross
each other at right angles to produce a woven
fabric The entire liquid waste from the textile
mills comes from the following operation of
slashing (or sizing), scouring and resizing,
bleaching, mercerizing, dyeing and finishing.

WOOLEN TEXTILE MILLS WASTE
• Wool wastes originate from scouring,
carbonizing, bleaching, dyeing, oiling, fuelling
and finishing operations.

Effects of the cotton textile and
woolen textile mill wastes on
receiving streams / sewers
• The alkalinity and the toxic substances like
sulphides and chromium affect the aquatic
life; and also interfere with the biological
treatment process; some of the dyes are also
found toxic.

Treatment of Cotton and Woolen
Textile Mill Waste
 The pollution load of the waste is dealt with in the
operations like segregation, equalization, neutralization,
chemical precipitation, chemical oxidation and biological
oxidation.
 Several chemicals are used to reduce the BOD by chemical
coagulation.
 These are alum, ferrous sulfate, ferric sulfate, ferric
chloride etc., lime or sulfuric acid is used to adjust the pH
in this process.
 Calcium chloride is found to be effective in treating wool-
scouring waste.
 The dye wastes may be treated economically by biological
methods, with prior equalization, neutralization and
chemical oxidation for certain wastes.

Synthetic Textile Mill Waste
• The most prominent man made synthetic fibers
are Rayon, nylon and polyester.
• These fabrics require no processing for the
removal of natural impurities as they are
manmade.
• Manufacture of synthetic fabrics involves two
steps
(i) Manufacture of the synthetic fiber
(ii) Preparation of the cloth

PULP AND PAPER MILL WASTE
• The paper mills use the 'pulp' as the raw
material , which is again produced utilizing
different cellulosic materials like wood ,
bamboo, jute, straw mainly of rice and
wheat, waste paper, bagasse etc. in the pulp
mills.

Manufacturing Process
The Process of manufacturing of paper may
be divided into two phases - Pulp making and
then making of final product of paper.
The major portion of the pollution from
papermaking originates in the pulping
processes.
Raw materials are reduced to a fibrous pulp
by either mechanical or chemical means.
The bark is mechanically or hydraulically
removed from wood before it is reduced to
chips for cooking.

Characteristics of pulp and paper mill
wastes
• The volume depends mainly on the manufacturing
procedure, and the water economy adopted in the
plant.
• It has been observed that a well operated and well
managed integrated pulp and paper mill
employing Kraft process for pulping, produces a
waste volume in the range of 225 to 320 m3 per
ton of paper manufactured.
• The mills manufacturing special quality of paper
produce larger amount of water for washing and
bleaching.

The effect of wastes on receiving
water courses or sewers
Crude pulp and paper mill wastes, or insufficiently
treated wastes cause very serious pollution problems,
when discharged into the streams
The fine fibers often clog the water intake screens in
the downstream side.
A toxic effect may also be induced upon the flora (all
plant life) and fauna (all animal life) of the stream
due to sulfites and phenols in the waste.
The bottom deposit of Lignin - Cellulosic materials
near the point of the discharge of the waste in a stream
undergo slow decomposition and may lead to the
dissolved oxygen depletion followed by the creation of
anaerobic condition and destruction of the aquatic
life.

The treatment of the waste may consist of all or a
combination of some of the following processes
1. Chemical treatment for color removal
2. Activated carbon for color removal
3. Physical treatment for clarification
4. Biological treatment of the waste

The treatment of the pulp and paper
mill waste

FERMENTATION
• The Fermentation industries include breweries
and distillery manufactures of alcohol and
certain organic chemicals and some parts of
the pharmaceutical industry such as producers
of antibiotics.
• The transformation of grape juice into wine,
the manufacture of alcohol from molasses,
and the use of yeast in dough to make bread
are familiar examples of fermentation.

TANNING INDUSTRY
Tanning Process
The tanning process consists of three basic
stages
1. Preparation of the hides for tanning.
2. Tanning proper.
3. Finishing.

Tannery wastes originate from the beam
house and the tan yard.
In the beam house curing, fleshing, washing,
soaking, remove haring, lime splitting,
bating, pickling and degreasing operations are
carried out.
In the tan yard, the final leather is prepared
by several processes.
These include vegetable or chrome tanning,
shaving and finishing.
The finishing operation includes bleaching,
stiffing and fat liquoring and coloring.

PHARMACEUTICAL INDUSTRY
• Pharmaceutical waste can result from many
activities and locations in a healthcare
facility.
• If you have a compounding pharmacy on
site, it generates drug waste.
• Anywhere medicines are employed can be
the site of spills, half-used bottles, and IV
equipment with residual medicine on it.

Sources of Pharmaceutical Waste
• Wastewater Treatment Plants (WWTPs)
These WWTPs focus on stopping waste from
reaching the water or sources of water.
• Humans and Animals
• Pharmaceutical Waste Treatment Plants
• Unused Drugs
• Healthcare Institutions.
• Homes and Farms Where Food is Grown
• Personal Care Products.

Characteristics of pharmaceutical
waste
In general, the composition of
pharmaceutical wastewater is complex,
which has
• High concentration of organic matter,
• Microbial toxicity,
• High salt, and
• It's hard to biodegrade

DAIRY WASTES
Units Operation in a Dairy
• Receiving Stations
The receiving station serves as a collection point for
raw milk from the farmers. When milk is delivered
to the dairy in cans and these cans are emptied,
rinsed and washed and in some cases sterilized
before returning.
• Bottling
Raw milk received is weighed and classified
(generally based on the fat content), it is preheated,
pasteurized, cooled and then filled into bottles,
polythene bags, cardboard packets etc.

Product Making
• Dry milk, milk powder, cheese, butter and other
products as ice cream, condensed milk are
prepared out of milk.
Sources of wastes
• Waste producing operations are washing of
bottles, cases, cans, tanks, cooling equipment,
Processing equipment and floors
• Dripping, leaks, spillages and overflows due to
improper equipment or inefficient operation.
• Discharges from evaporators
• Wasted buttermilk and whey (watery liquid left
when milk forms curds).
• Spoiled raw or treated products

Characteristics of diary wastes

Treatment of Waste
• As evident from the high BOD/COD ratio, the
dairy wastes can be treated efficiently by
biological processes.
Reduction of volume and strength of the
wastes by
a. Prevention of spills, leakages and dropping of
milk from cans.
b. By reducing the amount of water for
washes
c. By segregating the uncontaminated cooling
water and recycling the same.

SUGAR MILL WASTES
CHARACTERISTICS AND
COMPOSITION OF WASTE WATER
MANUFACTURING PROCESS SUGAR
MILL WASTES

Introduction
• In Countries like India, Cuba and Jamaica, the
sugar is produced from sugar canes, while in
many other places beetroots are used as the
raw materials for the sugar production.
• In India most of the sugar mills operate for
about 4 to 8 months just after the harvesting
of the sugar canes

Manufacturing Process
The sugar canes are cut into pieces and
crushed in a series of rollers to extract the
juice, in the mill house.
Juice is extracted from the sugar cane, leaving
a fibrous residue called bagasse, which can be
used as a fuel for the boilers or can be
disposed of as solid waste.

1. The milk of lime is then added to the juice
and heated, when all the colloidal and
suspended impurities are coagulated; much
of the color is also removed during this lime
treatment.
2. Lime is added to the extracted juice to raise
its pH and to prevent the inversion of the
sucrose molecule to glucose and fructose.
3. The coagulated juice is then clarified to
remove the sludge.

• The clarifier is further filtered through filter
presses, and then disposed off as solid waste.
• The filterate is recycled to the process, and
the entire quantity of clarified juice is treated
by passing sulphur dioxide gas through it.
• The process is known as “sulphitation
process"; color of the juice is completely
bleached out due to this process.

• The clarified juice is then preheated and
concentrated in evaporators and vacuum pans.
The partially crystallized syrup from the vacuum
pan, known as "massecuite“(massecuite
(countable and uncountable, plural
massecuites) A suspension of sugar crystals in a
mother liquor, after boiling of syrup; produced in
a sugar factory.) is then transferred to the
crystallizers, where complete crystallization of
sugar occurs.

Characteristics of Sugar Mill Waste

STEEL PLANT WASTES
• Integrated steel plants usually consist of five
main units, Viz; Coal washer, Coke oven blast
furnace, steel melting shop and rolling mills.
• In addition to the above the plants may have
auxiliary units like oxygen plant and power
plant for their own uses.

Characteristics of Coal Washeries

METAL PLATING WASTE
Plating is the application of a plate, or coat, of
metal to a surface for decoration, reflection of
light, protection against corrosion, or
increased wearing quality.
Electroplating is the most common method
because it permits the control of the thickness
of the plating. We offer: Gold, Nickel, Copper,
and Chrome plating.

OIL REFINERIES WASTE
Sources of Waste Water & Manufacturing Process
Crude oils are complex mixtures of hydrocarbons
of varying molecular weight and structure.
These hydrocarbons range from simply highly
volatile substances to complex waxes and
asphaltic compounds.
The final petroleum products are obtained from
the crude oil through a series of operations viz.
topping, thermal cracking, catalytic cracking,
catalytic reforming etc.

In general, the crude oil is first subjected to
fractional distillation in the process known as
“topping “.
The products obtained are called raw products
and include raw gasoline, raw naphtha, raw
kerosene, gas oil, fuel oil etc.
Now these intermediate refinery products are
again treated to yield various finished market
products as per the requirements.
The operations practiced include "catalytic
cracking" or "thermal cracking" and further
purification processes like "acid treatment”,
"sweetening treatment”,
"hydrodesulphurization" etc.

FERTILIZER PLANT WASTE
Fertilizer industry can be divided into three main
categories depending upon
1. Fertilizer raw materials
2. Fertilizer intermediates
3. Fertilizer products

Fertilizer Intermediates
• 1. Sulphuric acid
• 2. Phosphoric acid
• 3. Nitric acid
Fertilizer products:
SOLID
N - Fertilizers
• 1. Ammonium nitrate
• 2. Urea
• 3. Ammonium sulfate P - Fertilizers
• 4. Super phosphates NPK fertilizers

PETROCHEMICAL COMPLEX
WASTE
 Petroleum, known as "industrial blood", is important energy
and industrial raw material, as well as an important
production and daily necessities of human beings.
 With the rapid development of economy and society, oil and
its products have been widely used in various fields of the
national economy and people's daily life, and their use and
demand are gradually increasing.
 In the refining process, petroleum will produce by-products
that have an impact on the environment, including
petrochemical wastewater.
 As one of the main sources of petroleum pollution,
petrochemical wastewater has a serious negative impact on
economic development and the ecological environment.

The treatment process of oily
wastewater

CORN STARCH INDUSTRY
• Corn starch industry contributes almost 12%
of starch production.
• Maize starch, produced worldwide,
contributes huge amount of acidic effluent
(pH 3-5) containing high Chemical oxygen
demand (COD) (10000- 30000 mg/L),
biological oxygen demand (BOD) (4000-8000
mg/L), nitrogenous pollutant (400-900 mg/L)
and other pollutants.

• Conventional methods of anaerobic digestion
and nitrification-denitrification process are
widely being used to treat starch industry
effluent.
• The anaerobic digestion requires neutral pH
operation thus increases operational cost.
• Similarly, nitrification and denitrification
processes are lengthy processes consuming
high operational cost and require secondary
treatment for generated excess sludge.

• Starch is widely used in food,
pharmaceutical, paper & textile industry in
large quantities. Maize is used as a bulk
source of starch production in various
countries.
• It is the highest produced cereal crop and
widely cultivated throughout the world,
counts among major contributors of raw
material in bulk industrial scale.

• The main goal of all available technologies are to
remove maximal removal of carbonaceous and
nitrogenous contaminant from water and to
make the water reusable for irrigation purpose
or to make it potable by applying further
advanced technologies like reverse osmosis after
biological treatment
• The technologies developed over time for aerobic
and anaerobic treatment are in consideration to
neutral pH waste treatment, while starch
effluents are highly acidic in nature.
• Thus there is a compulsory requirement to
neutralize the effluent by dilution or chemical
addition before introducing it to treatment
system

Odour Removal
• Waste water treatment, is the process of removing
contaminants from wastewater and household sewage.
• It includes physical, chemical, and biological
processes to remove physical, chemical and biological
contaminants.
• Odors emitted by waste water treatment are typically
an indication of anaerobic conditions.
• Early stages of processing will tend to produce toxic
gases, like Hydrogen Sulphide (H S), Sulphur Dioxide
(SO), Bromine and Oxides of Nitrogen, Chlorine etc
• which can be even corrosive in higher concentrations,
which makes odor removal a necessary criteria.

Chemical Oxidation System
• Chemical oxidation process involves oxidizing
agents reacting with organic pollutants in the
air and oxidizing them.
• Essentially, these pollutants undergo a
chemical reaction that transforms them into
non-toxic substances and traps odor
efficiently.
• These advanced technology filters not only
remove odors but also destroys other harmful
organic matters.

• Chemical oxidation effectively oxidizes
99% organic pollutants to less dangerous
or harmless substances
• Removes other types of odor causing
substances like amines compounds.
• Helps to achieve immediate odor control.

Biological Oxidation System
• The knowledge and experience of Aqoza has
made it possible to adapt to the most eco-
friendly technologies for the changing times
and changing needs.
• Our emerging odour control units use
biological oxidation for the destruction and
removal of VOCs, organic matters, odors and
hydrocarbons.

WASTE MINIMIZATION AND
RESOURCE CONSERVATION
• Waste is also the inefficient use of utilities such as electricity, water,
and fuel, which are often considered unavoidable overheads.
• The costs of these wastes are generally underestimated by
managers.
• It is important to realize that the cost of waste is not only the cost
of waste disposal, but also other costs such as:
 ▪ Disposal cost
 ▪ Inefficient energy use cost
 ▪ Purchase cost of wasted raw material
 ▪ Production cost for the waste material
 ▪ Management time spent on waste material
 ▪ Lost revenue for what could have been a product instead of
waste
 ▪ Potential liabilities due to waste.

Classification of Waste Minimization
(WM) Techniques

Source Reduction
Under this category, four techniques of WM are
briefly discussed below:
a) Good Housekeeping
b) Process Change
(i) Input Material Change
(ii) Better Process Control
(iii) Equipment Modification
(iv) Technology change
c) Recycling
i) On-site Recovery and Reuse
ii) Production of Useful by-product
d) Product Modification

Unit-Iv
BIOLOGICAL
WASTE WATER
TREATMENT
PROCESS

LAGOONS
A lagoon is a shallow body of water separated
from a larger body of water by barrier islands,
reefs (ridge of material or near the surface of the
ocean), isthmuses(An isthmus is a narrow strip of
land that connects two larger landmasses and
separates two bodies of water) or peninsulas (an
area of land that is almost surrounded by water)..
When barrier bars and spits form at the mouth of
a bay and block it, a lagoon forms.
The lagoons would gradually get filled up by
sediments from the land giving rise to a coastal
plain.

Lagoon – Types
• Coral lagoons, and
• Barrier Island or coastal lagoons
• River Mouth Lagoons
• Artificial Lagoons

Coral Lagoons – Locations
 Coral lagoons have the conditions necessary for coral growth.
 For many island communities in the Pacific, the coral lagoons
are of great importance.
 Coral lagoons are restricted to tropical open seas.
 Coral lagoons are mainly found within 25° latitude of the
Equator.
 Coral lagoons are found in the isolated places of the
Caribbean, parts of the Indian Ocean, and found widely in
the western Pacific.
 • The atolls of the Pacific Ocean are the most spectacular
examples of coral reefs.
 • The Great Barrier Reef of Australia is another example
where coral lagoons are found.
 • These are the most common type of lagoon that find in the
coastal regions.

Coastal or Barrier Island Lagoons –
Locations
Coastal or Barrier Island lagoons are formed only
where there is abundant sediment for construction of
the protective barrier islands.
Coastal or Barrier Island lagoons rarely occur where
high cliffs form the coast.
These lagoons are usually associated with low coasts.
They occur where the swells are usually less violent.
Coastal or Barrier Island lagoons are characterized by
brackish marshes, fine-grained sedimentation, and
quiet water conditions.

River Mouth Lagoons
They form at the mouths of the coastal rivers.
These can also be considered coastal lagoons.
They have brackish water which means partly
fresh water and partly saltwater.
These can be seen most commonly in
Newzealand and South Pacific islands.

Artificial Lagoons
These are man-made and not natural.
These are increasing and becoming popular.
These can be used for recreation or residential or
other purposes.
They are more controlled and safe as they can be
made anywhere with suitable conditions and
requirements.
The only freshwater can also be found here
rather than brackish water.

STABILIZATION BASINS
• Waste or Wastewater Stabilization Ponds
(WSPs) are large, man-made water bodies in
which blackwater, greywater or faecal sludge
are treated by natural occurring processes and
the influence of solar light, wind,
microorganisms and algae .
• The ponds can be used individually, or linked
in a series for improved treatment

There are three types of ponds,
(1) anaerobic,
(2) facultative and
(3) aerobic (maturation), each with different
treatment and design characteristics.
WSPs are low-cost for O&M and BOD and
pathogen removal is high.
However, large surface areas and expert design
are required.

• WSPs should be linked in a series of three or more with
effluent being transferred from the anaerobic pond to
the facultative pond and, finally, to the aerobic
pond.
• The anaerobic pond is the primary treatment stage
and reduces the organic load in the wastewater.
• The entire depth of this fairly deep man-made lake is
anaerobic.
• Solids and BOD removal occurs by sedimentation and
through subsequent anaerobic digestion inside the
accumulated sludge.
• Anaerobic bacteria convert organic carbon into
methane and through this process, remove up to 60%
of the BOD.

• In a series of WSPs, the effluent from the
anaerobic pond is transferred to the facultative
pond, where further BOD is removed.
• The top layer of the pond receives oxygen from
natural diffusion, wind mixing and algae-
driven photosynthesis.
• The lower layer is deprived of oxygen and
becomes anoxic or anaerobic.
• Settleable solids accumulate and are digested on
the bottom of the pond.
• The aerobic and anaerobic organisms work
together to achieve BOD reductions of up to
75%.

Anaerobic and facultative ponds are designed
for BOD removal, while aerobic ponds are
designed for pathogen removal.
An aerobic pond is commonly referred to as a
maturation, polishing, or finishing pond
because it is usually the last step in a series of
ponds and provides the final level of treatment.

Anaerobic Treatment Ponds (APs)
• The main function of anaerobic ponds is BOD
removal, which can be reduced 40 to 85 %
(WSP 2007).
As a complete process, the anaerobic pond
serves to:
Settle undigested material and non-degradable
solids as bottom sludge
Dissolve organic material
Break down biodegradable organic material

Facultative Treatment Ponds (FPs)
• Facultative Treatment Ponds are the simplest
of all WSPs and consist of an aerobic zone
close to the surface and a deeper, anaerobic
zone.
• They are designed for BOD removal and can
treat water in the BOD range of 100 to 400
kg/ha/day corresponding to 10 to 40 g/m2/day
at temperatures above 20°C.

The facultative pond serves to:
• Further treat wastewater through sedimentation
and aerobic oxidation of organic material
• Reduce odour
• Reduce some disease-causing microorganisms
if pH raises
• Store residues as bottom sludge

Advantages of Stabilization basins
• Lower operating cost in terms of operators and
chemicals
• Large settling zone – less susceptible to poor
settling or sludge bulking
• Minimal operator attention
• Takes up less area – Smaller footprint
• Faster process
• Higher BOD reduction efficiency
• More concentrated bacterial population
• Can treat higher loaded waste streams

Disadvantages of Stabilization basins
• Harder to remove accumulated biological solids
• Poorer removal efficiencies , particularly in
cold weather
• Takes up more area – larger footprint
• More initial capital
• Higher operational cost – dewatering chemicals &
solids disposal
• Must be properly managed to better handle
upsets
• Susceptible to sludge settling Issues (bulking)
• Need for highly trained operators – more
testing to control & requires more attention.

AERATED LAGOONS
• 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, they
all have in common the use of oxygen (or air)
and microbial action to reduce the pollutants
in wastewaters.

Types of Aerated Lagoons
Aerated lagoons are deep waste stabilization ponds in
which sewage is aerated by mechanical aerators to
stabilize the organic matter present in the sewage,
rather than relying only on photosynthetic oxygen
produced by algae.
 Thus aerated lagoons represent a system of sewage
treatment that is intermediate between oxidation
ponds and activated sludge systems.
• Depending on how the microbial mass of solids is
handled in the aerated lagoons the same are classified
as:
(i) Facultative aerated lagoons and
(ii) Aerobic aerated lagoons.

Characteristics of Aerated Lagoons

Advantages of Aerated Lagoons
(i) The aerated lagoons are simple and rugged in
operation, the only moving piece of equipment
being the aerator.
(ii) The removal efficiencies in terms of power
input are comparable to some of the other
aerobic treatment methods.
(iii) Civil construction mainly entails earthwork, and
land requirement is not excessive. Aerated lagoons
require only 5 to 10 percent as much land as
stabilization ponds.
(iv) The aerated lagoons are used frequently for
the treatment of industrial wastes.

ACTIVATED SLUDGE PROCESSES
Activated sludge treatment can define as a
conventional method, which can separate the
solid wastes, suspended organic matter, soluble
matter and parasites.
Activated sludge treatment involves a series of
stages, which firstly separates the raw or
primary sludge, then separates the waste
activated sludge and finally involves disinfection
and clarification of the effluent.
Therefore, it contributes a significant role in the
control of water pollution by eliminating the
undesired chemicals, particulate matter and
parasites from the sewage and industrial waste.

Activated sludge treatment can define as the
wastewater treatment plant, which eliminates
the particulate matter like sand, unwanted
inorganic and organic wastes and harmful
microorganisms from the sewage waste.
The process is followed by the primary,
secondary and tertiary treatment methods.

• Primary treatment is a physical method, which
involves the separation of large solid matter like
leaves, sand, gravel particles etc.
• Secondary treatment is a biological method,
which separates the suspended and soluble
organic matter by making the use of bacterial
flocs.
• Tertiary treatment is a chemical method, which
is a final stage to disinfect the secondary effluent
by making the use of chlorine gas.

Flow Diagram of Activated Sludge Process

Advantages
• The process of activated sludge treatment releases high-
quality effluent (wastewater released from the sewage).
• It ensures the maximum reduction of BOD and
parasites upto 99% during the secondary treatment of
wastewater.
• Activated sludge process can resist different organic and
hydraulic shock load.
• The activated sludge treatment plant can be
established in the minimal land area compared to the
water stabilization pond.
• It also ensures maximum removal of nutrients like N2,
K, Ph from the organic matter.

Disadvantages
• The activated sludge process requires high capital.
• It also requires a continuous electricity supply.
•Its operation and maintenance require skilled
labour-power.
•The process cannot be established at the
community level.
•The construction of an activated sludge plant
requires expert design, and generally, all are
equipment’s are not locally available.
•Effluent from the wastewater requires proper
disinfection and appropriate discharge.

Trickling filtration
• Trickling filter process is one of the types of
aerobic wastewater treatment.
• It is a fixed-bed bioreactor that is the part of
secondary wastewater treatment, which
eliminates the coarse particles, suspended
organic and inorganic waste, small colloids etc.
• out of the primary effluent. A trickling filter is
also called biological filter, as it makes the use of
active microbial mass as a bioweapon to degrade
the waste out of primary sewage.

• Trickling filter process can define as the
biological system, which tends to separate or
degrade the maximum organic and inorganic
waste (up to 85%) out of the primary or raw
sludge via the slime layer.
• The designing of a trickling filter unit includes
a support structure, pebble or plastic filled
media and rotary distributor.

• Depending upon the hydraulic and organic
shock load, trickling filters can be categorized
into two types, namely
–high rate and low rate trickling filter.
The hydraulic loading rate can define as the
sewage flow (Q) per unit volume (V) of filter bed
in a day, while the organic loading rate can define
as the kilograms of BOD (Y5) introduced into the
per unit volume (V) in a day.

Advantages
• It is a simple and reliable secondary treatment unit of the
wastewater.
• It can be used to degrade a variety of organic waste.
• Trickling filter can resist shock loadings.
• It efficiently oxidizes the ammonia or efficient in
ammonium oxidation.
• Trickling filter aids to produce effluent free of BOD,
COD, nutrients, suspended colloids etc.
• Its construction requires a small land area, unlike
constructed wetlands.

Disadvantages
 Its designing requires high capital costs.
 The designing of a trickling filter requires expert skills
 Its operation and maintenance require regular
attention by the skilled labour personnel.
 The trickling filter process is a continuous process,
which needs an uninterrupted supply of electricity and
wastewater distribution.
 It sometimes causes flies breeding and odour problem.
 The effluent produced by the trickling filter needs to
treated further by the chemical disinfectants.
 Accumulation of excessive biomass may cause clogging
of the TF-unit.
 Not all parts and materials may be locally available.

ROTATING BIOLOGICAL CONTACTORS

• A rotating biological contactor (or RBC) is a type
of fixed media filter which removes both organic
matter and ammonia from water.
• It can be added to a packaged plant for more
efficient ammonia removal, replacing the aerator
in both location and function.
• Although RBC's are less prevalent than trickling
filters or oxidation ditches, they produce a high
quality effluent and wastewater operators should
be familiar with them.

Advantages
• High contact time and high effluent quality (both
BOD and nutrients)
• High process stability, resistant to shock hydraulic or
organic loading
• Short contact periods are required because of the
large active surface
• Low space requirement
• Well drainable excess sludge collected in clarifier
• Process is relatively silent compared to dosing
pumps for aeration
• No risk of channelling
• Low sludge production

Disadvantages
• Continuous electricity supply required (but uses
less energy than trickling filters or activated sludge
processes for comparable degradation rates)
• Contact media not available at local market
• High investment as well as operation and
maintenance costs
• Must be protected against sunlight, wind and rain
(especially against freezing in cold climates)
• Odour problems may occur
• Requires permanent skilled technical labour for
operation and maintenance

ANAEROBIC DECOMPOSITION
• Anaerobic digestion can be described as biological oxidation
of biodegradable waste by microbes under anaerobic
conditions or in simpler terms it is the process of converting
complex organic molecules into simpler molecules with the
help of microorganisms in absence of oxygen.
• The end product of this product has a high concentration of
carbon dioxide and methane.
• Anaerobic digestion is a biochemical process, it mainly utilizes
substrates with high organic matter, such as sludge, domestic
waste, sewage, and waste from a feedstock of cattle.
• It is mainly used in fermentation technology and the
management of waste.

Anaerobic Digestion Process
• Anaerobic decomposition is performed in anaerobic
digesters mainly by a group of anaerobic bacteria called
methanogens and acetogens, the group of bacteria do
not use oxygen as their source of electron donor rather
they accept electrons from acetate and methane for their
ener
1. Hydrolysis
2. Acidolysis or Acidogenesis
3. Acetogenesis
4. Methanogenesis

Hydrolysis
 It is also known as the liquefaction of complex
molecules.
 The process of breaking the chains with the help of
hydrolyzing enzymes is known as hydrolysis.
 High molecular weight polymeric components are
broken down into simple sugars and monomers which
can be readily accessible to bacteria.
 Acetate, hydrogen, and some VFAs (Volatile Fatty Acid)
produced during these steps.
 VFAs can not be directly used by the microorganisms so
they are first catabolized into small molecules that can
be utilized by the bacteria.

Acidolysis or Acidogenesis
• It is the process of acidic breakdown of oligo
polymers and compounds into simpler
molecules.
• Acidogenesis performed by acidogenic
bacteria, during this reaction ammonia,
carbon dioxide, and hydrogen sulfide, as well
as other byproducts, are formed.

Acetogenesis
Acetogenesis is the process of formation of
acetic acid with the help of acetogens.
This reaction produces carbon dioxide and
hydrogen as the main byproduct.

Methanogenesis
• This is the final step of anaerobic
decomposition.
• It is a pH sensitive reaction that occurs
between the range of pH 6.5 to pH 8. During
this step, the intermediate product from other
steps is used to produce methane, carbon
dioxide, and hydrogen.

The Breakdown of Three Major Food
Groups are as Follows
Carbohydrates → simple sugars → alcohol
and aldehydes → organic acids
Protein → amino acids → organic acid +
NH3
Fats and oils → organic acid

The Genera of Microbes Responsible for
Anaerobic Digestion are:
1. Pseudomonas
2. Flavobacterium
3. Escherichia
4. Aerobacter

• The Genera of Bacteria Responsible for
Methanogenesis:
1. Methanococcus
2. Methanobacteria
3. Methanosarcina

Advantages of Anaerobic Decomposition
1.The lower operating cost of the digester makes it
commercially viable.
2. Sludge occupies less volume and is easier to dry.
3. Reduce production of landfill gas, which when
damaged leads to an outburst of methane (major
greenhouse gas)
4. Methane produced in the digestor can be used as
biogas, an alternative source of energy.
5. It reduces the energy footprint of conventional
wastewater treatment technology.
6. It has reduced the use of chemical fertilizer as the
digestive (the content of the reactor after completion
of digestion) can be used as fertilizer.

LABORATORY EVALUATION OF
ANAEROBIC TREATMENT
 Conventional digesters are mainly used for the
stabilization of primary and secondary sludge, originating
from sewage treatment, and for the treatment of industrial
effluents with a high concentration of suspended solids.
 They usually consist of covered circular or egg-shaped tanks
of reinforced concrete.
 The bottom walls are usually inclined, so as to favour the
sedimentation and removal of the most concentrated solids.
 The covering of the reactor can be fixed or floating (mobile).
Since conventional digesters are preferably used for the
stabilization of wastes with a high concentration of particulate
material, the hydrolysis of these solids can become the limiting
stage of the anaerobic digestion process.

Depending on the existence of mixing devices
and on the number of stages,
Three main digester configurations have been
applied
• low-rate anaerobic sludge digester
• one-stage high-rate anaerobic sludge
digester
• two-stage high-rate anaerobic sludge
digester

Schematic Representation of A Low
Rate Anaerobic Sludge Digester

Schematic representation of a one
stage high rate anaerobic sludge
digester

Schematic Representation of a Two
Stage High-Rate Anaerobic Sludge
Digester

ADSORPTION
• Adsorption may be defined as the process of
accumulation of any substance giving higher
concentration of molecular species on the surface of
another substance as compared to that in the bulk.
• When a solid surface is exposed to a gas or a liquid
molecules from the gas or the solution phase
accumulate or concentrate at the surface.
• The phenomenon of concentration of
molecules of a gas or liquid at a solid surface
is called adsorption.
• "Adsorption" is a well established and powerfull
technique for treating domestic and industrial effluents.
• In water treatment, the most widely method is
"adsorption" once the surface of activated carbon.

Types of Adsorbents
1.Oxygen-containing compounds are typically
hydrophilic and polar, including materials such
as:
• Silica gel
• Zeolites

Treatment of Waste Water by
Adsorption

Mostly two common carbon
adsorption process such as
(1) Granular Activated Carbon (GAC)
(2) Powdered Activated Carbon
(PAC)

2.Carbon-based compounds are typically
hydrophobic and non-polar, including materials
such as:
✓ Activated carbon
✓ Graphite
3.Polymer-based compounds are polar or non-
polar function groups in a porous polymer
matrix.

Classification of Adsorbents
1. Engineered adsorbents
»(a) Activated carbon
»(b) Polymeric adsorbents
»(c) Oxidic adsorbents
»(d) Synthetic zeolites
2. Natural and low cost absorbents:
» (a) Mineral absorbents
»(b) Agricultural waste/by products
»(c) Industrial waste/ by products

Types of Adsorption
Depending on the type of attractions between
adsorbate and adsorbent, the adsorption can be
divided into two types:
• Physical Adsorption or Physisorption
• Chemical Adsorption Chemisorptions

Physical Adsorption (or) Physisorption
• When the force of attraction
existing between adsorbate and
adsorbent are weak undercoal
force of attraction, the process is
called physical adsorption or
physisorption.

Characteristics of Physisorption
o Energetic and kinetics.
o Effect of temperature.
o Effect of pressure.
o Specificity.
o Nature of adsorbate
o Surface area of adsorbent.

Chemical Adsorption (or)
Chemisorption
• When the force of attraction existing
between adsorbate and adsorbent
are chemical forces of attraction or
chemical bond, the process is called
chemical adsorption or
chemisorption.

Characteristics of Chemisorption
• ✓ Energetic and kinetics.
• ✓ Effect of temperature.
• ✓ High of pressure. High specificity.
• ✓ Surface area.

Factors Influencing Adsorption
Adsorption on a solid is influenced by a number of
factors such as
✓ Surface area.
✓ Nature of adsorbate.
✓ Hydrogen ion concentration (pH) of the solution.
✓ Temperature.
✓ Mixed solutes.
✓ Nature of adsorbate.

Modes of Operation
• ✓ Batch flow system
• ✓ Column flow system.

Types of Adsorption Isotherm
• ✓ Type I Adsorption Isotherm
• ✓ Type II Adsorption Isotherm
• ✓ Type III Adsorption Isotherm
• ✓ Type IV Adsorption Isotherm
• ✓ Type V Adsorption Isotherm

Theory of activated carbon
 Activated carbon, also known as activated charcoal ,
is a form of carbon processed to have small, low-
volume pores that increase the surface area available
for adsorption or chemical reactions.
 It has high degree of microporosity.
 The word 'active' is also sometimes used for 'activated'.
 The surface area may vary greatly depending upon
precusor (raw material) and the condition of
carbonization for making active carbon
 An activation level sufficient for useful application
may be obtained solely from high surface area.
 Chemical treatment has been found to enhance the
adsorption properties of activated carbon.

• AC is usually derived from charcoal.
• When derived from coal, it is referred to as activated coal.
• Activated coke is derived from coke.
• Therefore activated carbon, activated charcoal, activated
coke, active carbon may be said to perform the same
function.
• Chemical or physical activation methods and microwave
radiation methods are the commonly used techniques
adopted for preparation of activated carbon.
• They are used as an adsorbent by the separation and
purification industries.
• They are composed of a micro porous, homogenous
structure with high surface area and show radiation
stability.
• Their adsorption capacity depends on porosity and its
surface chemistry.

Activated Carbon Powder
Granules Pellets

TYPES OF ACTIVATED CARBON
(1) Powdered Activated Carbon (PAC)
(2) Granular Activated Carbon (GAC)
(3) Extruded Activated Carbon (EAC)

Powdered Activated Carbon (PAC)
• Powdered activated carbons generally fall in
the particle size range of 5 to 150 Å, with some
outlying sizes available.
• PAC’s are typically used in liquid-phase
adsorption applications and offer reduced
processing costs and flexibility in operation.

Granular Activated Carbon (GAC)
Granular activated carbons generally range in
particle sizes of 0.2 mm to 5 mm and can be
used in both gas and liquid phase applications.
GACs are popular because they offer clean
handling and tend to last longer than PACs.
Additionally, they offer improved strength
(hardness) and can be regenerated and reused.

Extruded Activated Carbon (EAC)
Extruded activated carbons are a cylindrical
pellet product ranging in size from 1 mm to 5
mm.
Typically used in gas phase reactions, EACs
are a heavy-duty activated carbon as a result of
the extrusion process.

Applications of Activated Carbon (AC)

• Activated carbon is an incredibly diverse material that lends
itself to thousands of applications through its superior
adsorbent capabilities various application of activated carbon
• The availability of high surface area of particles possessed
by AC as well its adsorptive ability makes it a significant
constituent in many industries.
• Industries like; petroleum, fertilizer plants, nuclear,
pharmaceuticals, cosmetics, textiles automobile, and
vacuum manufacturing all uses AC.
• AC has found to be good porous materials, which make it
very effective in adsorption of solutes from aqueous solutions.
• This was suggested to be due to the possession of large
specific surface area.

• Metal recovery
• Food & Beverage
• Medical
• Air Emission purification
• Biogass Purification
• Remediation
• Waste water purification

SLUDGE QUALITY
CONSIDERATIONS
To determining sewage sludge quality it depends
on three following parameters:-
 The presence of pollutants (arsenic,
cadmium, chromium, copper, lead, mercury,
molybdenum, nickel, selenium, and zinc)
 The presence of pathogens (e.g., bacteria,
viruses, parasites)
 The sewage sludge’s attractiveness to
vectors (e.g., rodents, flies, mosquitoes)

STRIPPING OF VOLATILE
ORGANICS
Air Stripping and VOC Removal - Moving air
through contaminated groundwater or surface
water in an above-ground treatment system.
Air stripping removes chemicals called
"volatile organic compounds" or "VOCs.“
 VOCs are chemicals that easily evaporate
which means they can change from a liquid to
a vapor (a gas).

Sources of volatile organic
compounds
•Man made
•Anthropogenic

Man made volatile organic
compounds emissions
• Transportation
• Petroleum and petrochemical industry
• Electrical power generation
• Chemical process industries

Effects of VOC’s
• Photochemical smog
• Health effects
• Global warming
• Odour
• Carcinogenicity

Harmful chemical of VOC’s
• Benzene
• Toluene
• Xylene
• Phenol
• Pyridine
• Chloroform
• Methyl Ethyl Ketone

Flowchart of VOC Removal Technology

NITRIFICATION AND
DENITRIFICATION
• Nitrification is the
conversion of ammonia
(NH3+) to nitrate (NO3-).
• Denitrification is the
conversion of nitrate (NO3-)
to nitrogen gas (N2).

NITRIFICATION AND
DENITRIFICATION
The conversion of ammonia
into nitrites is known as
nitrification.
The conversion of nitrates into
nitrogen is known as
denitrification

NITRIFICATION AND
DENITRIFICATION

Nitrification
 The process of conversion of ammonia or reduced
nitrogen compounds into the easily absorbable form
of nitrogen that is nitrates and nitrites.
 It is an aerobic process.
 Chemoautotrophic bacteria play a major role in this
process.
 First, the ammonia is converted into nitrite by the
process of oxidation.
 Nitrococcus and Nitrosomonas take part in this
process.
 Nitrite is oxidised to nitrate with the help
of Nitrobacter.
 Then, nitrate is taken up by the root of the plant.

Nitrification
Nitrification is a two-step process.
Bacteria known as Nitrosomonas convert
ammonia and ammonium to nitrite.
Next, bacteria called Nitrobacter finish the
conversion of nitrite to nitrate.
Biological nitrification is the process in which
Nitrosomonas bacteria oxidize ammonia to nitrite
and Nitrobacter bacteria oxidize nitrite to nitrate.
This process results in the overall conversion of
ammonia to nitrate.

• Nitrification is temperature sensitive. The
optimum temperature for nitrification is
generally considered to be 30°C.
• Nitrification consumes alkalinity and lowers pH
in the activated sludge mixed liquor.
• pH below 6.5 or above 8.0 can significantly
inhibit nitrification.
• Optimum pH values for denitrification are
between 7.0 and 8.5. Denitrification is an
alkalinity producing process.

Denitrification
The process of conversion of nitrates and
nitrites into the gaseous form of nitrogen is
called denitrification.
It is mostly converted to nitrogen and nitrous
oxide.
Bacteria participating in this reaction
are Pseudomonas and Thiobacillus.

UNIT - V
SLUDGE
TREATMENT
AND
DISPOSAL

INTRODUCTION
• Sludge is an odious, semisolid residual that resembles
thick soft mud produced from the solid–liquid
separation processes in wastewater treatment.
• It is usually very inconsistent in its composition and
most often unmanageable.
• The final destination of treated sewage sludge usually
is the land.
• Dewatered sludge can be buried underground in a
sanitary landfill.
• It also may be spread on agricultural land in order to
make use of its value as a soil conditioner and fertilizer.

SLUDGE IS CATEGORIZED INTO THE
FOLLOWING GROUPS
a. Primary sludge
• Primary sludge is generated by the separation
of settleable solids from the raw wastewater
during the primary sedimentation treatment
process.
• The total solids concentration in raw primary
sludge ranges between 5% and 9%, and is
typically 6%.

b. Secondary sludge
• Secondary sludge is the activated waste biomass
resulting from biological treatments.
• Some sewage plants also receive septic tank
solids from household on-site wastewater
treatment systems.
c. Sludge produced in advanced treatment
process
• It may contain viruses, heavy metals,
phosphorous, or nitrogen.

THE OBJECTIVES OF THE SLUDGE TREATMENT
• To decrease moisture content in the
sludge (Volume reduction)
• To remove organic matters
• To destroy microorganisms
• To eliminate toxic materials.

SLUDGE DISPOSAL METHOD
• Sludge from conventional wastewater
treatment plants (WWTP) is derived from
primary, secondary and tertiary treatment
processes.
• Most often, the sludge produced has a
concentration of a few grams per liter, and is
highly biodegradable.
• Each process has a different impact on the
water pollution load.

SLUDGE DISPOSAL METHOD
• Pre-treatment
•

Pre-treatment
• Pre-treatment consists of various physical and
mechanical operations, such as screening,
sieving, blast cleaning, oil separation and fat
extraction.
• Pre-treatment allows the removal of
voluminous items sands and grease.
• The residues from pretreatments are not
considered to be sludge.
• They are disposed of in landfills.

Primary sludge
Primary sludge is produced following primary
treatment.
This step consists of physical or chemical
treatments to remove matter in suspension
(e.g. solids, grease and scum).
The most common physical treatment is
sedimentation.
Sedimentation is the removal of suspended
solids from liquids by gravitational settling.

• Chemical treatments are coagulation and
flocculation.
• Coagulation and flocculation are used to
separate suspended solids when their normal
sedimentation rates are too slow to provide
effective clarification.

Secondary
sludge
• Secondary sludge is generated from the use of
specially provided decomposers to break down
remaining organic materials in wastewater after
primary treatment.
• The active agents in these systems are micro-
organisms, mostly bacteria, which need the
available organic matter to grow.
• There are various techniques such as lagooning,
bacterial beds, activated sludge as well as
filtration or biofiltration processes.

Tertiary sludge
Tertiary sludge is generated when carrying out
tertiary treatment.
It is an additional process to secondary treatment
and is designed to remove remaining unwanted
nutrients (mainly nitrogen and phosphorus)
through high performance bacterial or chemical
processes.
These treatments are necessary when a high level
of depollution is required, for example in
sensitive areas identified in the Member States.

SLUDGE
CHARACTERISTICS
• Wastewater sludge type is solid, semi-
solid, or muddy liquid where each of
those consists of the various organic or
non-organic materials, heavy metals,
pesticides, polycyclic aromatic, phenols,
and many other materials.

Screening
• Screening grinders are beneficial for medium-size
plants. Reduced-size solids are returned to raw
sewage or mixed with sewage sludge depending
on grinder location related to the treatment units
It contains both organic and inorganic matter.
Grit
• Final grit disposal is by burial. It may be in either
a sanitary landfill or other accepted landfill
operation. The grit must be having a minimum of
6 inches (15 cm) of soil covering. This is to
prevent vector attraction and odors It involves
organic and inorganic matter, especially fats and
grease.

Characteristics of Primary and
Secondary Sludge

ANAEROBIC AND AEROBIC
DIGESTION
 Anaerobic digestion is a common method of readying
sludge solids for final disposal.
 All solids settled out in primary, secondary or other
basins are pumped to an enclosed air tight digester,
where they decompose in an anaerobic environment.
 The rate of their decomposition depends primarily on
proper seeding, ph, character of the solids, temperature
etc. digestion serves the dual purpose of rendering the
sludge solids readily drainable and converting a portion
of the organic matter to gaseous end products.
 It may reduce the volume of sludge by as much as 50%
organic matter reduction. After digestion, the sludge is
dried and /or burned or used for fertilizer or landfill.

The following factors are measures of the
effectiveness of digestive action
• Gas production,
• Solids balance,
• B.O.D,
• Acidity and ph,
• Sludge characteristics and odors.

Aerobic sludge treatment
process in waste water

20CE501PE – INDUSTRIAL WASTE MANAGEMENT.ppt

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