The document discusses key terms and processes used in effluent treatment plants (ETPs). It defines terms like pH, BOD, COD, DO and explains their significance. It also summarizes different treatment stages in ETPs like preliminary treatment involving screening and grit removal, primary treatment using equalization, coagulation and flocculation, and biological treatment using activated sludge process. The document provides an overview of the various unit operations and treatment mechanisms involved in ETPs.
2. 2
1) Effluent in Different
processes
2) Basic terms used in waste water
treatment
3) Definition / Impact on
Environment
4) How to Reduce it
Contents
4. Effluent in Processing Unit
4
Desizing
Sizes (starch),
enzymes, waxes
Scouring
NaOH, surfactants,
soaps, fats, waxes
water softeners
FinishingDyeing
Colour, metals, salts,
surfactants, sulphide,
acidity/alkalinity,
formaldehyde , water
softeners
Printing
Urea, solvents,
colour, metals
Bleaching/Mercerisation
H2O2, AOX, organic stabiliser,
NaOH & high pH
Resins, waxes, chlorinated
solvents, spent
solvents, softeners
Let us know the terms used in effluent treatment
5. BASIC TERMS IN ETP
5
pH
• Measure of acidity or alkalinity
MLSS
• Mixed Liquor Suspended solids
MLVSS
• Mixed Liquor Volatile Suspended Solids
6. BASIC TERMS IN ETP
6
DO
• Dissolved Oxygen in water
COD
• Oxygen required to oxidise organic material by
chemical means in waste water
BOD
• Oxygen required to oxidise organic material by
biological means in waste water
7. BASIC TERMS IN ETP
7
Treatability study
• It is a study or test that tells us how the
wastewater might be treated.
Retention Time
• It is a measure at an average length
of time holding the wastewater in a tank.
Grab sample
• It is a sampling method in which a
single sample is taken at a specific time
8. BASIC TERMS IN ETP
8
Composite Sample
• It is a collection of several individual
samples taken at regular intervals over a period
of time, usually 24 hours. & combined testing is
done
Bio Mass
• It is a colony of living Bacteria, which digest
many organic and inorganic substances. An
essential part of the ecosystem including within
human beings
9. BASIC TERMS IN ETP
9
Activated Sludge
• Sludge that has undergone flocculation forming a
bacterial culture typically carried out in tanks.
Can be extended with aeration.
Clarifier
• A section of ETP equipment used to "clarify" the
wastewater, It is a holding tank that allows
settling. Used when solids have a specific gravity
greater than 1.00
10. BASIC TERMS IN ETP
10
Anaerobic Digester
• The breaking down of organic material and other
waste biologically by microorganisms in absence
of Oxygen. Results in by-products such as
methane gas, carbon dioxide, sludge solids and
water
Grit Chamber
• Usually in ETP, a chamber or tank in which
primary influent is slowed down so heavy
typically inorganic solids can drop out, such as
metals and plastics.
11. BASIC TERMS IN ETP
11
Flocculation
• The process whereby a chemical or other
substance is added to wastewater to trap or
attract the particulate suspended solids into
clusters -woolly looking mass
Sludge
• The solid waste material which settles out in the
wastewater treatment process, sometimes
biosolids. Can be dewatered and reused or
disposed.
12. pH
12
In chemistry, pH is the measure of acidity or alkalinity of
an aqueous solution.
The pH is equal to − log10 C, where c is the hydrogen ion
concentration in moles/ltr.
Solutions with pH less than 7 are acidic whereas above 7
are alkaline. pH of 7 is termed as neutral.
13. Impact of pH value
13
Affects the aquatic life if the pH is not in 6-9 range.
The bacteria involved in biological treatment will
not perform effectively outside 6-9 pH range.
When pH is not neutral it increases the
consumption of chemicals for coagulation and
flocculation.
14. How To Control pH value
14
Maintain pH as desired by dosing acid/alkali
Use Dilute Sulphuric Acid if the pH is alkaline
Use Lime if the pH is acidic.
15. TDS - Total Dissolved Solids
15
In textiles,
generally common
salt increases TDS
of water and
harmful to aquatic
life.
It also affects the
fertility of soil.
Fertile
land
Non
Fertile
land
16. Mixed Liquor Suspended Solids (MLSS)
16
Mixed liquor is a combination of raw or unsettled
wastewater or pre-settled wastewater and activated
sludge within an aeration tank.
Mixed liquor suspended solids (MLSS) is the
concentration of suspended solids, in an aeration
tank during the activated sludge process, which
occurs during the treatment of waste water. ...
17. MLSS - Mixed Liquor Suspended Solids
17
• The activity of bio mass
is measured by MLSS &
should be maintained
approximate 30% by
volume.
18. How to maintain MLSS
18
MLSS should be maintained in 30% range.
MLSS > 30% : Reduce and Dispose the sludge.
MLSS < 30% : Grow biomass, feed concentrated active
mass from Secondary Clarifier
Frequency of the test analysis : Once in a Day.
MLSS can depend upon effluent quality, Health of Bio-
mass & Retention time.
Take liquor, filter & dry at 105 °C & find Suspended
solids
19. Mixed Liquor Volatile Suspended Solids
(MLVSS)
19
MLVSS is generally defined as the microbiological
suspension in the aeration tank of an activated-
sludge biological wastewater treatment plant.
The biomass solids in a biological waste water
reactor are usually indicated as total suspended
solids (TSS) and volatile (at 550°C for 30 min.)
suspended solids (VSS).
MLSS is used to indicate the concentration of
suspended solids in activated sludge. MLVSS
represents the concentration of biomass in activated
sludge.
20. MLVSS
20
MLVSS should be maintained between 60% to 70%
of MLSS
Frequency of the test analysis : Once in a Day
21. Chemical Oxygen Demand (COD)
21
Definition
Chemical oxygen demand (COD) is a measure of
the capacity of sample to consume oxygen during
the decomposition of organic matter and the
oxidation of inorganic chemicals.
22. Impact of COD
22
Higher COD values affect land fertility.
Higher COD level will reduce DO levels.
Which affects the aquatic life.
Higher COD gives higher TDS
Sunlight cannot reach the below levels of sea water which
affects the aquatic plants.
23. COD : Chemical Oxygen Demand
23
Organic pollutant
Inorganic pollutant
Reducing chemicals
Definition:- Amount of oxygen needed to oxidize organic
and inorganic materials in a waste water effluent
mg/L
24. How to reduce COD
24
Optimisation of Process.
Recover and reuse of the chemical.
Coagulation and flocculation process.
Biological treatment.
Tertiary treatment.
25. Biochemical Oxygen Demand (BOD)
25
Definition:
• Biochemical oxygen demand (BOD) is a measure of
the amount of oxygen that bacteria will consume for
decomposition of organic material and oxidation of
inorganic material under aerobic conditions.
26. BOD - Biological Oxygen Demand
26
Organic pollutant
Inorganic pollutant
Microbes
Definition:- Amount of dissolved oxygen needed by
bacteria in ETP to break down organic material
present in the Effluent
If BOD level in effluent is not controlled, the rate of Oxygen
consumption > Oxygen replenishment from the atmosphere, thus
affecting the marine species in the water-body where the
effluent is discharged.
27. How to control BOD
27
Use Biodegradable chemicals in the process
If Non-Biodegradable
Reduce, Recover & Reuse
Focus on Primary Treatment To reduce Load
Advanced Oxidation/H2O2 Oxidation
Biological treatment
28. Dissolved Oxygen (DO)
28
It is the amount of oxygen
present in water.
DO is measured in ppm
DO levels can be increased
by surface aerators or
diffusion technique.
Desired DO levels for fish to
remain healthy & alive is >3
ppm
29. Impact of DO on Aquatic Life
29
Desired DO levels for fish to remain healthy & alive is
>3 ppm
When BOD levels are high, dissolved oxygen (DO)
levels decrease because the bacteria are consuming
the oxygen that is available in the water. Since less
dissolved oxygen is available in the water, fish and
other aquatic organisms may not survive.
30. How to maintain DO
30
Maintain BOD level.
Aeration of water.
Maintain the Temperature.
Remove dead bio-mass as Bio-sludge.
31. Treatability Study
31
It is a study or test that tells us how the wastewater might
be treated with some of the following tests:
pH
Colour
Odour
Chemical Oxygen Demand
Biochemical Oxygen Demand
Total Dissolved Solids
Total Suspended Solids
It also gives
The performance of treatment in ETP
Efficiency of dosing
32. Retention time
32
It is a measure at an average length of time holding
the wastewater in a tank.
• Primary Collection tank
• Flash mixing
• Flocculation
• Clarifier
• Aeration tank
33. Grab Sample, Composite Sample
33
It is a sampling method in which a single sample is taken at a
specific time.
It is a collection of several individual samples taken at regular
intervals over a period of time, usually 24 hours. &
combined testing is done
34. Effluent Treatment Plant
34
ETP (Effluent Treatment Plant) is a process design
for treating the industrial waste water for its
reuse or safe disposal to the environment.
Influent: Untreated industrial waste water.
Effluent: Treated industrial waste water.
Sludge: Solid part separated from waste water
by ETP.
36. Parameters for
Dyehouse
Untreated
waste water
Treated
waste water
pH 4.0 to 9.5 6 to 9
Colour Dark, offensive
No Colour,
not offensive
Foam Persistent
No foam or
dissipates
Heavy metals 10 to 15 ppm 0.01 to 1.5 ppm
Suspended solids 200 to 300 ppm 30 To 45 ppm
Total Dissolved Solids 3500 to 6000 ppm 2100 ppm
Chemical Oxygen Demand 900 to 1500 ppm 250 ppm
Biochemical Oxygen Demand 300 to 500 ppm 30 ppm
36
Quality requirements of effluent
36
One must follow the discharge norms as per Consent to operate issued by SPCB
41. 41
Preliminary Treatment
Screening-
Removal of large particles.
Screens- opening with uniform size
Screen element- parallel bars,
rods, grating or wire meshes or
perforated plates
Requires periodic cleaning
Set in channel at 600
•Removal of wastewater constituents such as rags, suspended
and floatable yarns, fibres.
•Removes 20-30% solids
Screening Unit
41
42. 42
Preliminary Treatment
Sedimentation
Use of gravity as settlable solids separate out as a watery sludge.
Flotation
Suitable for low-density solids
Facilitates separation of suspended matter from the waste
liquor and isolation of the sludge
The waste flow is pressurized ( 3 – 5 bar) in the presence of air
The pressurized waste flow is passed into the flotation unit
Minute air bubbles are formed; simultaneously sludge flocs and
suspended matter floats which can be skimmed off.
42
43. Grit Chamber
44
Usually in ETP, a chamber or tank in which primary influent
is slowed down so heavy typically inorganic solids can drop
out, such as metals and plastics.
44. Flocculation
45
The process whereby a chemical or other substance is added
to wastewater to trap or attract the particulate suspended
solids into clusters -woolly looking mass
45. 46
Primary Treatment
Removal of part of suspended solids and organic matters from
wastewater treatment.
Equalization-
Application- Temporary storage of effluent to equalize flow rates,
mass loading of BOD and suspended solids
Advantage- shock loadings are eliminated
Device- Equalization tank
46
46. 47
Primary Treatment
Chemical neutralization-
Removal of excess of acidity or alkalinity using suitable
chemical.
Polyester processing generates acidic effluent
Cotton processing generates alkaline effluent.
pH adjustment –
Alkaline waste water is neutralized with dil. Sulphuric acid
Acidic waste water is neutralized with NaOH and Lime.
Lime is more cheaper than NaOH.
47
47. 48
Coagulation
• A reasonable and economical method of lowering BOD and COD
and of reducing colour.
• The contaminants are in colloidal form having particle size in the
range of 10-7 to 10-9 m.
• The stability of non-gelatinous colloid is primarily due to
electrostatic forces.
• The degree of stability can be determined by measuring zeta
potential.
48
48. 49
Coagulation
Coagulants are used to reduce the zeta potential thereby
facilitate aggregation of particles
Lime, aluminum sulfate, iron(III) chloride are the most popular
coagulants
Aids to coagulant include silica and polyelectrolyte
Concerns:
Coagulation process is time consuming, tests are necessary to
optimize the coagulant concentration
Coagulation process produces large amount of sludge.
Running costs are high
49
49. It uses chemical precipitation to cause separation
The solids in the waste adhere to the coagulant particles and the
resulting bulky gelatinous material, known as floc, can be
removed by direct filtration, sedimentation or flotation.
Coagulation results due to lowering of the zeta potential at the
particle surface to permit closer approach followed by
association of the particles to form larger flocculated
agglomerates.
Lime, either alone or with ferric salts is the most popular
coagulant. It is often able to remove 90% of the colour present.
Flocculation
50
50. 51
Coagulation and Flocculation
Steps-
• Addition of coagulant with flash mixing
•Charge particle come closer to form clump
•Large particles removed by gravity sedimentation
•Device- Flash mixer, Flocculator, Primary Clarifier
51
51. 52
In primary treatment,
Color, colloidal, suspended and settling solids are removed
For getting better results, the reaction time during each process should
be maintained. (This time is known as Retention time)
Reaction of chemicals with effluent - 60 to 90 sec
Flocks generation - 5 to 10 minutes
Retention time in Primary Clarifier : 240 min
During primary treatment,
BOD and COD reduction: 45 to 65 %
Primary Treatment
52
52. Clarifier
53
• A section of ETP to "clarify" the wastewater.
• It is a holding tank, that allows settling & removes
solids from bottom having specific gravity greater
than 1.00 .
• It also removes solids have Specific gravity lesser
than 1.00 from top by scrubber.
• Solids from Top & bottom are transferred to Sludge
tank or recycled back to aeration tank.Conventional Clarifier
Slanting
plate
Clarifier
53. Anaerobic Digester
54
• The breaking down of organic material and other
waste biologically by micro-organisms in absence
of Oxygen.
• Results in by-products such as methane gas,
carbon dioxide, sludge solids and water
55. 56
Secondary Treatment
Removal of biodegradable organic matter and suspended
solids.
Soluble organic matter converted to simple substances by
microorganisms.
Org.C+O2 CO2
Org.H+O2 H2O
Org.N+O2 NO2
-
Org.S+O2 SO2
Org.P+O2 PO4
2-
56
56. 57
Secondary Treatment Important points
Aerobic Treatment-
Oxidative continuous reaction
Reaction depend on,
Microbial population
Oxygen availability
Nutrients
Anaerobic Treatment
Reductive reaction
Absence of oxygen
57
57. 58
Aerated Lagoon
Earthen basin provided with mechanical aerators.
Longer residence time require to achieve same effluent quality.
Microorganisms are more resistant than ASP.
Settling tank and sludge recirculation absent.
Types of Aerated Lagoon
Suspended growth aerated Lagoon- Fully aerobic from top to
bottom
Facultative aerated lagoon- lower part anaerobic, upper part
aerobic
58
59. 60
Attached Growth Processes
Microorganisms attached to inert packing material- biofilm.
Packing material – rock, gravel, plastic and other synthetic
material
Operated as aerobic or anaerobic processes.
Commonly used in Trickling Filter
Rotating Biological Contactor
60
61. Biomass
62
It is a colony of living Bacteria, which digest many organic
and inorganic substances. An essential part of the
ecosystem including within human beings
62. Activated Sludge
63
• Sludge that has undergone flocculation forming a
bacterial culture typically carried out in tanks.
• Can be extended with aeration.
63. 64
Activated Sludge Process
Production of activated mass of microorganisms capable of
stabilizing waste under aerobic condition.
Aerobic condition is achieved by using surface aerators or
diffused aeration system
64
64. Sludge
65
• The solid waste material which settles out in the wastewater
treatment process,
• Sometimes bio-solids can be dewatered and reused or
disposed.
• These solid waste may contain hazardous pollutants & may
be harmful. It must be disposed as per regulatory
guidelines .
65. Sludge Treatment and Disposal
66
Sludge filter press
Sludge separated for discharge
Sludge dewateringSludge drying beds
Sludge disposal area
66
67. 68
Anaerobic Lagoon
Suspended growth anaerobic processes
Treatment of high strength organic wastewaters and high quantity
of solids
Employed in textile wastewater treatment.
Degradation of organic matter by anaerobic bacteria, in two
stages, involves
First Stage- nonmethanogenic bacteria- hydrolyze wastes in
short chain organic compounds, organic acids and ammonia
Second Stage- methanogenic bacteria involves conversion of
intermediate products in to methane and carbon dioxide.
68
69. 70
Wastewater enters from bottom and flow upward.
Microorganisms in sludge layer degrade organic compounds.
Methane and CO2 released
Clarified effluent is extracted from top.
Methane gas collected in gas collection dome
Up flow velocity maintained- 0.6 to 0.9m/s
70
70. 71
Oxidation Techniques
Electro chemical Oxidation
PROCESS
Activated carbon UV peroxide / NaOCl
Various
Techniques used
To be selected
depending upon
effluent
characteristics after
secondary treatment
Tertiary treatment
71
71. Adsorption
The adsorption process is used to removes colour and other
soluble organic pollutants from effluent.
The process also removes toxic chemicals such as pesticides,
phenols, cyanides and organic dyes
Dissolved organics are adsorbed on surface as waste water
containing these is made to pass through adsorbent.
Most commonly used adsorbent for treatment is activated
carbon.
72
72. Activated Carbon
It is manufactured from carbonaceous material such as wood,
coal, petroleum products etc.
A char is made by burning the material in the absence of air. The
char is then oxidized at higher temperatures to create a porous
solid mass which has large surface area per unit mass.
The pores need to be large enough for soluble organics
compounds to diffuse in order to reach the abundant surface
area.
Colour removal is effective for non-ionic and cationic dyes
73
73. Limitations of Activated Carbon
Very expensive
For reuse, solvent treatment is necessary which puts heavy
economical burden
Alternate Adsorption Techniques
Clays
Ion-exchange resins
74
75. Chlorination
Use of sodium hypochlorite (NaOCl) for decolorizing waste.
Sodium hypochlorite is a powerful oxidizing agent and will
readily break down most dye molecules to smaller fragments.
If a dye is somewhat resistant to biological degradation, then
pre-treatment with hypochlorite can improve the total
mineralization
Disadvantages:
Disperse dyes are not discolored
Production of hazardous chlorinated organic compounds (AOX)
76
76. Hydrogen peroxide
By itself can be used for de-colorization
Can generate lower COD
Longer reaction times
Works effectively with activator
77
77. Fenton’s Reagent
Hydrogen peroxide, alone, is insufficiently powerful to
decolorize dye waste at a normal temperature and pH.
In acid solution, however, with iron(II) as a catalyst, the
peroxide forms the vigorous hydroxyl radicals and may be used
to decolorize dye wastes.
Fenton’s Reagent Reaction
78
79. Advantages of Fenton’s Reagent
Capable of treating both soluble dyes, such as reactive dyes, and
insoluble dyes, such as vat and disperse dyes
The vigorous oxidation also reduces the COD of the effluent.
Neutralisation of the effluents after treatment causes
precipitation of the iron oxide and hydroxide, which removes any
remaining insoluble dye from the effluent by absorption and/or
flocculation.
Other reagents that can be used are manganese dioxide, ferrous
sulphate, ferric sulphate, ferric chloride or cupric nitrate
80
80. Electrochemical Oxidation
The process involves the use of a sacrificial iron electrode, the
anode dissolving to form ferrous hydroxide.
The typical electrochemical cell consists of two electronically
conducting materials put into an electrolyte solution. When iron
electrodes are used as both the cathode and anode, and
electricity is applied, the following reaction takes place:
At the anode (oxidation):
Fe Fe2+ + 2e–
At the cathode (reduction)
2H2O + 2e– H2 + 2OH–
Suitable for acid dyes and the maximum colour removal takes place
in acidic conditions.
81
84. Principle -
The process of reverse osmosis is based on the ability of certain specific
polymeric membranes, usually cellulose acetate or nylon to pass pure water at
fairly high rates and to reject salts.
Waste water stream is passed at high pressures through the
membrane.
The applied pressures has to be high enough to overcome the osmotic pressure
of the stream, and to provide a pressure driving force for water to flow from the
reject compartment through the membrane into the clear water compartment.
85
85. Working of Reverse Osmosis System
The feed water is pumped through a pre-treatment section
which removes suspended solids and if necessary, ions such as
iron and magnesium which may foul the system.
The feed water is then pressurised and sent through the
reverse osmosis modules.
Clear water permeates through the membrane under the
pressure driving force, emerging at atmospheric pressure.
The pressure of reject stream is reduced by a power recovery,
which helps drive the high pressure pump and then is
discharged.
86
86. Characteristics of Reverse Osmosis
Reverse osmosis can be used as end-of-pipe treatment and
recycling system for effluent.
After primary, secondary and/or tertiary treatment, further
purification by removal of organics and dissolved salts is possible
by use of reverse osmosis.
RO membranes are susceptible to fouling due to organics,
colloids and microorganism.
scale causing constituents like hardness, carbonate. Silica, heavy
metals, oil etc has to be removed from the feed.
As the membranes are sensitive to oxidizing agents like chlorine
or ozone, they should also be absent.
87
87. Tertiary Treatment
88
Process Examples of removal
Microfiltration Bacteria, pigments , oils etc.
Ultrafiltration Colloids, virus, protein etc.
Nano-filtration Dyes, pesticides, divalent ions etc.
Reverse Osmosis Salts and ions
Nano-filtration
Reverse Osmosis
Microfiltration
Ultrafiltration
88. ETP Management
89
• How to monitor compliance,
• Sampling
• Testing requirements & frequency
• In-house monitoring daily checkpoints
• Formats for maintaining data.
89. Daily Monitoring of ETP
90
• The pH at flocculation tank should
be maintained between 8.5 to 9.5
as maximum flocculation takes
place at pH 9
• The optimum biological activity of
the microorganisms for the
treatment process is in the pH
range from 6.0 to 8.0.
pH of aeration and
flocculation tank
pH-meter
90. Daily Monitoring of ETP
91
Test helps to
decide the recipe
of coagulating
agents in primary
settling tank
Gives an
indication of how
settling occurs in
the clarifier
Settleability test
Test
Collect 1 liter
effluent from
Equalization tank
Dose required Alum,
lime, FeSO4 & PAC
Check Flocculation
time & volume of
sludge
Confirm the
required daily
dosage
Checkpoints
o Quantity of
clear water
o Settling time
o Volume of
sludge
91. Testing Frequency for plant operator
92
pH
Colour
Temperature
Once in Shift
TDS
BOD
COD
Once in a Day
Heavy metals
Toxic
substances
Random
check
Based on the parameters mentioned in the
‘Consent to Operate’
the testing requirements will vary from industry
to industry
Reporting system
Daily volume of effluent generated & discharged
Daily Power consumption in ETP
Daily chemical consumption
Daily test reports of effluent discharged
Daily volume of recycling of effluent
Weekly once “treatability study”
Record of random testing reports for heavy metals
& other parameters
92. Sampling & Testing
How do we know the characteristics of the waste
water?
93
sampling and further
testing
93. Sampling Methods
94
Water samples collected at
equal time intervals.
All the collected samples are
then mixed.
The representative sample is
known as composite sample.
Water samples collected at a
specific location, where
sample composition remains
constant over long period.
Grab Sampling Composite sampling
94. Systematic way of sampling
Parameters
Volume
Required
(ml)
Preserving
Method
Type of
Container
Temperature 100
On site
Plastic or
Glass
pH 25
Colour 500
Cool to 4 0C
TSS 50
Metals
100 per
metal pH <2 with
nitric acid
Mercury 500
BOD 1000 Chill to near freezing
Glass
COD 50
pH 2 with sulphuric
acid, maintain at 4 0C
95
98. Sustainable Development
Take care of mother
earth with social
responsibility and
environmental
protection.
This is our contribution to
a better future for us
and for coming
generations
It simply means: Give back what you take!
99