Introduction of Effluent Treatment Plant

EFFLUENT TREATMNT PLANT
(ETP)
Prepared by:
Akash Tikhe
January, 2015

Concept of ETP
Effluent treatment Plant covers the mechanisms and processes used to
treat such waters that have been contaminated in some way by
anthropogenic industrial or commercial activities prior to its release into
the environment or its re-use.
This effluent contains several pollutants, which can be removed with the
help of an effluent treatment plant.
ETP treat water and make free from all objectionable impurities present
in suspension, colloidal or dissolved form.

Why do weneed to treat Effluent?
To prevent groundwater pollution
To prevent sea shore
To prevent soil
To prevent marine life
Protection of public health
To reuse the treated effluent
For agriculture
For groundwater recharge
For industrial recycle
Solving social problems caused by the accumulation of wastewater

Needof ETP in Industry
Manufacturers face strict regulations on discharge and waste. Non-
compliance can lead to expensive fees and operations interference.
A wastewater treatment help them to:
Stay in compliance
Reduce transportation and off-site treatment costs
Reduce supply costs by recovering production materials out of the
waste-stream for re-use
Eliminate municipal fees
Eliminate unnecessary water usage during processing

MajorTreatment units in ETP
Preliminary Treatment
Screens
Detritor/scrapers
Grit Chamber
Skimming Tanks
Aeration
Primary Treatment
Sedimentation/ Settling tank
Clarifloculator
Equalization Tank
Neutralization Tank
Secondary Treatment
Activated Sludge Process (ASP)
Trickling Filter
Aerated Lagoons
UASB
Multiple Evaporator (ME) Plant
Rotating Biological Contactors (RBC)
Tertiary Treatment
Sand/ Membrane Filters
Activated Carbon Filters
Disinfection
Ion-exchange/ESP
Nutrient Removal

PreliminaryTreatment
Preliminary treatment removes gross solids and materials that can be
easily collected from the effluent and can damage or clog the pumps and
skimmers of primary treatment clarifiers.
These are in-organic materials and insoluble organic pollutants (i.e. large
floating and suspended solid matter, grit, oil & grease) which are inert and
cause problems to further chemical and biological treatments.
The presence and sequence of preliminary treatment units are totally
depend upon the characteristic of effluent that is to be treated.
All preliminary treatment consist of physical separation techniques by
controlling flow rate of effluent.

PreliminaryTreatment- Screens
Screens are used for removal of large floating and sub-merged material
such as plastic, paper pieces, rubber, etc. from effluent.
Major objectives are:
They prevent clogging in pump, pipes and valves, etc.
Prevent to interfere large material in primary and secondary treatment
units.
Screens are classified in number of ways as follows:
Based on the size of opening- such as coarse, medium and fine screens.
Depending upon shape- such as disc, drum, band, etc.
Based on method of cleaning- such as mechanical or manual.

Mechanical medium screen Fine screen
Corse bar screen

PreliminaryTreatment- Detritors/ Scrappers
Detritors are shallow circular ponds used in pre-treatment plants with the
purpose of grit removal.
Chain or blade type Detritors/scrappers are utilised in an adjacent
channel into which the collected grit is transferred.
Used when the soft and sticky substance, sticks on fixed bars and can not
get through the screen. Grits with a 6 m diameter are removed in the
detritor.

Detritor/ Scrapper
Detritor/ Scrapper

PreliminaryTreatment- Grit chamber
 Grit Chamber is used for removal of inert inorganic material consist of
sand, ash, cinder, silt, clay, glass pieces, etc.
 It provides safeguard against ant damage to pumps, pipes and other
equipments by avoiding settling in pipe bends and channels.
 The eliminated material is collected from chamber and used for land-
filling, road making and on sludge drying beds.
Major objectives :
Protection of pumps, valves, piping, etc.
Minimizing chances of pipe chocking with in-organic inert material.
Preventing grit from occupying volume in primary and biological treatment
units.

PreliminaryTreatment- Skimmingtank
 Skimming Tank is used for removal of oil and grease consist of fats, waxes,
fatty acids, soaps, mineral oils, etc. present in emulsified condition in
effluent.
 These materials have low solubility in water, therefore not readily
available for biological treatment and often accumulate on surface in form
of scum causing foul odors.
 The efficiency can be improve by aeration, chlorination or vacuum
floatation.
Objectives:
Removal of scum (oil & grease) which can otherwise create problem in
biological treatment units.
Increases DO content and remove undesirable gases.
Enhances flocculation of suspended particles.

Skimming Tank with separated oil & grease at top
Collection of separated oil & grease at edge

PrimaryTreatment
Primary treatment consists of temporarily holding the sewage in a inert
basin where heavy solids can settle to the bottom while oil, grease and
lighter solids float to the surface.
The settled material go for sludge treatment and floating materials are
skimmed off. The remaining liquid is passed to secondary treatment.
Tanks are usually equipped with mechanically driven scrapers that
continually drive the collected sludge towards a hopper in the base of the
tank where it is pumped to sludge treatment facilities.
Primary treatment can be either only physical or can be combined with
chemical methods depending upon the effluent characteristics.
At this stage, over 70% of the suspended solids and 40% of the BOD is
removed from effluent.

SedimentationTank (Clarifier)
 Sedimentation Tank are designed to remove suspended particles that are
heavier than water through gravitational force by reducing water velocity.
 So it’s a solid liquid separation process in which a suspension is separated into
two phases –
1. Clarified supernatant leaving the top of the sedimentation tank(underflow).
2. Concentrated sludge leaving the bottom of the sedimentation tank(overflow).
 An efficient sedimentation tank can remove about 90% of SS and 40% organic
matter with two hour of detention time.
Objectives:
To remove coarse dispersed phase.
To remove coagulated and flocculated impurities.
To remove precipitated impurities after chemical treatment.
To settle the sludge (biomass) after activated sludge process / tricking filters.

SedimentationTank (Clarifier)
Factors affecting sedimentation
Characteristics of solid particles- size, shape, specific gravity, concentration,
etc.
Characteristics of liquid- temp., viscosity, specific gravity, etc.
Physical characteristics of clarifiers- detention period, shape and depth of
basins, flow rate, etc.
Types of Sedimentation Tanks:
According to shape- Rectangular tank, circular tank
According to direction of flow- Longitudinal and radial flow, vertical flow.
According to nature of working- Fill and draw, Continuous flow
According to method of sludge collection- flat bottom tank with or without
scrapper, hopper bottom tank.
The most common are horizontal flow sedimentation tank and center-feed
circular clarifiers.

Circular Primary Settling Tank Rectangular Settling Tank
Working of Settling Tank

Clarifloculator
Clarifloculator consist of coagulation (chemical) and flocculation
(mechanical) process.
Employed when finely divided SS and colloidal particles nan not be
efficiently removed by simple sedimentation. In such cases chemical
assistance is taken.
The chemical used for coagulation are called coagulants.
The most common coagulants are Alum, hydrated lime, ferric chloride,
ferrous sulfate and PAC (Poly aluminum Chloride).

Coagulation, Flocculation
Coagulation
Coagulation is the conversion of finely dispersed colloids into a small floc
with the addition of coagulates.
Coagulation can either be followed by the process of settling or flotation.
Flocculation
The purpose of flocculation is to bring coagulated particles together by
mechanically inducing a velocity gradient within a liquid.
Organic polyelectrolyte flocculation aids are effective in promoting soluble
solids removal.
Flocculation improves the removal of finely divided solids by gravity
settling.

Clarifloculator
Clarifloculator

EqualizationTank
Some industries produce different types of wastes, having different
characteristics at different intervals of time.
Hence, equalization tank is used to mixed different type of effluent
thoroughly to produce homogenous and equalized effluent for uniform
treatment.
This are large holding tanks with aeration or mechanical agitation with
paddles manually to give better mixing of the different unit volumes of
effluents.
The effluent is hold and mixed for specified period of time.

Equalization by Surface Motors
Different Inlet in Equalization Tank

NeutralizationTank
Neutralization tank is used to provide treatment to highly acidic or
highly alkaline effluent trough neutralizing pH by addition of chemicals.
Industry require neutralization of discharged effluent when it has as
highly acidic and/or highly alkaline effluent.
Acidic effluent is usually treated with lime stone or lime-slurry or caustic
soda, depending upon the type and quantity of effluent.
Alkaline effluent is neutralized by sulphuric acid or CO2 or waste boiler
flue gas.

Secondarytreatment
Secondary treatment is a biological treatment of effluent which is typically
performed by indigenous, water-borne micro-organisms in a managed
habitat.
Secondary treatment removes dissolved and suspended organic (bio-
degradable) matter by consuming it as a food and convert it into new cell
mass, energy and CO2.
The most common micro-organisms are bacteria (aerobic or anaerobic),
protozoa and rotifers; least common are fungi and algae.
After secondary treatment almost 70-90% of BOD and 80-90% of
dissolved solids are removed from effluent.

TricklingFilter
In trickling filter treatment, wastewater is sprayed through sprinkling
rotating arm on circular beds consist of 3-10 ft deep coarse media (of
crushed stones, gravels or synthetic material).
Microorganisms get attach and grows on the media and results in
formation of film of micro-organisms called zoogloeal film.
This zoogloeal film consist of millions of micro-organisms breakdowns
organic material of effluent into simple and soluble matter. Treated
effluent is drain at bottom from where it is collected then undergoes for
sedimentation(SST).
It is simple to operate and give almost 80-90% of BOD removal with high
quality effluent.

Trickling Filter with rotating arm
Working of Trickling Filter
Media bed of gravels and stones

Activated Sludge Process(ASP)
This is most versatile biological oxidation method employed for the
treatment of effluent containing of dissolved solids, coarse and colloidal
organic matter.
In this method, effluent is aerated in a reaction tank consist of microbial
population in suspension form. Aerobic bacteria degrades effluent into CO2
and H2O for which oxygen is supplied through mechanical aeration or by
diffused aeration system.
The bacterial flora grows and remains suspended in the form of a floc called
activated sludge. A part of sludge is recycled for the same tank to provide an
effective microbial population for a fresh treatment cycle.
Industrial ww require 6 to 24 hours of aeration though which almost 90-
95% of BOD can be removed.

ASP combined with filtration
Aeration Tank in ASP

UP-flowAnaerobic Sludge Blanket Reactor(UASB)
UASB system is a three phase settler which separates sludge, liquid and
biogas in same tank under high turbulence without occupying large space.
Organic matter is degraded under anaerobic conditions by microbes
producing methane and CO2.
More effective than conventional aerobic process, produces only 5-10% of
sludge. Hence, more popular in anaerobic treatment methods.

Raw effluent is introduce from bottom of the reactor flow upward
through a sludge blanket composed of biologically formed granules or
particles. Treatment occurs as the waste comes in contact with this
granules.
Treated effluent rises to the top along with generated biogas in form of
small bubbles. Treated effluent is collected though overflow weirs and
biogas is collected through a gas collection domes from top.
The separated solids falls back through the baffle system on top which
allow to settle down SS in the sludge blanket.
UP-flowAnaerobic Sludge Blanket Reactor(UASB)

UASB working Mechanism
UASB Tank with gas holder doom

Tertiary Treatment
Tertiary treatment is the final treatment, meant for ‘polishing’ the effluent
and removal of pollutants not removed in primary and secondary
treatment.
These pollutants may include soluble inorganic compounds such as
phosphorous or nitrogen which may support algal growth in receiving
waters.
Also removes organic materials contributing BOD, COD, color, taste, odor;
bacteria, viruses, colloidal solids contributing turbidity; or soluble
minerals which may interfere with subsequent re-use of the wastewater.
Preferred when treated water is need to be reuse or discharge is into a
highly sensitive or fragile ecosystem (estuaries, low-flow rivers, coral
reefs, etc).

Tertiary Treatment
Tertiary treatment add additional cost to the treatment process but
produce high quality effluent which can be reuse further for commercial
and industrial applications.
Treated water can be reuse for the irrigation of a golf course, green way
or park, construction work, industrial process, etc. If it is sufficiently
clean, it can also be used for groundwater recharge.
Treated water is sometimes disinfected chemically or physically
depending upon the discharging location.

Filtration
Filtration is process of removing particulates and bacterial impurities that
could not be removed in earlier treatment, from water by passing it through
a porous medium.
It is used to remove colloidal and other impurities which impart turbidity to
water. Also for disinfection of water by reducing 90% of bacterial load.
It is also used to reduce odor and color by arresting them in filter media.
There are various type of filter available to treat certain type of wastewater.
Selection is totally depend upon characteristics of ww, efficiency of
absorbent, flow rate and pollutant to be removed from ww.

Sand Filters
Based on Filtration
Rate
Pressure
Filters
Gravity
Filters
Rapid Sand
Filter
Slow Sand
Filter
Based on Filter
media Material
Based on Depth of
Filter media
Types of Filters
Anthracite
Filters
Metal Fabric
Filters
Diatomaceous
Earth Filters
Deep Granular
Filters
Pre-coat
Filters

ActivatedCarbonFilters
ACF consist of activated carbon granules supported by very fine quartz
filter media. Various grades of carbon are available for specialized
treatment of wastewater.
ACF are used to remove free chlorine, organic residues, toxic heavy
metal ions and color from ww.
Most common adsorbents used are activated carbon, peat moss, brown
coal and other cellulose materials.
This treatment not only improves taste of water but also protects other
water treatment units such as reverse osmosis membranes and ion
exchange resins from possible damage due to oxidation or organic
fouling.

Different media used for ACF
ACF Tubes or channels

Ion-exchange
This treatment is used for removal of toxic materials and recovery of
valuable materials from effluent.
Ion-exchange is only economical when recovered material is reused. So
not economical when objective is only removal of pollutants.
Majorly used for recovery of Cr, Ni, Phosphate and H2SO4, Cu, Pb, Hg and
removal of cyanides from wastewater after Cr recovery.

Introduction of Effluent Treatment Plant

ETP Plant with Advance Treatment

ReferenceBooks
1) Vivek N. Upasani (2008) Applied and Environmental Microbiology, Nirav
Prakashan.
2) Millind R. Gidde, Ravi k. Lad (2010) Environmental Engineering, eighth
edition, Nirali Prakashan.

Air & Water, the two
essential elements on
which all life depends,
have becomes global
garbage cans now.

Introduction of Effluent Treatment Plant

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