Water treatment

Introduction
WaterTreatment
It is the process of removing contaminants from wastewater, including household sewage. It includes
physical, chemical, and biological processes to remove physical, chemical and biological contaminants.
Its objective is to produce an environmentally safe fluid waste stream and a solid waste (or treated sludge)
suitable for disposal or reuse (usually as farm fertilizer) with suitable technology,
Sewage can be treated close to where the sewage is created, a decentralized system (in septic tanks,
bio-filters or aerobic treatment systems), or be collected and transported by a network of pipes and
pumping stations to a municipal treatment plant, a centralized system. Sewage collection and treatment is
typically subject to local, state and federal regulations and standards. Industrial sources of sewage often
require specialized treatment processes.
Discharge of untreated sewage from urban centers is a major cause of river water quality
degradation. Since local authorities are not able to cope with the problem due to paucity of resources,
Govt. of India came forward and launched a program for cleaning the river Ganga, called Ganga Action
Plan.
We understand the fact that there is dearth of pure water on earth and considering the rapid pace at
which the existent reserves are being consumed, it raises an alarming situation for coming generations.
Realizing this indispensable need of pure and clean water, we offer you impeccable total water
management system and solution.
Nature of water :
Water (H2O) is a polar inorganic compound that is at room
temperature a tasteless and odorless liquid, nearly colorless with a hint of blue. This
simplest hydrogen chalcogenide is by far the most studied chemical compound and is described
as the "universal solvent" for its ability to dissolve many substances.[14][15]
This allows it to be the
"solvent of life".[16]
It is the only common substance to exist as a solid, liquid,
and gas in nature.[17]
Water molecules form hydrogen bonds with each other and are strongly polar. This polarity
allows it to separate ions in salts and strongly bond to other polar substances such as alcohols
and acids, thus dissolving them. Its hydrogen bonding causes its many unique properties, such
as having a solid form less dense than its liquid form, a relatively high boiling point of 100 °C for
its molar mass, and a high heat capacity.
Water is amphoteric, meaning it is both an acid and a base—it produces H+
and OH−
ions by self ionization. This regulates the concentrations of H+
and OH−
ions in water.

Plant capacity : 36 MLD
Type of : Effiwent of 30 mld UASB plant
Source : Collection well
Diamension : 21 . 10 . 3.5 m S.W.D
Type of water : Tennery wastewater
Flash mixing Tank : Flash mixing with the help of Flash mixer
Diamension : 3 . 3 . 3.5 m SWD
Clariflocculator : 34.6 . 2 m SWD . 2 nos
Slduge thickner : 24m . 3 SWD

Process Discription
Screenand grit chamber:
Influenttotreatmentplantscontainspiecesof wood, rags,plasticsandotherdebris.Sand,eggshellsand
othercoarse inorganicmaterial ispresentinthe flow inadditiontoorganicmatterfromhousehold,
industrial,commercial andinstitutional wateruse.Preliminarytreatmentprovidesforthe removal of
large debrisandheavyinorganicmaterial containedinthe wastewaterflow bypassingthroughscreen
and grits.

EqualisationTank :
The main functionof equalizationtankistoact as buffer.Tocollectthe incomingraw effluentthat
comesat widelyfluctuatingratesandpositiontothe restof the ETP at steady( Average ) flow rate.
Duringthe peakhours ETP comesat highflow rate. The equalizationtankstoresthiseffluentandletsit
out during the non peaktime whenthere isno/little incomingeffluent.

MIXING TANK :
It mixesthe discharge comingfromindustryandhouseholds.

UASB REACTOR :
The upflowanaerobicsludge blanketreactor(UASB) isasingle tankprocessinan anaerobiccentralised
or decentralisedindustrial wastewaterorblackwatertreatmentsystemachievinghighremoval of
organicpollutants.Wastewaterentersthe reactorfromthe bottom, andflowsupward.A suspended
sludge blanketfiltersandtreatsthe wastewaterasthe wastewaterflowsthroughit.
Bacterialivinginthe sludge breakdownorganicmatterbyanaerobicdigestion,transformingit
intobiogas. Solidsare alsoretainedbya filtrationeffectof the blanket.The upflow regime and
the motionof the gas bubblesallow mixingwithoutmechanical assistance.Bafflesatthe topof
the reactor allowgasestoescape and preventanoutflow of the sludge blanket.Asall aerobic
treatments,UASBrequire apost-treatmenttoremove pathogens,butdue toa low removal of
nutrients,the effluentwateraswell asthe stabilisedsludgecanbe usedinagriculture.

Treatment Process:
UASB Reactorsare constructedout of concrete or anotherwatertightmaterial andcanbe designedina
circularor rectangularway.Wastewaterispumpedfromthe bottomintothe reactorwhere influent
suspendedsolidsandbacterial activityandgrowthleadtothe formationof sludge.The sludge blanketis
comprisedof microbial granules(1to3 mmin diameter),i.e.,small agglomerationsof microorganisms
that, because of theirweight,resistbeingwashedoutinthe upflow.The microorganismsinthe sludge
layerdegrade organiccompounds.As aresult,gases(methane andcarbondioxide i.e.biogas) are
released.The risingbubblesmix the sludge withoutthe assistance of anymechanical parts
Upstream velocity and settling speed of the sludge is in equilibrium and forms a locally rather stable, but
suspended sludge blanket (SASSE 1998)Sloped walls deflect material that reaches the top of the tank
downwards. The clarified effluent is extracted from the top of the tank in an area above the sloped
walls. A gas-liquid-solids separator (GLSS) separates the gas from the treated wastewater and the sludge
(ROSE 1997, SANIMAS 2005).After several weeks of use, larger granules of sludge form which, in turn,
act as filters for smaller particles as the effluent rises through the cushion of sludge. Because of the
upflow regime, granule-forming organisms are preferentially accumulated as the others are washed out.
Fortunately, these bacteria are also more efficient for biogas production than flocculated biomass
(WENDLAND2008).

Collectionwell:
Collectionwell are usedtoholdwaste material thathasbeentreatedinaseptictank.

Preaeriationtank
Aeration is used in water treatment as a pretreatment in the process of removing
iron and hydrogen sulfide from water. Air is a powerful oxidizer of both iron and
hydrogen sulfide. It quickly converts unfilterable ferrous iron to filterable ferric iron,
and it reduces hydrogen sulfide to elemental sulphur, which is easily removed from
water by a filter.

Clariflocculator:
Clariflocculatorisa combinationof flocculationandclarificationinasingle tank.Ithastwo concentric
tankswhere innertankservesasa flocculationbasinandthe outertankservesasa clarifier.
As heavyparticlessettle tothe bottom,the liquidflowsradiallyupwordinthe clarifierzone

Sludge Thickener:
Thickeners and clarifiers are both used to separate liquids and solids by settling. Thickeners are
used to concentrate solids, while clarifiers are used to purify liquids.
Daimensions: 24.0 m . 3.0 SWD

Waste Water Treatment Processes :
By definition, process means a series of actions or changes. Treatment facilities incorporate
numerous processes which in combination achieve the desired water quality objectives. These
processes involve the separation, removal and disposal of pollutants present in the wastewater. The
treatment of wastewater is accomplished by four basic methods or techniques; physical, mechanical,
biological and chemical. Physical methods of treatment include the use of tanks and other structures
designed to contain and control the flow of wastewater to promote the removal of contaminants.
Figure: Flow Chart of Water Treatment Plant.
Mechanical treatment techniques involve the use of machines, both simple and complex in design
and operation. The action of bacteria and other micro-organisms are biological methods of treatment,
which play a vital role in the removal of pollutants which cannot be effectively achieved by other
means.
Chemical treatment methods enhance the efficiency of other process Operations and provide
specialized treatment as a result of their addition at various treatment stages.

Preliminary Treatment:
Influent to treatment plants contains pieces of wood, rags, plastics and other debris. Sand, eggshells
and other coarse inorganic material is present in the flow in addition to organic matter from
household, industrial, commercial and institutional water use. Preliminary treatment provides for the
removal of large debris and heavy inorganic material contained in the wastewater flow. One of the
first treatment operations involves screening of the influent Wastewater flow. Mechanical screens
consisting of parallel bars or stepped plates placed at an angle in the path of the wastewater flow are
used to remove this debris. Mechanical rakes clear debris from the bars and these screenings are
washed and compressed to remove excess water and ultimately disposed of by burial in a landfill.
Removal of these materials protects the treatment plant’s piping and downstream equipment from
blockage and/or damage.
Following screening operations the wastewater flow passes into aerated channels designed to slow
the flow velocity to 0.3 meters per second. Here heavy inorganic materials separate from the
wastewater and settle. The settled inorganic material is referred to as grit. Periodically, the settled grit
is removed from the channels, washed and ultimately disposed of by burial in a landfill. Grit is very
abrasive and its removal early in the treatment process reduces wear on pumps and other equipment.
This inorganic material would Otherwise eventually settle in other process areas and take up
Effective treatment volume or capacity.
Primary Treatment:
The wastewater, with large debris and grit removed is directed to primary treatment operations. By
volume wastewater is greater than 99.9 % water and less than 0.1 % solid material in the form of
dissolved, suspended, and settable solids. Although this may seem a very minuscule quantity of
material, if left untreated and discharged serious negative affects would be experienced in the
receiving waters. The separation and removal of a significant portion of this Material is accomplished
during primary treatment.
During the digestion period, typically 15 to 28 days, conditions suitable to maximize the biological
activity of the anaerobic bacteria are maintained. The digester tank contents are heated to maintain a
temperature of 35- 37 degrees Celsius, mixed to provide contact of organic material with bacteria and
prevent the formation of a scum blanket.
Chemical Treatment:
Although primary and secondary treatment operations are efficient in removing most wastewater
pollutants, some pollutants require special forms of treatment for their removal. Phosphorous is one
such pollutant of special concern. Left untreated, phosphorus contained in the final effluent of a
wastewater treatment plant may have a serious negative impact on receiving waters. Phosphorous is
one of the major nutrients associated with the growth of aquatic plants. Sources of phosphorous
include; human waste, detergents Containing phosphate additives and corrosion control chemicals
used in water supplies and industrial discharges. High concentrations of phosphorous in receiving
waters promote excessive growth of algae and aquatic plants which may disrupt the natural
ecological balance of the receiving water. Rapid deterioration of water quality could result in
acceleration of the eutrophicationprocess of the receiving body of the water. Phosphorus removal

methods may be characterized as being either biological or chemical precipitation techniques. The
present practice is the use of a metal salt which reacts with soluble phosphorous to form an insoluble
Precipitate. This precipitate settles with the sludge during settling operations and is thus
removed from the wastewater flow.
The most common metal saltine use is ferrous chloride, also known as “pickled
liquor”. This metal salt solution is a readily available waste by-product of steelmaking
operations.
Dewatering:
Dewatering is a solid handling process operation. Stabilized bios lids from secondary anaerobic
digestion are directed to Dewatering to remove excess water. This operation reduces the volume and
increases the dryness of the solids for further processing. Feed solids typically 1.5 to 2 % on solids
content are processed through mechanical belt filter presses, which yield filter cake typically 18 to
19 % in solids content.
The feed solids are conditioned with a Polymer-coagulating agent and squeezed between woven
mesh filter belts. The excess water removed, termed filtrate, and wash water used to clean the woven
filter belts is directed back into the wastewater flow for treatment.
Composting:
Composting is an aerobic biological process providing for the Decomposition of the organic matter
present in the dewatered cake by bacteria and fungi in the presence of oxygen. The City of Gulp is
the first wastewater facility in Canada to utilize a high rate, totally enclosed in vessel composting
facility. Composting occurs naturally such as decomposition of leaves on a forest floor. This
naturally occurring process can be optimized and accelerated by establishing ideal controlled
conditions in a biomechanical Process system. Temperature, food and oxygen availability is
controlled to provide for optimum composting conditions.
Tertiary Treatment:
Tertiary treatment process operations are incorporated at the City of Guelph waste water treatment
plant. These are necessitated by the sensitivity and assimilative capacity of the Speed River which
receives effluent discharge.
Tertiary treatment or effluent polishing operations practiced are nitrification for the removal of
ammonia nitrogen and sand filtration for the additional removal of suspended solids.
BiochemicalOxygenDemand Concept:
Sewage when ‘fresh’ has a musty odor, a grey color, and contains both organic material and
sufficient dissolved oxygen to support the growth of aerobic bacteria. Aerobic bacteria, as do
humans, need a food supply and a source of free oxygen to survive. The food supply is furnished by
the organic material in sewage, and the free oxygen is available as dissolved oxygen (DO). The DO
is depleted as the aerobic bacteria attack the organic material contained in the sewage. Some of the
DO can also be depleted through chemical action. The sewage will become ‘stale’ and then ‘septic’
as DO is depleted. Septic sewage contains no DO, and all bacterial action will be anaerobic.
The amount of oxygen necessary for the stabilization (decomposition) of organic material in sewage
under aerobic conditions is called BOD. It is an important indication of the amount of organic matter
present in the sewage. The BOD test is a measure of the oxygen requirements of bacteria and other

organisms as they feed upon and cause decomposition of organic matter. A high BOD will result in
water becoming anaerobic (depleted of oxygen). BOD is therefore a measure of the organic load
placed on the treatment facility. Industrial non-organic wastes can also deplete oxygen in the water,
and this is measured by the chemical oxygen demand (COD) test. COD is expressed as the equivalent
amount in oxygen of a strong oxidizing agent consumed by the waste under fixed laboratory
conditions.
The dichromate reflux method is preferred over other methods using other oxidants
such as potassium permanganate because of:
• its superior oxidizing ability.
B. applicability to a wide range of wastes, and
C. ease of use.
In the dichromate reflux method, a predetermined amount of waste is dissolved or dispersed in water
and oxidized by potassium dichromate in a strong sulphuric acid medium with silver sulphate as the
catalyst under reflux for two hours. The residual dichromate is determined by titration with
standardized ferrous ammonium sulphate. In the case of wastes containing chlorine, mercuric
sulphate is added to reduce chloride interference. The result of analysis for COD is expressed in
mg/L (ppm).
BOD is normally expressed in mg/L or parts per million for a specified time and temperature, the
standard being five days at 20ºC. The five-day, 20ºC BOD does not represent the total demand of a
sample for oxygen. Only about two-thirds of the total oxygen demand of a domestic sewage sample
is satisfied in five days at 20ºC, and almost all of the demand in 20 days at 20ºC. It would be very
time consuming to attempt to determine the total demand by incubating samples for 20 or more days.
For this reason the five-day BOD test has been accepted as a practical standard.
The five-day BOD test is used as a control at nearly all sewage treatment facilities. The adequacy and
degree of sewage treatment may be judged by the total reduction that occurs in the five-day BOD of
the sewage as it flows through the sewage treatment facility. Also, standards are established by
various governmental control agencies which set limits on the five-day BOD of treated sewage that
may be legally discharged into a receiving stream. Normally treated sewage effluent should have
suspended solids not exceeding 30 mg/L and a BOD not exceeding 20 mg/L. This standard is often
referred to as the 30:20 standards. Sewage effluent discharged into a river should have a BOD not
exceeding 4 mg/L. This can be achieved by diluting the effluent with clean water prior to discharge.
Most rivers can easily assimilate effluent with a BOD of 4 mg/L without affecting fish and other
aquatic life, so that effluent complying with the 30:20 standard is generally safe.
The general procedure for determining a BOD involves filling two BOD bottles with the water
sample that has had its pH corrected to 7, and any chlorine present neutralized with three drops of a
one per cent solution of sodium thiosulphate. DO is measured in the first bottle at time zero, and in
the second bottle after five days storage in the dark at 20ºC. The difference between the two when
multiplied by the dilution factor gives the BOD in mg/L or 10 ppm. This is the oxygen consumed by
microorganisms in the sample as they digest the organic matter present, over five days at 20ºC. A
rapid BOD can be determined in two and a half days at 37ºC and this has been determined to be
equivalent to the five day test at 20ºC.

Working PLANT:-
MLD= Million Liters Per Day
PST= Primary Settling Tank
FST= Final Settling Tank
Figure- Flow Chart of Water Treatment Processes
Plant receive waste water from the two sources first is tanneries and second is sewage water (civil
waste water or industrial waste water) pumping station.
: The tannery waste water is received separately from the tanneries through a separate collection
system with 4 pumping stations namely:
(a) Chabelepurwa pumping station (PS-1)
(b) Sheetla Bajar pumping station (PS-2)
(c) Wazidapur pumping station (PS-3)
(d) Budiyaghat pumping station (PS-4)
And is pumped through common rising main to tannery inlet of Common Effluent Treatment Plant.
After reaching to tannery inlet, the tannery waste water is:
· Screened using a fine SS Aqua Screen

· Grit separated in longitudinal constant velocity Grit separators
· The screened & grit free waste water is taken to either of the two equalization tanks where the
waste water is mixed using submersible mixers.
· The equalized waste water is transmitted at a controlled rate through intermediate pumping station
to a waste mixing chamber where it is mixed with domestic waste water to achieve the desired
dilution of 1:3.
: The domestic waste water which is pumped through raw sewage pumping station situated in the
campus of combined sewage pumping station at Jajmau enters the treatment plant in the flow control
box and is :-
• Screened using a fine SS Aqua Screen
• Grit separated in longitudinal constant velocity Grit separators.
• The excess pumped domestic waste water over flows and get again discharged to the 90” sewer
line.
• At present alum mixing is not being carried out as alum dozing has no impact on the treated
effluent. In place of it liquid polyelectrolyte is used.
• Filtrate from the sludge drying beds is pumped from the filtrate pump house and is brought to
thickener supernatant pump sump. Sludge produced in the UASB reactor is with12 drawn from eight
different locations of the reactor and at three different levels. The sludge with –drawn from both the
reactors is combined together before it is discharged on to sludge drying beds.
• Similarly post treatment sludge after thickening is dewatered on sludge drying beds.
• The biogas generated from the UASB reactors is brought to gas flaring unit of 130
mld STP and flared up due to non functioning of power generation unit including gas holders, gas
scrubbing system.
• The treated effluent is mixed with treated effluent of 130 mld STP and is used for irrigation by the
farmer
Sludge Management:
a) The lifting and carting of the dried hazardous sludge from the sludge drying beds is done by the
department and is kept in the campus on polythene sheets so that hazardous material could not come
in contact with the soil, otherwise it will penetrate into the soil and spoil it. The provision for the
above has been made in the estimate.

Sewageand Storm Water Pumping
Pumping stations handle sewage/storm-water either for lifting the sewage so as to discharge into
another gravity sewer or for treatment/disposal of the sewage/effluent.
Pumping for drainage is necessary , where gravity drainage is either not feasible as in low-lying
localities and areas close to the sea-shore or gravity drainage is not economical, because of the cost
of excavation, especially if a sewer has to pass across high spots like hillocks between the area to be
drained and the point of discharge.
The availability of land, scope of excavation, the type of equipment to be used and their arrangement,
the structure, its external appearance and general aesthetics are the basic considerations in the design
of pumping stations.
Location:
Proper location of the pumping station requires a comprehensive study of the area to be served, to
ensure that the entire area can be adequately drained. Special consideration has to be given to
undeveloped or developing areas and to be probable future growth, as the location of the pumping
station will often be determined by the future overall development of the area.
The site should be aesthetically satisfactory. The pumping station has to be so located and
constructed that it will not get flooded at any time. The storm-water pumping stations have to be so
located that water may be impounded without creating an undue amount of flooddamage, if the flow
exceeds the pumping station capacity. The station should be easily accessible under all weather
conditions.
Capacity:
The capacity of the station has to be based on present and future sewage flows, considering a design
period of 15 years. The civil structure and pipeline of both the dry sump and the wet well should be
designed for a flow of 30 years hence, the needs of future expansions need special attention ones,
increasing the capacity of the wet well and constructing new pumping stations to cope with the
studied before selecting the size of the pumps for the project to be commissioned, in order to avoid
too infrequent pumping operations and long retention of sewage in wet wells.
Types of Pumping Stations:
Pumping stations traditionally have two wells, the wet well receiving the incoming sewage having
alongside a dry well housing the pumps. Use of wet-pit pumps does not need the dry well. Wet-pit
pumps are installed vertically, either mounting the motor on the floor above the ceiling of the wet
well or using submersible pumps.
When both the wet and dry wells are to be provided, these may be of any of the following type
· Rectangular with dry and wet wells adjacent to each other
· Circular with central dry well and peripheral wet well and,
· Circular with a dividing wall to separate the dry and wet wells.

Structure and Layout of the Pump House:
The site should be adequately protected from flooding. The structure must be designed to withstand
floatation forces. Isolated pumping stations, particularly unmanned should be protected against
vandalism. The site should be aesthetically satisfactory. The dry wells should have a separate
entrance. For easy access to the sub-structure of wet wells, cast iron steps should be provided.
Alternatively, portable aluminum ladders may be used.
Both the dry and the wet wells are generally of R. C. C. constructions shall be followed for their
design and construction. In many parts of the country, especially in the arid western regions, the
ground-water contains very high concentrations of sulphates leached from the soils, which may cause
corrosion. Under these conditions sulphate-resistant cement should be used in the concrete.
Provision of Essential Accessories:
At all sewage pumping stations, flow-measuring devices such as venturimeter shall be provided. The
throat of the venturimeter should be a hard metal so that it would not get abraded fast by the grit and
sand entraining in the flow. The abrasion would give incorrect reading.
Provisions for Functional Requirements
Ventilation:
Since toxic gases emanate from the sewage, it necessary to ensure proper ventilation for hazard-free
working in the stations. Normally 8 to 12 air-changes per hour are recommended to be provided. For
dry wells upto 4 m depth, natural inlet with exhaust fans can be used.If the depth of dry well is more
than 4 m below Ground level and for the wet wells, force inlet and forced outlet may be used. Such
ventilation is mandatory as per the safety regulations for moderate and large sewage pumping
installations.
When the ventilation equipment is of continuous operation type, the minimum capacity shall be 6
turnovers per hour. Ventilation design should provided for the dissipation of the heat generated from
the electric motors, especially during hot weather. Wet wells and screen chambers with mechanical
equipment shall be provided with positive ventilation equipment to provide 12 turnovers per hour, as
the equipment is operated intermittently.
Safety Measures:
Railing shall be provided around all manholes and opening where covers may be left open during
operation and at other places, where there are differences in levels or where there is danger for
people falling. Guards shall be provided on and around all mechanical equipments, where the
operator may come in contact with the belt drivers, gears and rotating shafts or other moving parts of
the equipment. Staircases shall be provided in preferences to ladders particularly for dry well access.
Straight staircases shall be provided as against spiral or circular staircases or steps. The steps to be
provided in the staircase shall be of non-slippery type.
Telephone is an essential feature in a pump-house, as it will enable the operator to maintain contact
with the main office. In case of, injury, fire or equipment difficulty, telephone will provide facility to
obtain proper assistance as rapidly as possible.
Fire-extinguishers, first aid boxes and other safety devices shall be provided at all pumping stations.

A system of colours for pipes shall minimize the possibility of cross-connections.
To prevent leakage of explosive gases, the wet well should not be directly connected by any opening
to the dry well or superstructure. All electrical equipment and wiring should be properly insulated
and grounded and switches and controls should be of non sparking type. All wiring and devices in
hazardous areas should be explosion-proof.
Other Facilities:
All sewage and storm water pumping stations should have potable water supply, wash-room and
toilet facilities and precautions taken to prevent cross connections. Hoisting equipment shall be
provided for handling of equipments and materials which cannot be readily lifted or removed by
manual labour. In large pumping stations, gantries of adequate capacities shall be provided to lift the
pumps, motors and large piping. Fencing shall be provided around the pumping station to prevent
trespassing. The station should be landscaped to make it blend with the surroundings and to add to
the aesthetic effect, particularly when residential areas are in the near vicinity of the station.
Adequate lighting is essential at the plinth and all the working levels of the pumping station. Glares
and shadows shall be avoided in the vicinity of machinery and at floor openings.
Design Considerations for the Dry and Wet Wells
Dry Well:
The size of the dry well should be adequate for the number of pumps planned of such sizes as will
handle the sewage-load at the desire capacity of pumping. Allowance should also be made for future
requirements so that additional or larger pumps can be installed. Provision should be made to
facilitate easy removal of pumps and motors for periodic repairs overhauls or replacements. This
shall be done by providing a gantry of suitable capacity and with suitable travelling type chain and
pulley blocks. A dewatering pump of the non clog type shall be provided for the dry well. For easy
access to the dry wells of the pumping stations, the dry wells should have a separate entrance and
suitable stairways, preferably not less than 90 cm in width shall be provided alongwith 90 cm high
railings, wherever required.
Wet Well:
The size of the wet well is influenced by the storage capacity to be provided. The storage capacity is
required to be designed, especially for all sewage and storm water pumping stations, where automatic
controls and variable speed drives are not provided to match pumping rates exactly with inflow-rates
to the station. The selection of the proper storage capacity is critical because it affects.
· The time for which the liquid will be retained in the pumping station and
· The frequency of operation of the equipment.
The shape of the wet well and the detention time provided shall be such that deposition of solids is
avoided and sewage does not turn septic. The capacity of the wet well is also concerned with the
difference between the highest level of the liquid in the wet well and the minimum level after the
depletion by pumping. This should be such that the pump of minimum duty also would run for atleast
5 minutes. The capacity of the well is to be so kept that with any combination of inflow and
pumping, the cycle in the wet well will not exceed 30 minutes of average flow.

In the wet well, baffles should be provided at required places to ensure uniform flow at each pump-
suction. The wet well flooring should have benching like a hopper with a minimum slope of 1:1 to
avoid deposition of solids. Yet there should be provision for the removal of the accumulated sludge.
Suitable provision for overflow should also be made, where feasible, as a protection against flooding,
especially in the event of the breakdown of the plant on the failure of the powersupply. Wherever
possible, grit removal ahead of pumping should be adopted to increase the life of the pumps. Coarse
screens before the wet wells should have a clear opening of 40 to 50 mm between the bars for the
manually cleaned type and 25 mm for the mechanical type. The screening units shall always be
provided in duplicate. The screens shall confirm to IS:6280.
While positioning of the pump-intakes or wet-pit pumps in the wet well, the following points need to
be taken care of:
Flow approaching the pump-intake should be uniform along the width of the channel. No disturbance
which generates kinetic energy should take place in the proximity of the intake. The mean velocity of
the flow should be low, but not less than 0.7 m/s to prevent depositions of the solids. Benching the
corner fillets should be provided to prevent stagnation of the flow. In order to prevent flow
separation, bell-mouths should be provided at the entrance of the suction pipes. Diameter of the bell
mouth, D should be 1.5 d to 1.8 d, where d is the diameter of the suction pipe.
The clearance of the bell-mouth from the floor should be between 0.5 D to 0.75 D. unsteady flow in
the bell-mouth occurs, if the clearance is less than 0.25 D. If the clearance is too much, the upward
flow component becomes unstable and causes swirling and vortex formation.
The distance of any wall or fillet from the lip of the bell-mouth should be between 0.25 D to 0.5 D.
The proximity of the end and the side walls prevent swirling flow and vortex formation. The width of
the sump should be between 2 D to 3 D.The depth of water above the lip of the bell-mouth should be
greater than 1.5 D. Where multiplate pumps are used, the spacing between the lips of two adjacent
suction bell-mouths should be between 2 to 2.5 D. With splitters, i.e. separation walls between the
suction pipes, their lengths should not be less than 4 D.
Pumps:
The selection of pumps is based on many considerations such as the type of pumps, the size of
pumps, the number of pumps, the capacity of flow-rates of each pump, the range of throttling of each
pump, the head of pumping and others.
Capacity:
The capacity of the pumps shall be adequate to meet the peak rate of flow with 50% standby. To
obtain the least operating cost, the pumping equipment shall be selected to perform efficiently at all
flows, including the peak flow. Two or more pumps are always desirable at sewage pumping stations
shall be so selected that the variations of inflow can be handled by throttling of the delivery valves of
the pumps or by varying the speed of the pump, without starting and stopping the pumps too
frequently or necessitating excessive storage. The capacity of a pump is usually stated in terms of
Dry Weather Flow (DWF), estimated for the pumping station. The general practice is to provide 3
pumps for a small capacity pumping station comprising 1 pump of 1 DWF, 1 of 2 DWF and 3 of 3
DWF capacities. For large capacity pumping station, 5 pumps are usually provided, comprising 2 of
½ DWF, 2 of 1 DWF and 1 of 3 DWF capacity, including standby.

For protection against clogging, the suction and delivery openings of the pumps shall not be less than
100 mm and the pumps shall be capable of passing a ball of at least 5o mm dia.
Pump-Types:
Both the centrifugal type pumps, including the submersible pumps and pneumatic ejectors are used in
sewage and storm water stations. The pneumatic ejectors are not recommended, unless a centrifugal
pump is impractical as may be in small installations. Screw pumps of the single-screw, progressive
cavity helical rotor type also prevent themselves as a worthwhile option and are coming into vogue.
Pumps for sewage and storm water pumping are generally of all cast iron construction. If the sewage
is corrosive then the stainless steel construction may have to be adopted. Also, where the sewage or
storm water would entrain abrasive solids,the pumps in abrasion-resistant material or withelastomers
lining may be used.
Centrifugal Pumps:
These are generally classified as radial flow, mixed flow and axial flow pumps. The classification is
usually based on the specific speed of the pump (ns), which is obtained from the following formula:-
ns = (3.65n√Q)/H^0.75 where,
n = speed of the pump in rpm
Q = flow rate in m3/s
H = head of the pump in m
The specific speed of the pump is akin to a shape number and forms the basis for the design of the
impeller of a centrifugal pump. The shape of the impeller is identifiable by the relative proportions of
the inlet size, outlet width and the outside diameter. Broader inlet size and outlet width are logical for
larger flows. For higher head to speed ratio the impeller would be logically narrower than broader.
So, the specific speed is larger and the shape broader proportional to the flow rate and inversely
proportional to the head to speed ratio. The descriptions narrow and tall or broad and short are of
course relative, to be indicative of the shape and not the size. A large size impeller can yet be broad
and short by its shape. So also a small size impeller can yet be narrow and tall by its shape. In a
narrow and tall impeller, the flow through the impeller will be radial i.e. across a plane perpendicular
to the axis of rotation. Hence these are called as radial flow pumps and are pumps of low specific
speed, generally between 40 to150.

Units of Plant:
1 collection chamber
2- Screening
3- Grid Chambers
4- Parshali Flume For Flow recording fitted with ultrasonic flow recorder
5- Distribution Chamber- I
6- Primary Sedimentation Tank
7- Distribution Chamber- II
8- Aeration Tank
9- Distribution Chamber- III
10- Final Sedimentation Tank
11- Treated Effluent pump House
12- Return Sludge Pump House
13- Blending Tank
14- Gravity Sludge Thickeners
15- Thickened Sludge Pump House
16- Primary Sludge Digester
17- Secondary Sludge Digester
18- Digested Sludge Pump House
19- Centrifuges
20- Centrate Pump House
21- Gas Nolders
22- Gas Flaring Units
23- Gas Scrubbers
24- Bio Gas Compressors
25- Dual Fuel Generators

1: CollectionChamber:
Collection chamber is large waste water storage tank.
2: Screening:
Work: The function of the fine screen is to prevent entry of solid particles/ articles above a certain
size; such as plastic cups, paper dishes, polythene bags, condoms and sanitary napkins into the STP.
(If these items are allowed to enter the STP, they clog and damage the STP pumps, and cause
stoppage of the plant.) The screening is achieved by placing a screen made out of vertical bars,
placed across the sewage flow.
Figure-: Screening

3: Grid Chambers:
Work: Grit chamber is designed to remove grit, consisting of sand, gravel, cinders or other solid
materials that have subsiding velocities or specific gravities substantially greater than those of the
organic putrescible solids in wastewater. Grit removed particles are collected automatically through
clarifier mechanism. Classifiers are provided in Square Horizontalflow Grit chambers.
Figure-: Grid Chambers
4: Distribution Chamber for Primary Sedimentation Tank:
Work: Distribution Chamber in primary sedimentation tank works as distribution of flow after
separation of suspended solid particles.

5: Primary Sedimentation Tank:
Work: Primary sedimentation tanks are to separate the settleable solids from the liquid stream by
gravity settling. The primary sedimentation tank receives the wastewater passed through bar screens
and/or grit tanks. The objectives of primary are to produce a liquid effluent suitable for downstream
biological treatment and to achieve solids separation. The solids result in a sludge that can be
conveniently and economically treated before ultimate disposal. On an average basis, the primary
sedimentation tank removes approximately 60 and 30 percent of influent total suspended solids
(TSS) and 5-day biological oxygen demand (BOD5), respectively.
Dimensions:
3 Units, Dia- 44 m, SWD- 4.1 m
Depth of Hopper: Bottom portion- 1.79 m
Detention Period- 2.94 hours
Figure- Primary Sedimentation Tank

6: Aeration Tank:
Work: After leaving the primary clarifiers, the sewage goes to any one of ten aeration tanks.
Elmhurst uses a system of sewage treatment called activated sludge. The aeration tanks provide a
location where biological treatment of the waste water takes place. In these tanks, microorganisms
and waste water in various stages of decomposition are mixed, aerated, and maintained in
suspension.
Dimensions: 3 Units each of 52 x 34.5 x 4.302 m size
Figure-: Aeration Tank
7: Distribution Chamber:
Work: Distribute the waste water to primary settling tank.
Dimensions: 1 Unit, Size- 5 x 5 m, Depth 5.01 m

8: Final Sedimentation Tank:
Work: It is designed to substantially degrade the biological content of the sewage which are derived
from human waste, food waste, soaps and detergent.
Dimensions: 3 Units, Dia- 48 m, SWD- 3.802 m
Hopper:
Portion Depth- 2.06 m
Detention Time- 3.5 hour
Figure-: Final Sedimentation Tank
9: TreatedEffluent Pump House:
Work: Water that flows from a treatment facility after the wastewater has been treated and pumped.
Dimensions:
Pump House Size- 30.96 m x 7.1 m
Height Above the floor- 8.68 m
Sump Size- 32.07 m x 7.87 m
Depth- 5.01 m

10: Return Sludge Pump House:
Work: Another pumping system transfers treated water back into the plant for reuse.
Dimensions:
Pump House
Size- 12 m x 7 m
Height- 12.801 m
Sump Size- 12 m x 7.4 m
Depth- 6.218 m
11: Blending Tank:
Work: The settled sludge is pumped directly to blending tanks for further processing, with
microbiological biomass to breakdown the organic compounds in the presence of oxygen, after being
collected into a central hopper through scrapers.
Dimensions:
Dia- 10 m
Depth- 6.59 m
Figure- Blending Tank

12: Gravity Sludge Thickeners:
Work: The sludge thickener uses the air flotation process to remove water from the sludge.
Dimensions:
2 Units, Dia- 28 m, SWD- 3.485 m
Depth Of hopper bottom portion- 2.253 m
Solid loading rate- 40 kg/cm2
13: Thickened Sludge Pump House:
Work: Thickened sludge is pumped by this section.
Dimensions:
Pump Size- 7.65 m x 4.5 m
Ht- 9.15 m
Sump Size- 7.65 x 1.18
Depth- 7.65 x 1.18
Depth- 7.65 m
14: Primary Sludge Digester:
Work: The sludge digesters are anaerobic in that they utilize bacteria that thrive in a warm
atmosphere in the absence of oxygen.
Dimensions: 2 Units fixed RCC dome roof, Dia- 29 m, SWD- 9.1 m
Hopper:
Bottom Depth- 2.416
Rise of the roof dome- 4 m
15: DigestedSludge Pump House:
Work: It is used to pump the sludge which is digested.
Dimensions:
Pump House Size- 7 m x 4.5 m
Ht- 7.78 m
Sump Size- 7 m x 1.48 m
Depth- 4.1 m

16: Centrate Pump House:
Work: The Centrate Treatment System Facility is designed to concentrate (thicken) the solids using
dissolved air flotation to separate the solids from the centrate. Air is mixed with water in a pressure
vessel, causing the air to dissolve into the water. The pressurized air-water mixture is then fed to the
flotation tank. Solids are carried to the top of the tanks as they attach to the rising air bubbles.
17: Gas Holders:
Work: A gas holder is a large container where natural gas or town gas is stored near atmospheric
pressure at ambient temperatures.
Dimensions: 2 Units floating MS bell type
Dia-
23 m (RCC Portion)
Depth- 7.55 m
Figure-: Gas Holders

18: Gas Flaring Units:
Work: Gas Flaring Unit is used to flare the waste gases which comes out during the sewage
treatment.
19: Gas Scrubbers:
Work: Gas Scrubber systems are a diverse group of air pollution control devices that can be used to
remove some particulates and/or gases from industrial exhaust streams. Traditionally, the term
"scrubber" has referred to pollution control devices that use liquid to wash unwanted pollutants from
a gas stream. Recently, the term is also used to describe systems that inject a dry reagent or slurry
into a dirty exhaust stream to "wash out" acid gases. Scrubbers are one of the primary devices that
control gaseous emissions, especially acid gases. Scrubbers can also be used for heat recovery from
hot gases by flue-gas condensation.
Figure- Structure- Shed covered with GI Sheets.
20: Bio Gas Compressors:
Work: These are specially manufactured compressors suitable for biogas. These are high pressure
compressors upto 300 bar pressure. Structure- Building with brick masonary wall and RCC T-beam
roof.

21: Dual FuelGenerators:
Work: Duel fuel engine generators are installed at the shatin STW for supplying equipment with
electricity. Cooling water and heat released from flue gas are also transformed to hot water for
maintaining the temperature required for sludge digestion.
Conclusion:
It has been shown in related literatures the beneficial action of biological treatment of waste water
and it is for this fact that we would like to harness this appropriate technology by incorporating the
local environmental conditions. The main objective is to develop simple technology, easy operation
and maintenance and virtually low cost. Wastewater treatment processes are inherently dynamic
because of the large variations in the influent wastewater flow rate, concentration and composition.
Upflow Anaerobic Sludge Bed (UASB) wastewater (pre-)treatment systems represent a proven
sustainable technology for a wide range of very different industrial effluents, including those
containing toxic/inhibitory compounds. The Expanded Granular Sludge Bed (EGSB) system
particularly offers big practical potentials, e.g. for very low strength wastewaters (COD ≪1 g/l) and
at temperatures as low as 10° C.
It is our intention that we shall continue this study until such time that we can demonstrate the
beneficial effect of biological treatment using local conditions, a key to success of identifying vital
parameters through the action of tropical climate.

Water treatment

More Related Content

What's hot (20)

Similar to Water treatment (20)

More from translateds (20)

Recently uploaded (20)

Water treatment