OPERATION AND MAINTENANCE

OF SEWAGE TREATMENT

PLANTSPLANTS

Maintenance Scheduling

• Maintenance of each equipment is done as the

recommendations of manufacturer.

• A History card is maintained for each equipment so

that record is maintained for equipment performance

and maintenance.and maintenance.

• Good housekeeping is an important aspect of plant

operation.

Pumping Machinery

• To run the machinery in a way so as to have free fall from invert ofsewer.

• Mostly 2 or 3 pump sets are out of order.

• Guide Wire/ Guide Rail should be in good condition.• Guide Wire/ Guide Rail should be in good condition.

• Minimum one pump be operated during night hours so that sewersare empty in morning.

Screening Chamber & Wet well

• Regular Cleaning

• Disposal of Screenings

• Washing of Bar Screens

• Washing sludge layer from walls using water jet

• Desilting of wet well once a year• Desilting of wet well once a year

• Should be scoured minimum once in a week.

• Fine Screens should be kept clean of all obstructions. If

the screen are of mat type, its operation should be

Receiving Chamber & Fine Screens

the screen are of mat type, its operation should be

adjusted such that a mat is always on the screen.

Grit Channel

• (1W + 1S) grit channels for peak flow.

• Should be used one at a time, alternatively every day.

• Should be cleaned every day.

• Proper & efficient removal of silt in grit channel will improve

the functioning of treatment.

Proportional Weir

• It is provided to maintain uniform flow on upstream and

downstream of grit channel.

• Must be Calibrated so as to show the quantity of flow.

• Flow be recorded every hour. In SBR Plants the Flow

recording graphs are recorded in SCADA PC.recording graphs are recorded in SCADA PC.

Distribution Channel

Must be cleaned every day.

Moving Bed Biofilm Reactor (MBBR)

The STP is said to be running successfully, if:-

• The biofilm layer shall accumulate on the bio media.

• The flocs should generate in Clarifier.

• The smell of sludge should not be foul.

• When starting the plant initially, the air blowers should be

operated for passing the air through diffusers and run

continuously, otherwise the desired parameters will not be

achieved.

• Fill both aeration tanks to the normal operating sewage

depth, thus allowing the aeration equipment to operate at

maximum efficiency.

Moving Bed Biofilm Reactor (MBBR)

• Using all of the aeration tanks will provide the

longest possible aeration time.

• The effluent end of the aeration tank should

have a dissolved oxygen level of at least 1.0

mg/L. DO in the aeration tank should bemg/L. DO in the aeration tank should be

checked every two hours. Generally the DO is

approx. above 4 in aerated sewage.

• The COD reduction in treated sewage Vs. raw

sewage cannot be less than BOD reduction.

How to check DO in aeration Tank

The presence of DO in aeration tank requires the

elaborate procedure of using a meter operated

electronically and keeping the probes well cleaned at

all times. This is not always possible. Moreover,

typical plant control requires an answer to thetypical plant control requires an answer to the

question of whether residual DO is present or absent

in the secondary clarifier overflow. This can be easily

carried out in the field as follows:

1. Take a 10 ml well washed test tube.

2. Hold it gently against the weir overflow

sideways.

How to check DO in aeration Tank

3. Allow the sewage to fill the tube and overflow for a few minutes.

4. Gently take the tube and pour out about 2 ml.

5. Add few drops of manganous sulphate solution.

6. Add a few drops of potassium iodide solution.6. Add a few drops of potassium iodide solution.

7. Close the top with the thumb and invert a few times.

8. Allow to stand for a few minutes.

9. If there is a yellow precipitate, DO is present.

10. If there is a white precipitate, there is no DO.

• With help of electronic instrument

• Online sensors are required to be provided

Reactors /SBR

• 2 in nos. (Parallel & in series).

• The walls, walkway and the railing to be washed daily

using water jet.using water jet.

• The problem of foam can be solved using water jet .

• Reactors should be desludged every day to maintain

proper MLSS

Sequential Batch Reactor (SBR)

• The first is to make certain that all mechanical, electrical and controlequipment is operating properly.

• The purpose of Fill-React operation is to add substrate (rawsewage) to the reactor. The addition of substrate or filling iscontrolled by a timer to a set time period. The filling operation isalso controlled by level transmitter to limit filling volume uptomaximum level. Usually, SBR tanks are designed to take flowmaximum level. Usually, SBR tanks are designed to take flowas it comes into STP with all variations from peak flow tominimum flow without necessiating any equalization tank.

• The Settling process is controlled by time and is usually fixedbetween 30 minutes to an hour so that the sludge blanketremains below the withdrawal mechanism during the nextphase.

• The purpose of Decantation is to remove the clarified, treatedwater from the reactor.

Sequential Batch Reactor (SBR)

• When starting the plant initially, the diffuser should be

operated first and run continuously, otherwise the desired

parameters will not be achieved.

• The precaution needed is to make sure that power supply is

available continuously. If power supply fails, immediately

bring the genset on-line.

• COD to BOD ratio indicates the biodegradabitity of the• COD to BOD ratio indicates the biodegradabitity of the

sewage. Normally, sewage will have COD to BOD ratio

between 1.5 to 2. If the ratio is more than 2, entry of

industrial effluents into sewer network is a possibility.

• The daily tests shall be COD, TSS, pH, Dissolve oxygen,

Ammonia and dissolved phosphate. BOD can be a weekly

test.

Problem of foaming

• Foaming in aeration compartment in first week of

start be tackled with water hose using fresh water

with lawn sprinkler

• It will diminish when sufficient mixed liquor solids It will diminish when sufficient mixed liquor solids

are obtained

• Do not waste sludge until desired level of MLSS

obtained

Sludge Sump & Sludge Drying Beds

• Sludge from the sump be regularly pumped out.

• Generally the Sludge Drying Beds are empty without

any sludge shows that plant is not running.any sludge shows that plant is not running.

• Dried sludge cakes be removed regularly from

Sludge Drying Beds.

Compressors and VFD and DO meter

• (2W +1S) compressors.

• 2 compressors should continue running till desired D.O. level is

achieved.

• Generally compressors and VFD are found out of order.

• Most of the times, the compressors are found not working with the

excuse of power cut.

• At least one compressor should be in operation every time in case of

power cut also (with the help of D. G. set).

Clarifier

• The treated water flow should be uniform over the

entire length of the launder. It would ensure aeration

also.

• There should be no scum over the surface.

• Bridge should be kept running.

• Sludge should be continuously removed.

• Launders should be kept clean.

Magnetic Flow Meters

• Magnetic flow meters work on the principle of electromagnetic induction.

The induced voltage generated by an electrical conductor in a magnetic

field is directly proportional to the conductor’s velocity.

• These are non-invasive and used in almost all pipelines, but initial

calibration is needed. The output is the standard 4 to 20 mA signal, which

is relayed to the central monitoring system.

FLOW METERS

is relayed to the central monitoring system.

Ultrasonic Flow Meters

• When ultrasonic impulses are released onto a pipe surface carrying

sewage, the impulses are deflected along the flow direction based on the

velocity of the flow before they impinge on the opposite sidewall of the

pipe.

• The time taken by impulse wave is measured and is correlated to the

velocity and then to the diameter of the pipeline and hence the flow rate

is arrived at.

• Like magnetic flow meters, these are also non-invasive and used in

almost all pipelines but, initial calibration will be needed.

Visual Test

• The final effluent shall be clear and free from

suspended particles.

• Flocs exists in the clarifier.

• A film exist on the MBBR Media.

• Sludge is produced daily.• Sludge is produced daily.

• No odour or smell in the final effluent.

• No odour in sludge.

Discrepancies observed in construction of STPs

• Design mix with weigh batch mixer not followed

• Chemical protection on the RCC not done

• SS pipes not checked

• Cement store not constructed

• Site office not constructed• Site office not constructed

• Railing not provided as per agreement

• Sample test register not maintained

• No planned execution

Discrepancies observed in construction of STPs

• Stairs/ Steps not fitted in any of the chambers/ reactors/ sumpetc.

• V- notch weir plates not fitted around the launders.

• Circular S.S. peripheral wall not provided in the clarifier.

• Scum removal arrangement not made in the clarifier.

• Proportional weir has not been calibrated.

• Scour valves not provided in receiving chambers.• Scour valves not provided in receiving chambers.

• Arrangement for proper disposal of screens & grits not made.

• Level of outlet channel is such like that water remains stagnantin the launders.

• VFD and DO meter have not been installed.

General observations

• M. S. parts are not epoxy painted regularly and are

rusted.

• Screens and grit channels are not cleaned.

• Both Grit channels are run simultaneously where as it

should be one running & to be used alternatively

every day.

• Pumps are not run in proportion to the discharge

received.

• No pumps are run from 10:00 P.M. to 4:00 A.M.

• Sludge is not removed from reactors & clarifier.

• Dried sludge cakes are not removed from Sludge

Drying Beds.

• General maintenance of the lawns etc. is very poor.

General observations ….Contd….• The sitting room & the toilet are not in good condition.• D.G. set is not operated in case of power failure.• O & M staff is not as per the norms i.e. qualification and

experience.• Industrial effluent is being received at the Sewage Treatment

Plants for which no correspondence being made with HaryanaState Pollution Control Board.

• Consent to operate has not been obtained from Haryana StatePollution Control Board.

• Samples are not being tested in laboratory daily.• Samples are not being got tested regularly from some reputed• Samples are not being got tested regularly from some reputed

laboratory.• Quantity of BIO- MEDIA not checked with design approved by

SE.• Thickness and quality of SS pipes, DI pipes not checked.• Originality of Electrical equipment not checked and verified.

RECORD TO BE MAINTAINED BY CONTRACTOR

DURING O&M

• Attendance of O&M Staff engaged by the contractor.

• Quantity of Raw sewage/ treated sewage water.

• Quality of incoming/ treated sewage water based on laboratory testing to

be maintained by the contractor.

• Diesel consumption of Generating set based on Hour meter (Hour meter

to be sealed by Public Health Engineering Department immediately after to be sealed by Public Health Engineering Department immediately after

trail run period).

• Running hours of each prime mover.

• Total power consumption.

RECORD TO BE MAINTAINED BY CONTRACTOR

DURING O&M … CONTD.

• The contractor has to provide all consumables, spares, oil & lubricants,

Diesel for running of DG Sets, chemicals for laboratory testing,

consumables for electrical & mechanical plant & machinery.

• Public Health Engineering Department shall provide power & raw sewage

at desired flow & level free of cost.

• The payments for consumption of diesel shall be reimbursed as per actual• The payments for consumption of diesel shall be reimbursed as per actual

consumption based on hour meter basis as per prevailing market rates.

• The contractor shall maintain and submit statements to Public Health

Engineering Department on daily basis for consumption of Diesel quantity

& quality of treated sewage water & shall get the treated sewage samples

duly tested for submission to PCB for NOC/ Consent & shall submit

consolidated monthly statement at the time of claiming payment.

TESTS TO BE CONDUCTED BY THE

CONTRACTOR DURING O&MInlet chamber:- Measurement of flow, BOD, pH, SS, temp., COD

and oil & grease, TDS

Outlet chamber:- BOD, suspended solids, pH, COD and oil & grease,

TDS

Inlet of the reactor:- MLSS, Dissolved Oxygen and pH.

Outlet of reactor:- Dissolved Oxygen, Sludge volume Index and pH.Outlet of reactor:- Dissolved Oxygen, Sludge volume Index and pH.

Outlet of the secondary :- BOD, Suspended solids, pH, COD and oil & grease

treatment units.

Outlet of the SBR:- BOD, Suspended solids, pH.

Excess sludge:- Volatile suspended solids, total solids, specific

gravity.

TESTS TO BE CONDUCTED BY

CONTRACTOR IN LABORATORYSNO Parameter to

check

Dated 1/9/15 2/9/15 3/9/15 4/9/15

1. BOD

2. COD

3. TSS

4. MLSS4. MLSS

5. SVI

6 PH

7 DO

PROVISION AS PER AGREEMENT FOR OPERATION &

MAINTENANCE

• The plant machinery shall be operated 24 hours a day, 365 days in a year.

• Sewage flow received from the MPS is treated & disposed out without any

break.

• The plant shall never be operated at less than 50% of its design capacity.

• The period of 50% operation shall not exceed more than two consecutive

days and not more than three days in a month.days and not more than three days in a month.

• The maximum downtime of the whole plant shall not exceed more than 8

continuous hours.

• In case down time exceeds the above limit than the contractor shall not be

paid O&M charges.

• The record of incoming/ treated sewage water quality monitors during

every day of O&M period.

• Third party inspection by the expert be conducted once in year to examine

the performance of components of the plants.

Thank You !Thank You !Thank You !Thank You !