As per the statutory regulations issued by CPCB, various infrastructures like Apartments, Commercial Construction Projects, Educational Institutions, Townships, and Area Development Projects meeting certain criteria have to install STPs for the treatment of sewage that they produce.

The guideline rules cover aspects regarding the location of STPs, the STP technology to adopt, functioning as well as its maintenance to ensure efficient and safe operation of the machinery.

The Guidelines issued for STPs by CPCB are as follows:

CPCB Guidelines for Sewage Treatment Plants

1. The Technology of STP

The approved STP technologies to go with are-

A. Activated Sludge Process(ASP) (only when above 500 KLD sewage is generated).

B. Membrane Bio Reactor(MBR)

C. Moving Bed Bio Reactor(MBBR)

2. Unit Requirements of STP

STPs have various individual units where different sewage treatment processes occur. The units and their criteria as per the guideline’s requirement are as follows.

SNo.UnitActivated Sludge Process(ASP)Sequential Batch Reactor(SBR)Membrane Bio Reactor(MBR)Moving Bed Bio Reactor(MBBR)
1.Equalization TankShould have a Minimum
Holding Period of 8
Same as ASPSame as ASPSame as ASP
2.Anoxic TankReturn activated sludge should be pumped to anoxic tank for denitrification.Not requiredSame as ASPSame as ASP
3.Aeration TankDissolved Oxygen in an excess of 4 mg/L has to be maintained in the Aeration Tank. Same as ASPSame as ASPSame as ASP
4.Membrane TankNot requiredNot requiredMembranes should be replaced regularly as per its manufacturer’s specifications Not required
5.Sludge Holding TankSludge holding should be madatoriliy provided for holding excess sludge before its dewatering.Same as ASPSame as ASPSame as ASP
6.Final Treated Water Holding TankCapacity of the tank should be enough to hold water for 2 days minimum.Same as ASPSame as ASPSame as ASP
7.Sludge Drying BedInstead of sludge drying bed, horozontal centrifuge system should be used for >500KLD STPs.

For <500 KLD STPs, belt press or screw press system should be used.
Same as ASPSame as ASPSame as ASP

3. Mechanical Equipment Requirement for STP

There should be clear and easy access to the Bar Screen Chamber and Oil & Grease Chamber of STPs installed. Also, the equipments should be of the submersible type with an easy removal/dismantling option whenever maintenance is required.

Air blowers of STP should have Vibration mounts and acoustic enclosures to reduce the noise pollution.

4. Location of STP

STP should be located under the driveway, play area, or clubhouses, and far away from the residential housings to not cause any nuance to the people living.

Also, STP should not be installed in the basement of any building. Access to the STP room should be from Ground Level or Upper Basement through well-designed walkways or headroom, and not from the lowest basement to avoid nuances that may happen due to rain flooding, smell or sound.

5. Treated Sewage Standards

The sewage treated should meet the following standards.

S. No.Parameter Required Standards
2BOD(5th day)<10mg/l
4Suspended Solids<10mg/l
5Ammonical Nitrogen<5mg/l
6Total Nitrogen<5mg/l
7Fecal Coliform<100 MPN/100 ml

6. Guidelines for installing sensors

It’s mandatory to install sensors for monitoring sewage parameters like BOD, COD, TSS, flow, and pH.

The CPCB recommended sensor types with their communication protocols are as follows.

S.No.ParameterMeasurement TypeSensor TypeCommunication protocol
1.pHInlineIon Selective Glass ElectrodesRS 485 Communication with Modbus
2.TSSInlineTurbidity to TSS correlation with
Nephelometric technique
RS 485 Communication with Modbus
3.BODInlineUV-Vis Spectrophotometry
& combustion(Double beam
with entire spectrum scanning
RS 485 Communication with Modbus
4.CODInlineUV-Vis Spectrophotometry
& combustion(Double beam
with entire spectrum scanning
RS 485 Communication with Modbus
5.FlowInlineElectromagnetic Flow MeasurementRS 485 Communication with Modbus

7. Caution Board at STP

Proper cautionary signboards should be displayed and safety protocols should be followed at the STP locations.

“Danger” Sign Boards should be installed at the STP location for the maintenance personals and the public. And “water not fit for drinking” should also be highlighted at the taps delivering sewage water.

8. Use of Treated Sewage

The treated water should be mandatorily used for toilet flushing purposes that should have a dual plumbing system.

9. Modular Operations of STPs

Modular operation of STPs implies that the STP should be developed/constructed in smaller units so that it can be used as per the load or occupancy of people. In large projects where a higher capacity of STPs required, the occupancy in the initial stages isn’t able to meet the operational criteria of the STP. So, the factor should be considered in the design phase itself.

Official Source of CPCB Guidelines for STP

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