Why sewage treatment plants in apartments are messed up, and how this can change

Apartment STPs (Sewage Treatment Plants) are set up after getting government approvals, yet they malfunction soon and residents keep spending lakhs to correct defects. This scenario can change with some reforms in the STP approval process.

Today, a large number of apartment complexes, malls and tech parks in Bengaluru have their own STPs (Sewage Treatment Plants). If an STP is working properly, its treated water would look just like tap water – clear, without any odour. In addition, it must meet the specifications set by the State Pollution Control Board (KSPCB).

If the treated water looks dark brown, or stinks, the STP owner knows that the STP has some trouble. But even if the treated water looks clear and odour-free, it may still not meet specifications; and the owner may not be even aware that his STP has a problem. And the truth is, there are many such defective STPs running in Bengaluru, about which the owners may not be aware.

This article explains why we have so many faulty STPs, and what needs to be done to change this.

But why should apartments have STPs at all?

Many of us may think that running STPs is a specialized job; so why should we attempt to run an STP in our apartment complex in the first place? Why can’t the Bengaluru Water Supply and Sewerage Board (BWSSB) operate STPs as a public service?

Well, there is a sound reason for that: using a local STP allows us to recycle nearly half of our total daily water usage. This brings down our freshwater demand by 50%. Then BWSSB will be able to distribute the same quantity of Kaveri water to double the population!

STPs should be regulated

Since 2005, the number of privately-owned STPs has been growing fast in the city. But in an unregulated market, a lot of substandard STPs were sold. These STPs have design and fabrication flaws, and cannot treat sewage even if they are run by the best operators. Even if the STPs are good, most of the operators in the market are unqualified, which again means they cannot treat the sewage properly.

Hence the solution is to regulate the design, fabrication, operation and maintenance of STPs. Section 17 of the Water (Prevention & Control of Pollution) Act, 1974 lays down several measures to regulate these aspects. These responsibilities are assigned to KSPCB. These responsibilities include inspection and approval of new STPs, training of operators, spreading awareness among the public, etc.

Unfortunately, the Water Act remains mostly unimplemented even today. As a result, these areas have remained weak, and need reforms.

First, we will see what reforms are needed in the STP-approval process, and then, reforms needed in other areas.

1. Reforms needed in the STP-approval process

The STP-approval process has two stages – CFE and CFO:

  1. In the first stage, KSPCB checks the design of the STP, and if the design is acceptable, issues CFE (Consent For Establishment) to the developer. This permits the developer to construct the STP as per the submitted plan.
  2. The developer constructs the STP and then applies for the second approval, called CFO (Consent For Operation). Here, KSPCB checks if the STP is built correctly (as per the approved CFE) and is defect-free. If the STP passes the checks, KSPCB issues a CFO.

The developer can operationalise the STP only if they have the CFO.

Subsequently, throughout the life of the STP, KSPCB conducts annual inspections to check for ageing-related problems and tampering. When the STP passes each inspection, KSPCB extends the CFO by another year.

This process may seem perfect, but isn’t. At present, the CFE-CFO procedure is not formally documented. KSPCB does not use data collection forms to ensure that the process is executed consistently for all STPs. Most importantly, the developer simply abandons the STP, and quietly slips it over to the RWA without its explicit acceptance. Due to such factors, multiple defects remain in the STP, and apartment owners end up spending their hard-earned money to rectify these.

The following diagram shows the current practices for STP construction and approval on a timeline. (Click to see full-size image):


And the diagram below shows the timeline for the desired/ideal workflow.


  • The timeline is not accurate; the gaps are only indicative.
  • The part above the timeline shows the actions taken by the developer or the RWA (Residents Welfare Association).
  • The part below the timeline shows the actions taken by the authorities (KSPCB/BBMP).

In all, the revised workflow has eight additional steps; and one step (CFO) is split into two separate steps (PCFO+FCFO).

The following table explains each event shown on the timeline. The table highlights the additional steps to be taken as per the desired/ideal workflow in pale green; and the step to be removed is highlighted in pink. The additional steps are also mentioned in bold letters.

Design STP Developer
  • Declare the number of apartments and quantity of sewage
  • Select an STP type (Several STP types are available, but some types are not approved)
  • Finish the engineering calculations and drawings
Apply for CFE Developer Apply to KSPCB, and submit the details mentioned above
Verify the STP design1 KSPCB
  • Verify STP type (whether approved)
  • Verify calculations
  • Verify engineering drawings where required;
  • Check feasibility
  • Check ergonomics and safety of the design
Rectify problems Developer
  • Rectify all problems pointed out by KSPCB, and re-offer.
  • Repeat the cycle until all problems are sorted out.
Issue CFE KSPCB All the calculations, plans and engineering drawings are treated as frozen at this point, and the developer is expected to construct the STP strictly in compliance with those documents.
Construct the STP Developer The constructed STP must comply with the calculations and drawings approved as per the CFE.
Apply for CFO Developer
Inspect STP
(but not the effluent)
KSPCB At this stage, the STP is completely dry, as there are no occupants in the building. Without sewage, the KSPCB inspector cannot check how various stages of the STP function. Therefore the inspection is limited to physical checks.
Rectify problems Developer Attend to all problems detected by KSPCB. Repeat the cycle till all problems are resolved.
Issue CFO KSPCB KSPCB issues full clearance to operate the STP although the inspector was not able to check its functioning.

This is because, unless the CFO is given, the building cannot get OC (Occupancy Certificate). And without OC, the buyers cannot move in. Without residents, the complex cannot generate sewage. Without an adequate quantity of sewage, the STP cannot operate.

Hence KSPCB has to issue a CFO prematurely to break this logjam.

Issue PCFO
(Provisional CFO)
KSPCB KSPCB issues a Provisional CFO. PCFO is issued with Terms Of Reference (preconditions to be met)2.
Finish the construction Developer Finish the construction of other plants and machinery; clubhouse, common facilities, etc.
Apply for OC Developer Submit Completion Certificate to BBMP, and apply for OC.

This signifies that:

  • The construction is completed (including common areas)3
  • The construction complies with the sanctioned plans
Issue OC BBMP Issued only after verification of facts and full compliance.
Transfer the property Developer
  • Execute Sale Deed for all apartments with clients
  • Hand over the common areas to the Managing Committee (MC)
Sewage starts The apartment owners start arriving one-by-one. They generate sewage. Initially, the quantity is so small that the STP cannot treat it. Therefore the developer keeps the STP off4.
Sewage builds up As more owners arrive, the sewage quantity increases gradually. But the STP cannot be started until a certain minimum quantity (as per design) is available.
Start STP operation Developer The STP can be started only when it gets sufficient sewage on a daily basis. Thus the STP start date would be delayed by several weeks.

An STP needs several days to stabilise. The designer must keep a close watch to ensure that the STP functions consistently, without intermittent failures. If there are any issues related to operations, ergonomics or safety, rectify those.

Inspect STP
Test the effluent
KSPCB KSPCB is invited to inspect the STP when it’s operating with almost rated load (the final quantity for which the STP is designed). KSPCB inspector is also required to test the treated sewage.

In the ideal workflow, the KSPCB inspector is required to actively look for operational flaws in the working STP and to report these.

Rectify problems Developer Attend to the issues pointed out by the KSPCB inspector.

Note that the STP is rectified at the developer’s cost. (This cost must not be passed on to the buyers.).

Inspect the STP,
test the effluent
KSPCB Repeat the “inspect STP and test treated sewage” cycle, till there are no issues at all.
Issue FCFO5
(Final CFO)
KSPCB The KSPCB inspector actively looks for operational flaws. The FCFO is issued only after the STP is able to pass two consecutive inspections without any problems. (If the system is unstable, it cannot be given FCFO.)
Operate STP for a minimum statutory period Developer The developer must continue to operate the STP for a minimum of two years. There will be annual CFOs during this period also (not shown in timeline).

This system makes sure that any residual problems in the STP are detected during the inspections, and they are rectified at the developer’s cost.

Conduct third-party audit Developer The third-party auditor is typically selected by the RWA, which means the developer cannot manipulate the results. This gives confidence to the RWA that all the issues related to design, engineering, construction, operation, ergonomics and safety would be detected.
Rectify problems Developer Attend to all comments given by the auditor.
Get MC’s concurrence Developer The MC accepts that henceforth it will take over complete responsibility of the STP. This includes attending to any issues that come up in future.
Transfer STP to RWA KSPCB KSPCB makes a change in its database to show that the MC has taken over the STP.
Annual CFOs KSPCB Annually, KSPCB inspects the STP to ensure that:
  • There are no ageing-related problems (e.g. corrosion, wear out)
  • The STP is not tampered with
  • The STP does not exceed the approved quality and quantity of sewage
Rectify the problems MC (RWA) Attend to all the problems pointed out by KSPCB and get the CFO extended by a year.

2. Reforms needed in other areas:

If the CFE-CFO process is revamped, the RWA will get defect-free STPs. But is that enough?

For a moment, compare an STP with your car. How do you keep your car in the best condition? You begin by buying the best-possible car, and then take care of three human factors:

  1. Even the best car can be ruined by a reckless driver. So you must have a careful driver for your car.
  2. As the owner, you must be fairly conversant with its well-being. At the first sight of trouble, you must take it to service.
  3. You must use a qualified service. Cutting corners means ruining the car.

Exactly the same factors work for STPs. We need STPs that are designed and fabricated well. In addition, we need good operators, knowledgeable owners and good maintenance service. But in the case of STPs, none of these factors are guaranteed currently!

  1. Good STP designers:
    KSPCB has failed to develop a support system for the rapidly-growing number of private STPs. There is no system to ensure that only well-qualified STP designers are allowed to design and construct STPs. Worse, if your STP designer has neglected safety and ergonomics, you may be held liable for any accident inside the plant.
  2. Good STP operators:
    KSPCB has not set up an education/training system to produce well-trained STP operators. So, even if you have a well-designed STP, if it is operated by an untrained person, your STP may not produce good results consistently.
  3. Knowledgeable owners:
    Yes, you have an important role to play. But how knowledgeable are you as an STP owner? Worry not, we have published an STP Guide, which is downloadable from the KSPCB website. This comprehensive book covers the design, construction, operation, maintenance and troubleshooting of STPs. KSPCB should also arrange regular public training programmes on STPs for RWA members.
  4. Good service:
    STPs need regular maintenance service and occasional breakdown service. This calls for qualified service providers. In addition, we need the services of tank cleaners who can handle raw sewage and sludge. An unqualified contractor can only ruin an STP. However, KSPCB does not maintain a list of approved vendors.

To conclude, KSPCB must revamp the CFE-CFO process, and also make major efforts in the four areas listed above.

See Also:

1. This is the idea behind CFE stage. But in practice, KSPCB does not check these aspects.

2. Typical conditions are:
(a) Do not take external sewage for treatment in the STP;
(b) If either the quantity or quality of sewage changes, the proponent must seek a fresh CFO.

3. The STP is part of common areas. Other examples of common areas are clubhouse, swimming pool, water treatment plant, fire hydrant system etc.

4. Ideally, the raw sewage has to be transported to the designated BWSSB STP, but that is too expensive. So the developer simply dumps the raw sewage in a UGD line or even SWD, thus polluting it.

5. The current workflow does not have this step at all – once the STP gets CFO, it’s in the clear, and no one actively searches for operational faults.


  1. Rajeev Gupta says:

    The annual CFO is too much of an expectation. CFO should he considered once in every 3 year cycle.
    secondly at present there are huge under the table expectations from the KSPCB officials for CFO renewals. The only way out is to make the process transparent and online. This is being prevented by officials of KSPCB themsekves as it is a source of perpetual bribe money

    • Nagesh Aras says:

      Well, a 3-5 year cycle would reduce the KSPCB’s load tremendously. But then we have to also look out for the possible tampering by the STP operator (who are all unqualified at present!)…

  2. Bhaskar says:

    Good solutions to treat sewage in small STPs are available in Bangalore. Unfortunately, these are not yet recognised by PCB and therefore not being used. PCB does not have any policy of evaluating and approving new technologies.

    • Nagesh Aras says:

      On the contrary, KSPCB has commissioned studies to comparatively evaluate various types of STPs.

      The second version of our STP Guide (due shortly) will cover all the commercially available STPs and compare them.

  3. Dia says:

    Good evening.
    The builder had installed STP of low quality .It’s giving trouble to residentssmell and sound).
    Where shall I apply for help?
    Its new complex and does not have RWA.
    Builder refused to any kind negotiations and help
    Any guidandlines for STP plants in India?
    Any department can help?
    Feeling totally helpless over the issue.
    The noise is a killer.
    Please, guide me about the issue
    Its not in Bengaluru,it is in Uttarakhand.

    • Anand.g says:

      For sound issue, accoustic sound proof enclosures can be used for airblowers and mono block pumps can be replaced with submersible pumps.

      • Nagesh Aras says:

        Yes, sound-proof enclosures are standard (they are also used for large gensets). Another possible factor is that often the pumps and blowers are mounted on top of STP tanks, which act as acoustic amplifiers! For best result, they must be mounted on solid ground, and enclosed.

    • Anand.g says:

      Smell comes because of the sewage become septic in the Aeration tank. Appoint a good STP consultant to fix the issues.

      • nagesh says:

        Please refer to the STP Guide (link in the article), and search for odor (or any other problem you are facing). There may be more than one reasons for the odor, noise, etc.

    • Nagesh Aras says:

      Well, Uttarakhand has its own State PCB (http://ueppcb.uk.gov.in/), so you must complain to them. The rest of the factors are the same as described in the article.

      Also bear in mind that the SPCB staff is directly liable/culpable if your STP suffers from design, engineering, fabrication, safety or ergonomic issues. (see my follow-up article http://bengaluru.citizenmatters.in/defective-sewage-treatment-plant-apartments-kspcb-notice-legal-liability-42768). So when you complain, they will not remain neutral, and try to scuttle your effort to defend themselves. So you need to persevere!

      You must consult a good layer and check your best option: Lokayukta (dereliction of duty), High Court (Writ of Mandamus) or Consumer Forum (defect in service).

  4. DEWAN CHAND. says:

    The sewerage water having no way to improve the dissolved oxygen in the water will generate bad odor as the anaerobic bacteria need no oxygen so they spread the bad odor.We have solution to this problem.you can try & contact me if required.
    Dewan Chand.Mobile No. 9729370239.
    Ambitious – Air Water Technologies.
    AMBALA – 133001. Haryana, India.

    • Nagesh Aras says:

      Rather than trying to add an anaerobic stage to an existing STP (or converting a given STP to anaerobic type), it is best to keep its original design and deal with its issues in design, engineering and fabrication. Even bad operation will lead to such issues. Please refer to the STP guide. Most STPs are of EAAS type, and adding anerobic stages is not recommended.

  5. Raj Shankar says:

    We are a group of plot owners who run Aishwarya County which has 626 plots but only 5 houses of which only two are occupied. BMRDA is insisting on setting up STP. But will it function?

    • Nagesh Aras says:

      Well, it is curious how they allowed people to occupy without an STP. Secondly, the current production of sewage would be <1%. An STP designed for 626 units will not work properly unless the sewage is substantial (say, 70%). Some designs have parallel streams, but even in that case, you will need about 35% sewage to run the STP.

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