Why STPs for older apartments won’t work in Bengaluru

Apartment dwellers do not want to hinder the efforts to save lakes. However retrospective STPs are not going to work, say apartment owners.

It’s been a protracted battle that lasted for over 15 months, involving lakhs of apartment residents, thousands of apartment complexes, hundreds of representations to Government and Bengaluru Water Supply and Sewerage Board (BWSSB), tens of court cases and one protest rally. The Government of Karnataka has finally made BWSSB withdraw the retrospective Sewage Treatment Plant (STP) notification imposed on apartments, based on a presentation done by the Governing Council of Bangalore Apartments’ Federation (BAF).

During this period, apartment residents have been unreasonably and unfairly accused of not doing their bit for the city, by “opposing STPs”. To clear up the air one last time, apartment residents were not opposing STPs. They were only opposing retrospective STPs.

BWSSB issued a notification in 2016 and subsequently served notices to more than 1,000 apartment complexes constructed in the 1970s, 80s, 90s and 2000s to install STPs on a retrospective basis, without ascribing any reason whatsoever, failing which penalties were to be imposed on them.

So, what was the genesis of this issue? BWSSB has so far steadfastly refused to give any reason for issuing this senseless notification. One possible trigger was the Bellandur lake pollution issue. The other possible trigger was the looming water crisis for which treated water reuse is one mitigant. However, this notification does not serve either purpose.

These apartments are connected to the underground sewage and are not polluting any lake bodies. They have very limited scope to reuse treated water since they neither have open spaces nor have a dual-piping system to take the treated water back to toilet flushes. These apartments were not designed to have STPs when they were constructed so it is completely impractical to retrofit an STP due to safety issues and space constraints. In this background, this notification made absolutely no sense!

From an environmental perspective, this would have been a disaster, since thousands of non-polluting apartment complexes were potentially being converted into “cesspools”, which could start polluting, given the complexity of managing STPs. In addition, monitoring and compliance is virtually impossible with thousands of STPs.

From an economic standpoint, this was hugely inefficient and unjust as these apartments had already paid lakhs of rupees each amounting to tens of crores of rupees to BWSSB as sanitation cess over a period of time to set up STPs, which it failed to do. If these thousand apartments were to set up STPs now, the total cost would have more than Rs. 500 crores (at an average cost of Rs. 50 lakhs for a small STP + civil works + dual piping)! If BWSSB were to set up one centralised STP to treat the same quantum of sewage, it would cost not more than Rs. 25 crores!

BWSSB, under the cover of seemingly noble intentions, was just trying to find innocent scapegoats (who had absolutely nothing to do with this matter), to cover up its own incompetence. The Government had to finally intervene to drive some sense and annul the absurd notification.

Lake pollution is not because of apartments

Lake pollution in Bengaluru is real and STPs are at the heart of this issue. However, before trying to find a solution, we need to first understand what the real problem is. To do that, we need some facts and statistics. The National Green Tribunal (NGT) had ordered the Government last year to initiate a study on Bellandur lake pollution. BWSSB and KSPCB did a survey for a few months and submitted an affidavit before the NGT. Here are some interesting statistics from that affidavit:

  1. Total sewage from BWSSB Underground Drainage (UGD) into Bellandur lake – 480 MLD
  2. Number of apartments in the Bellandur lake catchment area, which were inspected – 755
  3. Sewage generated by these 755 apartments – 66.87 MLD
  4. Out of this, 46 apartments are under construction, expected to generate ~5 MLD of sewage
  5. 390 apartments generating about 48.21 MLD of sewage have their own STPs
  6. 309 apartments generating about 13.66 MLD of sewage, do not have STPs but let out sewage into the UGD, like the rest of the city does
  7. 13.66 MLD of sewage let out by these apartments into the UGD out of 480 MLD is 2.8%!
  8. Here is an executive summary of the above
    1. Larger apartments have been putting up STPs (390 apartments generating ~125 KLD of sewage each, having about 175 flats on an average)
    2. Smaller apartments have been letting out sewage into the UGD (309 apartments generating ~45 KLD of sewage each, having about 65 flats on an average)
    3. Contribution of sewage of smaller apartments without STPs into the UGD is ~2.8%
    4. ~97.2% of the sewage in the UGD comes from independent houses!
  9. At the time the affidavit was submitted, BWSSB had put up centralized STPs near Bellandur lake with a capacity of only 248 MLD out of total 480 MLD, which means that almost half of the sewage from the UGD is entering Bellandur lake untreated!

Central Pollution Control Board (CPCB) had issued a notification on 21st April 2015 mandating BWSSB to set up a sewerage system for sewage collection, underground conveyance, treatment and its disposals to cover the entire local / urban area to bridge the widening treatment gap.

The sewage generated in Bengaluru has not shot up overnight – it has been continuously increasing over a period of time. But BWSSB has failed in doing even its basic duty of setting up STPs to treat the city’s sewage. Interestingly, three years back, BWSSB had promised to set up STPs to treat the increasing quantum of sewage, but no new STPs were commissioned. BWSSB has now promised to put up STPs by the year 2020 to take the capacity up to 518 MLD.

Larger apartments have been putting up STPs, and will continue to do so. Smaller and older apartments are in no way contributing to lake pollution. The simple and primary solution to the lake pollution issue is for BWSSB to set up fully functional centralised STPs at the exit points to the underground drainage.

The author is General Secretary of Bangalore Apartments’ Federation (BAF). BAF represents the interest of apartment residents & is also trying to find reasonable solutions to the city’s problems.


  1. Rohan Chowdhury says:

    This ball game of throwing responsibilities back and forth will hurt the “citizen” most in the long run. Just to remind everyone that there will be a time when things will go completely out of hand. Things are too big to fail right now, but the problems will become bigger someday and it would be too late by then.
    Environmental apathy is all time high right now specially in Indians, and it’s a big concern when population this large has no concern about this imminent danger, well, to sum it up for people to understand – you’re creating a future which will kill your children.

  2. Tharun Kumar says:

    One more point to add is that there are ‘STPs and STPs’. The prevailing paradigm is to use motor based STPs which use ‘aerobic bacteria ( which means air has to be blown into fecal matter tank )- Instead consider zero power zero maintenance no moving parts eco friendly STPs ( also called ECOSTPs) which use ‘anaerobic bacteria’ . Many Bangalore apartments with crunched spaces are using them and are happy . Time to think different!

  3. ranjith vp says:

    Nice Blog i read so far!

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