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Extended aeration based STP under near zero temperature

Can anyone refer to any published literature/document/declassified report regarding performance of Extended aeration based STP under cold climatic condition (near zero). It would be great if it is in the south-east Asia, however any other place will also be useful. The main emphaisise will be on BOD removal efficiency, the deterioration of nitrification efficiency is well accepted. 

I am also interested to know if there is any extended aeration based system in Inida/South Easter Asia of  capacity more than 50 MLD.





In Bangalore BWSSB has built 7 new Sewage Treatment \plants all of them are with Extended aeration biological procress. Out of the 2 are with UASB followed by extended aeration. The location and capacities of these 7 plants are as under

1) Mailasandra (Mysore Raod) 75 MLD capacity
2) Kadabeesanahalli 50 MLD
3) EJ canal 40 MLD
4) K & C Valley 30 MLD
5) Nagasandra 20 MLD
6) K.R. Puram 20 MLD
7) Jakkur 10 MLD

With best wishes
ex-Chief Engineer, Bangalore WSSB


Dear Sandeepan,
I had come across in 2003, a case study of a pilot STP serving 20 seater toilet boxes in Leh for an Army Unit done by a researcher at IIT-Delhi at CES-Centre for Energy Studies, This had a bio-gas plant start up done on warming up feed initially by oil burners and when bio-gas plant was matured/ primed and in production, bio-gas ( methane) burners were used for warming the bio-sludge-feed and cattle dung, kitchen waste and other bio-wastes at the Unit base. Similar configuration can be used to approach thermophelic temperature for proper functioning of theSTP i.e Bio-gas plant which does the function of appropriate STP. If mor info is required pl provide more details of the site/ flow particulars etc..
with well wishes from
Ajit Seshadri

Er. Ajit Seshadri,Head- Environment, The Vigyan Vijay Foundation


Dear Er. Seshadri
Thanks for your reply. U r talking about anaerobic process - with heating, in a cold climate. That is fine. But I am talking exclusively about extended aeration based system of large capacity (say in the order of 50 MLD or more). In that temp. anaerobic based proceses are not so useful as the anaerobes are mainly mesopohilic. Although there are UASB installations operating at lower temperature with external heating using the generated biogas.
I was eager to know if there is any reported performance of this kind of large extended aeration system in cold weather. The problem is mainly operational - generally with low F/M ratio, BOD removal performance is not expected to be critical problem. But if u have lower Oxygen transfer rate, u require a larger volume of aeration tank. In fact nitrification process is considerably affected at low temperature for ext. aeration process. Also thin layer of snow on the surface can affect the settling tank performance. There isa extended aeration plant in Alaska for small population way back in 1974 - but no detailed info is available.
Hope i can clarify my point

Er M.N. Thippeswamy
Thanks a lot for your information. I did get the capacities of Mailasandra and the other 50 MLD plant from the VA Tech Wabag site. But no information rearding project cost or performance information. Is anything available in public domain. Thanks again for your help.



Besides warming up the sewage for treatment, you can go in for Bioaugmentation. Some blends of culture provide for psychrophyllic micro organisms which can work.
Certain strains have been found and isolated for such purposes in Alaska

Keshav Agarwal


Is your extended air activated sludge plant operating in continual freezing conditions or periodic conditions? My experience with periodic freezing conditions is that the plant will operate, but with reduced removal efficiencies, mostly related to settling problems. Adjusting the air supply may help, if this is possible. Keeping in mind the diurnal flow rates and the also the oxygen absorption at lower temperatures.

If your system is to operate at prolonged freezing conditions, you may want to look for another type of plant. For example, the RUCK system was used in Antarctica with good results. (Contact:

I am looking for a manufacturer in India of pre-fabricated extended air activated sludge package plants. Do you know of any? I had a reference to a company in Bangalore, but misplaced it and now cannot find it.

6. Low pH & nitrification

Hello all,

I am operating a small STP with 600 cum per day with extended aeration technique. My problem is related to temperature, nitrification is reduced considerably. I would like to know if there is any effect of pH (low pH) on nitrification and bacterial activity.

Thanks in anticipation

7. Low pH & nitrification due to the increase of BOD/COD

Dear Sir,

Low pH in sewage in a ambient temperature condition is primarily due to the increase of BOD/COD and reduction of Dissolved Oxygen (DO), thereby increasing anaerobic activity and forming organic acids as by products.

Microbes best work in a pH between 6-8, if it is lower or higher it affects the microbial activity and hence also the nitrifcation process.

Thanks and regards,
Chandan Mohanty
Technical Advisor
Amrit Clean Water Technologies Pvt. Ltd.

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