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Gas Production Estimates&Recovery.

We have a STP of a cap of 225 kld, we want to recover gas from the system to reuse it. The COD is 500 mg/l, how much gas will be produced & what will be the way to recover it?.

Mr.Parveen Sharma





Let's be honest. Small STP shall not give you sufficient gas since the volume recovered per kg BOD is rather less. The gas generation for your plant shall be approximately 6.4 cum. This is if the average BOD in your STP is 500 mg/l.I do not think that the average BOD over 24 hours shall exceed 300 mg/l. The grab samples shall give you higher figures.

Also, you do not have anaerobic process where methane shall be recovered. And also, the bacteria must be digested properly in your process. I assume that you have adopted ASP or EAT process which is aerobic in nature.

Taral Kumar
Akar Impex, New Delhi


An STP of 200kl per day as per data of COD-400mg/l would have BOD- say 200 to 250mg/l, hence as per thumb rule

200(ppm) x 200000 mg gas per day would be avai;lable but the efficiency is 30 to 40% hence say

i.e 40000 grms per day/ 40kgs x 30- 40 % an equivalent of 15 kgs i.e like one LPG cylinder per day can be realised

certain factors to be kept in view, its ideal if the BOD is in the range of say 600 to 1000mg/L as usually got in CTC-Community Toilet Complexes, where minimal water is used. Also to make some alterations to make the primary process(anaerobic) of intended STP to function like a BGP-Biogas plant.

This is indeed is a good eco-san and green-initiative. As if the same methane say 50kgs are released in the environs per day, it creates local warming as CH4 is a GHGas and most people cannot feel methane in air as it happens to be odourless, methane's presence is felt because of the accompanying H2S (rotten-egg odour)

When viewed in CC-carbon- credit perspective also it reveals a good indicator,

Any specifics , pl feel free to be in touch with our Ngo.


trust the above answers, it requires more info to proceed further..towards design..implement etc..

Er. Ajit Seshadri
Head-Environmental Wing
The Vigyan Vijay Foundation
H-2/2-5, Mahavir Enclave,
Palam Dabri Road,
New Delhi-110 045
Ph. : 011-25058853 (NGO)

Website :


225 CUM with COD of 500mg/l gives a daily gas production of 22.5 CUM.

225000 l/d x 500mg/l = 112.5kg/d
we can expect that 200l of biogas get produced out of 1kg COD, so we get a daily gas production of l = 22.5 CUM

It is to point out that this gas gets only produced in a anaerobic treatment process, not in a aerobic!
I don't think that you have a anaerobic STP of 225 CUM; if you have, you have to make your treatment system gas tight
to capture the gas. If you need more details, contact me.

All the Best!

Nanchoz Zimmermann
seecon international GmbH
c/o Ecosan Services Foundation (ESF)
"Vishwa Chandra"
1002/42 Rajendra Nagar
Tel/Fax: 0091/(0)20 64 000 736

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