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Backwash Effluent to Defunct Well or to STP inlet? - Advice Required!

I live in a complex housing 380 flats. We have WTP treating raw well/ bore water. We carryout prescribed Back wash of filters- & this back wash water is red brown in colour indicating heavy amount of iron that had been filtered. This water is fed into a defunct well close to other wells from which we draw water.

I have some queries regarding this practice:

1. I am of the opinion that this should not be done as it is going to contaminate the water table with more iron concentration. Is my view correct?

2. Is there any harm to divert this back wash water into the raw sewage collection sump? We have STP also,& which processes the sewage to treated water.

3. Will the back wash water from WTP rich in iron if let into the raw sewage collection sump affect the functioning of the STP?

Kindly clarify on the above aspects.

V.Muralidhar rao




1. Yes. you are right. surely the backwash water should not be dumped into the well/recharged to the ground as such. because it will lead to seepage and contamination.

2. The backwash shall be let into STP. The STP will have aeration process in which the iron in the water will get oxidised, precipitated and filtered.


1. yes you are right. the backwash should not be let to the well/ recharged.

2. The stp will sure take care of your iron water.


Dear mMr. Muralidhar,

I congratulate you for your concerned about the ground water quality. You are absolutely right and stop the practice of sending backwash water to the defunct well. To send it to STP you have to check whether STP can take this additional hydraulic load. If it can take the load you may slowly release the water to STP.

Prof. R. V. Saraf
Viraj Envirozing India Pvt. Ltd.
21 Radhakrishna, Near SBI
Paud Road, Pune 411 038
Tele/Fax: (020) 25433445
E Mail:


Dear Muralidhar,

Its good to note your intention not to allow remedied back-wash water of your WTP back to aquifers thruogh the old dug-well.

Prudently, if your society is very serious, have the final effluent tested, and if Iron and others are within limits, have a plantation-bed as a filter and lead the processed water to a maturation pond,

this pond can also be used / doubled up as a Rain-harvesting storage, The water stored in the pond can be used for horticulture and also for toilet flusing uses. The water requirement in your complex is around 150 to 200kl per day. and hence considerable saving is possible.

pl feel free to be in touch for any specific details

with well-wishes from VigyanVijay,

Er. Ajit Seshadri.
The Vigyan Vijay Foundation

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


Dear V.Muralidhar Rao,

Discharge of backwash water to STP inlet:

Considering 5 persons per flats and approximately 200 lpcd (higher side for HIG), the water treatment plant has a capacity of around 400 m3/d. So the volume of back wash water is expected to be around 2-3% of it i.e., 10 -12 m3/d. If this amount of water with high total suspended solid is added to the STP inlet, any problem is unlikely to occur due to higher hydraulic loading and additional TSS load.

However, nothing is mentioned regarding the nature of STP, it must be checked with the vendor that it does not hamper with that it is not sensitive to higher iron content.
In fact addition of iron salt in Activated sludge based system is common for better coagulation purpose. But there is always an inhibitory limit. So better to check with the STP vendor if there is any problem from his end.

Recharging of groundwater:

Certain water quality is to be maintained for recharging the aquifer. TSS content as well as the iron content are both important. Water for well recharge usually must meet Drinking water quality standards if directly recharged. So some pre treatment is necessary for that. If it is infiltration recharge then also some pre-treatment is necessary to meet the desired quality.

Best regards

Sandeepan Chowdhury

6. Looking for a backflush water treatment solution

Hi all,

I saw some useful water treatment tips in this forum. I have got one query.

I am residing in a small group housing society in Mumbai having 65 flats in it. We were getting very dirty water quality through BMC which made us install a water filter which wastes around 1500-2000 lts of water with every back flush. We would like to utilize this for toilet and gardening purposes. Is there ant low cost basic solution available for this?

Please Guide.


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