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Central Water Treatment Facility: Need or Waste of Resources, Advice Required - Noida

We live in a multistorey housing complex in Noida. We use water which is a mix of water supplied by the Noida authority and our own bore wells. The TDS of the mixed water ranges between 600-700ppm. Almost all residents use individual RO systems for drinking water needs. We are planning to install a water softening plant for the housing complex. This will cost us about Rs. 250000 to install and the regular operating expenses.

Please let us know whether it is desirable to treat water of this level of TDS and incur this regular cost. We are also concerned about the use of a large amount of salt and the wastage of water used in the recharging of the ion exchange resin.

Can rain water harvesting be useful in this situation?

Additional Details: Amount of water drawn from municipal supply has not been measured but based on our experience, we believe it varies from day to day. Also amount of water drawn from bore wells has not been measured. There are a total of 166 apartments, and we feel that the total consumption of water is about 1 lakh liters per day. This is the quantity that is being used as an estimate for the water softening plant. The central unit is being considered as many of the residents feel that this will lead to less deposits in the pipelines, less clogging of shower holes, less deposits in hot water geysers and overall increase in quality of water.

Manohar Malhotra




Dear Manohar.

Endorsing the response from Mr. Anshuman of TERI, we add that you should plan and implement RWH.

In the longer run centralised RO-Unit would be more economical, to maintain than the ones in each homes.
Also year by year TDS levels would raise, requiring up-graded RO-Unit, and here again a Central Unit would be more economical and sustaining.
As regards individual desire, one could opt for RO system at one's home also.

RO- Reject water is another issue, if within limits could be used for irrigating greens, horticulture. An element of caution is to be exercised.

We also suggest wwt-recycling plant and re-use water for greens and horticulture.

We are a Ngo working in this sector at Delhi and have implemented water- projects at NCR including Noida, pl feel free for any guidance.

With well wishes,

Ajit Seshadri

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


Dear Manohar Malhotra,

TDS though is a good indicator of the total salt content of water but it alone may not necessarily tell the kind of treatment required for water.
You would need to understand complete profile of the water quality of the water being used for different purposes at your complex.

Since you also mentioned that each house has its own treatment (RO) unit installed, it is likely that water meets the desirable drinking water standards. However I would suggest that you get a water audit done for your complex to understand the demand/supply as well the water quality status to be able to understand if such an intervention (water softening plant) is required or not and then undertake appropriate/suitable treatment intervention alongwith conservation measure.

Rainwater harvesting in any case would be beneficial in water conservation for your complex.

In case you need further assistance you may contact us at the details below. We at TERI assist residential complexes like yours to understand water scenario (availability and quality) and suggest scientific and sustainable solutions including water treatment and conservation measures like rain water harvesting.

Kind regards

Associate Fellow
Water Resources Policy and Management
Water Resources Division
The Energy and Resources Institute (TERI)
New Delhi


Dear Manohar Malhotra,

A centralised unit would cost less than the expenses on individual RO units. However, since the individual RO units have already been installed, there is no reason to also install the centralised unit, given that the TDS of water mixed from two supply sources is only up to 700 ppm.


Paritosh Tyagi
Chairman (Retired)
Central Pollution Control Board
New Delhi


Dear Manohar ji,

If you consider only TDS for treatment of water then R.O.treatment is not required for this level of TDS. If the water source of Municipal Supply is river water then you should go for complete analysis of your mixed water and specially for Heavy Metals contamination. If some contamination is found then you should go for R.O.treatment of this water otherwise only UV filter is sufficient.

The wastage of water is very high in R.O.treatment, if you are installing this process the waste water which is received after treatment is very high in salts and you should use it for domestic purposes after mixing some fresh water.


Amit Kr. Singh,
Govt. of Haryana,
Public Health Engg. Department,
Water Testing Lab,Karnal-132001(haryana)


Dear Malhotra,

First I would like to mention here that a water softner can not reduce TDS level. It only converts Ca and Mg salts to equivalent Na salts. sodium deposits are soft so water hardness can be lowered up to zero ppm but TDS level will be same as it is at present.

You like to process 1000 M3 of water. In my opinion you will require to keep atleast 100 ppm hardness at final water.

Your plant will require 500 Kg NaCl (brine solution) for regenration of resin. each regenration will cost you about Rs 3000 and will give you 1000 M3 soft water.
there will be about 50 M3 waste water of high salt content.

In my opinion except less clogging of shower there will be no other benefit it will give.
I do not consider this project worthwhile. 600 ppm TDS water is just ok for washing bathing.

For drinking indivisual RO systems are already there.
If Cost does not matter than i think centralized RO plant with high recovery rate and permeate level at 300 TDS will solve your purpose technically what you want.

AK Singla
Power utilities Engineer
Indian Oil corporation Ltd
Panipat Refinery




I calculated the system for 1000 M3 water/day. It is actually 100 M3/day. so accordingly NaCl quantity, cost and effluent quantity will be 1/10 th of the calculated values in previous reply.

With best regards
AK Singla



7. drinking water filters

I’m impressed, you know what you’re talking about

8. Need or Waste of Resources, Advice Required - Noida

Dear Malhotra,

we could offer solution to treat the wastewater.. we have an unique oxidation technology wherein oranic / inorgani / heavy metal contaminants are oxidized .. it is proved that tds too is reduced between 30 / 40%.if interested please feel free to call us at any time or reach us on 


Madan Iyengar


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