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topic 41130

Alternative uses for high TDS waste from RO system?

A discussion started in 2006 & continuing through 2017 . . .


Q. I am working as a ETP in charge in a private oil & gas company in India. We have a small treatment plant to treat the effluent before safe disposal. We are getting all the parameters except Total dissolved solids well within the limits given by state governing body at the outlet of plant.
Now we are thinking of Reverse Osmosis plant to fix the high TDS problem. We are getting around 7000 ppm of TDS at the outlet of ETP.
In RO system there will be two outlet streams: one is clear pure water & another is concentrated stream having high TDS.
My question is what are the possible methods for disposal of this concentrated stream.

Patel Jayesh Manaharbhai
- Ahmedabad, Gujarat, India


A1. What is the TDS measurement before your treatment? If you are adding TDS by treatment then you should examine that process. Chances are, your reject water is worthless. The most effective way to dispose of high TDS water is a deep well. The next is probably evaporation. But the best is to prevent the TDS to begin with.

paul morkovsky
Paul Morkovsky
- Shiner, Texas, USA


A2. Hi
The various methods of disposal of 7000 ppm TDS RO reject is as follows.
1. watering plants.
2. send to sewage disposal.
3. can reuse by passing through softener bed.
4. you can also evaporate , condensate can be reused, but costly, will lead to scaling/fouling.
5. you can also use this High TDS water for toilet flushing.

Hope this may help you.

Panjala Mukesh Panjala Mukesh
     fashion jewelry mfgr.
Hyderabad, India


A3. My company uses a phased approach to this problem - We build the RO system with multiple passes, using interstage pumps and membranes designed for the high TDS water.

Then, to get rid of the very high TDS waste stream this creates, use a precipitation stage and clarifier to settle the solids, and put the water back into the front of the process.

You should be able to achieve 95%+ usage of the water.

Jeff Watson
Jeff Watson
- Pearland, Texas


Q. Hello.

I am a student of M.Sc. Environmental Science. I am doing a project on Water Quality of Gujarat and ways to provide safe water to the rural areas. Here these villages have these RO plants installed. Now there are mainly 2 problems coming out of this:

1. it gives of 60% of the waste water which contains high TDS and also the uptake of ground water is high which decreases the water table.

2. Now what to do with this reject water from these RO plants?

Will wait for your reply.

Urvish Ishwarbhai Vadgama
ISTAR college, V.V. Nagar, Gujarat, India - Vallabh Vidhya Nagar, Gujarat, India.


A. Hi Urvish. Please try your best to express your question in terms of what has already been said by Mssrs. Morkovsky, Mukesh, and Watson. We won't win points with them by blowing off the effort they've already put into this page and starting over :-)

My suggestion is that you try to synthesize a proposed/tentative answer to your questions from the enlightenment which they've already offered us, and then ask if your idea sounds promising or not. Okay? Good luck!

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

December 29, 2010

Q. Dear sir, we are facing high TDS in our area; we want to convert this water for drinking. The TDS limit is 5000 hardness 800 ppm --so could you please give me right RO membrane for high TDS?


July 24, 2012

Q. Hello

In one of the projects I am working on for an automobile industry, we have 70 cubic meters of RO reject effluent to be reused/ disposed off. This contains around 4000 ppm of Total Dissolved Solids.

I would appreciate being enlightened about the options available and their viability -- apart from deep well injection, evaporation, disposal by dilution in a sewage stream. Can this be used for flushing of toilets either directly or after pH adjustment, coagulation, precipitation followed by settling and filtration?


Komal Dixit
engineering - Mumbai, India

A. Hi Komal. Panjala has indicated that flushing toilets is likely a good application, as is watering plants. I doubt that it can practically be directly precipitated and clarified at this concentration, as Jeff was describing a substantially more complex operation. But in any case, such answers are probably more along the line of "food for thought and experiment" than simple yes/no responses. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

November 29, 2012

Q. Dear Sir,
We want to know how we treat the ETP (effluent treatment plant) water and then it convert it into R.O. water. What can I do for this treatment and what chemical we use for treatment. This is chemical industries waste water. Please give me reply.

Vikram Singh
biotech - Bhiwadi, Rajasthan, India

November 29, 2012

A. Sorry for the difficulties, Vikram, but I don't know exactly what question you are asking...

A generalized ETP regimen to handle any volume of any ETP waste under unknown conditions is a subject which fills whole aisles in technical libraries :-)

Or are you saying that you've already treated the waste, and now you want to put this treated waste into an R.O. system to pull some pure water out of it, to be used for some purpose?

Sorry, but if you can clarify and limit your question the readers may be able to help answer that specific question, whereas if you want to learn the subject of chemical and R.O. treatment you would need a book or a course on the subject. Please clarify. Thanks.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

June 30, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Can someone throw light on usage of waste R.O Water or how waste R.O water can be used somewhere to conserve the water resource?

Manish Chandra
- N.Delhi, India

June 2014

A. Hi cousin Manish. As you see, this question has been addressed before in this forum, so we appended your inquiry to it. If the previous answers aren't sufficient for your needs, please expand upon the matter. Thanks.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

October 6, 2014

Q. Hi Ted

To be a little specific on the previous question. For one of my clients I am planning to propose a multi-stage RO system to treat their raw water (ground water) for process. The inlet water TDS is 1700 ppm, the expected volume of reject is 5 KLD at a TDS of around 25000 to 30000 ppm. I understand that leather industry uses water with high salt content for pickling but there will be chemicals added in the water stream for pH adjustment, biocide, anti-scalant, etc. The question is can this be used in the leather industry or can you recommend if there is any other industry which will find use of this high concentration of salt water?

Wilson Dhanaraj
consultancy - Chennai, Tamilnadu, India

January 2015

thumbs up sign Excellent question, Wilson. Unfortunately, it requires a good knowledge of the subject of leather pickling and tanning, about which I know nothing. Hopefully another reader has experience there. Sorry I don't know any industrial use for this type of salty water.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

Can RO water be re-used for drinking?

January 13, 2015

Q. Hey,
Can the water that is coming out of the RO units be reused for drinking?? If so, HOW?

- Chennai,Tamil Nadu,India

January 2015

A. Hi Adithya. If you are speaking of the 'reject' water, first it sounds very unlikely. Please see
for a really quick intro to the subject. But further, the idea that reject water that is unfit for other purposes should be drunk is hard to swallow :-)

If you are asking whether the 'good' portion of the water coming out of an RO unit can be drunk, the general answer is yes -- desalination plants, for example are built with this in mind. But simply passing the water through an RO unit is of course no guarantee that it is drinkable ... the water must still be analyzed for, and possibly treated for, all sorts of contaminants; and there may have been contaminants in the influent that rule it out. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

January 15, 2015

A. While RO reject water is usually not suitable for drinking, there are many possible ways to re-use it. If the hardness is low, it can be used in cooling towers or fume scrubbers. It can also be used to flush toilets, and if the TDS concentration is no more than 600-800 mg/L, then is could be used for irrigation (some plants are more tolerant than others to water with over 600 mg/L of TDS).

Lyle Kirman
consultant - Cleveland, Ohio

September 22, 2015

Q. How do you precipitate the water hardness of the RO reject? is this being done feasibly already?

mel villar
- Bataan, Philippines

September 23, 2015

A. It is fairly easy to precipitate the hardness from RO concentrate by raising the pH and settling out the precipitate. After settling, the pH can be re-adjusted lower.

There are also electrochemical devices that will do this.

Lyle Kirman
Consultant - Cleveland Heights, Ohio USA

February 24, 2016

Q. Dear Sir,
If we have TDS 5000 and the RO plant covers from 15000 TDS up to 25000, is it applicable? Can we use this station to work for us and we have 5000 TDS?

kassem ghareeb
- Beirut lebanon

April 20, 2016

Q. We are establishing a 500 lph RO system for coin operated dispensing in a dry village. Since the reject water quantity is large (~50% of input, totaling 2000 liters per day), we need to devise a method to recycle it.
Can we use an additional membrane in series to cut down the waste by half??

Saji Salk
Individual - Bangalore Kanataka India

April 20, 2016

Q. Sir,

Can rejected water of R.O. be used for recharging the aquifers?

Peeyush Sharma
- Jaipur, Rajasthan, India

April 27, 2016

A. Uses for the RO reject depend mainly on its composition. If it is < 600 mg/L in TDS, then it could be used for irrigation.

Lyle Kirman
Consultant - Cleveland, Ohio USA

May 16, 2016

Q. We are a Paper Mill based in India, and after treatment from our ETP the outgoing water has a BOD<15, COD- 125 to 150, and TDS 2500. The volume of water is 1500 M3. We wish to reuse 1000m3 after passing through the RO. Can someone suggest a means of treating/ safely disposing the RO reject without evaporation technique?

Rajeev Gupta
- Uttar Pradesh, India

June 15, 2016

Q. Hi. We Apartment members have installed an RO system to back up drinking water source from local municipality. The plant gives 1000 liter/hour permeate water and @ 500 liters of reject water. The raw water to the plant is from a bore well.
The quality of raw water is fairly good and total dissolved salts are marginally exceeded, i.e., 220 PPM as compared to 200 PPM allowed in India. The pH is 7.0. However, local lab has advised to use this raw water after treatment. This is the reason the RO system is used. Now we need to know if the reject water of 500 liters/hour can be used to for gardening, dumping in common drainage lines or for bore well recharging. The reject water test shows total dissolve to be 560 PPM. Thanking You. Please advise.

Dilip Halbe
Residential complex - Pune, Maharashtra, India

June 16, 2016

A. Hi Dilip,
If you are going to use the water on the garden, the conductivity will be fine for that.
It may be worth a biological lab test to be certain it does not contain any bacterial or viral hazard.
Ground water can pose a health hazard if you are not certain as to the sources of water draining into it from the environment in the wider neighbourhood.
After all, the lab you mentioned did advise that you filter the water before you drinking it anyway.
Check with them what they found in the water.
You can add a simple U.V. lamp system to the reject water stream to bring any bacteria count down.
Best regards

Mark Lees
- A foresaken rock in the Irish sea

June 24, 2016

A. Well it is not always cost effective to make an RO system double pass or multiple pass since with increase in TDS the electricity consumption will increase tremendously.

3.5 HP high pressure Pump verses 7 HP Pump.

Secondly the type of membranes will more than double once you step up from brackish (less than 7000 TDS) to Sea water, (over 12000 TDS)

Thirdly the life of membrane will reduce to 12 months rather than a normal 36 months.

Therefore recycle of RO reject can only be worked out once you know the following.

a) Cost and quantity of feed water.

b) Electricity cost.

c) Membrane replacement cost.

d) Whether the product is acceptable for industrial, domestic use (upto 380 TDS) or you need theoretically zero TDS (actually 12 to 40TDS) where minerals are added to create desired flavour or taste.

The best use of RO waste I have seen so far is its use in huge artificial sea water fish ponds (33000 to 40000 TDS).

Riaz Yousuf Siddiqui
Reverse Osmosis - Karachi Pakistan

July 18, 2016

Q. Hello All

Whilst I have the same question as everyone else which is "Can we treat the reject water from RO plants" , I also wonder if the same can be used to create DM Water for Industries. DM water is basically used in Cooling applications with the addition of coolants. DM water is pretty expensive and if we can find an economic way to create DM water..

srinidhi Iyengar
- Bangalore, Karnataka, INDIA

July 2016

A. Hi Srinidhi. The reason DM water is expensive is that you remove the contaminants chemically, by a substitution reaction, and you must consume a lot of chemical to do so. So the more contaminants, the more expensive.

Thus you might be able to reduce the cost of DM water by passing raw water through an RO unit and then demineralizing the RO water, but not by demineralizing the reject water. I only recently heard of electronic demineralizing, which uses no chemicals, but I assume that the electricity use and additional maintenance means it isn't cheap either.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

August 29, 2016

Q. Dear sir,
I just want to know if I feed treated high TDS Reject water to my RO system what will be the impact. Otherwise can I use this high TDS waste water mixing with normal raw water? Is it possible? Or else kindly guide me to make useof this RO reject water. And one more thing, what should be the ratio between product and reject water in LPH. I'm maintaining 700 LPH as product and 400 LPH as reject (plant capacity is 1000 LPH). Is it right?
Kindly guide me sir.

Arun Mani
- Bangalore,Karnataka,India

October 3, 2016

Q. Good Day!
I am currently having project study in using the reverse osmosis concentrate for a nonproduct use like for boiler feed water. So what different method im going to use?

Ruby Joy Paglinawan
beverage industry - calamba laguna philippines

October 29, 2016

Q. Can reject water coming from RO purifier be reused by using again in RO purifier. ?

Prakash Sahoo
- Junagarh, Odisha, India

December 13, 2016

Q. Dear sir, myself Suresh, I am working in sugar industry, I have a problem with my r.o reject water with high TDs around 20,000 - 24,000 ppm which is coming out from our ETP r.o plant, treating ETP R.O feed water.

TDS around 5,000 - 7,000 ppm, with a flow around 35- 40 m3 as its feed. For treating this high TDs R.O reject , we are using evaporation method with capacity of 6 m3 per hour. Here my problem is generation of r.o reject is 15 - 18 m3. I have to maintain this flow compulsory to avoid overflows, is there any other way to use this high TDs water? Please suggest sir.

- Kakinada , andhra Pradesh, India

May 13, 2017

Q. When we drain the reject RO water having TDS >6000 to the ground, won't the dissolved solids get filtered in a natural way before entering the underground aquifer?

Deepak Kumar
- India, Delhi

May 2017

Hi Deepak. It certainly sounds plausible to me, but we also used to think it was okay to bury drums of waste.

I think it's a matter of analyzing what is actually in that RO water (hopefully nothing but the original water hardness ingredients) and then doing a lit search to find out what people have actually determined regarding that thesis, and then also checking with the authorities regarding what is legal and what is the structure of your aquifer because you don't want to dump into a spring. Some foolish stuff is legal and some wise stuff is illegal, and we want to both be smart and obey the law rather than making assumptions :-)

Luck and Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

June 1, 2017

Q. Dear Sirs!
I start to grow Gray Mults fish and Spirulina in My system on RO rejects water 7000 ppm. Does anyone have experience or can send a link to reprints about it?

Yankale Peretz
- pardess hanna, Israel

June 2017

thumbsdownReaders: With 7 questions posted in a row and no answers (except my musings as site curator), we need people to start offering their thoughts about possible answers. One of the best ways to learn is to attempt to teach, so if you have a question, also include your thoughts on one of the already open questions.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

June 6, 2017

! Well said @Ted. The best way to Learn is by trying to educate. In that spirit, I would like to say what I have in mind. First, I got here as I was trying to find the best solution (which am still in search of) to RO waste water.
I hail from a region that's not well developed in road systems and there isn't much ground cover. It's a fairly arid/semi-arid area. So I was thinking this waste water from my RO system could be sprinkled along roads to reduce and avoid dust.
Better yet, it could be used to irrigate/grow grass for playing fields.
Well, I don't know how effective this is. I mean, in either way, I shall be engaging in some sort of evaporation related solution. Just my thoughts.
Looking forward to readers' input.


Jaqwibz John
- Naivasha, Kenya, Africa

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