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Alternative uses for high TDS waste from RO system?


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
     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
- 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. I doubt that you'll win points with them by ignoring the effort they've already put into this page and starting over :-)

Please try to synthesize a proposed/tentative answer to your questions from the enlightenment they've already offered us, and ask if your idea sounds promising or not, okay? Good luck!

Ted Mooney   Teds signature
Ted Mooney, P.E. RET
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

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. RET
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 what question you are asking...

Are you asking for a generalized ETP regimen to handle any volume of any ETP waste under unknown conditions? That subject 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. RET
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
  ^- Privately contact this inquirer -^

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. RET
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

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.


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

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.


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

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

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