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Reverse Osmosis is a Boon or Bane in the present day water quality arena?

How sustainable is this technology if we consider the ecosystem approach? I know this is best possible technology available when we one has to treat multiple water quality problems at one go and also aware that there are various options available to treat the waste water generates from the process but on the ground I hardly find it in use! 

Now it is increasing in use, to provide safe drinking water as the problem of water quality is huge. But I am wondering if we let the waste water remain untreated: will not be there problems as this waste water containing high concentrations of chemicals will destroy the ground water aquifer or the eco-system?? 

I know many of members will not agree with me as the water quality problem is huge and everyday thousands of people die due to bad quality of water. Butt again as a citizen and working in the development field we just cannot ignore the environmental impact. If we do not take necessary corrective measures at present, we will definitely have problems in future which is irreparable. 

Therefore I request the members/experts in this field to provide me the valuable suggestions/ practical experiences if any especially with R.O. Plants for providing safe drinking water and its waste disposal mechanisms with any case studies.

 Mr.M.Manoj Kumar




You have raised an important issue that needs urgent attention of one and all.

The current approach to water supply we are adopting is some thing like running pillar to post. We often tend to find solutions to a newer problem that we have created due to the unsustainable practices we adopt.

RO is one such classic example of the story.

This issue needs urgent attention as most of the urban households are shifting towards it where such water treatment is not at all required. If unchecked, we are going to face greater consequences in the coming days.

Greater focus towards localised water conservation and implementing proper water legislation frameworks must be given priority given the precarious situation that we are facing. Water harvesting and ground recharge can only minimize the risks.

The unending queries related to RO and TDS handled by this service serves as an indicator of this serious problem.

Ramesh Sakthivel
WES-Net India


Dear Manoj Kumar,

There are several things wrong with your question and therefore it requires a somewhat lengthy answer.

First, I am not aware of any recommendations to treat the reject water of RO. (and incidentally, reject water is a better term to describe what you call waste water. The term "waster water" is used for the sewage/effluent from houses and industries). All that is recommended is, you can use the reject water for mopping the floor, or such uses. So it is no surprise you do not find people treating the reject water.

Two, question of treating water before releasing it in the hydrologic cycle arises only when we are adding any pollutants to water. RO process does not add any thing to water. The input to RO is water already having some dissolved substances, and from this RO extracts some water with less concentration of these substances, and returns the remaining water which now has a higher concentration of these substances. Nothing new is added.

Three, your remark supporting the use of RO because "water quality problem is huge and everyday thousands of people die due to bad quality of water" is out of place. Deaths due to bad quality of water are due to water born diseases, i.e. microbiological impurities.

However, our life style has inevitably changed from what it was say 100 years ago. Increased use of man made substances – from plastics and detergents and colours used in homes to more harmful chemicals used in various industries – are now a part of life. It would have been very nice if that wasn't so. But it is, and it is utopian to think that we can entirely do away with these substances. Therefore, it is inevitable that some times some of these chemicals find their way in to our drinking water.

Till the invention of RO, there was no way (other than distillation) to remove dissolved substances from water. RO is without doubt a boon, and I wish RO was cheaper. Then people in West Bengal would not have to suffer from chronic arsenic poisoning or people in Punjab would not have to suffer fluorosis. Sure, the reject water would have an even higher concentration of arsenic or fluoride than the input water, but that arsenic/ fluoride was already there in the environment. RO did not add anything.

Four, you did not work out the numbers. Let us for a moment suppose that we are concerned even about the locally increased concentration of pollutants from the RO reject stream, and let us also suppose that the Government distributes RO free of cost to any one who wants it and every one processes through RO some 3 L or so that is needed for drinking and cooking every day. So how much will be the local increase in pollution levels in %? If you worked that out, you will find that the number is so small that it does not even deserve a discussion.

I often feel that is the one major difference between environmentalists and technocrats - the concern for numbers. Often there are things that may look horrible in principle, but harmless when one works out the numbers. Concern for the environment is a good thing. But it should not be allowed to escalate into technology phobia or fear psychosis. I assure you, and other readers, there is no threat to environment from the reject water from RO process.

Chetan Pandit
National Water Academy


Dear Mr.Kumar,
Your question has been sent to me for an answer.I am a water management consultant with 40 years experience in water management and one of the resources on Indiawaterportal.You have raised a really interesting issue.

By and large, in India we have 'abused' water not 'used' it with the care it deserves.An excessive reliance on ground water has resuted in dangerous over exploitation of the ground water table which results in water with excessive dissolved solids content which makes the water unfit for any use without treatment.In such a scenario, RO is one of the most efficient methods of purifying water which contains a high level of dissolved solids.

Any water purification process involves the creation of a certain quantity of waste water which is increasingly difficult to dispose of and creates a huge problem now that waste disposal standards are getting increasingly tighter.

It is a curse we in India have brought upon ourselves.We have polluted all surface waters with sewage & industrial waste, and continue to do the same with ground water, in addition to exploiting it without taking care to put in place measures that will ensure ground water is recharged as much as it is used.Rain water harvesting needs to be done on a massive scale to recharge ground water as it will prevent deterioration in quality and make it possible to use it for drinking with minimal treatment.A lot can be done to improve the situation,but I would need several pages to explain.

In the immediate future, the one great hope is the availability of domestic sewage which can be treated to make it fit to drink.Singapore is one innovative country which meets approx 30% of its drinking water requirments by recycling sewage.We will soon have to do this in India too!


Consultant, Ion Exchange, Bangalore


Dear Mr. S.S.Ranganathan,

Thank you very much for the detailed explanation. I am just thinking that, the waste water which comes out from these treatment plants could be recycled(could be expensive), Solar evaporation by constructing solar evaporation ponds(rate of evaporation may be low and expensive). In Moondali village of Jaipur district of Rajasthan, effluent from the defluoridation plant is being treated by solar evaporation but ofcourse the rate of evaporation is very low and depends on the number of sunny days available and the maximum temperature. But these are some of the initiatives which are taken up by few, we need more sustainable practices on the field.

We hardly have surface water resources which can be seen, if available as you mentioned are polluted by different ways/means. In different forums we have discussed the Singapore model, Canada water supply systems,etc. but everytime it has come out that country like India, people will not drink water which is sewage treated water as the mind set , attitudinal problems, religious issues and blah-blah.. and everytime people make it as the political issue. There is no effective governance in place. we have got very stringent laws, acts and regulations, but enforcement is the issue. As the population of the country is increasing day by day, we need the action on ground, We have spoken enough, time for action.

We need to promote Integrated models-IWRM with site specific conditions, Domestic water management, effective governance and the lessons learnt from these successful case studies need to share at a wider platform and thenreplicate the models into wider geography by tunning.

At present R.O. is the best possible option for removal of the contaminants(Mainly Chemical contaminants-Dissolved solids), but I feel personally that India has traditional and modern and advanced scientific wisdom/knowledge in any field be it Water, Energy, Environment,etc. Then why do not we strive for the betterment of mankind. We taught the world on different aspects of the developmental issues.

Why don't we try something on Nano-technological applications??

I have discuss a lot on these issues, but through e-mail we can not.

Thanks and regards,

Manoj Kumar
Development Alternatives
New Delhi.


Manoj Kumar has raised an important problem of how surface and ground waters are being progressively enriched by TDS and other contaminants owing to inadequate care taken in the disposal of high reject water from RO process into the environment and on the need to use effective methods to check this type of pollution.

Our studies in Sri Venkateswara University on the geochemistry of groundwater in and around industries practicing large-scale RO have indicated a 2- to 3-fold increase of groundwater TDS in a few years period.

Artificial recharge of groundwater practiced by some of these industries has done more harm than good owing to RO reject water somehow entering the recharge wells along with rainwater. The care taken to upkeep the wells in use in India is very often not taken with abandoned wells or recharge wells. The picture at the following URL

shows the pitiable condition of an abandoned well in an urban area. The condition of some recharge wells is equally bad. There is again a tendency to make use of abandoned wells as recharge wells without properly reclaiming them. There is need for legislation for scientific sealing of all abandoned wells, besides imparting knowledge to all concerned that care taken to keep discharge wells in good condition should be extended to recharge wells also.

Where feasible, RO reject water can be mixed with high quality canal water so that the quality of the resultant blended water is suitable to grow salt-tolerant crops. There is also an urgent need to take up “Integrated On-Farm Drainage Management” (IFDM) to substantially increase the TDS and reduce the volume of RO reject water by growing water-loving and salt-tolerant crops, forages, halophytes and microbes and thereby make final evaporation in solar evaporators economically feasible.

Dr. R. Jagadiswara Rao
Sri Venkateswara University
Tirupati, AP 517502, India

Dr. R. Jagadiswara Rao, Professor of Geology Retired, Sri Venkateswara University, Tirupati, AP 517502, India


Although “Ask a Question” is not a discussion forum, but a few things have been said in response to this question that can not be ignored.

1. In amateur discussions salt-tolerant crops are often thought of as a remedy to water with high salt content. This is not correct. What is required is salt scavenging crops. There is a difference. Salt-tolerant crops are those which can merely withstand a higher salt content in the water, but they do not uptake any salt. They take only water and leave the environment with an even higher salt content. (one can think of them as a RO in nature).

Salt tolerant crops are fine if the objective is to grow crops. i.e. a salt tolerant variety of paddy will enable you to grow paddy even with salty water. But it will certainly not improve the salt parameters in the ground water. Which is why bio-drainage is not as attractive a solution as it appears in seminars. Trees that take up large quantity of only the water, but NOT the salts, will reduce water logging, but will leave the soil with higher salt content and thus actually make matters worse.

Salt scavenging crops are those which not only tolerate salty water but also use the salt in their metabolism. A chemical analysis of the entire plant biomass is required to establish whether the crop is salt scavenging. And it is not easy to find suitable salt scavenging crops.

2. Contrary to what Manoj Kumar, and perhaps Dr. Rao also, seem to believe, solar pond is NOT recycling of water. The water evaporates away to atmosphere, no recycling there.

3. And how do you dispose off the remaining solid residue ? Unless you dispose it off sealed in leak proof containers a-la radioactive waste (and of course that is not possible) the salts are going to get back in to the aquifer, minus the water which has evaporated away. Now, does solar pond solve the problem or does it add to the problem ?

4. As regards Dr. Rao’s studies that showed a 2- to 3-fold increase of groundwater TDS in and around industries practicing large-scale RO, it would be interesting to know what was the change in TDS in control samples, i.e. the samples from nearby geo-hydrologically identical area where there were NO industries practicing large-scale RO ?

Chetan Pandit
National Water Academy


This article by CSE raises few questions on the water treatment technologies being promoted in India. Kindly visit to read it.

This may help people who are looking for water treatment solutions to some extent.


Dear Manoj,
Thanks for raising an "important" point for discussion. The following are my views on RO plants for drinking water applications.

1. The solution of RO for drinking water is accepted world wide
2. The 'need' for treated water and its relevance to human life has to be considered during deciding the technology.
3. Any technology has its pros and cons but the answer lies in whether it will solve my problem. If yes then we could work out a strategy for cons
4. The reject as raised by you does not contain any chemicals as it is just a concentration of the salts through the RO process. There are techniques available which comes at a cost and its feasibility has to be worked out.
5. We always tend to see the environment is affected but do we think that Humans are being affected due to fluorosis, Salinity, Arsenic etc.
6. RO systems has to be promoted in areas where water quality is bad and there is no other option then to go for RO technology.

with best regards

Premesh Balan
Doshion Limited


Dear Manoj,

I agree with you that RO reject is very high in concentration and does have it's effect on ground water. However, survival is the first law of nature and we need water to survive. Also, the only way to find a solution is to allow technology to go forward. So far, we have found solution to treat water; next challenge is to find solution for reject. It is the same situation as treatring effluentsd and converting it to usable water but having a sludge problem. I think that others must join in and give their own opinions so that you choose the better ones and leave out the rest.


As rightly pointed out by Chetan Pandit, any study on the increase of groundwater TDS affected by industrial activities should also take into account changes in groundwater TDS in the nearby geo-hydrologically comparable areas unaffected by industrial activities. Our studies in several areas occupied by human habitations without any industrial activity also showed progressive increase in the TDS of both surface and ground waters over a period of time. Unlike in the industrial areas where there was a 2- to 3-fold increase of groundwater TDS in a few years, the increase in groundwater TDS in habitations is only around 1.5 to 2 times over a period of a few decades. This increase in TDS is attributed to people’s ignorance that their routine activities in everyday life were responsible for this deterioration and they have a role to play to improve and protect the quality of natural waters.

Most abandoned dug wells used for drinking in the past have now become point-sources of pollution owing to using them as sanitary sinks to dispose all sorts of solid and liquid contaminants besides performing certain religious rituals such as idol immersion. The picture at

depicts one of the many such abandoned wells polluted by human activities.

When an industry uses reverse osmosis to obtain low-TDS process water from moderate-TDS groundwater source and disposes the high-TDS reject water near to the source water, there will be a gradual increase in the TDS of source water over time depending on the quantum of process water treated and the connectivity between the high-TDS reject water and the source water. In addition, the treated wastewater (TWW) generated by the industry also having high TDS enhances the TDS of groundwater and TWW in and around the industry.

Halophytes (salt-scavenging crops) such as Bermuda grass and bacteria such as Pseudomonos not only tolerate salt water but also accumulate substantial quantities of salt in them. They are periodically removed for use as cattle fodder. The main purpose of growing them is to achieve a 10-fold reduction in the volume of the high TDS water so that small-sized solar evaporators rather than solar ponds could be used to obtain salt that could be disposed in sealed leak-proof containers for dumping elsewhere such as a brackish water estuary connected to the sea. Many industries find this way of disposal of salts better than allowing groundwater to become unfit for any use and thereby face problems with the pollution control boards or public that can threaten their closure.

When RO is used to remove toxic substances such as fluoride, it could be prevented from entering groundwater in dissolved state through immobilisation. For example, it is known that the Earth’s crust consists of 950 ppm of Fluorine and seven times less than that of chlorine. Despite that, seawater contains 1.3 mg/l fluoride as against 19,500 mg/l chloride. This indicates that the natural environment of the Earth has a favourable mechanism to immobilise toxic fluoride for the safe existence of life. Only in hot semiarid tracts characterised by wide fluctuations in groundwater levels, both natural waters and soils become alkaline with high pH. Such alkaline waters become impoverished in calcium by precipitating as calcium carbonate. In the process, groundwater gets enriched in highly soluble sodium carbonate, sodium bicarbonate and sodium fluoride. Gypsum treatment is extensively used by agricultural scientists to reclaim alkaline soils into good soils. The same method could be used to convert high-fluoride groundwater into low-fluoride groundwater through immobilisation of fluoride as insoluble calcium fluoride. Even the high-fluoride reject water obtained during RO of high-fluoride groundwater could be immobilised and thereby prevent it from enhancing the fluoride content of groundwater.

Dr. R. Jagadiswara Rao
Retired Professor of Geology
Sri Venkateswara University
Tirupati, AP 517502

Dr. R. Jagadiswara Rao, Professor of Geology Retired, Sri Venkateswara University, Tirupati, AP 517502, India

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