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Recommended Water Purification Technique - Vadamanapakkam Village, Tamil Nadu

     My name is Harish. I am looking into various methods for water purification in Vadamanapakkam, Tamil Nadu. This village has approximately 3500 people and the groundwater is the only water source. I have added as an attachment  the test results. Some of the samples have a TDS above 2500 ppm and the total hardness >1000 ppm for CacO3. Would RO be the best solution? Is there any other cost effective method? 

 

Thank you for your help,

Harish

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1. Recommnded Water Purification Technique.

Dear Harish,

As per the test report attached by you the samples marked as B,C,E,F & G has TDS and Hardness in the acceptable range but as the Na & Cl are very high the water must be brackish in taste. Further the Nitrate level in almost all the samples is also very high which is also not fit for drinking as it may cause Blue Baby Disease in infants. for this kind of water quality the Reverse Osmosis (R.O.) Technique is the best method for purification.

regards,

Amit Kr. Singh,
Govt. of Haryana,
Public Health Engg. Department,
Water Testing Lab,Karnal-132001(haryana)
09416204204,09729248248,
ak_ranaji3@yahoo.co.in

2. Water Purification Methods

Hi Harish,

In my opinion, while Reverse Osmosis (RO) is a viable treatment option, your situation may not warrant it.  

 The only treatment that is really needed in this case looks like reduction of hardness or softening which can be done by chemical precipitation or by ion exchange. The latter might be a better option: 1) availability of efficient resins, 2) ion-exchange produces softer water than precipitation, 3)avoids large quantities of sludge, 4)the apparatus is much smaller and simpler to operate

Since turbidity is not a problem there is no risk of the resin functioning as a filter and becoming plugged. Softening of clear groundwater should be done immediately before aeration occurs and the water should not be chlorinated before ion-exchange softening. 

RO is generally used in water treatment for the removal of dissolved salts and can operate at 90 percent efficiency or better with respect to TDS.  In addition to inorganic ions, RO systems also remove organic molecules, turbidity, bacteria and viruses (might come in handy in places that have water borne diseases). 

RO can be an expensive treatment method. It requires a high degree of pretreatment: removal of dissolved organics to prevent fouling, pH adjustment to be slightly acidic to prevent inorganic precipitation that causes scale formation, removal of Fe and Mn to decrease scaling potential and removal of suspended solids.  In short, a very high-quality feed is necessary for efficient operation. Pretreatment of a secondary effluent with filtration and carbon adsorption is usually necessary.  The treatment can produce a waste stream that may range from 10 to 25 percent of the feed water, which means an additional volume of water needs to be processed to offset this loss.  The wastewater has to be disposed of properly. RO removes some minerals that are actually good for health.  

I noticed that phosphate and nitrate levels are on the high side.  Nitrates can be harmful to infants. While phosphates do not pose a direct health threat, they might promote undesirable aquatic growth if they reach the surface water.  Phosphates also interfere with water treatment processes.  You may want to take a look at the source of these constituents and try to curb it at the source.  It may be coming from the use of fertilizer in the area.  If there is agriculture activity in the area, RO does not remove pesticides and herbicides that may end up in the treated water unless a carbon filter is used. 

You will have to do a cost analysis based on capital, chemical and labor costs all of which are linked to various factors such as, efficiency of treatment, influent constituents, cleaning and maintenance requirements etc. 

Do write in when you decide on a treatment method. It would be nice to know what criteria most affected your decision. 

Good luck

Janaky Ramaswamy

Janaky Ramaswamy

3. Dear Harish, The most

Dear Harish,


The most effective treatment would be Reverse Osmosis (RO). However; it would be very expensive too depending on the total quantity to be treated. If we take approximately 10 to 15 litres/day/person, just for cooking and drinking purposes, it works out to a total of between 35000 to 53000 litres of water per day for a population of 3500 people.


The silica content of the sample analyzed is 50 ppm and this would reduce the 'recovery' from and RO plant making it more expensive. There are the following drawbacks to this system.



  1. Waste water from an RO plant would be substantial and it would have a very high TDS content of several thousand ppm. Disposing of this would be a very major problem.

  2. The RO plant would have to operate at a flow rate of anywhere between 4.5 to 5.5 cubic metres/hour in order to supply the water the entire village needs, and this would be the major contributor to the cost factor of a suitable RO system, storage tank and piping. My very rough estimate of the capital cost is between Rs. 12 to 16 lacs. You would also have to ensure there is sufficient power to run the plant and this further pushes up the cost.

  3. Operation and maintenance cost of the plant and related infrastructure would be quite high. Who would bear this cost and also who would operate and maintain the plant?

I recommend that the village on a community level does Rain Water Harvesting (RWH) and store a part of the harvested rain water using the bulk of it for ground water re-charge so that quality of ground water improves over a period of time.


Those who take decisions for the village (Panchayat?) should consider solar distillation of water for drinking. TERI can be contacted for this kind of system, but, again this is not a solution on large scale. Small solar stills will have to be considered and several such plants to be shared by the villagers. If I can find any useful information on this I will provide it.


Regards


S.S. Ranganathan


Advisor             


Ion Exchange


Bangalore

4. Dear Harish, The most

Dear Harish,

The most effective treatment would be Reverse Osmosis (RO). However; it would be very expensive too depending on the total quantity to be treated. If we take approximately 10 to 15 litres/day/person, just for cooking and drinking purposes, it works out to a total of between 35000 to 53000 litres of water per day for a population of 3500 people.
The silica content of the sample analyzed is 50 ppm and this would reduce the 'recovery' from and RO plant making it more expensive. There are the following drawbacks to this system.
a. Waste water from an RO plant would be substantial and it would have a very high TDS content of several thousand ppm. Disposing of this would be a very major problem.
b. The RO plant would have to operate at a flow rate of anywhere between 4.5 to 5.5 cubic metres/hour in order to supply the water the entire village needs, and this would be the major contributor to the cost factor of a suitable RO system, storage tank and piping. My very rough estimate of the capital cost is between Rs. 12 to 16 lacs. You would also have to ensure there is sufficient power to run the plant and this further pushes up the cost.
c. Operation and maintenance cost of the plant and related infrastructure would be quite high. Who would bear this cost and also who would operate and maintain the plant?
I recommend that the village on a community level does Rain Water Harvesting (RWH) and store a part of the harvested rain water using the bulk of it for ground water re-charge so that quality of ground water improves over a period of time.
Those who take decisions for the village (Panchayat?) should consider solar distillation of water for drinking. TERI can be contacted for this kind of system, but, again this is not a solution on large scale. Small solar stills will have to be considered and several such plants to be shared by the villagers. If I can find any useful information on this I will provide it.

Regards

S.S. Ranganathan
Advisor
Ion Exchange
Bangalore

5. drinking water treatment

RO is water robbery( 50% water waste). It is used in industrial effluent for TDS removal. Later this has been put to people for drinking.

The TDS is such a nonsense factor and we all running after TDS. Once the water comes out from RO and that is acidic water and when contact with atmospheric air it will covert co2. While drinking such water where all essential minerals are removed and the result is that we lose our calcium from bones and teeth. Hence joint pain is guaranteed, simillarly the it boost many diseases as it is with low disolved oxygen. 

Also worth to note that many bacteria and viruses are less size than RO membrane. and many heavy metals are all less than water molecule. Hence these dangerous part can not be removed by RO.

Take an example: coconut water TDS is around 4500ppm but we drink everyday. bcoz it contain all cations. So we have to worry when water contains only anions( pesticide,herbicide,petrochem products,mixing of drained water from various industries and so on. Therefore we first need to know the TDS contents in water.

I propose to see my website for a new water purification technology which may give you an clear idea how the must be treated for drinking.

www.envirolyteindia.com

Rgds

Dr.Balan

 

6. Recommended water purification technique- Vadamanapakkam Village

       Pl give the following details:

1.      You are using the word ‘ground water. Is the source a borewell or a surface body?

 

2.      Is the source a common one like the village well, pond or tank or some common borewells or is it a problem with any water source in the village?

3.      Is the problem of recent origin or a long time one? If the latter, how have you been man aging it so far?

4.      How much rainfall do you get in your village?

5.      Is there a large amount of irrigation activity?

6.      If so, is the water source(s) near these source?

 I would venture to offer advice only on the basis of these details before venturing into softening or RO. and such other techniques.

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