The Need to Replace RO from the filtration monopoly

                                       

Preamble

The basic fact one should know before basking into all that follows is this: China, a country with 0.147 billion more people than us uses 28% lesser freshwater by volume than us. So the issue to be dealt with is not just inadequacy but  the reckless usage of water resource already present. And we should know the definition of potable water. We have to think in multiple level of impacts, because everything are connected at some level. For example, one crore litre of water is sold packaged in PET bottles daily in Chennai alone producing as much non-disposable waste, the effects of which are, in turn, a clear denotion of failure of the metro water supply board and the government failing to provide clean tap water to its citizens. We must be aware that being toxin-less doesn't  mean that the water is healthy. 

What is Reverse Osmosis? 

                                       

It's simple. Nothing you wouldn't have learned in your class 8.   Take an U-tube separated at bottom by a semi-permeable membrane that allows only water molecules to pass through. Fill it with water of two different mineral concentrations on the two limbs. After sometime, water level on the side with higher concentration would naturally rise effectively equalizing with that of the other. The pressure that pushes this imbalance in levels is osmotic pressure. This pressure, when applied externally would do exactly the opposite--the side with lower concentration will get still more diluted. This is 'Reverse' Osmosis (RO). This RO process forms an important penultimate step in the overall drinking water filtration:

• Sedimentation 
• Second sedimentation
• Activated Carbon filter
• RO filtration
• UV sterilization

This layout is found in almost all filtration processes. Sedimentation filters out most of the suspended impurities like rust, CaCO3 etc., Activated Carbon traps organics and chlorine after which the RO filter comes into play. Other common filtration processes are: Boiling, Distillation and Chlorination. While Boiling and Distillation are energy-intensive and incapable of removing certain contaminants, Chlorination is directly linked to causing health hazards, depending upon situation.

Why is it so widespread currently?

Simple. The need to hydrate billions and industrialization. And it removes 95 to 99 percentage of Total Dissolved Solids (TDS) and contaminants, such as Arsenic, Fluoride, Hexavalent Chromium, Nitrates etc., not removed by Activated Carbon and Distillation.  It's affordable, portable and hence it's ultimately needed in developing countries. And RO process is quick and adaptable to any scale of discharge required.

What developed as a research to desalinate sea water (which, by far is the most suitable way) has become the most common method to purify water. Countries like India didn't have to filter well-water some decades back, at least not for taste (the taste that we are accustomed to, not meaning undrinkable salinity). But they have had to, after years, for two reasons: Industrialization and Epidemic. Contamination of ground and surface freshwater by heavy metal pollutants off industries and death of people in multitude by Epidemic diseases like cholera, typhoid all stopped after the advent of mass disinfection and filtration methods. Chlorination was the disinfection-aid and RO turned out to be the filtration monopoly. It also helps where water is naturally degraded.

Where does it score too low in terms of sustainability?

While looking into, the cons outweigh the advantages both in terms of sustainability and health effects. Number one thing is RO leaves a lot of water behind as slag, in a ratio of 1:3.75 to put exactly. That is, for every litre of output, there is about 4 litres of water dumped out which is a grave concern in the current scenario. Add to this, the unusability of the ejected water in many ways (but it has its ways). The brine (ejected water) concentration varies from 50 to 75g/l and so is denser than sea water. So large scale RO Brine disposal into the sea will make it fall on the sea floor (plume effect) impacting negatively on the marine flora and fauna there adversely. One such example is the AMMA kudineer  scheme--crudest commodification of life resource. A state-owned plant at Gummidipoondi producing  three lakh litres of RO water daily and packaging it in (non-recyclable) PET bottles (which would fill the dumpyards and clog the sewage-ways) to be sent throughout the state surely does more bad to the world than good. 

Also we are using RO where it is actually not needed, let alone the wastage while using it at truly needful place. As a matter of fact, RO filtration isn't worth employed unless your water has 500 mg/l or more of TDS, exempting water with heavy  and poisonous metal contaminants. Also, at a large scale, RO plants are expensive, maintenance-intensive and unsustainable in its withdrawal of water. It is thus inevitable to point out  the infamous AMMA kudineer scheme and it's serious flaws.  Healthwise too, RO is not good as it is not mineralizing water as it is claimed to be--it actually demineralizes  it by removing all essential elements along with the unwanted ones. This can be certainly attributed (along with others) to the current widespread prevelance of gastro-intestinal problems, bone density issues, joint pains and cardio vascular diseases. All these can be well studied in WHO's report over disadvantages in drinking low-mineral, which states "such water has definite adverse influence on animals and humans"

Which are the measures that we can implement? 

For existing RO facilities:

1. Remove RO unit

Those who have RO fitted filtration device at household level (almost everyone) can simply detach RO from the supply chain and by-pass it directly to UV sterilization unit. That's the simplest thing we can do to save as much as four times. But before that you will have to ensure the water you're gonna drink has

• No poisonous and heavy metal contaminants
• No chances for breeding of infectious pathogens

       2. Add Re-mineralization cartridge

If the water in your region happened to have the above mentioned parameters, then it is recommended to get a remineralization cartridge at the end of the line or add liquid ionic minerals to your RO purified water.

      3. Dispose Brine carefully (at a plant level)

Large scale plants need to place the outfall terminal in a strong sea current to aid mixing of it with sea.  

• Evaporation Ponds in areas of hot climatic conditions.
• Irrigating plants which are tolerant to high salinity (halophytes)
• Disposing into running water bodies like rivers and streams or Careful deep-well injection into porous rocks 

         

New alternative:

         

Solar Disinfection      

                                    

     (Source : http://www.sodis.ch/)

It is free and effective method applicable at household level. The SoDis method uses UV light in combination with increased temperature obtained from solar radiation. It is recommended by WHO as the most viable method for household water treatment. Exposure to sunlight is proven to deactivate diarrhoea-causing pathogens which is attributed to the UV part of the sunlight.

So our idea for a typical process sequence is:

1. Rock layer filtration
2. Cloth filtration to bring down turbidity to lowest possible
3. Carbon filtration (requires pressure to be given)
4. Shaking in a three-fourth filled container to improve oxygen saturation
5. Checking for turbidity again
6. Exposure to the fullest possible sunlight in PET containers or anything that doesn't filter out UV part of sunlight.

Or polythene covers maybe employed as the light permitting heat insulation which briefly evaporates water up by 60° and condenses it upon the cover. It can be installed in rooftops.

With India in the most favourable region for application of SoDis (15°N and 35°N) and given its simplicity and affordability, it has the potential to serve as the mass water purification method if people together come to explore it and attempt it at an individual level. So consider spending some money experimenting and finding the most suitable setup for your water and need.

Keep visiting...