Recently I read a write up in the Times paper giving details about how potable water tanks on top of buildings are creating pollution in the water that is stored in it. That article suggests that we should get these tanks periodically cleansed; and further gives tips on how to do it.

I had written on this topic one post three years ago in my earlier blog, which was eventually hacked. In that post I had proposed similar technique and that was not all, I went further and convinced one friend of mine to take up to start a service to do cleaning of tanks of co-op housing buildings in Thane city in Maharashtra. Here I want to give details of our experience in this subject. Initially societies were not ready to do cleaning of the tanks, they could not believe that potable water that municipality supplies could be already contaminated. After some counseling they were ready to get their tanks cleansed. We experienced many problems in that process. First problem was of time required to do cleaning and then applying a coat of protective paint to avoid formation of algae on its surfaces. Even if we do work with optimum efficiency generally for tanks of that size require at least three days to complete the task. For that period there is no facility to store water of daily requirement. Residents had great difficulty in managing their routine house work with water stored in their houses. Many did not have additional storing capacity for that period. This problem was extensively discussed by different housing societies and that resulted in only one reaction and that was that they refuse to get their tanks cleansed. They told us that we workout an alternative to this problem so that they can manage their daily routine; if that was possible they were having no objection to cleansing of tanks. A few societies had two tanks and they could manage by shifting supplies to tank that was not under cleaning and after that was cleaned again shift it back to original tank. Some times water tank for toilet purpose was also used in this way. Nevertheless, difficulties were enormous.

My friend and me came to know after this bitter experience that cleaning potable water tanks of housing buildings is not any easy work. The problem that was faced had real value and we cannot say that housing societies should do it somehow. We tried direct chlorination of water stored in the tanks. But there are other problems because it is a poisonous and highly corrosive gas. If any municipality makes any rule to that effect I am sure it cannot be successfully executed for difficulties as given above. All the same we cannot undermine importance of this difficulty. Finally we solved it but before I give as to how it was solved I would like to elaborate on many factors those contribute to this crisis of polluted water.

Apart from many leaks in the mains and distributor pipes put under ground so that sewage water and other contaminators can mix with potable water I found one measure factor that makes this water turbid or colored. This happens because pipes to carry water are made of mild steel having no protective paint in its inner surface. Water with oxygen and other chemicals dissolved in it cause rusting of surface of these pipes. This eventually separates from the surface and mix with flowing water. Making water turbid. When that water reaches store tanks of the building that rust along with other contaminants settle at the bottom and continue to spoil water. We know that chlorine gas is used to kill germs in that water before that water goes to the tanks. This addition of chlorine is found to be one measure culprit in this case. By addition of chlorine pH value of water becomes something around 6 or 5; water having this pH value encourages corrosion of Iron. This caused formation of additional rust and also reduces useful life of the pipeline. Normal practice, as I was informed by the municipal authorities, is to do chlorination near the housing localities. That means, pipes in those thickly populated localities are being corroded by this chlorination. This may eventually cause breaking of the pipe, bursting it and creating one additional problem. By science we know pH of all water flowing through iron pipes must be maintained at 7.5 level. If this norm is obeyed iron will not rust because electrolytic reaction require to continue rusting needs pH to be below 7. Some electrostatic procedure practice suggests to get the complete pipeline electrostatically managed to keep pH higher than 7. As per my information we do not have any such provision on our supply pipes. That means, these pipes are going to be rusting and spoiling our water supply. In earlier times during British all pipes were made of cast iron of special type containing Mn and so they were rust resistant. That is why we did not have this problem in older pipes. If we desire our government can make it mandatory that pipes for water supply are made from manganese steel plates; if that condition comes we may be able to have better pipes and problem of bursting of pipes and also making water turbid automatically resolved.

Finally let me explain how tanks we kept clean using natural forces and resolved the problem. For that I observed our traditional method of keeping water wells clean. I saw they keep tortoise in well water to keep it clean. Tortoise eats all algae formed and does not allow additional growth. To make it possible we have to treat our water tanks on terrace like a fish pond. For that top of the tank must have a clean glass so that sun rays go into the tank and reach water surface. In addition to that an air pump fitted to supply air to continuously supply air to that water this is similar to fish tanks we have in house. This is a simple solution to this problem of water contamination.

Line of working is, first allow water to pass through a filter to remove all turbidity and any solid particles, this cleaned water now pumped up to the tanks on terrace. There a few tortoises are kept to clean that water. Sun rays coming from above and air supplied by air pump does the other work. If you have to clean tanks; before you do anything else think of this advice. This method is cheap and more reliable. You will need a fish expert to guide the society on how to keep tortoises healthy.

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