QUESTION
Issues related to rainwater harvesting in Guwahati, Assam - Need process details of disinfecting the filtered rain water

In the recent past, I have managed to ensure Rain water harvesting arrangements in one multistoried building at Guwahati ( Assam ). The provisions include rain water pipes for leading the rainwater from terrace to baffled wall sedimentation followed by sand filtration and finally the under ground ( partly ) sump. The filtration process is provided with backwash arrangement for periodic cleaning of the filter. Arrangements are made for periodic cleaning of the terrace also.

The owner has become fully dependant on the harvested rainwater and he is now very happy, because of the fact that he need not use his borewell for most of the time in the year, except for the lean period ( February &  March ). But the owner wants to know about the following :

(a)    What will be appropriate process for disinfecting the filtered rain water in the sump?

(b)   In case of using Bleaching powder as disinfectant, what will be the appropriate dose & and the desired interval for its use?

At present, the quarterly dose of Bleaching powder is used as 4mg/l and the water is used from alternate sump, after seven days of application of Bleaching powder ( the owner has two sumps ).   

(c)    Since the borewell remains unused now for a long period of times, is there any possibility ( even if it is remote ) of any harm to the borewell? Is it necessary that the borewell should also be used time to time ( monthly once or twice ) for ensuring more sustainability of the borewell?

Thanking you and waiting for the valuable responses in this regard.

 

Nripendra Kumar Sarma

Guwahati, Assam     

by
6 April 2010