Manual. I would go back to ...
Published by Peter Naylor, Operations and Maintenance Manager
Manual. I would go back to basics first. What is the ultimate use of the water? Why are coliforms not allowed if they are not of faecal origin? Where are they coming from? Are they actually of faecal origin (even though faecal coliforms have not been detected), for example from land run-off? Are they seasonal and associated with rainfall? Review the historic data. Can you prevent them getting into the mine by catchment control? Are they from incorrect water fittings allowing coliforms to grow? This can easily be resolved with the use of approved fittings.
The level of treatment will depend upon the likelihood of future contamination and the risk to public health (if consumed). If this is high, then simple UV or chlorination will not be sufficient. If the quality of the source water does not change, and all you want to do is eliminate the coliforms, then UV is an easy and cost effective option. It has lower handling risk and easier maintenance compared with chlorine/hypochlorite. Chlorine will however give you a residual downstream, but this will only confirm that the water remains uncontaminated, it will not prevent contamination. Hope this helps.
1 Comment
Thanks for the reply. The pdf that I've attached is all the chemical info that I have. The mines are horizontal, one has 0.5 metres, another 5 metres and the longest one is 30 metres long. There is a 10 X 5 X 1.5 metre open tank and a tube goes from the middle water mine to another closed tank, 2 X 2 X 2 metres that is 70 metres away and near the houses. The water from the larger tank is for agricultural use, the smaller one for punctual human consumption and to fill the swimming pool.
I will not use chlorination in water for human consumption. I assume that the coliforms come from the 70 metres pipe or from the mine itself, as the sample I took from the pipe before the smaller, closed tank.
The water mine is not used most of the time and the local company water has low chlorine (except for their seasonal system maintenance), as this is a rural area with little industry or major pollution outlets.
It is more of a safety option and something that I want to keep an eye on, since they've probably been made thousands of years ago.
Thanks!
Published by Manuel Trindade, University of Exeter - One Planet MBA