THE surface water treatment, typically, revolves around pumping of water from a river and its treatment in a water treatment plant. Conventional water treatment plants (rapid-sand filters for major cities; and slow-sand filters for rural towns), depending on the quality of raw water, design and operation of the plant, remove conventional pollutants to a varying degree. For example, coagulation and sedimentation are effective in removing colour and turbidity; slow-sand and rapid-sand filters are effective in removing bacteria, colour and turbidity; but have no effect on the hardness of water.

The water treatment system for rural areas, for treating surface waters is slow sand filters. This system usually consists of treatment units like storage tanks or equalisation basins, pre-treatment unit (roughing filters), slow sand filters, disinfection, and clear-water tanks, in that order (five treatment units).

Safe drinking water would be produced only, if ‘all’ the above treatment units are provided in the water treatment system. In Sindh, only the storage tank (the first unit, in the treatment train) and the clear-water tank (the last unit) are provided. The question is: how can the safe water be produced by this technically-incomplete water treatment system?

The following action needs to be taken, if it is desired to provide safe drinking water: (a) water treatment plants should be, technically, full and complete ; (b) plants should be operated by knowledgeable operators, (c) each water treatment plant should have a full-fledged water quality monitoring laboratory; (d) at the municipal or town level, reverse osmosis, as a stand-alone water treatment system, should never be provided; and (e) the departments concerned (public health engineering department, town municipal administrations, etc) should be manned by persons having master’s degrees in water and wastewater engineering from foreign institutes.

F. H. Mughal

Karachi

Published in Dawn, March 1st, 2017