INDUSTRIALISTS are being told to install septic tanks as a ‘treatment plant’ for their enterprises whereas septic tanks are no substitute for an industrial wastewater treatment plant.

Septic tanks are meant for domestic purposes in rural areas, where there is no municipal sewerage system. Septic tanks stabilise the organic matter in ‘domestic’ wastewater anaerobically (devoid of oxygen). One septic tank serves one household of about eight persons in rural areas.

An industrial wastewater treatment plant, typically (the process varies from one plant to another), comprises of influent chamber (flow equalisation basin), pH adjustment, flocculation, coagulation, sedimentation (precipitation), aeration and tertiary units (total 7 units). How can the function of one septic tank (one unit) be equaled to the function of 7 unit treatments? Industries need to install full-fledged wastewater treatment plant.

A septic tank can be used for ‘domestic’ wastewater produced in an industry, but in an industry with over 100 employees that generates significant quantities of wastewater, a septic tank, is not an apt choice to treat domestic wastewater.

A septic tank is not even appropriate, as a pre-treatment system, for industrial wastewater. To remove the inhibitory substances in the industrial wastewater stream, a combination of pH adjustment, precipitation, and coagulation is frequently used, as a pre-treatment system. This makes the industrial wastewater amenable for further treatment in subsequent secondary treatment.

Wastewater treatment plants are becoming buzzwords. The KWSB, KPT and DHA are being asked to install treatment plants. Simply asking agencies to install treatment plants is not the correct approach. Other than hoodwinking the authorities, an inappropriate system will not serve any purpose.

The rational approach is to ask the industries to ensure that their treatment plant waste should contain less than the prescribed limit of effluents. The permissible limits of different effluents can be had from the concerned department and even the internet. This has to be strictly monitored and enforced, Why? Because the receiving streams, in this case, Clifton beach, KPT discharge points, Lyari and Malir rivers, Korangi Creek, KB Feeder Canal, and other surface water bodies, are highly (over 100 mg/L BOD) polluted.

This is not the end of the treatment system. Sludge treatment and disposal, a costly and more important component, remains to be dealt with.

A Senior Citizen
Hyderabad

Published in Dawn, July 29th, 2018