Zero Discharge in Tirupur Dyeing Factories
By
R. Manivasagam, B.Tech., MBA, MIE.,
Chartered Engineer and Technical Consultant
(1) What is Zero Discharge ?
Its full name is Zero Liquid Effluent Discharge (ZELD) or Zero Liquid Discharge (ZLD). It means not discharging any Waste Water or Liquid Effluent from the Dyeing Factories.
(2) Why was Zero Discharge enforced on Tirupur Dyeing Factories ?
Tirupur Dyeing Factories’ final mixed Effluent has always got a TDS in the range of 4000 to 6000 ppm. But the Tamilnadu Pollution Control Board norms for Discharging Effluent are a TDS less than 2100 ppm. Therefore Tirupur Dyeing Factories can not discharge their Effluent conforming to the norms. Hence the concept of Zero Discharge was enforced.
(3) How is Zero Discharge achieved ?
(i) Water recovery and reuse by Effluent Treatment & RO (Reverse Osmosis) Plants.
(ii) Salt recovery and reuse by Multiple Evaporators.
(iii) Solid Waste disposal into Secured Land Fills.
(4) Is Zero Discharge technically possible ?
Zero Discharge is technically possible but with lot of difficulties. It needs lot of technical knowledge in Plant selection, design, implementation and management.
(5) Is Zero Discharge commercially viable ?
Zero Discharge plants need huge investment and incur lot of running costs. Small scale Dyeing Factories can not invest and bear the running costs. If every-body runs a Zero Discharge plant, then there will be a level playing and there is no question of commercial viability. But Ecological consideration is more important than commercial viability.
(6) Why the present Zero Discharge plants in CETPs did not achieve the goal ?
CETPs have done some small mistakes in selecting Effluent treatment & RO Plants.
But they have done a major mistake by selecting a wrong technology for Multiple Evaporators for Salt Recovery.
(7) Why some individual Zero Discharge plants did not achieve the goal ?
(i) Plant design inadequate and unproven technology.
(ii) Inability to maintain the plant properly.
(iii) Unable to bear the running costs.
(8) Is Sea Discharge possible ?
(i) Sea Discharge is possible subject to the following conditions.
(ii) Sea Discharge norms can be achieved only by doing most of the primary, secondary and tertiary treatments.
(iii) It needs a complete Environment Impact Assessment.
(iv) It will take lot of time.
(9) Is 2100 ppm Inland Surface Water Discharge possible ?
Theoretically it is possible by mixing 1 to 2 times with fresh water with the treated effluent and then discharging. Here also we have to carry out most of the primary, secondary and tertiary treatments. But we need at least 15 to 20 Crore Litres of fresh water every day for mixing and discharging. This is not logical and is also against the principle of Water Conservation.
(10) How can we successfully implement the Zero Discharge?
(i) Selection of proper and proven treatment scheme.
(ii) Installing the right quality plant & machines.
(iii) Proper running and maintenance of the plant.
(iv) Avoiding short-cut methods in treatment.
(v) Employing qualified people to run the plants.
(11) What are the other things to be considered for successfully implement the Zero Discharge?
(i) A technical committee has to be formed consisting of TNPCB, Dyeing Experts, Industrialists and ZLD Consultants for the following.
(ii) Fixing suitable norms for Dyeing capacity and Effluent Discharge capacity.
(iii) Fixing suitable norms for % of water recovery, % of water loss, % of salt recovery and % of salt loss.
(iv) Fixing suitable monitoring methods.
(v) Fixing suitable methods for Secured Land Fills.
(12) What are the Ecological Merits and Demerits of Zero Discharge ?
Merits
(i) Prevention of Discharge of more than 15 Crore Litres of high TDS effluent.
(ii) Prevention of increase in soil salinity.
(iii) Recovery and reuse of water.
(iv) Recovery and reuse of salt.
Demerits
(i) Use of huge amount of chemicals in treatment.
(ii) Use of huge amount of Power.
(iii) Use of huge amount Fuel.
(iv) Generation and storage of enormous quantity of hazardous Sludge and other solid waste.
