As a water conservation measure, three major industries in Manali and Basin Bridge area are utilizing about 25 MLD (million liters per day) of city sewage for cooling purposes in their plants after tertiary treatment. The textile processing dyeing units in the State including units at Tiruppur have provided reverse osmosis plants for recovering the process water from the effluent. The recovered water is reused in the process. In sugar industries, water condensate from evaporators is reused. As a condition for issue of consent, industries have been instructed to provide rainwater harvesting arrangements. All the industries have set up rain water harvesting systems. The roof top rainwater harvesting system has also been provided in the offices of the Tamilnadu Pollution Control Board.
TNPCB has been concerned in promoting a holistic approach to environment protection by enforcing adoption of cleaner technology rather than mere end-of-pipe treatment. Several industrial units in Tamil Nadu have switched over to cleaner technologies such as;
- Adoption of membrane cell process replacing mercury cell process in caustic soda manufacturing.
- Adoption of dry process instead of wet process to reduce air pollution in cement factories.
- Utilization of 25 to 30% of fly ash in Portland Pozzolana Cement manufacturing.
- Adoption of double conversion and double absorption technology in sulphuric acid manufacturing.
- Gas carburizing instead of cyanide salt in heat treatment and cyanide free electroplating.
- Pulp and paper industries are encouraged to go in for elemental chlorine free bleaching to reduce the formation of organo-chlorides including dioxins.
- Industreis consuming ozone depleting substances are systematically changing to environment friendly compounds.
With the adoption of cleaner technologies there has been progress in waste recovery and waste minimization. Examples include recovery of materials such as chrome from tannery effluent and ammonia from fertilizers. Distilleries have been insisted to provide zero liquid discharge system and 7 distilleries have gone for bio-composting of their effluents with press mud of sugar factories for achieving zero liquid discharge of trade effluent and 5 distilleries have established concentration cum incineration system to dispose spent wash effluent and has achieved zero liquid discharge of trade effluent.
As a measure for fuel conservation and recovery, all the distilleries are recovering methane gas from their spent wash through anaerobic digestion. Major sugar factories have installed co-generation power plants. The sago units recover methane gas from their trade effluent through anaerobic digestion. Activated carbon manufacturing units have gone for waste heat recovery boiler and eliminated the dedicated boiler to produce steam for the activation purpose. This system eliminated the consumption of coal / wood as fuel for the boiler and thus avoided greenhouse gaseous emission. Other industrial units are encouraged to use less energy and it is being audited through the environmental statements of the unit. TNPCB has installed solar panels for all its 18 own office buildings to get solar energy. The new buildings which are under construction will be provided with solar panels.
Technology Demonstration Centre
TNPCB on enforcement and its monitoring encourages Cleaner Technology, Waste Minimization Technology, Hazardous substance elimination by alternate process, reuse, and recycle systems, zero liquid discharge and best available technology to promote industrial development within the sustainable development in the State of Tamilnadu. As the number of industries in Tamil Nadu is increasing at a rapid rate, crossing over 46000, the enforcement authorities and industries find it challenging to attain sustainable development and to derive suitable solution to address the environmental issues. In order to find a solution, TNPCB has established a Technology Demonstration Centre at Indian Institute of Technology Madras and have entered into a Memorandum of Understanding (MoU). A sum of Rs.5 crores has been allocated for this purpose. The Technology Demonstration Centre has conducted treatability studies for rice mills, sago and small scale textile processing units. The Centre has conducted awareness programme on fire management on waste landfill site for the Municipal Authorities, Fire Department and TNPCB officials. The Centre has also conducted technical workshop for sago industries for better understanding of the characteristics of sago waste water, anaerobic treatment, biogas generation, optimizing the process parameters to enhance the composition and quantity of biogas generated. This Centre designed and fabricated the Upflow Anaerobic Sludge Blanket Reactor (UASB) to demonstrate best available technology for anaerobic treatment of sago waste water and energy generation. Further work in this regard is continuing.
Green Cover Programme
As a measure of pollution check, industries have been directed to utilize 25% of their land area for developing green belt with trees having a thick canopy cover. Accordingly, industries have taken action to plant adequate number of trees in and around the industrial premises.