To make textile processing units of Tirupur environmentally sustainable and achieve zero liquid discharge, scientists of Gujarat-based Central Salt and Marine Chemicals Research Institute (CSIR-CSMCRI) have helped set up Tamil Nadu state's first common effluent treatment plant (CETP) in Chinnakarai, which will separate sodium chloride and sodium sulphate from solid residue.
Over the years, solid residue from the textile units has piled up to the extent of 6,000 tons and is going to landfills, posing a major environmental hazard.
Textile dyeing units in Tirupur and surrounding districts have been facing heat for polluting the environment and the Madras High Court in 2011 ordered closure of all units which violated pollution norms and asked the units to achieve zero liquid discharge. The region has over 600 textile processing industries and several common effluent treatment plants (CETP) are operating to manage the waste water discharged from these industries.
Amitava Das, the director, CSMCRI, said that waste water (effluent) generated from textile processing contains sodium chloride and sodium sulphate as a major contaminant. After primary and secondary treatment, the high TDS (total dissolved solid) effluent is processed for recovering and recycling the water back to the industries and the associated solid residue was used for land filling. Since 2000, textile units are partly meeting their requirement of sodium sulphate by recovering the same through adiabatic crystallisation system, implemented by M/s Chemprocess Systems P. Ltd, (CPSPL).
This initiative helped to reduce about 70% load of land filling solids ( a mixture of sodium chloride and sodium sulphate). However, such operation over the years resulted in an accumulation of a large quantity of land filling solids having an approximate composition of 30% sodium chloride and 70% sodium sulphate. Since both of these salts are already needed for textile processing, albeit in pure form, the thought was originated by Chinnakarai CETP in association with Tamil Nadu Water Investment Company Limited (TWICL) to separate and reuse the same, he said.
"With this objective, the Dyers Association of Tirupur (DAT) approached us. We developed the process for separation of sodium chloride and sodium sulphate in usable purity based on differential solubility behaviour and demonstrated the process successfully in the laboratory as well as in pilot plant.
After the successful pilot-scale demonstration, the Chinnakarai CETP decided to implement the technology. Subsequently, a commercial scale project for separation and recovery of sodium chloride and sodium sulphate from textile processing effluents based on CSMCRI technology know-how has been set up," he said.
M Shanmugasundram, managing director, Chinnakarai CETP, said that the upgradation process was over and the plant was in pre-commissioning stage and will be operational in a week's time.