In Tirupur, Tamil Nadu, around 80 bleaching and dyeing units form part of the Angeripalayam common effluent treatment plant (ACETP) project; these dyeing units consume large volumes of water which they were purchasing at around
र50-60 per cu.m through tankers. During the dyeing process, 10 MLD (million litres per day) of waste water with high TDS, organics and colour is generated by the individual units of the ACETP.
This ACETP and other CETPs had been set up to treat the effluent discharged from these units. The partially treated effluent, without reduction of total dissolved solids (TDS), was being discharged by the various Tirupur dyeing units into the Noyyal River, polluting the water and making it unfit for agriculture and domestic use.
Ion Exchange carried out extensive piloting to identify the right solution to overcome the problem and a scheme for the 10 MLD zero discharge system was developed and constructed.
The main treatment scheme comprises the flat sheet membrane bio-reactor and two stage reverse osmosis for effluent recycle followed by, for the RO reject stream, silica removal, sand filtration and nano filtration for zero discharge. The RO permeate has TDS of <6200 ppm, COD of <5, with nil BOD, suspended solids and colour.
Apart from satisfying the High Court mandate of zero liquid discharge, the ACETP/individual units derive a host of benefits. More than 82% of the feed water (10 MLD capacity) is obtained as RO permeate of much better quality than available raw water. This improves the quality of the dyeing.
- 11% of the feed water, obtained as pure brine solution from nano filtration, will be used effectively for dyeing. This means around 93% of effluent is recycled and reused by the dyeing industries.
- A much smaller footprint, as it uses the membrane bio-reactor instead of a conventional biological system.
- Sludge production is vastly minimised as the physico-chemical process is avoided.