The water requirements at an export center housing around 729 textile bleaching & dyeing units producing hosiery and knitwear, are met by tanker water supplies from a cluster of open borewells in and around the areas for which the units pay around Rs.50 to Rs.60/m3.
CETPs (Common Effluent Treatment Plants) have been built to treat effluent discharged from individual dyeing units. Around 80 bleaching and dyeing units form a part of this case study CETP. After primary treatment for colour removal, the treated effluent is discharged into the river resulting in its pollution and turning it unfit for agriculture and domestic uses.
Discharge of the high TDS effluent into the river and its subsequent percolation into the water system has also affected ground water quality. In view of this, textile units have been directed by the court to implement zero liquid discharge. Another problem faced was disposal of the huge quantity of sludge produced due the physico-chemical process used for colour removal.
Ion Exchange carried out extensive pilot plant studies to identify the right solution to overcome the problems faced by the textile units. Based on trials, a treatment scheme was designed, to achieve zero discharge.
Inlet and outlet characteristics as follows.
Inlet |
Outlet |
TDS - 8000 to 9000 ppm |
TDS - < 200 ppm |
Silica - 40 ppm pH - 7.5 to 9 |
Suspended solids - Nil |
BOD - 100 – 200 |
BOD - Nil |
COD - 300 – 800 |
COD - < 5 |
Color - 3000 Hazen units |
Color – Nil |
FINAL SCHEME SUGGESTED FOR ULTIMATE CAPACITY PLANT
The Result :
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The system uses advanced biological process (Membrane Bio-Reactor) for removing colour/organics, avoiding chemicals like Lime/Feso4 which are difficult to handle. | |
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Capacity of the feed water is 10 MLD. 89% of the feed water is obtained as fresh water, of quality much better than raw water quality available. This water has a TDS of 200 ppm as against 1500 ppm of tanker water. This improves the quality of dyeing and also saves costs on fresh water. | |
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Around 10% of the feed water is also obtained as pure brine solution as nano permeate which can be used for the dyeing process. | |
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The system is designed for zero liquid discharge. | |
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Zero discharge systems |
