Textile industries are one of the largest water users. When discharged as effluent, that water is polluting the rivers and surface water. Department of Environment (DoE) is working to enforce Effluent Treatment Plant (ETP) in the dye houses of the country.  Setting up ETP is a pre requisite for having clearance from DoE for factory setting. As per DoE Director General, 52% of our existing industries have established ETP and other 48% industries have not. The smaller industries including local market oriented industries do not afford to install a proper ETP. Those factories are directly discharging to the water body. But the factories having ETP, all of them are also not running that always. Most of those ETP’s are being kept for displaying to the buyer and to be in the safe position from DoE supervision.

As DoE has limitation in man power & equipments, they are not capable of ensuring forced running of ETP’s 24*7 a week. Currently DoE enforcement team found that many big textile mills are not running their ETP and polluting the water bodies of the surrounding locality. Those factories are heavily fined. But still these penalties are being unable to make sure that all the factories are properly running their ETP’s. So, even for the environment authority it is a big question that what is the sustainable solution regarding these effluents and their treatment.

It is clear that biological ETP’s are better option both for the factories and law enforcers. These biological ETP’s are cheaper to run & as living bacteria are in the ETP, it is not possible to stop the blower to keep bacteria alive. These biological ETP’s nicely can bring the ETP discharge water within the DoE standard norms.

Table: Effluent standards for the textile sector

Source:

• Schedule - 12 (B), Environmental Conservation Rules, 1997, Bangladesh



• Practice of Textile Coloration, Volume-1,M Forhad Hossain



• Textile Talent Hunt (TTH 2010) Project of Md. Rashaduzzaman

Note:

1) BOD limit of 150 mg/l will be applicable only for Physicochemical processing method

2) Standards applicable for composite textile plants and large processing units (with investment worth more than Taka 30 million).

As per many test reports of ETP discharged water, it is found that all parameters other than TDS can be very easily brought to the standard value. If we even think about reusing the ETP discharged water in the process, we can see that only TDS is well out of required range. In fact these ETP’s can do nothing with TDS. This TDS is mainly caused from the used Glauber Salt/ Common Salt in the dyeing operation and the ETP’s cannot remove those.

The factories are bringing TDS to the standard discharge norms mainly by dilution of the effluent. If any factory reduces its water use in total than their average TDS will increase. So, to keep TDS within the norms factories need to use good amount of water (at least the quantity enough to bring TDS concentration to the required level) which is discouraging to reduce water use per kg of fabric. Average water use per kg of fabric in our cotton processing mills is 180-220 litres whether global standard is much below. So, if we can remove this TDS from the effluent, we can take all necessary initiatives to reduce water use in the process. From the above table we can also see that it is indeed possible to reuse the ETP discharged water in the process which may lead the factory to a zero discharge industry.

The idea of “Zero Discharge Textile Industry” is no more a dream. Many of the similar industries are zero discharge in countries like India & Turkey where cost of water is high and there is water scarcity as well. Though water is not priced here in Bangladesh making a zero discharge industry will be still feasible considering the benefits from chemical recovery.  A proper “Salt Recovery Plant (SRP)” is the possible solution to take out the dissolved salts which will bring the water quality even to reusable level. This will eliminate the problem of TDS and also help to recover used salt up to a considerable amount. In addition, focusing to all possible “Cleaner Production” practices inside the factory premises which will reduce the amount of water used per kilogram fabric processed.

These initiatives will bring value to the water being used and at the same time will keep the effluent processing (making reusable) cost low. Working in the process for “Process Modification” to achieve all possible benefits of greening the dye houses is a big part of making a factory zero discharge. Necessary process modification is obvious for effective implementation of all main objectives of a “Zero Discharge Textile Industry”. Using best possible water, chemical & energy conserving technologies in the process will help to make the factory a “Green” establishment.