Technical solutions and problems

Print edition : August 26, 2005

The collection tank at Chemtech Processors, which uses reverse osmosis technology for treating effluents. - K. ANANTHAN

ONE of the standard excuses offered by dyers in Tirupur over the years is that they do not have "cost-effective" or "viable" technologies for zero discharge of effluents. However, the fact that several units have implemented the reverse osmosis (RO) process well before the outbreak of the present crisis refutes this contention.

Reverse osmosis is a process by which a membrane is used to filter particles - dyeing salts in this case - in the water before it is discharged. Water from the process house is first sent for primary treatment in an effluent treatment plant. The osmosis process, actually done in two stages, and nano filtration, ensures that not only water but also the salts that are used in the dyes can be recycled for reuse.

RO thus appears to be an attractive proposition, especially in a situation in which enforcement of pollution control rules is stringent. So long as dyers could get away without having to pay for the damage they were causing, avoiding investment in RO appeared attractive. This has changed after the High Court ruling making RO mandatory so that there is zero discharge of effluents into the river.

K.L. Palaniswamy, partner in Chemtech Processors, a large dyeing unit in Tirupur, and a chemical engineer, said he invested in an RO plant in 2002 because it made sense businesswise. That year was bad and water had to be ferried in tankers from villages in a 20-km radius around Tirupur. Water quality would vary and the Total Dissolved Solids (TDS) would often be above 2000-3000 parts per million (ppm). This was not only far in excess of the norm but also resulted in inconsistent dyeing quality. This also resulted in delays, forcing him to use air shipment in order to meet deadlines.

The promise of RO enabling the recycling of 70-80 per cent of the water requirement appeared attractive. But water-handling capacity had to be increased from 1 lakh to 5 lakh litres in order to make the RO plant viable. Chemtech uses a three-stage RO process. It also uses an ozonisation process, which Palaniswamy says extends the life of the RO membrane, which is a crucial (and costly) part of the process. Membranes are still imported but Palaniswamy is sure that prices will fall because of the spread of the use of the technology in India.

Despite all the advantages that RO offers, the downside is that it still results in very high levels of TDS in the sludge that is generated. The effluent, after primary treatment, has a TDS of about 3,000 ppm. After going to the first stage membrane, the residue has a TDS level of 12,000 ppm; by the next stage it reaches 24,000 ppm; and at the end of the three-stage cycle, the residue has a TDS of 30-35,000 ppm.

The Tamil Nadu Pollution Control Board (TNPCB), in particular, has come in for criticism. It has two basic functions: to enforce environmental legislation, and to promote technologies. Critics allege that it has failed to do both. There are also fears that dyeing units, even if they claim to be using an RO process, may actually end up dumping untreated effluent into the Noyyal river. The TNPCB's enforcement of environmental rules has been tardy; by its own admission it is hamstrung by the lack of personnel and resources to perform this function in Tirupur.

First Planet Engineering, a consultancy, also claims that it can bring a Russian technology as a solution. It claims that the technology, an offshoot of technologies used in submarines in the Cold War era in the Soviet Union, will effectively compete with the RO-based solutions because it will be cheaper.

Although everybody in Tirupur regards RO as the saviour it is obvious that a solution has to be found for the growing quantities of sludge that will be generated. It is expected that exports from Tirupur will quadruple in the next few years, spurred by the possibilities offered by the phasing out of the Multi Fibre Agreement earlier this year. Palaniswamy believes that industry needs to spend more on research and development to find a solution. And, the government needs to do its bit too.