In times of scarcity of water here's some encouraging news. Indian scientists have developed a simple method to recover usable water from industrial waste.
The technique, using a nanofiltration membrane, ensures the separation of harmful chlorides and cyanide from the contaminated waters in certain chemical industries.
The membrane is economical and the process low pressure, which can substitute the regularly used reverse osmosis for specific applications. Developed by the Hyderabad-based CSIR-IICT (Indian Institute of Chemical Technology), it was demonstrated in Tata Steel's Jamshedpur plant in 2016.
Explaining the process, the IICT scientists led by S. Sridhar said during one of the critical steps of its manufacture, steel from the blast furnace is quenched in a tower, which results in the release of excessive chloride and cyanide into the aqueous stream. Chloride levels above 800 mg/L cause corrosion in the blast furnace.
The team developed a high flux, low fouling nanofiltration membrane which provides high water recovery and sufficient chloride separation. After a laboratory-scale trial run for Tata's was conducted, the design of a pilot plant was taken up under a sponsored project, for prospective installation at Tata Steel's Haldia Metcoke Division, West Bengal.
The capital investment for the pilot plant is Rs 12 lakh and operating cost, including power consumption, filter replacement, chemicals for maintenance, etc, comes to only Rs 20 per cubic metre.
The IICT team successfully installed and commissioned the nanofiltration pilot plant of capacity 5.5 M3/h capacity (1.1 Lakh Litres/Day) for the removal of excess chloride from the steel quenching tower effluent at Haldia recently. The plant is now under full fledged operation and its success could result in replication of similar plants of higher capacity (commercial scale of 150-200 M3/hr) for the steel industry to facilitate zero liquid discharge enforced by pollution control boards, to minimise environmental contamination, the IICT said.
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