Industrial Development Corporation of Odisha Ltd. (IDCOL), Govt. of Odisha organization awarded the contract of 8.64 MLD Effluent Treatment Plant to Effwa on Turnkey basis for construction of new ETP for remediation of hexavalent chromium in mine discharge effluent and surface runoff. IDCOL Ferrochrome and Alloys Ltd., A wholly owned subsidiary of the Industrial Development Corporation of Odisha Ltd. is a State Government undertaking located at Jajpur Road, District – Jajpur, State – Odisha, India; started its operation in the year 1969 producing High Carbon Ferro Chrome. Almost 97% of India’s Chromium reserves are concentrated in Sukinda, Odisha. In Sukinda, at present, there are seventeen mines leased out to nine companies including IDCOL.
Talangi mines in Sukinda belonging to IDCOL, started its mining operations in June 1999. The mine meets the Captive requirement of IFCAL Plant and other sister units. It operates by opencast method of mining. Opencast mining results in the generation of huge quantities of overburden, which is dumped within the respective mine lease area and it contains the mineral, although in a lesser concentration (about 3-5%) compared to the ore.
All of the operational mines generating Chromium (VI) contaminated mine drainage water have installed Effluent Treatment Plants (ETPs). But still concentration of Chromium (VI) higher than surface water quality standards (IS 2296-1982) was reported in Damsala Nalla, the main drainage channel of the area. To address this problem IIT Kharagpur has studied the overall mine areas and suggested certain measures for environmental sustainability.
Talangi chromite mine had existing two ETPs but it is required to upgrade and construct new ETP for treatment of hexavalent chromium with provision to canalize the surface runoff of mine to main drain as per plan suggested by IIT Kharagpur and as per directions of Odisha State Pollution Control Board, Bhubaneshwar for improvement of quality of water and overall environmental scenario.
As a trusted brand providing effluent treatment services, Effwa received the order from IDCOL for Design, Engineering, Supply, Construction, Erection, Commissioning and Performance Guarantee of Chromite Mining Effluent Treatment Plant of capacity 360 KL/h on turnkey basis at Talangi Chromite Mine of IDCOL.
Design Philosophy for Talangi Chromite Mine Effluent Treatment
Chromium is found in two forms in waste streams i.e. hexavalent (Cr6+) and trivalent (Cr3+). Treatment of chromium usually consists of two stage process; first, the reduction of hexavalent chromium to trivalent form and second, precipitation of the trivalent chromium. While carrying out study for capacity of proposed ETP, present maximum generation of wastewater from mines & maximum surface runoff from OB dump area has been taken into account. So ETP of capacity 360 m3/h is designed.
The mine water characteristics keep on changing based on strata, depth and location of mine. Effluents generated from surface runoff shall be collected in collection sump and pumped at controlled rate to Flash Mixing Tank where reducing agent (FeSO4) shall be dosed along with polyelectrolyte through metering pumps.
The effluent from the flash mixers shall then be let into Clariflocculator, which reduces consumption of reagents and can tolerate fluctuation in turbidity of feed while yielding consistent output quality. The clarifier supernatant shall be let into Rapid gravity sand filter. Acid will be dosed prior to filter beds for bringing the pH in the range of 6.5-7.5. The filtered water shall be let into treated water tanks. The output from the filter shall be of reusable quality or safe for disposal as Odisha State Pollution Control Board (OSPCB) norms. The same filtered water shall be used for backwashing the filter beds.
The sludge from the clarifier is continuously withdrawn in sludge sump and pumped through fully automated PLC operated Filter Press for dewatering. The dewatered sludge shall contain Cr(OH)3 and Fe(OH)3 which could either be reprocessed or disposed off safely in landfills.
The plant shall be completed in 8 months. Effwa Infra & Research Pvt. Ltd. will thus provide high-end engineering solutions to the environmental issues faced by chromite mines at Sukinda.