Treatment of wastewater from a low-temperature carbonization process industry through biological and chemical oxidation processes for recycle/reuse: a case study.
Low-temperature carbonization (LTC) of coal generates highly complex wastewater warranting stringent treatment. Developing a techno-economically viable treatment facility for such wastewaters is a challenging task. The paper discusses a case study pertaining to an existing non-performing effluent treatment plant (ETP). The existing ETP comprising an ammonia stripper followed by a single stage biological oxidation was unable to treat 1,050 m(3)/d of effluent as per the stipulated discharge norms. The treated effluent from the existing ETP was characterized with high concentrations of ammonia (75-345 mg N/l), COD (313-1,422 mg/l) and cyanide (0.5-4 mg/l). Studies were undertaken to facilitate recycling/reuse of the treated effluent within the plant. A second stage biooxidation process was investigated at pilot scale for the treatment of the effluent from the ETP. This was further subjected to tertiary treatment with 0.5% dose of 4% hypochlorite which resulted in effluent with pH: 6.6-6.8, COD: 73-121 mg/l, and BOD(5):<10 mg/l. Phenol, cyanide and ammonia were below detectable limits and the colourless effluent was suitable for recycle and reuse. Thus, a modified treatment scheme comprising ammonia pre-stripping followed by two-stage biooxidation process and a chemical oxidation step with hypochlorite at tertiary stage was proposed for recycle/reuse of LTC wastewater.
Biswas
R
R
National Environmental Engineering Research Institute, Nagpur, India. ra_biswas@neeri.res.in
Bagchi
S
S
Urewar
C
C
Gupta
D
D
Nandy
T
T
D000641:Ammonia / Q000032:analysis; D002244:Carbon; D003031:Coal; D003077:Coke; D003247:Conservation of Natural Resources; D004867:Equipment Design; D005579:Fossil Fuels; D005740:Gases / Q000032:analysis / Q000302:isolation & purification; D019216:Metals, Heavy / Q000032:analysis; D009281:Naphthalenes / Q000032:analysis; D010084:Oxidation-Reduction; D010865:Pilot Projects; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods
D003031:Coal; D003077:Coke; D005579:Fossil Fuels; D005740:Gases; D019216:Metals, Heavy; D009281:Naphthalenes; C031721:naphthalene; D002244:Carbon; D000641:Ammonia