Water Science & Technology Vol 52 No 10-11 pp 325–334 © IWA Publishing 2005
High Performance Biofilm Process for Treating Wastewater Discharged from Coal Refining Plants Containing Nitrogen, Cyanide and Thiocyanate
Y. Jeong*, B.-G. Park** and J.S. Chung***
*School of Environmental Science & Technology, POSTECH, Pohang, Korea, (E-mail: jys@postech.ac.kr)
**Department of Chemical Engineering, POSTECH, Pohang, Korea, (E-mail: byounggi@postech.ac.kr; jsc@postech.ac.kr)
***School of Environmental Science & Technology, POSTECH, Pohang, Korea, (E-mail: jys@postech.ac.kr); Department of Chemical Engineering, POSTECH, Pohang, Korea, (E-mail: byounggi@postech.ac.kr; jsc@postech.ac.kr)
ABSTRACT
Wastewater discharge from coal refining plants contains a number of biologically toxic compounds; 2000-2500 mg/l of COD of which 40% is composed of phenol, 100-400 mg/l of thiocyanate, 10-40 mg/l of cyanide, 100-250 mg/l of NH4+-N and 150-300 mg/l of total nitrogen. In order to treat this kind of high strength wastewater, we have developed a high performance biofilm process using fluidizing bio-carriers of the tube chip type. The fluidizing biofilm carriers are made of a composite of polyethylene and several inorganic materials, whose density is controlled at 0.97-0.98 g/ml. The fluidizing biofilm carriers show sound fluidization characteristics inside bioreactors. The wastewater is treated using three consecutive series reactors in oxic-anoxic-oxic arrangement. Each reactor is charged with the fluidizing biofilm carriers of 50 vol%. Furthermore, newly cultured active microorganisms for the thiocyanate biodegradation are added in the biofilm process. At total hydraulic retention time of 2.2 days, this process can achieve steady state removal efficiencies: COD, 99%; thiocyanate, 99%; NH4+-N, 99% and total nitrogen, 90%. Keywords Biofilm process; coal wastewater; fluidized-bed; thiocyanate; nitrogen removal
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