| Popis: |
Biological treatment with a stable activated sludge process, followed by chemical treatment is one of the potential and accepted cyanide treatment process for coke plant waste water treatment. Biologically treated coke plant wastewater contains free cyanide above permissible limit. Presently chemical treatment with NaOCl is being used to attenuate free cyanide below permissible limit in biologically treated water. This process increases the TDS and colour content in discharge water. Ca(OCl)2 can be used as an alternative to NaOCl for cyanide remediation in biologically treated coke plant waste water without increasing TDS. In the present work, cyanide removal efficiency of NaOCl and Ca(OCl)2 for real coke plant waste water after biological treatment has been studied. Optimisation of chemical dosage, treatment time and pH has been done for Ca(OCl)2 and NaOCl treatment. It was found that up to 90% of free cyanide removal could be achieved through Ca(OCl)2 treatment without increasing the TDS value. In addition, more than 50% colour of the waste water has been removed. pH elevation step required in NaOCl treatment can be eliminated in Ca(OCl)2 treatment, thereby reducing caustic consumption. In conclusion, use of Ca(OCl)2 is economically more viable than that of NaOCl in cyanide treatment. |
