Abstract
Bacterial strains in an activated sludge aerobic reactor from a coke wastewater were found to be able to utilize thiocyanate as carbon source when the thiocyanate-containing wastewater was deprived of carbon source. This study showed that three thiocyanate-oxidizing bacterial strains, Burkholderia sp., Chryseobacterium sp., and Ralstonia sp. were isolated from the activated sludge of a coke wastewater treatment plant as evidenced by the fact that complete decomposition of thiocyanate was achieved either by coculture or individual pure culture. The thiocyanate biodegradation by the coculture occurred with an optimal pH range between 6.5 and 8.5 and an optimal temperature range between 30°C and 40°C. The biodegradation kinetics of thiocyanate was well fitted with the Andrew-Haldane model, which demonstrated a distinct substrate concentration-inhibited bacterial growth pattern. The effects of different types of additional carbon, nitrogen or sulfur sources on thiocyanate biodegradation were also investigated. Analysis of the end-products indicated that thiocyanate degradation by these strains should proceed via two pathways.
Highlights
Coke wastewater is a typical industrial wastewater primarily present in most of steel production facilities, as coke produced by heating coal in the absence of air is an indispensable material in the metallurgical industry
Bacterial strains in an activated sludge aerobic reactor from a coke wastewater were found to be able to utilize thiocyanate as carbon source when the thiocyanate-containing wastewater was deprived of carbon source
This study showed that three thiocyanate-oxidizing bacterial strains, Burkholderia sp., Chryseobacterium sp., and Ralstonia sp. were isolated from the activated sludge of a coke wastewater treatment plant as evidenced by the fact that complete decomposition of thiocyanate was achieved either by coculture or individual pure culture
Summary
Coke wastewater is a typical industrial wastewater primarily present in most of steel production facilities, as coke produced by heating coal in the absence of air is an indispensable material in the metallurgical industry. The liquid effluent of coking process contains considerable amounts of toxic compounds such as phenol, benzene, pyridine, quinoline, ammonium, thiocyanate and cyanide [1]. Current laboratory and field studies [2,3] have demonstrated that activated sludge systems are effective in removing these compounds under aerobic conditions. In this manner, the degradation of phenols and other readily biodegradable substrates always proceeds much faster than thiocyanate degradation [4]. The aerobic reactor has the capability of removing thiocyanate as evidenced from our field data (obtained from a real coke wastewater treatment plant located in Shaoguan, Guangdong, China). The thiocyanate-oxidizing bacteria available in the activated sludge were believed to be responsible for thiocyanate biodegradation due to the consumption of readily biodegradable carbon sources by heterotrophic bacteria
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