A Study on Arsenic Methylation by Microorganisms in Sludge Tank of Arsenic Removal Unit

An arsenic removal unit was constructed by the Miyazaki University research group in Bangladesh. The sludge drained from the arsenic removal unit was directed to a sludge tank and allowed to settle down. Then the supernatant in the tank was released to an artificial pond. Biomethylation of arsenic is usually considered as a detoxification of arsenic because toxicity of most organic methylated arsenic is much less than that inorganic arsenic. Microorganisms in the sludge tank were evaluated growth characteristics and arsenic methylation. As a result, dimethylarsinic acid was detected in the broth, and the amount of total arsenic compounds in the broth decreased. It is thought that this loss was contributed by biogenic activity induced by inorganic arsenic biomethylation to gasified volatile organic species, such as monomethylarsine and dimethylarsine. These results suggested that microorganisms in the sludge tank may be utilized for natural attenuation of arsenic sludge from the arsenic removal unit.