Effect of Malathion on the Microbial Ecology of Activated Sludge

Decontamination activities may cause the release of contaminated washwater into the wastewater that eventually flows into a wastewater treatment facility. This raises concerns about the effect of chemical warfare agents (CWAs) on the microbial consortia that are responsible for cleaning the wastewater. This study investigated the impact of malathion on the microbial ecology of laboratory scale activated sludge communities. The Simpson Reciprocal Index decreased for three bioreactors operated in the absence of malathion, which showed that the microbial assemblage became less diverse during the course of the study. The species identified in the bioreactors belonged to well-known groups of heterotrophic and autotrophic bacteria, and these groups were represented in the presence and absence of malathion. Nitrospira, a key player in autotrophic nitrogen removal, decreased in relative abundance for the bioreactor exposed to 0.1 mg/L of malathion but increased in the bioreactor exposed to 3 mg/L of malathion, possibly due to interactions with heterotrophic groups that suffered inhibition. To the author???s knowledge, this study is the first to document the ecological impacts of long term malathion exposure in bioreactors carrying out COD removal and nitrification.
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