Abstract: In natural environment, arsenic is usually adsorbed on iron oxide, aluminum oxide and other oxide minerals, or formed co-precipitation with these oxide minerals. Microorganisms can reduce arsenate directly or reduce Asbearing iron oxides and other arsenic bearing minerals under anaerobic condition, which could influence the transformation of arsenic. In this study, a bacteria strain was screened and identified as Bacillus sp. (strain DX04), and the reduction behavior and pathway of the strain on different speciations of the arsenic was studied. Under anaerobic conditions, reduction rate of arsenate with the strain DX-04 was highest in 12-24 h. Arsenate in the medium promoted the growth of the strain DX-04. In the liquid medium inoculated with strain DX-04 and FeAs coprecipitation, the concentration of dissolved As(III) showed the trend of increase at first and decrease several hours later. Arsenic reduction and release occurred, and then the second precipitation was formed. Under the reduction of the strain DX-04, the As(V) adsorbed on aluminum hydroxide minerals released into the liquid phase, and then the dissolved As(V) was reduced. The role of microorganisms can cause the release of arsenic from arsenic bearing minerals into water and sediment environment, which becomes a potential threat to human health.

Key words: composting, maturity, manure, Fourier transform infrared (FTIR).