Roxarsone (3-nitro-4-hydroxy benzene arsenic acid) is an organoarsenic feed additive and has been widely used in the poultry industry to prevent
coccidiosis and improve feed efficiency. The presence of
roxarsone and its degradation products results in the instability of the anaerobic methanogenic process. This study investigated the degradation and speciation of
roxarsone in an anaerobic granular sludge (AGS) system and the impacts of
roxarsone and its degradation products on the structure of AGS.
Roxarsone inhibited methane production, and the added
roxarsone was rapidly degraded into 3-amino-4-hydroxyphenylarsonic
acid (HAPA). After 240 days of incubation, the distribution of
arsenic differed between the aqueous
solution and the AGS in the assays of 20 and 350mg/L
roxarsone. Species analysis indicated that HAPA was completely degraded in all of the assays with
roxarsone addition after 240 days of incubation. Species distribution was affected by the phases and the initial concentration of
roxarsone added. The concentration of As(III) was higher than that of As(V) in both the aqueous
solution and the AGS in all assays with
roxarsone addition. The toxicity of
roxarsone and its degradation products resulted in changes in the structure and the microorganism species in the AGS.