Bio-electrochemical Transformation Of Roxarsone In Animal Husbandry Wastewater

Roxarsone(3-nitro-4-hydroxy phenylarsonic acid,ROX)is widely used as feed additives,it can inhibit intestinal pathogens after feeding to livestock and poultry.Most of roxarsone excreted in prototype with feces,where the proper treatments of animal waste water were missing.Roxarsone can be reduced to 3-amino-4-hydroxy phenylarsonic acid(HAPA)in anaerobic environment.However,the transformation mechanism in bio-electrochemical condition remains unclear.In this work,we explore the fate of roxarsone in bio-electrochemical system to manifest the pathways of roxarsone biotransformation.The experimental system was setup to study the effects of substrate level and system configuration on the pathways of roxarsone biotransformation,with main results showing as follows:(1)In the presence of rich organics(6.2 g/L),approximately 92.5% of ROX were transfered within 48 h,with 9.29 ?mol/L inorganic arsenic produced,in which three pathways were proposed,including: oxidation,reduction and methylation.In contrast(0.62 g/L),the idental amount of ROX were transfered,but with merely 1.97 ?mol/L inorganic arsenic produced.It indicates that the orgnic substrate impactes roxarsone transformation slightly.(2)At constant biomass amount,power generation was dependent on the electrodic area,rather than suspended bacteria in the anodic solution.While at identical electrodic area,biomass is critical.The proposed pathway of roxarsone transformation includes:Firstly,roxarsone contacted with attached or suspended bacteria in the anodic chamber,following HAPA production and other speices of arsenics.(3)After 48 hours,the area of roxarsone concentration in series electrochemical system of 6.3 cm~2 reduced to 8.3 mol/L,8 h conversion efficiency had increased2.8%;the area of roxarsone concentration series electrochemical system of 37.5 cm~2 had tranfered completely in 32 h,8 h conversion efficiency had increased 30.2%.Two parallel area of 25 cm~2 anode electrochemical system transformed roxarsone in 32 h,8 h of roxarsone conversion efficiency increased 21.8%.Two different carbon felt area of the battery in parallel,an area of 50 cm~2 parallel electrochemical system transfermed ROX completely in 32 h,8 h of roxarsone conversion efficiency increased 28.4%;An area of 0.0 cm~2 parallel electrochemical system transfermed ROX to 0.02 mmol/L in 48 h,8 h of roxarsone conversion efficiency decreased 10%.