Transformation Of Roxarsone And Recovery Of Arsenic In Biochemical Treatment Process Of Livestock Wastewater

As a common organic arsenic feed additive,roxarsone has been widely used in livestock and poultry breeding owing to the improvement of meat color,functions of anti-parasites and promoting growth.However,the amount of roxarsone degraded by animal body is only account for about 10% of the fed,so there would be a lot of roxarsone discharged to the environment by manure,causing potential environmental pollution.In this study,the interaction of moicrobes and roxarsone in the process of anoxic / aerobic(A/O)treatment of lives wastewater was mainly studied.The degradation process of the bioreactor was analyzed,and the migration and transformation pathway of roxarsone in bioreactor was summarized as well.Research on adsorption of roxarsone and recovery of arsenic in simulated livestock wastewater by preparation of polymeric organic-inorganic composite materials was performed.The main conclusions are as follows:1.Low concentration of roxarsone can promote the growth of sludge,but high concentration of roxarsone can weaken the function of sulfate reduction,organic matter degradation and microbial denitrification in anoxic reactor.At the same time,it can also inhibit the nitrification and phosphorus removal in the aerobic reactor.2.The migration and transformation of roxarsone in these bioreactors and the possible biological metabolic pathways were analyzed.And the results showed that the structure of microbial community have changed obviously with roxarsone dosage changed,at the same time,roxarsone is also easily degraded by anaerobic microbes to inorganic arsenic and small molecular organic arsenic.In this process,arsenic produced by the C-As bond breaking in the anoxic reactor account for about 10.6% of total arsenic in the effluent of anoxic reactor.In the stable operation stage,the arsenic content in the excess sludge discharged in one cycle accounts for 3.91% of total arsenic,the content of arsenie was 0.08% of total arsenic,and the arsenic content in the effluent accounts for 96.01% of the total arsenic.3.Adsorption of roxarsone can be achieved by SA-ZVI and SP-Fe(III).Adsorption capacity of materials were 156.42 mg/g and 129.90 mg/g.The arsenic content in arsenic products were 105.64±1.58 mg/g and 106.58±2.25 mg/g,and the recovery rate of arsenic were 92.8% and 95.2%,respectively.