Fenton-MBR Process For Avermectin Fermentation Wastewater Treatment

Avermectin fermentation wastewater (AFW) is extremely toxic pharmaceuticaleffluent that requires adequate treatment before discharge to the water bodies. Up-flowanaerobic sludge blanket reactor (UASB) has shown an obvious advantage on AFWtreatment in term of COD removal, but its effluent is hardly biodegradable.Accordingly, treatability test, treatment process design and operation were conductedto develop an optimized treatment process for treating the UASB effluent to meet thedischarge requirement. The major outcomes are described below.The UASB effluent has very low biodegradability. Its COD can hardly beremoved by biological techniques, either anaerobic, anoxic or aerobic process. Fentonoxidation process showed good results for both plants wastewaters (WWA and WWB)in biodegradability improvement and toxicity removal as well as COD removal.The Fenton-AO/MBR process provided an excellent approach for WWAtreatment in term of COD and ammonia removal. Different HRT have influence onCOD, ammonia and TN removal. The best operation conditions for WWA were40hrHRT and200%reflux ratio, under which the average removal rate of COD, ammoniaand TN was42.4%,98.1%, and14.8%, respectively. The effluent pollutantsconcentrations were119mg/L COD,0.87mg/L ammonia.The Fenton-AO/MBR system showed low ammonia removal rate for WWBcomparing with that of the WWA resulting in high effluent ammonia concentration.Different HRT showed significant effect on COD, ammonia and TN removal.Optimum operation conditions were66hr HRT and200%reflux ratio, under which theaverage removal rate of COD, ammonia and TN was59%,56%and17%, respectively.The effluent pollutants concentrations were170.18mg/L COD,84mg/L ammonia. PostFenton oxidation on the Fenton-AO/MBR process effluent of WWB can furtherremove the COD to79mg/L to meet COD discharge standard.It is apparent that the rapid trans-membrane pressure (TMP) increase duringoperation period was mainly due to the accumulation of cake layer on the membranesurface. The cake layer could be removed by tap water washing. Irreversible foulingcaused by gel layer can be removed by chemical cleaning, which was mainly caused by inorganic materials formed from O2, Fe2, and Na1ions etc as indicated by EDX,and polysaccharides, proteins, amid I&II and other kinds of organic compounds asindicted by FTIR. The sequence of chemicals used in the membrane cleaningprocedure has an influence on the fouling removing efficiency. In this study theefficiency of HCl+NaOCl cleaning procedure is the best comparing to other methodsapplied.