Study On The Effects Of Sulfamethoxazole On The EBPR System

In recent years, antibiotics has become a current research focus at home andabroad as a new type of environmental pollutants, and sulfamethoxazole(SMX) wasone of the most-frequently-detected antibiotics. Municipal wastewater treatmentplants had become the main resource of antibiotics into the environment. Currently,the study of antibiotics affecting on sewage treatment system was rare. Therefore, thisstudy focused on the impact of different concentrations SMX on microbial communityin EBPR system. At the same time, using the constant broth dilution method for thedetermination of minimum inhibitory concentration on sulfamethoxazole onphosphorus accumulating bacteria strains.When the reactor was well started up,20ng/L,5μg/L,5mg/L SMX was added tothe reactor continuously, the water quality indicators including the concentration levelof phosphate, ammonia nitrogen, COD and the sludge indicators including mixedliquor suspended solids, mixed liquor volatile suspended, sludge volume index weremonitored. In the meanwhile, we observed the changes of microbial communities inEBPR system by the experiments of FISH and DGGE.The reseach showed that SMX nearly has no effect on the ammonia nitrogenremoval rate, the ammonia nitrogen removal rate has been maintained at98%. SMXhas a lesser impact on the COD removal rate, it fluctuated between81%~91%. SMXhas a great impact on the phosphate removal rate. When the SMX concentration was20ng/L, the rate gradually recovered after being affected. When it was5μg/L, the ratereduced to81%. When it was5mg/L, the rate reduced to50%.The higher the concentration of SMX, the bigger the mixed liquor suspendedsolids, the smaller the mixed liquor volatile suspended solids. SMX has a lesserimpact on sludge volume index, which meant sludge settleability was almost notaffected. SMX could change the structure and amount of microbial communityand,inhibited the phosphorus accumulating function of PAOs. The higher theconcentration of SMX, the stronger the inhibition effect.Experimental measurement of SMX for two kinds of PAOs’ minimum inhibitoryconcentrations were40mg/L~80mg/L,20mg/L~40mg/L respectively.5mg/L SMX made Shewanella decolorationis phosphorus removal rate decreased from69%to35.9%, made Aeromonas punctata phosphorus removal rate decreased from47.8%to29.6%.