The Study On Biodegradation Of Di-n-butyl Phthalate In A Bioreactor

Phthalate esters(PAEs) are a class of refractory environmental hormone widely used in the manufacture of plastics. PAEs have been found in sediments, natural water, soils and aquatic organism as a result of both the large quantities produced and their wideapread distribution, and now they have become one of the most prevalent contaminants or the second type PCBs pollutants. In this study di-n-butyl phthalate(DBP) was used as a representative PAEs, and a bioreactor was studied in bench-scale experiment focusing on the removal characteristics and relevant impact factors. In addition, a probable pathway of the degradation of DBP and microbe on the media in the bilogical treatment process were also discussed.The results indicated that temperature and hydraulic retenting time impacted much on DBP and endocrine activity removal,and higher temperature or longer HRT led to better effluent quality when the reactor was operated at pH=7.00±0.20,DO=2.0~3.0mg/L and a 6.00±1.00 mg/L DBP concentration of the influent. Removal efficiency of 99.4%,96.5%,98.5% were achieved at the temperature of 30℃,10℃and 20℃respectively, corresponding to a good effluent quality achieving the primary standard level of the Integrated wastewater discharge Standard GB8978-1996. Estrogenic activity tests suggested that the biodegradation was also followed by removal of the endocrine disrupting activity, while all the effluent samples showed estrogenic activity yet.Two metabolites of DBP degradation were identified as mono-butyl phthalate and phthalic acid by gas chromatography-mass spectrometry. A proble pathway of the degradation of DBP involved sequential cleavage of the ester bond between each alkyl chain and the aromatic ring, forming first the monoester and subsequently PA.The electronic microscopy images showed that the multi-hole structure of ceramic carriers provided a good environment for microbial growth and reproduction. Finally it formed relatively stable microorganism. The bacillus, cocci attached to the natural section and the side of carriers with some filamentous form, microbial metabolites, and other impurities forming a thick biofilm.