Study Of Aerobic Ultimate Biodegradation Of Phthalates And Their Degrading Kinetics

Phthalates (PAEs) used widely as plasticizers are ubiquitous organic pollutants in the environment. Some of them may cause mutagenic, carcinogenic and toxic effects on living organisms. Aerobic ultimate biodegradation of several phthalates, namely, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), di-n-octyl phthalate (DnOP), di(2-ethylhexyl) phthalate (DEHP), and their degrading kinetics have been studied with the help of modified Sturm method in the present study.The experimental results of phthalates by acclimated activated sludge from a municipal sewage treatment plant demonstrated that aerobic ultimate biodegradation of phthalates follows the first order kinetics equation; the rate constant (kb) of biodegradation decreases with the increase of carbon number (n) of the alkyl chain, accordingly half life (t1/2) increases, and linear phthalates have better biodegradability than branch phthalate; When the initial concentration is more than 200 mg-L-1 (as ThOC), lag phase occurred obviously in the degradation of phthalates; The addition of Easily biodegradable organics, e.g. glucose, has favorable effects on the aerobic biodegradation of phthalates.Then, the microbial degradative characteristics of phthalates was investigated by strains Pseudomonas sp. PS-1, Xanthomonas sp. PS-2 that were separated from the activated sludge, respectively. The optimal growth conditions were determined by an orthogonal test: namely, pH 7.0, temperature 30 癈, ratio of C to N = 20 : 1, phthalates concentration 300 mg-L"1. The results of phthalates degradation by the two strains indicated that the preponderant strains have stronger ability than activated sludge to degrade phthalates. Logistics model successfully fitted the biomass growth curve when phthalates were used as the sole carbon source of growth of mixed strains.