Transformation Of Clofibric Acid In Wastewater Treatment Process

Pharmaceuticals and personal care products(PPCPs) is a new trace organic pollutants in the environment, and there are many different kinds of types and sources. Currently the concentration of the PPCPs is very small, but most of them are removed difficultly in the wastewater treatment plants. They discharge with the secondary effluent and excess sludge. So they can accumulate constantly in the environment, and have certain risk to human health and environment. Clofibric acid is the pharmaceutically active metabolite of lipid regulators, and it is considered both environmentally persistent and refractory. It can be as a representative refractory organic, and study its transformation in the wastewater treatment process.Two sets of aerobic sequencing batch reactors(SBR) were constructed in the experiment. This paper studied the removal and biotransformation of clofibric acid in the wastewater treatment process in the SBR 1. At the same time, the production and variation of metabolites of clofibric acid were monitored. The SBR 2 was used as a reference with no added clofibric acid. By the analysis of clofibric acid concentration in the sewage and sludge phase, adsorption effect was relatively weak(about 6%). However, the biological removal mechanism was shown to be primary, which achieved 10%~12% removal efficiency. A lot of the clofibric acid discharged with the effluent. HPLC analysis showed that, clofibric acid mainly produced three biodegradation metabolites: α-hydroxyisobutyric acid, lactic acid and 4-chlorophenol. α-hydroxyisobutyric acid was the major metabolite and its largest concentration about 200 μg/L. The second was lactic acid with largest concentration about70 μg/L. The two substances exhibited such trend in the wastewater: they accumulated for a period, and then gradually utilized by microbial microorganisms. The concentration of 4-chlorophenol was very few.High-throughput sequencing analyzed the activated sludge in the SBR 1 and SBR 2, and the dominant phylums were Proteobacteria, Actinobacteria, Bacteroidetes. After adding clobric acid, the component of Actinobacteri and Bacteroidetes dropped from 30.57%, 28.01% to 25.07%, 24.26%, respectively. And the ratio of the classes were also fell. Showing that may be affected by clobric acid. However, the difference of Proteobacteria was smaller in the two reactors. Comparing the composition of genus concluded that a new Porphyromonadaceae genu emerged in the SBR 1 with clofibric acid. The genus may have a certain relationship with the degradation of clofibric acid.