Development of Advanced Wastewater Treatment System for Efficient and Complete Degradation of Refractory Chemicals by Combination of Biological Treatment and Ultraviolet Irradiation

研究了以二氧化钛为催化剂，采用生物处理和紫外光照射相结合的方法完全降解废水中难降解物质的可行性。以壬基酚聚氧乙烯醚(NPE)为模型化合物，研究了分离的假单胞菌TR01对NPE的生物降解性。尽管菌株TR01能有效地降解NPE中的聚氧乙烯部分，但在培养基中仍有死端产物积累。该代谢物经鉴定为含短乙氧基链的NPE(NP2EO，NP3EO)及其羧化衍生物(NP2EC，NP3EC)。这些难降解的末端代谢物在紫外光照射下能被悬浮在反应混合物中的二氧化钛降解，没有检测到副产物，经GC和GC-MS分析表明完全降解。降解率随温度升高而增加，但不受pH值的影响，反应混合物中的可溶性和悬浮物降低了降解率。在构建真正的处理系统时，应考虑这些因素。

The feasibility of complete degradation of refractory chemicals in wastewater by combination of biological treatment and ultraviolet irradiation with TiO_2 as a catalyst was investigated. Nonylphenolethoxylate (NPE) was selected as a model chemical and its biodegradation by a isolated bacterial strain Pseudomonas sp.TR01 was investigated first. Although the polyoxyethylene part of NPE was efficiently degraded by strain TR01, dead-end products were accumulated in the culture medium. The metabolite was identified as NPE with short ethoxy-chain (NP2EO,NP3EO) and their carboxylated derivattives (NP2EC,NP3EC). These refractory dead-end metabolites could be degraded by ultraviolet irradiation with TiO_2 being suspended in the reaction mixture without occurence of detectable by-products by HPLC,GC,and GC-MS assays, suggesting complete degradation. The degradation efficiency increased with increase of temperature, but was not affected by pH.Soluble and suspended materials in the reaction mixture lowered the efficiency. These factors should be taken into consideration for constructing real treatment systems.