脱氮除磷膜生物反应器工艺耦合混凝过程优化

Optimization of biological nitrogen and phosphorus removal membrane bioreactor process coupling with coagulation process

采用脱氮除磷膜生物反应器（UCT-MBR）工艺处理碳源受限型市政污水,考察氯化铁（FeCl_3·6H_2O）的投加对UCT-MBR工艺运行效能与膜污染的影响,用傅里叶红外光谱（FT-IR）和能谱（EDX）对膜污染物质进行分析。研究结果表明：氯化铁的投加强化除磷效能,在最优除磷投加浓度运行时（投加浓度为1.8 mmol/L）,能够最佳协同生物除磷的作用使得系统总磷（total phosphorus,TP）的去除率达到最高。氯化铁主要是通过增加污泥粒径、降低相对分子质量大于10~5的溶解性微生物产物（soluble microbial products,SMP）来实现减缓膜污染程度。在最佳污泥可滤性投加浓度运行时（投加浓度为2.6 mmol/L）,UCT-MBR工艺的膜污染速率达到最小,但该投加浓度严重地影响污泥的生物活性,降低污泥的硝化与释/吸磷性能,成为制约脱氮除磷效能的主要因素。铁盐的投加没有改变膜污染物质的组分,无机污染对膜污染速率的影响程度比有机污染的小,无机元素协同有机高聚物形成密实滤饼层时存在一定的滞后性。

A bench-scale biological nitrogen and phosphorus removal membrane bioreactor（UCT-MBR） process was operated to treat carbon-limited municipal wastewater regarding on the influences of ferric chloride（FeCl_3·6H_2O） addition on the process performance and membrane fouling. FT-IR（Fourier translation infrared spectroscopy, FT-IR） and EDX（energy dispersive X-Ray, EDX） were used to analyze membrane surface foulants. The results show that the phosphorus removal is strengthened with the addition of ferric chloride. The highest removal efficiency of TP（total phosphorus, TP） can be obtained in UCT-MBR process under the condition of the optimal-phosphorus-removal dosing（dosage of 1.8 mmol/L） combined with the biological phosphorus removal process. Membrane fouling is alleviated with the addition of ferric chloride mainly through increasing the sludge particle size and reducing the SMP（soluble microbial products, SMP） fraction concentration with relative molecular mass above 105. The lowest membrane fouling rate in the UCT-MBR process can be obtained under the condition of the optimal-sludge-filterability dosing（dosage of 2.6 mmol/L）, while the optimal-sludge-filterability dosing exhibits a strong influence on sludge bioactivities and reduces the sludge capabilities of nitrification and phosphorus release/uptake, which limits the performance of nitrogen and phosphorus removal. The ferric chloride addition has no effects on their compositions. Moreover, the influence of inorganic fouling on membrane fouling rate is found to be smaller than that of organic fouling. Besides, lag effects are found for inorganic elements combined with biopolymers to form a dense cake layer.