浸没式超滤膜在大型给水厂的应用与思考

Application and Consideration of Submerged UF Membranes in Large-Scale WTPs

浙江省某地两个大型水厂(J水厂和T水厂)的生产规模分别为2.0×10^(5)m^(3)/d和5.0×10^(5)m^(3)/d,其运行时间分别为2年和7年,均采用浸没式超滤膜为核心净水工艺。文章结合两个水厂的实际运行情况,研究和总结了两个水厂的运行管理经验,得到如下结论:膜运行方面,两水厂膜进水浑浊度日常在0.15~4.25 NTU,台风季偶有短时13.6~35.2 NTU的情况下,膜出水浑浊度一直稳定在0.1 NTU以下,2μm以上的颗粒数偶有检出;膜污染控制方面,物理清洗时两水厂均在产水中间阶段进行一次气冲清洗,可有效缓解膜污染;化学清洗时发现J水厂仅采用柠檬酸清洗效果好,T水厂采用先次氯酸钠、后柠檬酸清洗效果好;水厂设计方面,J水厂泵吸式产水整体能耗高达27 kW·h/km^(3),T水厂虹吸式产水最低能耗仅为13 kW·h/km^(3),有效降低了能耗;运行管理方面,扩大清水池容积可有效解决因清水池调蓄能力不足导致的超滤膜长时间超负荷运行的问题;同时在膜池的进水管上增设膜前加氯点,保证出水余氯质量浓度稳定在0.2 mg/L左右可有效解决藻类滋生问题。

The production scales of two large water treatment plants(WTPs),J WTP and T WTP,in Zhejiang Province are 2.0×10^(5)m^(3)/d and 5.0×10^(5)m^(3)/d,respectively,with operation times of 2 years and 7 years.Both WTPs utilize submerged ultrafiltration membranes as the core water purification technology.Based on the actual operation of the two WTPs,this paper studied and summarized their operational management experiences as following regarding membrane operation,the daily inflow turbidity in both WTPs ranged from 0.15 NTU to 4.25 NTU,stabilizing below 0.1 NTU in finished water turbidity with occasional detection of particles over 2μm,even at conditions of occasional short-term spikes of 13.6~35.2 NTU during typhoon seasons.In terms of membrane fouling control,both WTPs conducted air scouring during the middle stage of water production,effectively extending the water production time.For chemical cleaning,citric acid was found to be effective for J WTP,while a combination of sodium hypochlorite followed by citric acid was effective for T WTP.Regarding WTP design,pump-assisted production process of J WTP exhibits a relatively high overall energy consumption of 27 kW·h/km^(3),while T WTP,with its gravity-assisted production process,achieved a significantly lower energy consumption,as low as 13 kW·h/km^(3),effectively reducing energy consumption.In terms of operational management,increasing the clear water reservoir′s volume effectively resolved issues stemming from inadequate clear water reservoir storage capacity,which led to prolonged membrane overloading at J WTP.Simultaneously,the introduction of a chlorination point ahead of the membrane feedwater in the membrane tank ensured stable effluent residual chlorine levels of approximately 0.2 mg/L,efficiently addressing problems related to algal growth.