广州市某净水厂MBR膜丝检测及清洗优化

Detection of MBR Membrane in a Sewage Purification Plant in Guangzhou and Its Cleaning Optimization

为解决某净水厂MBR中空纤维超滤膜清洗效果欠佳问题,采集膜丝开展了机械强度、孔径分布、清水通量等全面检测,分析污染成因,优化清洗剂及清洗顺序。新膜和清洗后的使用膜单丝拉伸断裂强力分别为(4.7±0.9)N和(2.0±0.1)N,平均/最大孔径分别为0.0278μm/0.0676μm和0.0524μm/0.1316μm,接触角分别为99.8°±1.4°和101.1°±2.4°。清洗后的使用膜外表面存在硫酸钙、硅酸钙,以及铝、硅、钙的氧化物等无机结垢污染。污染膜采用柠檬酸和草酸清洗后,其清水比通量增加值[0.66~1.38 L/(m^(2)∙h∙kPa)]均高于次氯酸钠清洗的[0.20~0.65 L/(m^(2)∙h∙kPa)];先草酸后次氯酸钠清洗的清水比通量增加值[1.73 L/(m^(2)∙h∙kPa)]显著高于先次氯酸钠后草酸清洗的[1.19 L/(m^(2)∙h∙kPa)];先草酸清洗的效果[清水比通量增加1.38 L/(m^(2)∙h∙kPa)]略好于先柠檬酸清洗的[清水比通量增加1.19 L/(m^(2)∙h∙kPa)],且草酸用量显著低于柠檬酸。为提高清洗效果并降低成本,建议与该净水厂类似,存在无机、有机复合污染的MBR膜采用先草酸后次氯酸钠清洗顺序。

This paper sampled membrane fibers from a membrane bioreactor(MBR)and conducted a comprehensive test including items such as mechanical strength,pore size distribution and clean water flux to analyze the causes of membrane fouling and optimize the cleaning agent and cleaning sequence,so as to solve the problem of poor cleaning performance of hollow fiber ultrafiltration membrane in a sewage purification plant.The tensile breaking force of the new membranes and the cleaned membranes in use were(4.7±0.9)N and(2.0±0.1)N,respectively,their average/maximum pore sizes were 0.0278μm/0.0676μm and 0.0524μm/0.1316μm,respectively,and the contact angles were 99.8°±1.4°and 101.1°±2.4°.There were inorganic scales such as calcium sulfate,calcium silicate and oxides of aluminum,silicon and calcium on the outer surface of the cleaned membranes in use.After the fouled membrane was cleaned with citric acid and oxalic acid,the increase of clean water specific flux[0.66-1.38 L/(m^(2)∙h∙kPa)]was higher than that of the membrane cleaned with sodium hypochlorite[0.20-0.65 L/(m^(2)∙h∙kPa)].The increase of clean water specific flux of the membrane cleaned with first oxalic acid and then sodium hypochlorite[1.73 L/(m^(2)∙h∙kPa)]was significantly higher than that of the membrane cleaned with first sodium hypochlorite and then oxalic acid[1.19 L/(m^(2)∙h∙kPa)].The performance of first oxalic acid cleaning[1.38 L/(m^(2)∙h∙kPa)increase in clean water specific flux]was slightly better than that of first citric acid cleaning[1.19 L/(m^(2)∙h∙kPa)increase in clean water specific flux],and the dosage of oxalic acid was significantly lower than that of citric acid.The oxalic acid cleaning followed with sodium hypochlorite cleaning was proposed to improve the cleaning performance and decrease the cleaning cost of fouled MBR membrane with inorganic and organic fouling in similar sewage purification plants.