污泥龄对膜生物反应器污泥特性及膜污染的影响

研究了污泥龄对胞外聚合物(EPS)总量、紧密粘附胞外聚合物(TB)和松散附着胞外聚合物(LB)含量及其中蛋白质与多糖比例的影响.结果表明,随污泥龄的延长,混合液EPS总量增加,TB和LB中蛋白质与多糖比例发生变化.这种变化改变了细菌表面电荷分布,增大了细菌表面亲水基和疏水基的比例,使细菌的存在状态由不稳定型(R型)向稳定型(S型)转变,降低了混合液Zeta电位,SVI值增大.采用SPSS软件对膜污染的主要因子进行了相关性分析,Zeta电位、上清液悬浮固体浓度、相对疏水性的相关系数分别为-0.818、0.853、0.832.综合考虑膜污染阻力和污泥特性,膜生物反应器的污泥龄应控制在优势菌最小世代时间的120倍以下.

Effects of sludge retention time on the sludge characteristics and membrane fouling in membrane bioreactor

The effect of sludge retention time (SRT) on the total extracellular polymeric substances (EPS), contents of tightly bound EPS (TB), loosely bound EPS (LB) and the ratios of protein and polysaccharide in TB and LB was investigated. The total EPS increased and the ratios of protein and polysaccharide in TB and LB changed with the extension of SRT. The above changes influenced the distribution of surface charge of bacteria, increased the proportion of hydrophilicity and hydrophobicity on the surface of bacteria, transformed the existence state change of bacteria from the instable (R type) to the stable (S type), decreased the Zeta potential and increased the values of sludge volume index (SVI). The correlation analysis for the main parameters of fouling resistance displayed that the correlation coefficient (rp) was -0.818 for Zeta potential, 0.853 for the content of suspended solids in supernatant and 0.832 for relative hydrophobicity, respectively. SRT of the membrane bioreactor (MBR) should be controlled below 120 times of the minimum generation-time of dominant bacteria considering the membrane fouling resistance and sludge characteristics.