污泥浓缩过程下膜生物反应器的生物特性与膜渗透性评估

采用中试规模的好氧膜生物反应器(MBR)工艺处理城市污水,考查了在浓缩过程下膜生物反应器的生物特性对膜渗透性及渗透性恢复的的影响.在试验中通过投加蔗糖溶液使系统维持恒定污泥负荷(food to microorganisms, F/M)在0.13,测定了活性污泥的一系列的生化与理化参数,并通过SPSS软件对污泥性质与动态变化的膜渗透性及渗透性恢复水平的相关性做了进一步的评估.结果表明,混合液悬浮固体(MLSS)浓度对膜渗透性的影响最大(rp=-0.958,P=0.000);溶解性微生物产物(SMP)浓度、溶解性化学需氧量(sCOD)浓度、污泥粒径(PSD)及毛细吸水时间(CST)对膜渗透性的影响属于同一个水平(|rp|=0.82~0.85,P=0.000);而污泥沉降性能与丝状菌指数对膜渗透性的影响不大.并且发现随着MLSS浓度的增大,膜丝廊道内积累的堵塞固体(ACS)的质量以及膜渗透性的绝对恢复量(ΔL)也有增加的趋势,表明MLSS浓度直接影响着膜生物反应器的堵塞性能,也进一步证明了膜堵塞是除膜污染之外影响膜渗透性的另一个重要因素.在低通量5~6L/(m2·h)] 的操作条件下离线清堵联合强化化学反洗(CEB)的方式可以保证膜生物反应器工艺在高MLSS浓度运行下实现膜渗透性的可持续恢复.

Assessment of biomass characteristics and membrane permeability in a membrane bioreactor under thickening operation

A pilot-scale aerobic membrane bioreactor (MBR) process was operated to treat municipal wastewater regarding on the influences of biomass characteristics on membrane permeability as well as the membrane permeability recovery. Sucrose solution was added to maintain system operation of a constant food to microorganisms (F/M) ratio at 0.13 and a series of physicochemical and biochemical parameters of activated sludge were also measured throughout the whole trial, with correlations between biomass properties and membrane permeability as well as the membrane permeability recovery were further assessed by using Statistical Product and Service Solutions (SPSS) analyses. Results showed the mixed liquor suspended solids (MLSS) concentration exerted the greatest influence on membrane permeability (rp=-0.958, P=0.000); soluble microbial products (SMP) concentration, soluble chemical oxygen demand (sCOD) concentration and particle size diameter (PSD) had similar weaker effects on membrane permeability (|rp|=0.82~0.85). Whereas the sludge settleability, and filamentous index (FI) had no evident influences on membrane permeability. The accumulated clogged solids (ACS) in membrane channels and absolute membrane permeability recovery increased with the increasing MLSS concentrations, implying that the MLSS concentration had direct effects on membrane clogging propensity and further proved that membrane clogging being another important factor affecting the membrane permeability except for membrane fouling. The off-line declogging combined with enhanced chemically backflushing (CEB) could ensure the sustainable membrane permeability recovery under the condition of low-flux 5~6L/(m2·h)] operation at high MLSS concentrations.