降雨过程对污水处理厂无机颗粒物特性及活性污泥的影响

Influence of rainfall process on inorganic particle characteristics and activated sludge in wastewater treatment plant

取消初沉池的污水处理厂,粒径小于200μm细微无机颗粒物将直接进入生化池,或悬浮或沉积,进而影响生化池的运行。以山地城市某污水处理厂为例,跟踪监测了夏季2个月的6次降雨过程中旋流沉砂池进出水无机颗粒物的粒径和浓度,并同期测定了生化池活性污泥浓度以及污泥MLVSS/MLSS比值。研究发现:旱季旋流沉砂池进出、水中的无机颗粒物平均粒径分别为65.25μm及54.14μm,浓度均值分别为146 mg·L-1及128 mg·L-1,无机颗粒去除率12.33%;降雨旋流沉砂池进出、水中的无机颗粒物峰值平均粒径分别为140.48μm及94.54μm,峰值平均浓度分别为2 167 mg·L-1及1 591 mg·L-1,无机颗粒去除率26.58%;旋流沉砂池对粒径≥200μm颗粒的去除较稳定,对细微无机颗粒物的去除效率约10%。研究进一步发现,降雨中颗粒物浓度分别与雨前晴天数及平均雨强呈线性正相关关系。通过核算生化池无机颗粒物的物料平衡关系,得知研究期间生化池累积无机颗粒物总量410.25 t,其中399.45 t沉积在底部,其余悬浮于活性污泥混合液中。活性污泥MLVSS/MLSS由0.52降至0.40,MLVSS由1 410 mg·L-1降至930 mg·L-1,污泥活性下降,系统运行效能受到影响。

Fine inorganic particles with sizes of 〈 200 μm will enter bioreactors in wastewater treatment plants （WWTPs） lacking primary settling tanks, and whether these inorganic particles become deposited at the bottom of bioreactors or suspended in activated sludge will affect the operation of biorcactors. In this study,the si- zes and concentrations of inorganic particles were monitored in the influent and effluent of swirl grit chamber dur- ing six rainfall events over two months during the summer at a WWTP located in a mountainous urban area. The concentrations of mixed liquor volatile suspended sollds/mixed liquor suspended solids （MLVSS/MLSS） in the activated sludge were also measured. During dry periods, the removal rate of the swirl grit chamber was 12.33% , during which the average diameters of inorganic particles in the influent and effluent were 65.25 μm and 54. 14 μm,respectively;meanwhile, the mean concentrations of these particles in the influent and effluent were 146 mg·L-1 and 128 mg·L-1, respectively. During rainfall events,the removal rate of the swirl grit chamber was 26.58% ,during which the peak volume average diameters of inorganic particles in the influent and effluent were 140.48 μm and 94.54 μm,respectively;meanwhile,the mean peak concentrations of these particles in the influent and effluent were 2 167 mg·L-1 and 1 591 mg·L-1 ,respectively. The removal rate of the swirl grit chamber for inorganic particles with sizes of ≥200 μm was stable,but for particles with sizes of 〈 200 μm,val- ues as low as 10% were observed. Further research revealed that the concentration of inorganic particles during rainfall events was positively related to the length of the dry weather period preceding the rainfall and the average rainfall intensity. Balance analysis of inorganic particles in the bioreactor during the study period showed that the cumulative amount of inorganic particles reached up to 410.25 t,of which 399.45 t were deposited at the bottom of the reactor while the remaining particles were suspended in the activated sludge; this corresponded to a de- crease in the MLVSS/MLSS from 0.52 to 0.40 （MLVSS decreased from 1 410 mg·L-1 to 930 mg·L-l）. De- creases in the activity of sludge can be harmful to the effective operation of WWTPs.