Separate Mechanism Of High Concentration Sludge And Applicable Sub-millifiltration Module

To ensure the effusive water quality in sewage biological disposal system,process ending are in need of solid-liquid separation, in which the secondary settling tank and membrane separation are more common. Practice shows that when the sludge concentration increased within the system, the stable operation of solid-liquid separation more difficult.a) When sludge concentration into the secondary settling tank more than 4gMLSS/L, the effusive water quality will deterioration, effluent suspended solids increased significantly.b) The high sludge concentration (>10gMLSS/L) leads to severe membrane plugging,increased enery consumption and costs of membrane cleaning/ replacement.Therefore, high sludge concentration is the common key to constraint secondary settling tank and membrane separation stable operation.If we can develop a cheap and reliable technology, making the sludge concentration into the reactor control 3-5gMLSS/L, then the high sludge concentration on the solid-liquid separation unit of the restrictions can be resolved. Thus, biochemical unit can be maintained at a relatively high sludge concentration and stable operation, so as to enhance processing efficiency, reduce excess sludge and lower overall energy consumption.A homemade sub-millifiltration module was introduced in this research,by separate function that confined high concentration of activated sludge within one tank,for desired appropriate sludge concentration in another tank, to ensure the sludge concentration access to the secondary settling tank and MBR in the context of better.so that sewage biological disposal system can relieve the restraint of high concentration sludge.Research contents as followed:a) separate mechanism of high concentration sludge,b) study on the application modules in different working conditions (the temperature in the container are 20℃and 5℃), and provide appropriate pore size range for application modules.the following outcomes can be achieved:(i) Through mass balance of the system,we can get the theory formula about sludge concentration(MLSS) of the two subareas(A and B area) under stable operation conditions. Except that,we can also gain the variation law in the theory:XA decreases while HRTA increases, XA increases while influent COD increases, XB decreases as R ascendes. And the higher the XA,B,the higher the XB.(ii) Operation condition one(the temperature in reactor was setted in 20℃):the operation in a cycle,the optimal module appropriate size was 1.236mm, and initial flux was 450L/m2.h,after 20 minutes, the average flux was 380 L/m2.h and SS was obtained 3.5g/L.The operation in multicycles,the best suitable size was 0.581mm,the stable flux and SS were 140L/m2.h and 2.5g/L respectively, stable operation cycle period from 18 to 80 cycles. The following module of which 0.581mm, effluent SS can remain stable long-cycles and meet requirement.(iii) Operation condition two(the temperature in reactor was setted in 5℃):In this operation condition, filter module size above 0.329mm can not meet the requirement, does not apply to engineering practice.The optimal module suitable size was between 0.05mm and 0.1mm.Under appropriate size 0.05mm and initial flux 450L/m2.h conditions, after 20 minutes, the stable flux was 170L/m2.h,15～30-folds higher than ultra/microfiltration.and the system can operate steadily 80 cycles.A comprehensive consideration of operating condition one and operating condition two, for subarea of high concentration sludge of the modules were introduced should be between 0.05-0.1mm.