The Research On Domestic Wastewater Treatment Using New Process Combined By Submerged Micro-filtration Membrane And Oxidation Ditch

By experimented in the laboratory and the plant the removal characteristics and the impact factors of organic matter, total nitrogen, total phosphor, heavy metal, bacteria were researched. The stability of new process and the characteristics of the sludge were studied. Membrane fouling and the technology about membrane fouling control were discussed. The stability and instability mathematics models were established.The experiments show that the new process combined by micro-filtration membrane and oxidation ditch can remove organic substance and heavy metal with high efficiency. The removal rates of CODcr, BOD5, COD, iron, manganese, chromium can reach 90%, 96%, 75%, 90%, 88%, 86% respectively. Without adding coagulation into bioreactor the removal rate of phosphor is 50% and the phosphor removal rate can reach 85% if it was done. The turbidity of effluence is bellow 5NTU and the concentration of dissolved total substance is bellow 100mg/L. But there are even small amount of bacteria and Escherichia in the effluence. After disinfecting the effluence quality can reach The Reuse of Urban Recycling Water-Water Quality Standard for Urban Miscellaneous Water Consumption of China(GB/T 18920-2002) and The Reuse of Urban Recycling Water-Water Quality Standard for Scenic Environment Use of China (GB/T18921-2002).The analysis on the molecular weight of organic substance shows that almost all the organic matter was removed in the oxidation ditch and the organic matter with molecular weight of 4000 can be removed efficiently by micro-filtration membrane so the organic matter in effluence has small molecular weight. The new process has strong anti-shock loading capability so the effluence quality is reliable when the influence quality is fluctuating. And the process can resume in a short time after interruption. The proportion of aeration time and interruption time and the hydraulic retention time (HRT) has great effected the efficiency of nitrogen removal. As the proportion of aeration time and interruption time is 3:1 and the HRT is 4h the removal rates of ammonia and total nitrogen can reach 95% and 80% respectively. The removal rate of ammonia can not be increased if the HRT is prolonged. Adding coagulation into bioreactor can enhance the removal efficiency of phosphor. The activated sludge in new process has some characteristics such as low dehydrogenase activity, small sludgegain and lots of protonema in it so the sludge has bad sedimentation capacity But it do not effect the effluence quality. Filtration resistance increased gradually so the membrane must be washed periodically. Propriety hydraulic wash can resume the membrane flux and intermittent effluence can less the membrane fouling. The membrane fouling is attributed to the accumulated cakes on the membrane composed by sludge gain, microorganism, and the microbial products. The operating status and parameters affecting the stability of process can be simulated and estimated by using mathematics model.