Study On The Correlation Of Microfauna On Porous Carrier And Excess Sludge In Situ Reduction

As the accelerating of urbanization process, a large number of sewage treatment plants are being constructed, in the urban sewage treatment plants in our country, currently activated sludge process is a widely used method for biological sewage treatment, the method can generate a large amount of sludge that are not easy to treat and dispose, which has a huge investment and operating costs. The costs for treatment and disposal of sludge in developed countries account for 50%~ 60% of all the construction and operating costs of the sewage treatment plant, while the number reaches 30% ~40%[1, 2] in our country. Because the environmental regulation has increasingly high requirements for treatment and disposal of surplus sludge, the treatment of surplus activated sludge is faced with severe challenges. In this situation, we can start from the source, and reduce the output of surplus sewage during sewage treatment with technical progresses and technology improvements and so on, besides, we can develop sewage treatment technology that has low sludge yield to reduce the amount at the source, which has great significance.The paper takes porous carrier system as the core, and takes microfauna, suspended sludge of the system and water quality as the research objects, and successively tests them in different time and spaces during the operation of the reactor, and implements statistical calculation and correlation analysis, and comes to a final conclusion as below:(1) The density of microfauna in porous carrier system was up to 1200/ml, which was about 750/ml larger than the system without carrier. The advantageous species in porous carrier system were opercularia and epistylis, while the advantageous species in system without carrier was cup vorticella. The porous carrier system had generated long and complex food cycle during the mature period of cultivation, which provides advantageous conditions for the reduction of sludge. There was no food cycle in the system without carrier.(2) Among the analysis of diversity index H of representative microfauna, sessile microfauna and metazoan are easy to suffer the gravity sedimentation, which can cause the diversity index of lower level to be higher than the upper level. The difference of diversity index of swimming ciliates between the upper and lower levels is not big, they can secrete a kind of mucus, which does benefit to accelerate the formation of zoogloea, it has the function of balancing upper and lower levels and water surface. The diversities of swimming ciliates and sessile ciliates are easy to be affected by the water flow. Stabilizing changes of diversities of swimming and sessile ciliates and metazoan during the operation period, and making the system in dynamic balance, both of them have certain buffer actions for resistance ability.(3) During the stable operation of porous carrier for 60 days, changes of concentration of suspended sludge were smooth and steady, and settle-ability had obvious increased, and the activity of sludge was relatively high. The real yield of system sludge was 0.054 g SSD/g COD, the apparent yield of sludge was between 0.045~0.052 g SS/g COD, the real yield basically matched with the apparent yield, which means that during the period of stable operation of porous carrier system, the growth and metabolism of activated sludge were good, and the reduction of original surplus sewage was obvious.(4) COD、NH3-N and DO in different positions had no abnormal fluctuations because of the function of hydraulic shear force, the removal rate of COD was more than 90%, and the removal rate of NH3-N was more than 93.2%. The effluence of COD and NH3-N can meet the first class B emission standard of urban sewage which was specified by the national standard(GB18918-2002).(5) Vorticella and A.hemprichi can be the indicative creatures of concentration of suspended bacterium, correlation indexes were separately 0.915 and-0.811. When many vorticella appear in the system, it means the concentration of suspended sludge in the system is a little high, and they are positively associated. When many A.hemprichi appear in the system, it means the concentration of suspended sludge in the system is a little low, and they are negatively associated.