Study On Excess Sludge Degardation By Microbial Agents

A large number of excess sludge have produced during the process of activated sludge treatment of sewage.The untreated sewage sludge is piled up and discharged into the environment,which has caused a new pollution,and its treatment and disposal has become a bottleneck restricting the development of urban sewage treatment industry.Excess sludge contains a large amount of water,but also contains a large number of organic compounds,heavy metals and salts,as well as pathogenic bacteria and parasitic ovum.In this paper,different species of bacillus and surplus sludge were taken as research materials to bulid a strong sludge degradation microbial agents.The main results were as follows:(1)Screening bacillus for degrading sludge.Selecting 24 kinds of bacillus as the original strains.After primal selection,six bacillus were screend out from the original strains by testing them degradation ability to amylum,protein,sludge MLS S,antimicrobial actions and biosecurity.(2)Screening bacillus with high efficiency sludge degradation.Using restricted culture technology in which dry sludge do only nitrogen source in the limiting substrate medium to screen strains.The primary screen strains were inoculated into the limiting substrate medium with ratio of 5%v/v,cultured with shaking at 30?,150rpm/min and passaged every 48h with same ratio of 5%v/v,a total of 3 generations.Taking the stability of the strains and the degradation effect to organic matter and TN in the process of passage as the second selection standard.Eventually sieve three efficient degradation strains respectively Bacillus subtilis R10,Bacillus licheniformis 10001 and Bacillus amyloliquefaciens 11009.(3)Preparation of microbial inoculants and study its application effect.By testing the strains growth curve to get the optimal sampling time of R10,11009 and 10001 was 22h,14h and 15h,respectively.The strains were used to make microbial agents after expanding culture by the fermentor.During this process,the drying technology,which is the core process of the liquid microbial agents technics was optimized.In order to achieve the optimum treatment,the agents adding amounts and the sludge concentration were optimized by response surface.And the best result was got when the agents 10001,11009 and R10 adding amount respectively 0.43w/v%,0.83w/v%and 0.64w/v%,sludge concentration 6570mg/L.The removal rate can improve 25.6%and 47.3%compared with the control group.After aerating the excess sludge in the environment conditions,the microbial agents were proved safe and reliable in the application without causing any pollution to the water.Meanwhile,the surface of the sludge particles in the process of degradation was observed by the SEM,the results of which showed that the agent failure time is about 3 days.(4)Analysising on the change of excess sludge bacterial community in the process of degradation.The bacterial community changes in the process of sludge degradation were analysised by molecular biology method PCR-DGGE.Results showed that the bacillus R10 and 11009 played a leading role on the begining,but 10001 had an obvious latter effect.The microbial agents can occupy the dominant flora in a short period of time and achieve efficient degradation of sludge.