Study On The Characteristics Of Strengthen Circulation Anaerobic Reactor For Treatment Of Domestic Sewage

Recently it has become one of the hot topics to treat domestic sewage with high-rate anaerobic biotechnology. The technology has been widely used for various types of wastewater treatment because of its low investment, saving energy, stable operation and being easy to operate, and it has broad prospects in domestic sewage treatment.The Strengthen Circulation Anaerobic Reactor(SCAR) was used to treat domestic sewage in this study, the startup characteristics and operating characteristics of treating domestic sewage by SCAR were studied to find out the optimum operation conditions and analyze the relation between operation results and microbial characteristics. A preliminary analysis of the population structure characteristics of the microorganism in the reactor was also launched. The results of this study may provide some data basis and practical experiences for treating domestic sewage by anaerobic reactor.The research shows the results as follows:(1) The domestic sewage was treated by SCAR, the reactor started by using simulated domestic sewage as influent with CODCr of about 350mg/L under conditions of HRT=16h and R(reflux ratio)=0.5, the start-up stage completed after continuously running for 65 days while the effluent CODCr and the ramoval rate were stable at about 80mg/L and 77%. The concentrations of DHA and coenzyme F420 gradually increased in general, the concentrations of DHA from outlet1 and outlet2 were respectively 3.16mg/(gVSS·h) and 2.72 mg/(gVSS·h), and the concentrations of coenzyme F420 from outlet1 and outlet2 were 0.017μmol/gVSS and 0.015μmol/gVSS when the start-up stage completed. The concentrations of DHA and coenzyme F420 were on the normal level, it was weak alkaline in the system, and the VFA did not accumulate during the start-up stage. The concentrations of SS, VSS and VSS/SS from outlet1 and outlet2 gradually increased reached stable values, active components in the sludge increased during the start-up stage in the system, and the quantity and activity in each outlet were higher than that of last stage.(2) When the start-up stage completed, the HRT was adjusted and the HRTs were set at 12 h, 8h, 6h and 4h, furthermore, the reflux ratios were set at 0, 2, 4 and 7 under each HRT. The removal rate reduced with the HRT reducing and first increased and then decreased with the reflux ratio increasing. The optimum removal rate of the reactor was obtained when the reflux ratio was 4, and the average removal rates were respectively 83%, 84%, 69% and 70%. The nitrogen removal was obvious under the experimental conditions and the removal was between 82% and 90%, the removal was mainly by the denitrification process.(3) The concentrations of DHA and coenzyme F420 gradually increased with HRT reducing during the target stage, the activity of acid-producing bacteria and methanogen increased when the sludge load became larger. The concentrations of DHA and coenzyme F420, SS, VSS and VSS/SS in each outlet first increased and then decreased when the reflux ratio increased. The concentrations of DHA and coenzyme F420, SS、VSS and VSS/SS reached respective maximum when the reflux ratio was 4, this trend was consistent with the trend of removal rate of CODCr, and the treatment effect of the reactor was relatively good. The trend of concentrations of PS, PN, EPS and PN/PS were consistent with that of the enzymes.(4) When the startup stage ended, the SEM showed that granular sludge from outlet1 mainly consisted of bacillus, filamentous fungi and a spot of spherical bacteria, filamentous fungi of the granular sludge from outlet2 increase evidently. The biocoenosis of the granular sludge of outlet1, outlet2 and outlet4 was sequenced by the means of high-throughput sequencing combined with sequencing quantitative PCR. The results showed that the granular sludge from oulet2 had the most quantity of biological communities, followed by that of oulet1 and oulet4. On the level of phylum, the dominant bacteria of outlet1 were chloroflexi and bacteroidetes, and that of outlet 2 were chloroflexi, proteobacteria and bacteroidetes, and that of outlet4 were proteobacteria.