| On-site treatment of sewage at drain outlet is a possible way to achieve pollution interception in the areas where municipal drainage networks remain imperfect, however, the related technology is far from mature. The present paper attempts to use the combination of hydrolysis/acidification bio-contact oxidation process and hydrophyte for on-site wastewater treatment, in order to achieve on-site pollutants interception, and to test the feasibility of this technology and device in practical application, so as to provide technological support for the processed selection and operation condition optimization of the on-site sewage interception treatment at drain outlet. The main research contents and conclusions are as follows:1. Research on pollutant intercept of sewage employing hydrolysis/acidification,two-stage bio-contact oxidation and hydrophyte. The influence of hydraulic retention time(HRT), volume load, aquatic plants on the treatment efficiency was researched. The results indicated that the mean removal ratios of COD, NH4+-N, TP were 77.6%, 60.52%, 53.37% respectively while HRT=6 h, and the optimal volumetric loading rates were 216, 11.575 and 1.52 g/m3?h respectively. The NH4+-N, TP removal ratios reached 81.39% and 53.78%, with increases of 28.94% and 10% respectively, while the system runs with eichhornia crassipes involved under HRT=4h. The effluent quality can reach the GB18918-2002 1B discharge standard.2. Research on microbial community of hydrolysis/acidification,two-stage bio-contact oxidation and hydrophyte process. By high-throughput sequencing analysis, it’s found that the microorganisms on the biological membrane of elastic filler includ Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria, Firmicutes, Acidobacteria and Chlorobi, with average relative abundance 16.45%, 27.92%, 6.35%, 12.12%, 3.15%, 12.74%, 7.5% and 4.92% respectively, accounting for 91.16% of the total number of bacteria. By comparing the abundance of the main OTUs which caused community differences in the three groups, it’s found that aerobic bacteria such as Myxococcales and Pelomonas exist mainly in the B contact oxidation pool with abundant dissolved oxygen; while anaerobic bacteria such as Bacteroidales,Veillonellaceae and Bacteroides mainly exist in the hydrolytic acidification pool, little survival in a contact oxidation pool. The results show that the community composition of biofilm bacteria has a direct relationship with the concentration of dissolved oxygen in water.3. Experimental study on purification of black odor waterbody by synergistic of aeration and eichhornia crassipes. The growth of eichhornia crassipes under aeration and non aeration conditions and the effects on organic matter removal were studied. The results indicate that the eichhornia crassipes’ total biomass was increased by 1.7 kg/m2 in the aeration tank, and the average growth rate of biomass was 80.9 g/m2?d, which is 4.3 times of that of the anaerobic pool under temperature 25 ~ 30 and running for 21 days.The removal efficiencies of COD, NH℃ 4+-N, TP in the aeration tank were 89.7%, 81.39% and 53.62% respectively, which were 2.8, 4.0 and 1.9 times of that of the anaerobic pool.4. The feasibility and practical application of the floating device for on-site sewage interception process. According to the above process, a floating type device for on-site sewage interception at drain outlet was designed and it’s field test was conducted. A ring of DN160 PVC pipe was connected to the periphery of the device, and a layer of plastic foam was connected to the water inlet end of the device, making the device floating on the surface of the river without sinking and draining water off smoothly. Under conditions of low temperature in winter, the removal rate of COD, NH4+-N, TP can still keep 68.9%, 52.3%, 47.77% respectively, and the effluent quality of COD and NH4+-N can reach GB 18918-2002 discharge standard II, indicating that the combined method of hydrolysis/acidification two-stage bio-contact oxidation and hydrophyte process is feasible for on-site pollutants interception of urban rivers. |
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