| With the social and economic development of rural residents' living standard, rural sewage emission load is growing. A survey showed that rural sewage was one of the main pollution sources exited in water environment, imposing a potential threat to water resources security and restricting the sustainable development of the rural area.The selection of treatment technology and the construction of facilities play a key role in the sewage treatment. This study set the treatment processes for rural domestic sewage in Jiangsu province as the research object to analyze the technology classification, treatment scale and operation cost of the existing treatment processes. After summarizing the characteristics of rural sewage treatment projects, the data of long-term follow-up monitoring of inlet and outlet water quality in the typical decentralized rural sewage treatment system were analyzed to determine whether the chosen technique was suited both economically and optimally. In order to test the most reasonably treatment craft, an elaborate hierarchy structure model of evaluation index was set up. Then the standardization of equipment for a suitable technology was studied. Researches and conclusions can be summarized as follows.(1) 33 processing technologies were divided into biological and the combination of ecological and biological technology by analyzing the treatment principle, scale and investment characteristics of all used domestic sewage treatment technologies, among which biological technology accounted for the largest proportion (49%). The scale of solo decentralized wastewater treatment facility was small. Among those facilities, the treating capacity less than 100m3/d occupied 88% of the total. There were differences in the investment and the operation cost of different process. The construction investment was similar to the operational cost, the regularity was:biological technology> bio-ecological technology> ecological technology.(2) Water quality and material consumption of sewage treatment facilities were monitored. The pollutant concentration of influent had considerable fluctuations due to different seasons, which were presented the highest in January and lowest in July. The average annual value of COD TP, TN and ammonia nitrogen concentration were 15.46 mg/L,3.4 mg/L,38.3 mg/L L and 27.8 mg/L, respectively. The results of the evaluation of the pollutant removal effectiveness of all three technologies demonstrated that bio-ecological technology operated steadily and pollutant removal efficiency was optimal because it contains the advantages of both biological and ecological procedure. The monitor results of construction material consumption revealed that, organic filler type constructed wetland had the lowest construction cost (2.8 thousand Yuan/(t·d-1)), while MBR had the highest construction cost (18.3 thousand Yuan/(t·d-1)). In terms of operating expenses, the combined type constructed wetland had the lowest operation power consumption (0.00028 kW·h/(t·d-1)), whereas household cleaning tank had the highest operation power consumption 1.50 kW·h/(t·d-1)).(3) Based on hierarchical analysis method and the statistical theory, a software, which was consisted of 4 layers and 16 indicators was established to evaluating rural domestic sewage treatment efficiency by considering the processing technology, economy, ecological environment and operation maintenance management. The established evaluation index system was used to evaluate the effectiveness of the 13 treatment techniques, and the results showed that comprehensive evaluation results of high loading subsurface infiltration technology, organic filler type constructed wetland, pulse biological filter and combined constructed wetland were "Positive", which means the evaluation results conformed to actual situation.(4) The equipment standardization research of pulse biological filter was conducted according to the different operation scale and production equipment specification. The diameter of the equipment was 1.6,2, 2.2,2.6,2.8 and 3.0m respectively. The installation steps of equipment from the bottom to the top were catchment, wellbore (including biological filler), pulse water distributor, annular water tank. Then the production requirements of each component and the assembling process of the filter were established, and the construction and installation steps of the pulse biological filter were put forward.In this thesis,7 suitable technologies for different characteristics of rural sewage treatment in Jiangsu province were obtained. And a software for evaluating rural domestic sewage treatment efficiency has been established. Then the equipment specified construction content was put forward based on pulse biological filter. All of these results provided technical support for the rural sewage treatment in Jiangsu province. |
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