Studies On Domestic Sewage Treatment Using ABR-constructed Wetland And Performance Of Improved ABR

With the development of rural economics and the improvement of living standards, domestic sewage has become the main source of rural pollution. It has been a consensus of all sectors of the community that the prevention of rural domestic sewage should be strengthened.In the past few decades the main point of environmental protection in China has been urban environment and key pollution source control. Rural pollution was not pay due attention. To strengthen rural water pollution control and water environmental protection has become the emphasis of China's environmental protection. In rural area which takes nearly 90% of the domestic area,96% of the villages do not have drainage and sewage systems, the majority of untreated sewage is discharged directly into nearby rivers, which is a serious threat to the national environmental security.In this thesis, the treatment of domestic sewage with low concentration using ABR-wetland combined technology was studied. Besides, to get better treatment result, we did structural improvements according to characteristics of ABR reactor. The major contents are:By selecting ABR as anaerobic process of wastewater treatment, constructed wetlands as a following aerobic treatment process we investigated the two processes in the best working conditions in the treatment of low concentration domestic wastewater.Effects of ABR-wetland combined process in domestic sewage treatment were discussed.Two sets of ABR with the same effective volume, a traditional ABR and a topic-based improved ABR were set up. Two devices are run in the same conditions, the starting conditions, operating parameters and the effects of sewage treatment were investigated and discussed. Results are shown as follows:1. In treating domestic sewage, results showed that the optimum HRT for ABR is 12 hours. The removal rate of COD, BOD and SS can reach up to 76%,71% and 82.6%, respectively. In addition, BOD/COD ratio increased from 0.45-0.56 (influent) to 0.53-0.67 (effluent), which improves the wastewater biodegradability and is conducive to subsequent aerobic treatment.2. Wetland influent COD concentration was controlled below 100 mg/L. Under natural conditions when sunshine is sufficient, the optimum HRT for the wetland is 4d, and the COD removal efficiency can be stabilized at 50%.3. ABR-wetland combined process has ideal treatment effect in sewage treatment. The removal rates of COD, BOD, SS and ammonia nitrogen can reach 89%,95%, 95% and 66%, respectively. All indicators above in effluent could meet the I-class B criteria specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002) with the exception of ammonia nitrogen.Compared with conventional ABR, improved ABR significantly enhanced resistance to impact, and to some extent, improved the COD removal efficiency. When treating domestic sewage at low concentration, the optimal HRT is 9h, which is lower than the conventional ABR (12h). Therefore, improved ABR greatly improves the wastewater treatment efficiency, which has practical applications with practical significance.