| In the recent years, the quality of drinking water sources are generally suffering contamination in Chinese small towns, and the drinking water security has become an important social problem. Based on the investigation of drinking source water quality in Hang-Jia-Hu area, the enhanced biological nitrogen and phosphorus removal in immobilized biofiln systems purifying contaminated source water was studied in this thesis, which was hoped to provide the technique support for the security of drinking water sources in China.The main results are as follows:1. Effects of start-up method on bio film formation and its pollutant removal performance in simulated river bioreactors purifying contaminated source water were studied. After applying the modified constant aeration-sludge discharge start-up method, the performance of the bioreactor was better than the natural one and its start-up period reduced 7 days. In the steady running stage, the removal efficiencies of ammonium (NH4+-N) and permanganate index (CODMn) in two bioreactors both reached 92% and 82%, respectively. Furthermore, the operation performance of the bioreactor applying the modified start-up method was more steady than the natural one when aeration condition changed.2. Under the condition of 8h-16h anoxic-aerobic intermittent aeration, the average removal efficiencies of NH4+-N, total nitrogen (TN) and CODMn in the immobilized biofilm reactor for contaminated source water were (93.0±2.6)%, (19.4±4.6)%, (78.1±3.4)%, respectively. The removal efficiencies of NH4+-N and CODMnmaintained at (81.2±5.3)% and (76.4±4.0)% with the anoxic phase lengthened to 16h, and the TN removal efficiency reached more than 50% in a long-term running. Results showed that the growth and activity of nitrite oxidizing bacteria were inhibited via controlling the length of aeration phase, which contributed to long-term low dissolved oxygen (DO) concentration at 0.5mg·L-1-1.5mg·L-1, thereby the nitrogen removal via shortcut nitrification-denitrification was finally accomplished in the remediation system. With non-aeration and two step feeding enhanced biological nitrogen removal process, DO concentration in the system was maintained at 0.22mg·L-1-0.85mg·L-1 and the utilization of organic carbon source was optimized, and the issue of carbon limitation for denitrification in the latter section of bioreactor was addressed. Nitrogen removal was enhanced in the remediation system after optimizing the operation parameters, and the NH4+-N, TN, CODMn in effluent could reach the gradeⅢof 'Environment Quality Standard for Surface Water'(GB3838-2002).3. Focusing on the issue of phosphorus removal deterioration caused by phosphorus accumulation in immobilized biofilm process, effects of two biofilm discharge patterns on phosphorus removal in the biofilm remediation systems purifying contaminated source water were investigated. The phosphorus removal efficiency reached 46.9% on the 7th day, then declined quickly. After full biofilm discharge (FBD) pattern applied, the phosphorus removal was effectively enhanced and higher dissolved phosphate (DP) removal efficiency (>30%) was maintained over 30 days, and the saturated adsorption capacity of phosphate in the biofilm reached (318.5±21.5)mgTP·m-2. While the phosphorus removal performance of the system applying surface biofilm discharge (SBD) pattern has not been improved obviously, and the saturated adsorption capacity of phosphate was only 0.68 times of that applying FBD. Results demonstrated that the heterotrophic denitrifying bacteria was suppressed during the beginning of biofilm re-growth after FBD pattern applied, which benefited the colonization and enrichment of phosphate accumulating organisms. Compared to new filler, higher porosity and biocompatibility caused by residual microorganism and its extracellular polymeric substances with FBD pattern favored biofilm re-growth, and the removal efficiencies of NH4+-N, CODMn and TN could recovered quickly.
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