생물막 공정을 이용한 폐수 고도처리에 관한 연구

Abstract

The rapid development of human activity has resulted in large amounts of nutrients flowing from wastewater into rivers and lakes. Consequently, the water environment has deteriorated. To improve water quality, it is very important to remove nutrients such as nitrogen and phosphorus from wastewater. Nitrogen and phosphorus constitute a relatively large part of the nutrient load of closed water bodies. Especially, increased input of phosphorus and nitrogen to lakes, bays and other surface waters causes the growth of phytoplankton, which is called an algal bloom. Hence, the considerable attention has been paid to the efficient removal of phosphorus and nitrogen from wastewater. In this study, for solving these problems, first, Nitrosomonas sp. and Nitrobacter sp. for nitrogen oxidation, Pseudomonas sp. for denitrification, and Chromobacterium sp. for phosphorus accumulation were isolated from soil and wastewater. The removal efficiencies of ammonia nitrogen using Nitrosomonas WS and nitrite nitrogen using Nitrobacter WS were 90 and 93 % after 4 days of culture, respectively. In the case of nitrate nitrogen using Pseudomonas WS, it was 100% after 18h of culture. Especially, at 28℃, the removal efficiency of ammonia nitrogen using Nitrosomonas WS was higher than those of other temperature. The removal efficiency of nitrate nitrogen using Pseudomonas WS was stable at range of 28-40 ℃. Among various nitrogen concentrations, The removal efficiency of ammonia nitrogen using Nitrosomonas WS at the below 100 mg/L was increased up to 7 mg/day and then it was decreased at above 100 mg/L. The removal efficiency of nitrite nitrogen using Nitrobacter WS was increased with the increase of nitrogen from 50 to 100 mg/L and at above 200 mg/L of nitrogen, it was not increased. However, the removal efficiency of nitrate nitrogen using Pseudomonas WS was 100% after 12 hr of culture in spite of nitrogen concentration. When the initial pH was increased from 3.0 to 7.0, the removal efficiency of nitrogen was increased. Especially, at 7.0 of initial pH, the maximum removal efficiency of nitrogen was obtained. Comparison of Chromobacterium WS, A. globiformis, and A. calcoacetius on phosphorus removal, cell growth, and carbon source consumption were carried out in the medium containing 150 mg/L of phosphoric acid at 30℃ for 48hr. The cell concentration and growth rate of Chromobacterium WS were low, but the removal efficiency of phosphorus after 32 hr of culture was 92%. The glucose was all consumed after 24 hr of culture. However, the removal efficiencies of phosphorus using A. globiformis and A. calcoacetius were 78 and 63% after 32 and 40 hr of culture, respectively. Second, to investigate factors affecting the removal of phosphorus in batch and continuous mode using a loess and loess ball with Chromobacterium WS, the loess ball size and calcining temperature, pH, and working temperature were studied. The compressing strength and specific gravity of loess ball were increased with the increase of the calcining temperature. A 5-10 mm of loess ball made at 860℃ of calcining temperature was suitable one and the loess ball made at low calcining temperature the using same size of loess ball was suitable one for the removal of phosphorus in batch mode. On the other hand, the loess ball made at low calcining temperature the using large size of loess ball was suitable one for the removal of phosphorus at continuous mode. When the operating temperature was 30℃, the maximum removal efficiency of phosphorus was obtained. When the initial pH was increased from 4.0 to 8.0, the removal of phosphorus using loess ball B was decreased from 4.0 to 2.5 mg/L for 10hr. The cell concentration was 28.5 g biomass/㎡ loess ball after 48hr. Third, using optimum conditions, various flow orders of biofilm filter systems on total nitrogen (TN), ammonia nitrogen, nitrate nitrogen, total phosphorus (TP), COD, BOD, and SS using practical wastewater were investigated at continuous mode. When the biofilm filter process A (anaerobic area→oxic area→anoxic area →phosphorus adsorption area) was used, the TN concentrations were ranged from 1.3 to 5.7 mg/L and the average efficiency of TN removal was 88.1%. The efficiencies of nitrification and denitrification were 87.2 and 86.5%, respectively. The concentrations of COD and BOD were ranged from 2.1 to 14 and 1.8 to 26.3 mg/L and the averages removal efficiencies of COD and BOD were 76.5 and 82.7%, respectively. In the case of the biofilm filter process B, the TN concentrations were ranged from 0.7 to 5.0 mg/L and the average efficiency of TN was 81.2%. The efficiencies of nitrification and denitrification were 80.5 and 81.5%, respectively. The concentrations of COD and BOD were ranged from 8.7 to 23 and 9.0 to 20.9 mg/L and the average removal efficiencies of COD and BOD were 57.9 and 73.0%, respectively. Using the biofilm filter process C, the TN concentrations were ranged from 4.8 to 8.5 mg/L and the average removal efficiency was 74.3%. The efficiencies of nitrification and denitrification were 76.2 and 54.3%, respectively. The concentrations of COD and BOD were ranged from 7.5 to 14.7 and 8.1 to 15.3 mg/L and the averages removal rate of COD and BOD were 73.2 and 82.3%, respectively. Scale-up for the effective denitrification using the real farm wastewater were carried out at pilot for 3 months at 30℃ of working temperature under the optimum process consisted of flow order A. The removal efficiency of TN was 90.6 %. In the case of efficiency of denitrification, it was 97.5%, which was increased by 12.7%. The removal efficiencies of COD was 63.7%, which was increased by 20% and in the case of BOD, it was 82.7%. From the process systems using loess balls, the wastewater treatment showed a lower concentration of nutrient salts than the standard of terminal disposal plant of sewage (the special counter plan area) and wastewater treatment facilities (sanitary sewage and wastewater treatment facilities of industrial and rural areas). Therefore, the biofilm filter process A will be applied for biological treatment of wastewater containing nitrate in the future.