Artificial Aeration Strengthening Aerobic Denitrification Denitrification Technology To Improve Water Quality For Slightly Polluted Source Water

With the economic development of regional areas and the increasing of people’s demand for water, more and more reservoirs are used as drinking water sources. However, problems such as eutrophication and micro-pollution have become ubiquitous in these reservoirs. Such problems will affect drinking water quality. In order to solve these problems, this study is to combine the artificial aeration with aerobic-denitrified bioremediation, study on the denitrification characteristics of combined aerobic denitrifying bacteria, and carry on the pilot-scale experiment of raw water, in order to provide reliable basis for artificial aeration and bioremediation to improve reservoir water quality. The main conclusions are as follows:(1)126 strains of efficient aerobic denitrifying bacteria are screened out from the sediment of a reservoir in Shandong Province. And among them, bacterium JY78, a much active one is chosen as the study object with a better denitrification character Based on morphological and molecular biological identification, JY78 is identified as gram negative Acinetobacter oleivorans and possess a functional gene of aerobic denitrification bacteria, namely, periplasm nitrate reductase subunit gene(napA). Under the condition of culture medium, after 72 hours of aerobic denitrification, the NO3-N removal rate of JY78 reaches 83.65% and the TN removal rate reaches 58.46%. In the research of heterotrophic nitrification, the NH4-N removal rate of JY78 in 36 hours reaches 93.53%, and TN removal rate reaches 76.15%. By response surface analytical approach, the optimal conditions of NO3-N denitrification for strain JY78 are: C\N ratio 8.0, temperature 23℃, rotate speed 38 r/min, and initial pH 8.15, which lead to a maximum removal rate of nitrate nitrogen to 89.79%.(2)Through two pilot-scale raw water experiments with oligotrophic aerobic denitrification addition, this study does a research on the improving effect of bacteria on slightly polluted water quality. The results show that the denitrification effect of mix bacteria combination 2 with an additive amount of 1 ‰ is the best, with an optimal total nitrogen removal efficiency of 60.35%. Compared with blank control, its removal rate reaches 40.60% and nitrate nitrogen removal rate reaches 63.31% in the mean time.(3)Pilot-scale raw water experiments also studies the suitable additive amount of bacteria for improving the denitrification effect. Through two experiments, conclusion could be made that the additive amount of bacterium solution does not have direct ratio relations with the denitrification effect, the optimal dosing amount of bactericide is 0.1 ‰ of the raw water volume.(4)Based on the reservoir characteristics of low temperature, micro pollution and oligotrophy, this thesis is to simulate the water-lifting aerator to improve raw water quality by taking advantage of artificial oxygen aeration and confirm appropriate scope of dissolved oxygen for water self-restoration by nitrogen pollutant concentration variations. The experiment shows that the most appropriate scope of dissolved oxygen for low-temperature, micro-polluted and oligotrophic water is 4 to 5 mg/L. Compared with the initial concentration, under such condition the highest total nitrogen removal rate can reach 50.82% and nitrate nitrogen removal rate can reach 90.08%.