| The aerobic biological treatment is the most commonly used method in wastewatertreatment. Traditional aerobic biological treatment processes(TABTP) have severaldisadvantages such as low volume load, high energy consumption, high landoccupancy and low processing efficiency. Moreover, Activated sludge process yieldslarge amount of sludge resulting in higher overall operating costs. To overcome theshortage of the TABTP need to disposed a new wastewater aerobic biologicaltreatment process named pressurized aeration bioreactor(PAB) was studied in thisthesis, and the results were obtained as the following.The oxygen dissolving performance of the PAB was characterized in the thesis.Improve ment of the oxygen transfer performance in the PAB was observed under thepressurized condition. At he same time, effectively overcome the limitations ofoxygen transfer in conventional aerobic biological treatment, and the air-water ratioreduce significantly. When control the pressure as0.18-0.24MPa, air-water ratio is3,dissolved oxygen concentration of liquid phase in the reactor can reach above4mg/L.Experimental results have shown that the COD removal efficiency is significantlyincreased in the reactor under pressurized condition comparing with non pressurizedcondition, and it has good resistance to impact load under pressure condition. Whenthe pressure rises to0.26-0.3MPa, the COD removal efficiency reduced.Hydraulicresidence time(HRT) has also effects on COD removal efficiency. The COD removalrate increased as the increase of the residence time and reached the top when the HRTis2h. The COD removal no long significantly improved when the HRT increasingfurther from2h. The residence time of PAB is much shortern than that of theconventional aerobic biological processes. The tested PAB got a high COD removalratio up to92.54%under the condition of0.18-0.24MPa，HRT is2h，air-water ratio is3.The experiments demonstrated that the use of flotation device in the pressurizedaeration bioreactor as sludge-water separation unit is feasible. The effluent SSremoval ratio can reach about83%which met the national discharge standard whenthe inffluent SS is30-90mg/L.The pressurized aeration bioreactor has nitrification function. The removal ratio ofNH3-N under pressurized is better than that at the atmospheric conditions. When the pressure control in the range of0.18-0.24MPa, the nitrification is achieved the best.HRT has great impact on nitrification of pressurized aeration bioreactor. Itsnitrification is not consistent with that in the conventional biological wastewatertreatment. When the HRT is2h, the maximum removal efficiency of NH3-N reached,the removal rate will decline when the HRT is lower than or higher than2h. Thereactor can get a high NH3-N removal ratio up to92.04%at the condition of thepressure0.18-0.24MPa，HRT=2h，G/W=3.The function of the biological phosphorus removal for pressurized aerationbioreactor is weak and the removal ratio is only23%. With the aid of PAC asphosphorus removal agent, and the phosphorus removal improved significantly.Experimental results show that the TP removal can reach about92.60%with dosagePAC of0.015mg/L when the inffluent TP is3.0-4.5mg/L, the effluent TP meets thenational discharge standards.Dynamic model for the pressurized aeration bioreactor under pressurizedconditions was derived. And the kinetic parameters of the model were determined asVmax769.23mg/(L·h), Ks37.89mg/L respectively by graphical method. Thus come tothe kinetic equation for the pressurized aeration bioreactor. |
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