Pressurized Aeration And Dissolved Air Flotation Process For Treating Domestic Wastewater

In recent years, the process that integration of urban and rural areas are increasing rapidly. It’s necessary to research novel technology which is more efficiency, more quickly, covered less space and easily conducted because of the total increasing emissions of wastewater.A pressurized aeration-dissolved air flotation reactor (PA-DAF) was developed by combining the pressurized aeration bio-oxidation technology and the dissolved air flotation process. The process can not only maximize the function of high-efficiency biochemistry but also lead the sludge quickly separate from water.The reactor is consisted of flotation equipment air dissolved vessel with several fillers of levitated sphere which were filled up with polyurethane foam. The probability of the new process and the effect of pressure, G/W and HRT on the removal efficiency of organic matter by using sewage were studied in this paper. The denitrification function and the simultaneous nitrification and denitrification mechanism were investigated which may provide reliable parameters and useful scientific instruction in engineering application.The principal conclusions were obtained as follows.(1)The separation of water mixture was completed rapidly by using the flotation device after the pressure released. The best performance of coagulation was achieved by using PAC after the comparison of three flocculants among FeSO4, FeCl3and PAC.The results showed that pressure significantly affected air flotation, the SS removal efficiency decreasing from25mg·L-1to12mg·L-1at different pressures ranging from0.10to0.50MPa.(2)The influence of pressure, HRT and gas/water ratio (G/W) on the removal of organic matters was investigated. The results reveal that the removal efficiency of COD reaches about90%when the conditions are pressure of0.40MPa, HRT of1.5h and G/W of3:1.(3)Dissolved oxygen (DO), HRT and C/N were taken to find the denitrification efficiency change in PA-DAF. The conclusion was that when DO turned out to be2.5mg·L-1, the efficiency of denitrification got better, the removal rate of TN was78%and the removal rate of NH4+-N was about99%When DO was3.5mg·L-1. When C/N was5, the efficiency of denitrification was83%and the effluent concentration of TN was6.0mg·L-1.(4)This experiment proved PA-DAF had denitrification and simultaneous nitrification and denitrification ability. The surface of packing was suitable for nitration, but inside was suitable for denitrification because of the concentration gradient of oxygen.(5)The method that use dissolved air flotation solving the mud separation after pressurized aeration was proposed, and denitrification under pressure was studied.