The Experimental Investigation On The Inverted A~2 /O Integrative Oxidation Ditch Process In Domestic Sewage Treatment

In this paper for the common problems of high energy consumption and low phosphorus removal efficiency of oxidation ditch, some optimum improved technologies were put forward to solving. Based on the application of various improved technologies, the consideration which to remove phosphorus in raw water by the improved technology of oxidation ditch was proposed. This paper adopted the test equipment of inverted A²/O integrative oxidation ditch, through tests of continuous aeration and intermittent aeration, the removal rates of COD_Cr, NH₄⁺-N and TP in different ways were researched, and the better optimum phosphorus removal process parameters of inverted A²/O integrative oxidation ditch were determined in domestic sewage treatment.Analyses of the conclusions of this research were as follows:(1) By the test of start-up and commissioning of inverted A²/O integrative oxidation ditch, test results showed that:Three-stage method of activated sludge cultivation was used in this test. This method consisted of three phases, which were aeration cultivation adding seed sludge, continuous cultivation in low hydraulic loading and continuous cultivation in full hydraulic loading. It showed that the completion of activated sludge cultivation spent 15 days.(2) In the running way of continuous aeration, by analyzing the test results of inverted A²/O integrative oxidation ditch in domestic sewage treatment, it showed that:1) This system had good ability to remove organic matter. The average removal rate of COD_Cr was 81.33%⁸8.08% in all operating modes. The COD_Cr of effluent was below 60 mg/L, and effluent quality achieved the First-Level B standard of "Pollutants emission standards of urban sewage treatment plant"(GB18918-2002).2) This system had good ability to remove NH₄⁺-N. The average removal rate of NH₄⁺-N was 90.56%⁹2.09% in all operating modes. The NH₄⁺-N of effluent was below 3 mg/L, and effluent quality achieved the First-Level A standard of "Pollutants emission standards of urban sewage treatment plant"(GB18918-2002).3) The ability to remove TP of this system was not very good. The average removal rate of TP was 64.26%⁷3.09% in all operating modes. The TP of effluent was above 1 mg/L, and effluent quality didn't achieve the First-Level B standard of "Pollutants emission standards of urban sewage treatment plant"(GB18918-2002).4) In the condition of operating mode two, the removal efficiency of TP was highest. This operating mode was the optimum in the running way of continuous aeration.(3) In the running way of intermittent aeration, by analyzing the test results of inverted A²/O integrative oxidation ditch in domestic sewage treatment, it showed that:1) In the running way of intermittent aeration, the system had good ability to remove organic matter. The COD_Cr removal of operating mode one was better than operating mode two. In the condition of operating mode one, the removal rate of CODC r was 85.52%, and the effluent quality achieved the First-Level A standard of "Pollutants emission standards of urban sewage treatment plant"(GB18918-2002).2) This system had good ability to remove NH₄⁺-N, the effluent NH₄⁺-N quality was significantly better than the First-Level A standard of "Pollutants emission standards of urban sewage treatment plant"(GB18918-2002). The NH₄⁺-N removal of operating mode two was slightly better than operating mode one. In the condition of operating mode two, the average removal rate of NH₄⁺-N was 94.47%, and the average concentration of effluent NH₄⁺-N was 1.37 mg/L.3) In aspect of phosphorus removal, the system showed significant differences between operating mode one and operating mode two.the phosphorus removal rate of operating mode one was significantly better than operating mode two. The average TP removal rate of operating mode one was higher 20.27% than operating mode two. In the condition of operating mode one, the average concentration of effluent TP was 0.56 mg/L, and the effluent TP quality achieved the First-Level B standard of "Pollutants emission standards of urban sewage treatment plant"(GB18918-2002).4) The length of aeration time played a significant impact on phosphorus removal of inverted A²/O integrative oxidation ditch. In this test, it was appropriate to aeration for 1 hour and non-aeration for 1 hour. In this condition, the system had good ability to remove TP.(4) By comparative analysis of the test results of continuous and intermittent aeration of inverted A²/O integrative oxidation ditch in domestic sewage treatment, it showed that the running way of intermittent aeration was significant superior to the way of continuous aeration in the aspect of phosphorus removel efficiency and energy saving. In the way of intermittent aeration, the optimal operating conditions were that SRT was 10 days, HRT was 20 hours, aeration cycle was aeration for 1 hour and non-aeration for 1 hour. In the optimal condition, the removel rates of COD_Cr, NH₄⁺-N and TP were 85.22%, 93.57% and 81.33%.