| In this paper, sewage with low ratios of carbon (C) to nitrogen (N) was treated with the integrative and continuous flow technology (ICFT) of simultaneous denitrifying nitrogen and phosphorus (P) removal (SDNPR), and the main results were as follows:1. In the experiment in which nitrate N was taken as electron acceptor to absorb P,10,15, and 20 mg·L-1 were selected as the initial concentrations of nitrate N, the average P absorption rates within the first two hours were 4.61,5.46,3.46 mg·(L·h)-1, and the maximum P absorption rates were 10.1, 10.4,6.57 mg·(L·h)-1, respectively. Neither lower nor higher concentrations of nitrate N were benefit to the experiment in efficiently and stably. At the stage of anoxic-P absorption,12.6 mg·L-1 of P was absorbed, and the optimal concentration of nitrate N was 14.8 mg·L-1. The ratio of nitrate N consumption to total P absorption was about 1.17, and this ratio remained quite stable under the conditions of the three initial concentrations of nitrate N.2. When nitrite N was used as electron acceptor, it was found an obvious slower rate of P absorption when nitrate N was higher than 11 mg·L-1. If nitrite N was 10 mg·L-1, the average rates of P absorption was 2.07 mg·(L·h)-1 in within the first two hours. When initial nitrate N was 20 mg·L-1 and higher than 11 mg·L-1 at the end of experiment, the average rates of P absorption was only 0.715 mg-(L·h)-1 in within the first two hours. Whatever P absorption rates were, the ratios of nitrite N consumption to P absorption were stable as about 2.29.3. Oxygen was used as an electron acceptor and a comparison, common PAOs system which using oxygen as an electron acceptor had higher rates of P absorption. There was 7.30 mg-L"1 of P removal in 5 hours in the DPB system using oxygen as electron acceptor, and the average rates of P absorption was 3.27 mg·(L·h)-1 within the first two hours. When the bacteria using oxygen as electron acceptor at final stage of strengthen and enrich in PAOs system, P absorption was 12.6 mg·L-1 in 5 hours and the average rates of P absorption was 6.15 mg·(L·h)-1 within the first two hours. The ability of DPB taking oxygen as an electron acceptor to absorb P was increased after suitable culture. P absorption of the DPB system was increased by 3.10 mg·L-1 in the experiment of two weeks.4. No matter what kind of electron acceptor was used, the fastest reaction rate was observed in the half an hour and then reached a gent period. Within the first two hours the P absorption accounted 84% of the total P absorption. In the experiments taking nitrate N, nitrite N, and oxygen as electron acceptor and with the optimal concentrations, the P absorption rates in the first two hours were sequenced as:the bacteria using oxygen as electron acceptor at final stage of strengthen and enrich in PAOs system> DPB system using nitrate N as electron acceptor> DPB system using oxygen as electron acceptor> DPB system using nitrite nitrogen as electron acceptor. However, the reaction efficiency with low concentrations of nitrite N was much higher than that with any concentrations of nitrate N others in the first hour.5. In continuous operation of the integrated device, the factors influencing the treatment efficiency were studied, and a set of reasonable parameters keeping the system running efficiently and stably were obtained. The hydraulic retention appropriate time (HRT) in anaerobic, aerobic, and anoxic stages was 2-3 h,4-6 h, and 2-4 h, respectively. The appropriate DO concentrations in anaerobic, aerobic, and anoxic stages was less than 0.1 mg-L-1, between 3.0 and 4.5 mg-L"1, and lower than 0.2 mg-L-1. The appropriate redox potential (ORP) in anaerobic, aerobic, and anoxic stages were-256 mV,45 mV, and-138mV. The suitable reflux ratios in anaerobic and anoxic stages reached 35%,20 days were suitable sludge age (SRT) for DPB system, suitable nitrification temperature was about 30℃, and suitable pH values were in 6-8.6. In continuous operation of the integrated device with the parameters described above, effects of different ratios of C:N:P in the initial sewage on the reaction efficiency were studied. The results showed that when C:N:P was70:10:(1～1.25), the effluent COD was about 30 mg·L-1, the ammonia N was only 0.60 mg-L-1, and the effluent total P was lower than 0.5 mg·L Meanwhile, the residual concentrations of nitrate N and nitrite N was very low, and the total N in outlet was lower than 2 mg-L". Under these experimental conditions, the removal efficiencies of COD, ammonia N, total P, and total N reached 91%,98%,90% and 90%, respectively, and the water quality in outlet was satisfied with the emitting standard A in GB 18918-2002 for sewage treatment plants.
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