Nitrogen Removal Performance Studies On Treatment Of Polluted River Water In Suspended Carrier SBR

In this study, multi-face hollow plastic balls and reticulated polyurethane sponge blocks were added into SBR system. The polluted river water was treated by using the suspended carrier SBR and a comparison with traditional SBR was made. The study focused on the nitrogen removal performance, sludge activity in the reactors under different conditions and defined the optimum operation conditions, discussed the nitrogen characteristic. This study is divided into four parts. In the start-up phase, the treatment performance of reactors was investigated and compared. Secondly, the optimal operating mode was defined. Thirdly, the impact of initial pH,C/N,DO,suspended sludge SRT on the nitrogen removal performance was researched. Fourthly, under different conditions, the sludge activity including nitrosation activity, nitrification activity and denitrification activity in the three reactors was investigated.The conclusions of this study were summarized as follows.(1) In the start-up phase, the NH4+ removal rates of the reactors with plastic balls, sponge blocks keep about 70% as the reactor without carriers about 58%; the TN removal rates of the reactors with plastic balls, sponge blocks are all escalate and then maintained 15%, while that of the reactor without carriers keep about 6% all along.(2)The optimal operating mode is determined as 2 h anaerobic stirring,6 h aeration, following by 3 h anaerobic stirring, and then 1 h sedimentation and drawing. Under the optimal operation mode, the NH4+ removal efficiencies of the reactors with plastic balls, sponge blocks and without carriers are all 100% and the TN removal rates are 30.2%,29% and 16.9% respectively.(3) At pH value of 7.0, the nitrogen removal efficiencies of the three reactors are all best. Moreover, the nitrogen removal performance of suspended SBR is better than the traditional SBR, and the reactor with plastic balls is best.At pH value of 7.0, both the suspended and attached sludge in the three reactors have the highest nitrosation activities; the abilities of nitrification of suspended sludge in the three reactors are highest at pH value of 9.0 while that of attached sludge in the reactors with plastic balls, sponge blocks achieve maximum at pH value of 8.0 and 9.0; at pH value of 8.0, the denitrification activities of suspended and attached sludge in the three reactors are greatest. (4) At C/N ratio of 4.8, the average NH4+ removal efficiencies of the three reactors are all best which all reach 100%; At C/N ratio of 9.6, the TN removal rates of the reactors with plastic balls, sponge blocks and without carriers reach maximum which are 67.3%,55.1%,49.3% respectively.Adjusting C/N ratio from 2.4 to 9.6, the nitrosation activity, nitrification activity and denitrification activity of the suspended and attached sludge in the three reactors achieve maximum at C/N ratio of 4.8,2.4 and 9.6. Under the same C/N ratio condition, the denitrification activities of the suspended sludge in the three reactors are almost the same, while the suspended carrier SBR reactors have better TN removal efficiency than the traditional SBR. This result indicates that the attached sludge in the reactors with plastic balls, sponge blocks play an important part in the denitrification process.(5) At DO value of 4.0 mg/L, the average NH4+ removal efficiencies of the three reactors are all best which all reach 100%; at DO value of 2.0 mg/L, the TN removal rates of the reactors with plastic balls, sponge blocks and without carriers reach maximum which are 49.6%,40.9%,31.3% respectively.As increasing DO from 1.0 mg/L to 4.0 mg/L, the nitrosation activities of the suspended and attached sludge in the three reactors all increase; the nitrification activities increase at first and then decrease, achieve maximum at DO value of 2.0 mg/L; the denitrification activities of the suspended sludge in the three reactors decrease obviously while that of the attached sludge did not change significantly.(6) As decreasing suspended sludge SRT from 30d to 10d, the MLSS in the three reactors all decrease and the MLSS in the reactors with plastic balls, sponge blocks are lower; the average NH4+ removal rate of the reactor without carriers decrease more obviously; decreasing suspended sludge SRT has little influence on TN removal efficiencies of the three reactors.As decreasing suspended sludge SRT from 30d to 10d, the nitrosation activity, nitrification activity and denitrification activity of the suspended sludge in the three reactors all decrease obviously; moreover, the nitrosation activity of the attached sludge have no change and nitrification activity escalate, denitrification activity significantly increase.