Modified AAO Process For Denitrification Of Domestic Sewage Phosphorus Removal Research

Nowadays,the problem of water pollution has become a worldwide problem.The massive discharge of nitrogen and phosphorus has caused serious eutrophication of water bodies.At the same time,the main task of sewage treatment in China has also been changed from the removal of organic pollutants in the traditional concept to the removal of nitrogen and phosphorus pollutants,and the emission standards have become stricter.However,at present,the traditional AAO and its deformation process,the problem of simultaneous nitrogen and phosphorus removal in urban sewage treatment is not good,and the energy consumption,land occupation and cost in the process of transformation.In view of the above problems,this study only added the suspension filler to the anaerobic section of the traditional AAO system,and compared the removal effects of COD,ammonia nitrogen,total nitrogen and total phosphorus by the composite AAO process and the traditional AAO process.The removal characteristics of pollutants by the AAO system.Aiming at the characteristics of pollutant removal in the composite AAO system,especially its removal characteristics of total phosphorus,the anaerobic section of the composite AAO system is further improved,and the anaerobic section is divided into sludge zone and muddy water separation zone.And the three parts of the filling zone,the removal effect of COD,ammonia nitrogen,total nitrogen and total phosphorus in the AAO process before and after the improvement was investigated.The main conclusions of this experiment are as follows:(1)The system MLSS is stable at 2500~3500mg/L,the reflux ratio of nitrifying solution is about 250%,the sludge reflux ratio is 360%,the organic load is 0.22~0.26[kgCOD/(kgMLSS · d)],and the water temperature is 22 ?,SRT 20 d.The dissolved oxygen in the anaerobic section is lower than 0.1 mg/L,the dissolved oxygen in the anoxic section is less than 0.2 mg/L,and the dissolved oxygen in the aerobic section is maintained under the working condition of 2~4 mg/L.After inputting the filler to the anaerobic section of the traditional AAO system at a volume ratio of 10% by volume,the average concentrations of COD,total nitrogen and ammonia nitrogen in the effluent of the composite AAO system are 35mg/L,13mg/L and 4.8mg/L,respectively,which can be stably reached the first level.A discharge standard,the average concentration of total phosphorus in the effluent is 1.3mg/L.Compared with the traditional AAO process,the removal effect of COD,ammonia nitrogen and total nitrogen was not much different after adding the filler in the anaerobic section,and the removal trend was similar.(2)Compared with the traditional AAO system,the composite AAO system has significant differences in the removal of total phosphorus.When the anaerobic section of the composite AAO system exhibits phosphorus uptake,the effect of total phosphorus in the effluent is better than that when phosphorus is released.It indicates that the dosing of the filler may cause the microorganisms in the anaerobic section of the composite AAO system to absorb phosphorus in the environment,and the absorbed phosphorus is converted into gaseous phosphine,which causes the phosphorus concentration in the anaerobic section to decrease.(3)After the stable operation of the improved AAO system,the average concentration of COD in the effluent is 43 mg/L,the average removal rate is 95%,and the average concentration of ammonia nitrogen in the influent is 37 mg/g.Under the condition of L,the average effluent concentration was 3 mg/L,and the average removal rate was 92%.Under the condition of the total influent total nitrogen concentration of35 mg/L,the average effluent concentration was 10 mg/L,and the average removal rate was 69%.Comparing the two systems before and after the improvement,the removal effects of COD,ammonia nitrogen and total nitrogen were not much different,and the removal rate was high.(4)The effect of the modified AAO system on the removal of total phosphorus is much different than that before the improvement,and the phosphorus removal effect of the system is significantly improved.Under the condition of the average concentration of total phosphorus in the influent was 3.7mg/L,the average concentration of total phosphorus in the anaerobic section of the domestication stage was 4.3mg/L,and the average concentration of total phosphorus in the system effluent was 2.9mg/L,showing anaerobic stage phosphorus release.State;after acclimation,the average concentration of total phosphorus in the anaerobic section is 2.8mg/L,the average phosphorus uptake in the anaerobic section is 0.7mg/L,the removal rate of anaerobic phosphorus is 18%,and the average concentration of total phosphorus in the effluent is 1.0mg/L,and there is a tendency to meet the Class A standard.