Study On The Treatment Of Medium And High Concentration Domestic Sewage By Multi-point OAO And AO Process

The amount of domestic sewage produced in China is huge.With the rapid development of economy and the improvement of living standard,the concentration of domestic sewage has an upward trend,and the standard of sewage discharge is also strict.Therefore,it is of great practical significance to study the efficient nitrogen and phosphorus removal process to treat higher concentration of domestic sewage.Based on the double-mud and multi-point water intake OAO process,the effects of water flow ratio,internal reflux ratio and volume ratio on the removal of pollutants by multi-point OAO process were investigated.Experiment set up three different concentration range of influent water quality,and compared with the traditional AO process,comparing the treatment effect of the two processes on different concentrations of domestic sewage,the main conclusions are as follows:(1)During sludge culture period,combined with the removal rates of ammonia nitrogen,total nitrogen and total phosphorus each device,sludge culture time of OAO1,OAO2 and AO was respectively 10 days,16 days and 10 days.OAO sludge culture time is longer than AO due to the use of"double sludge method",with a complex sludge reflux system,whose launching time is longer than that of AO.(2)The removal effect of different influent flow ratio of COD and ammonia nitrogen is not significant.when r=3:1,the COD average removal rate is the largest,for 96.5%;when r=2.5:1,the ammonia nitrogen average removal rate is the largest,for 97.2%;the influent flow ratio has a significant effect on total nitrogen removal effect.when r=2:1,the total nitrogen average removal rate is the largest,for77.3%.When r=2:1,the average removal rate of total phosphorus was the largest,for71.2%.Comprehensively,r=2:1 is chosen as the most suitable influent flow ratio.(3)The different internal reflux ratio of OAO has little effect on the COD and ammonia nitrogen removal effect;the removal rate of total nitrogen increased with the increase of the internal reflux ratio,and the total nitrogen average removal rate was the largest when r=300%,which was 75.1%.When r=200%,the average removal rate of total phosphorus is the largest,which is 77.4%.To sum up,r=200%is the optimal internal reflux ratio for the OAO device.(4)The effect of OAO1 and OAO2 on the treatment of medium concentration domestic sewage was compared:the average removal rate of COD?ammonia nitrogen,total nitrogen and total phosphorus of OAO1 was significantly higher than that of OAO2.so the volume ratio(1.5:1:3)of OAO1 is more reasonable than that of OAO2(1:1:3.5).(5)When treating medium concentration of domestic sewage,the average removal rate of COD and ammonia nitrogen of OAO plant is obviously higher than that of AO,but the difference of average removal rate of total nitrogen and total phosphorus between OAO and AO is not obvious.Significant analysis of their effluent showed that there was significant difference between them about the removal rate of COD,ammonia nitrogen and total phosphorus.And there was no significant difference between them about the removal rate of total nitrogen.(6)When treating medium-high concentration domestic sewage,the device can run stably by adjusting the influent flow ratio of the OAO,while the AO device can run stably only by prolonging the HRT.The results show that even if the HRT of AO is prolonged,the removal rate of pollutants is not higher than that of OAO,which indicates that the OAO is more efficient than the AO device.(7)when treating high concentrations of domestic sewage,the AO device showed strong inadaptability to the sudden increase in influent concentration,while the OAO operation was relatively stable,so OAO was more resistant to impact load than AO.The suitable HRT for the steady operation of the OAO device is 16 h,the organic load is 1.08 kg COD/m~3·d,the influent flow ratio is 2:1.The suitable HRT for the operation of AO is 24 h,and the organic load is 0.72 kg COD/m~3·d.The total nitrogen average removal rate of the two is not different,indicating that the OAO is more efficient in denitrification.