Study On Stability On Wastewater Land Biological Aerated Filtration Syetem

With the improvement of people's awareness of environment protection,the state has intensified the protection of water,but the small towns' wastewater treatment rate is still less than 30%,so it is urgent to enhance the wastewater treatment in small towns.Wastewater land treatment technology has the advantages of low cost,simple operation,etc.So it is widely used in villages and towns,but the traditional wastewater land treatment system also has the disadvantages of large occupation,blocking easily,etc.This test applies the wastewater land biological aerated filtration system.The operation parameters of the system for wastewater treatment are studied to provide technique support to the system application in practical project,and the effects of backflushing on the system operation stability are also analyzed.Firstly,the biofilm start-up speed of the winter and the spring system is analyzed,and the results show that the wastewater land biological aerated filtration system in winter?the average temperature of 6.8??needs 30 days for biofilm,while it is 19 days in spring?the average temperature of 16.7??,and the removal rate of COD is about 60%,while the removal rate of NH₄⁺-N is about 40%.By adjusting operation parameters,the effects of hydraulic load?0.7 ? 1.0 ?1.4m3/?m2.d??and aeration rate?1.2?1.8?2.4m3/h?on the system operation are studied.The results show that the operation temperature of the wastewater land biological aerated filtration system is 21³0?,and the best treatment effect is achieved when the hydraulic load is 0.7m3/?m2.d?,and the removal rate of COD and NH₄⁺-N is 82%and 90% respectively.In addition,when the aeration rate is 1.8m3/h,the best treatment effect is reached,and the average removal rate of COD,NH₄⁺-N and SS is81%,90% and 82% respectively.Through the continuous operation of the wastewater land biological aerated filtration system,it is found that the system is easy to be blocked and the biofilm is easy to perish,so backflushing of the system is necessary,but unsuitable backflushing conditions will affect the operation stability of the system.The backflushing patternused in the wastewater land biological aerated filtration system is mainly air impact,with small water discharge flushing sewage sludge;the air intensity is respectively14L/?m2·s?and 7L/?m2·s?;the backflushing time is 1min,2min,4min and 6min;the backflushing interval is 4d and 8d;the influences on the operation stability of the system under different backflushing conditions are analyzed and compared.In different backflushing intervals,the effects of the backflushing time on the system are different.In the occasion of the same backflushing intensity,effects on the operation stability of the system are enhanced as the backflushing time adding during the 4d of backflushing interval;during the 8d of backflushing interval,under different backflushing time,the treatment efficiency is different and the regularity is weak,which is mainly related to the expansion the the test cycle and the complexity of the water quality.The increase of the backflushing intensity has greater influences on the stability of the system.In the 4d of backflushing interval,the COD removal rate under the backflushing intensity of 7L/?m2·s?is about 7% higher than that under the backflushing intensity of 14L/?m2·s?,and the NH₄⁺-N removal rate is the same.In the 8d of backflushing interval,the COD removal rate under the backflushing intensity of 7L/?m2·s?is about 7% higher than that under the backflushing intensity of 14L/?m2·s?,while the NH₄⁺-N removal rate is about 3% higher.What's more,backflushing interval has less influence on the operation stability of the system.In the condition of the same backflushing intensity and the same backflushing time,the removal rates of COD and NH₄⁺-N have unobvious changes when the backflushing interval changes.