Study On Strengthening Phosphorus Removal Efficiency By Reflux Type A/O-BAF

The research is designed by two main thought, which are add anaerobic pretreatmentsection and sludge return on the traditional BAF, as the adoption of environmental protectionsponge as the main processing period of packing, the total and section removal rate areobserved when adjust the impact factors, the results show that the optimized process is moreefficient than the traditional BAF in the same condition.Anaerobic aerobic environment which is supplied by anaerobic period promote thegrowth of PAOs and the removal rate of phosphorus, the process of anaerobic phosphorusrelease and aerobic phosphorus absorb are achieved by the sludge return designed, and theeffect of backwash for nitrification performance is slight by using porous environmentalprotection sponge.The result in intermittent test indicated that the removal rate of COD is higher when theside length of the sponge is longer. The SRT and the removal rate are positive correlation. TheSRT and the removal rate of TP are negative correlation, there is a negative effect on thenitrification process when the SRT is overshort. Therefore, SRT is5d and shorter no more;The removal rate of COD and SS of aerobic period in section A increase as the gas water rateincrease, but the removal ratio of TP is gradually decrease, which is because that the high gaswater ratio will overoxidate PHA; The removal rate of COD, SS and TP reached higher valuesin section A when gas water ratio is10:1, respectively,65.95%,54.84%,20.27%, and theconcentration of COD, SS and TP were75.11mg/L,58.32mg/L and7.88mg/L; The removalrate of COD is high in several gas water ratio for section B. Effluent quality has not beenmore than60mg/L, the removal rate were higher than80%, considered from economy,10:1asthe removal of COD the best gas water ratio; SS removal effect is obvious, which close to75%under the gas water ratio of8:1and10:1, therefore, gas water ratio of10:1is the best;The removal rate of TP is low under the gas water ratio of6:1and8:1, which is because thelack of dissolved oxygen, and the removal rate is higher when10:1and12:1, up to47.87%,the best gas water ratio of10:1is chosed from the economy and the removal rate of otherindicators;The result of section B are that: The removal rate of COD decreased, but not much, andthe removal rate of SS was steady, and the removal rate of TP was also decreased as much as16.36%when the hydraulic loading increased from0.25m3/m2*hto0.5m3/m2*h, therefore,there is a nagtive influence on the COD and SS removal rate as the hydraulic loading increase,hydraulic loading which stay in0.25m3/m2*h is more appropriate for the removal rate of TP,and for the whole device as well; The removal rate of COD and SS were less when thebackflushing period reduced from2d to1d, but not TP, the frequent backflushing periodmakes more excess sludge out of the system, so the removal rate of TP is higher, because theremoval of TP depends on the removal of excess sludge which come from backwash,therefore, the phosphorus removal rate increase when the frequency ofbackwash increase. Compared the results of section A with B, the conclusion isthat section B is moreefficiency.