Study On Nitrogen Removing By Bafanammox Combined Process

With the improvement of sewage discharge standards,some wastewater treatment plants meet new challenges.Upgrading of the original sewage treatment technology unit has the advantages of strong operability and small engineering volume,so it is widely used.With the improvement of the urban drainage system and the increase in sewage discharge,most urban sewage plants are under pressure to increase the volume of treated water.It is the key to solve the existing problems to improve the treatment capacity of the sewage plant on the basis of meeting the discharge standards.The currently widely used aerated biological filter(BAF)-denitrification biological filter(DN)combined process is proposed to transform the post-DN into an anaerobic ammonia oxidation(ANAMMOX)unit.The COD removal needs to be completed,and the ammonia nitrogen is removed by the ANAMMOX unit.Therefore,the BAF-ANAMMOX combination process has the potential to reduce the aeration of the aeration filter or increase the amount of water treated by the process.Since anaerobic ammonia oxidation denitrification requires the participation of nitrite,and the current domestic mainstream process is difficult to use domestic sewage to achieve a stable accumulation of nitrite,this topic explores the direct addition of nitrite to achieve the purpose of efficient nitrogen removal.The main research contents and results are as follows:First,the decontamination efficiency of BAF started according to conventional operating parameters was explored.Under aeration intensity of 2.1 m3/(m2·h)and EBCT of 1 h,the average removal rates of COD,ammonia nitrogen,and total nitrogen were 75%,87% and 10%,respectively.Then,the decontamination efficiency of the BAF process was studied under the scenario of reducing aeration intensity and increasing hydraulic load.When the BAF aeration intensity is as low as 0.4 m3/(m2·h),the effluent COD can be maintained below 60 mg/L,and the ammonia nitrogen removal rate drops to 9%.When the BAF empty bed residence time(EBCT)is as low as 0.4 m3/(m2·h),the effluent COD can also be maintained below 60 mg/L,and the ammonia nitrogen removal rate drops to 13%.Both scenarios can meet the requirements of this study claim.Second,the start-up methods of the two-filter media ANAMMOX units were explored.When both ceramsite and sponge were used as the filter media,they could be successfully started.After the start,the total nitrogen removal rate stabilized at about 80%.Higher water inlet load can shorten the start-up time.The effect of EBCT,ammonia nitrogen and COD concentration on the nitrogen removal of ANAMMOX unit was investigated.The results showed that the appropriate EBCT for ceramsite was 60 min and the appropriate EBCT for sponge was 40 min;when the concentration of ammonia nitrogen in the feed water of ANAMMOX unit did not exceed 35 mg/L,COD When the concentration does not exceed 60 mg/L,the ammonia nitrogen concentration in the ANAMMOX filter effluent is basically kept below 5 mg/L.The nitrogen removal effect and economic analysis of the BAF-ANAMMOX combined process was studied and carried out in two scenarios of reducing BAF unit aeration and increasing BAF unit hydraulic load.The results show that in both BAF scenarios,the COD and ammonia nitrogen of the combined process effluent can meet class A discharge standards.According to the preliminary estimation of operating costs from the perspectives of pharmaceutical and electricity costs,it can be seen that the operating costs of BAF-ANAMMOX in both scenarios are higher than the aeration filterdenitrification filter process.But in fact,compared with aeration filter-denitrification filter,BAF-ANAMMOX can achieve the same treatment effect under double the hydraulic load,and through conversion it is found that BAF-ANAMMOX is more effective than aeration filter-denitrification filter.The cost of the pool process is 0.119 yuan/ton.