Research On Chemically Enhanced Phosphate Removal By UBAF

In recent years, with the phenomenon of red tides of Dianchi Lake and algal ofTaihu Lake broke out, it is urgent that the problem of eutrophication be solved.One of the key work for managing the eutrophication is to remove nitrogen andphosphorus from the water.Biological Aerated Filter (BAF) is a new biological wastewater treatmenttechnology, which integrates many advantages of activated sludge and biologicalcontact oxidation. BAF provides microorganisms with carrier to grow by packingwith high specific surface area of particles in the bioreactor. It is paid more and moreattention by its features which include small size, low investment, no sludge bulking,good water quality, and so on. BAF series process has a better effect on the removalof organic matter and nitrogen, but the effect on removing phosphorus is not ideal.So a method called chemically enhanced phosphorus removal was often adoptedrecently. The combination of the biological and chemical phosphorus removal canenhance the effect of BAF on the removal of phosphorus to make the effluent reachthe discharge standard. According to different adding points, it generally divided intopre-dosing, synchronization, post-dosing.This paper firstly introduced the mechanism, development and the presentapplications of Biological Aerated Filter and chemically enhanced phosphorusremoval technology. And then the experiment described chemically enhanced thetechnology of two-stage UBAF on phosphorus removal and its properties. Withreal-life wastewater test, the paper respectively studied the effect of pre-dosing,synchronization, post-dosing chemically enhanced BAF on phosphorus removal. Theresults showed that: with volcanic, the startup of BAF was shorter, with reflux ratiowas 200%, gas-water ratio was 3:1～5:1, and the filtration rate was 1.2m/h, COD,NH4+-N and TN of the UBAF effluent could meet the national standards. Threechemical methods of enhancing BAF on removal of phosphorus could all achievegood results. Either ferric chloride or aluminum chloride, when the total phosphorusof raw water was 5~6mg/L, the pre-dosage was 80mg/L, and when the totalphosphorus of raw water was 8~10mg/L, the pre-dosage was 90mg/L, the effluenttotal phosphorus could be stably less than 0.5mg/L. Simultaneous dosage were Fe/TP= 3, Al/TP = 2.5, to ensure the effluent TP be stably less than 0.5mg/L. The best pHvalue of coagulants for phosphorus removal were determined throughpost-coagulation: ferric chloride was 6~8, ferrous sulfate was 6~7, PFS was 7~9,aluminum chloride was 6~7, PAC was 6~8. Because pre-dosing and post-dosingrespectively need mixing equipment and traps, and that could increase the cost of the investment Various factors are taken into account, synchronization dosing is a kindof effective method and a very promising method, especially in place which is lackof land resources.