Pilot Study On The Treatment Of Municipal Wastewater With High Emission Standard By BAF-MBR

Faced with the tension of water resources, the sewage reuse is becoming more and more important.Reuse water high requires high water quality. Conventional treatment process is difficult to meet the requirement in general.This paper combines the traditional BAF technology and new MBR technology, forcing BAF-MBR process, which combines the advantages of both, while enabling their weaknesses get complementary. BAF-MBR process effluent is superior to the first level A standard, close to the surface water IV water standards(except TN),and can be used for wastewater reuse.Starting up BAF should adopt the composite membrane method. The start period is 40 days. Starting up MBR should adopt the inoculation culture method. The start period is 12 days. After the success of the BAF-MBR process start, control the water flow rate of 0.8, BAF period of gas water ratio of 6:1, nitrifying liquid reflux ratio of 200%, the MBR period of gas water ratio of 8:1, reflux ratio of 100%.At the same time, Dosing PAC of 20mg/L in BAF front. In this suitable condition, BAF-MBR process has a good effect on an area south of the sewage treatment, BAF-MBR process on COD, ammonia nitrogen, TN, TP average removal rates were 93%, 97%, 58%, 87%. The effluent COD, ammonia, TN, TP concentrations are respectively stable at 10mg/L, 0.5mg/L, 12.5mg/L,0.4mg/L or so.The effluent can meet the first level A standard During the period of process operation, it can be found that the sludge concentration in MBR reactor has a slight downward trend. The sludge contains a lot of Vorticella Convallaria and Epistylis, and a small amount of nematodes and rotifers, indicating that the sludge in the mature period, good quality of effluent. In addition, the PAC dosing amount up to 30 mg/L, the system of TP removal rate reached 94%. TP concentration of effluent at around 0.15 mg/L, TP index can meet the surface water class IV water standards. COD, ammonia nitrogen index have met the surface water class IV water standards, only TN is difficult to meet the surface water class IV water standards.When BAF-MBR system requires depth denitrification, adding carbon source to the influent MBR, increasing the C/N ratio of MBR influent can significantly improve the denitrification efficiency of MBR reactor. Test found that increasing MBR influent C/N ratio of 5:1 or so. the MBR reactor for average TN removal rate reached 60%.For membrane fouling during the process operation,more applicable membrane cleaning solution is a combination of aeration cleaning and on-line chemical cleaning cleaning.Under this scheme, the membrane flux can be maintained at a level of 83.3% of the new membrane flux for a long time, and the chemical cleaning cycle can be extended to 60 days. Aeration volume of aeration cleaning should be controlled to 8 cubic meter per hour. Online chemical cleaning is suitable to use Na Cl O solution of 2000 ppm.The effluent of the BAF-MBR process reached the first level A standard. Phosphorus removal reagent cost is 0.036 yuan / tons of water, and membrane cleaning reagent cost is 0.0017 yuan/tons of water.According to the parameters determined by the test, the BAF-MBR process is used to deal with 10 thousand tons / day of the sewage treatment system. The total operating cost of water to achieve an A standard is 0.393 yuan/tons. Compared with conventional process, the cost of phosphorus removal agent can save more than 50%, and the cost of chemical cleaning agent can save more than 65%.It is estimated that the cost of the power consumption is 0.355 yuan/tons of water, the total operating cost is 0.393 yuan/tons of water. When deep denitrification is required, the additional cost of the drug is 0.045 yuan / ton of water.