Polyaluminum chloride used in the process of foam treatment method Polyaluminum chloride in sewage treatment appeared foam and sludge expansion of the reasons and conditions are what should be done? First of all, it was found that sludge expansion and foam were mainly caused by the abnormal proliferation of Microbacterium. The occurrence of the sludge was seasonal and periodic, which mainly occurred when the temperature was low in winter and spring. Batch testing and continuous flow testing take process adjustments such as reducing the age of the sludge and increasing the load, as well as adding chemicals such as NaCLO, AFP, PAM and PAC ), Etc., these methods can reduce sludge volume index SVI, to varying degrees, the effect of sludge expansion and foam control. In practical applications, shortening the mud age and adding sodium hypochlorite foam and sludge expansion in different stages can also get some control. This paper presents the prevention and control of foam and sludge expansion caused by the abnormal proliferation of filamentous bacteria. First, to experiment with different water quality: sewage treatment process, because of the different water quality pollination pollination of polluting conditions also will be different, so when we add water purification agent, first look at the required Treatment of water quality, sewage treatment process, the most appropriate ratio depends on your water quality, we can do a little test, for different water polyaluminium chloride dosing range 100-1000mg / l; PAM dosing range 4- 20mg / l, polydimethylsiloxane dosing as much, I do not know is not a follow-up of a large number of biochemical aeration tank foam, if it is PAM may be added too much, or too much in the production process like dispersant, Then there is the poor pretreatment caused by the aeration tank sludge load is too high, there is aeration tank sludge culture will appear early phenomenon, probably maintained for about a week gone. Second, the site of productive test: If the sewage treatment plant design capacity of 150,000 t / d, the treatment unit is divided into A, B, C three oxidation ditch, each designed to assume 50,000 t / d of sewage treatment capacity. Currently only A trench and C trench water work. Due to various reasons, sludge expansion and foaming have occurred in different degrees since the operation of both ditches. Adding sodium hypochlorite and shortening the age of mud test in the field are all carried out in the A oxidation ditch. The sodium hypochlorite test was conducted in the late spring of 2003 for 2 weeks. Twice NaCLO was added to the oxidation ditch on June 5 and June 13, respectively. The first dosage was about 25 gCL / KgMLSS. The second The dosage of 12.5gCl / KgMLSS was added to reduce the sludge age. The sludge age was shortened from 11-14 days to 6-7 days by sludge discharge starting from December 3, 2003 for one month. . Third, the results summary: polluting wastewater treatment polyaluminium chloride we can use the above method, according to the data show that from 2003 to 2004 within 20 months, SVI oxidation ditch showed a significant seasonal changes in winter and spring Seasonal Sludge SVI will increase, up to 350mL / g. Actual observation of the scene in winter and spring oxidation ditch surface often accumulate a large number of foam, and sometimes foam coverage reached 90%, affecting the effluent and operation management. The summer and autumn relatively stable, SVI index of sludge is usually less than 150mL / g, basically no observed foam phenomenon.