Membrane Fouling Controlling For Tungsten Smelting Wastewater By The O₃/PAC-MBR Process

Membrane pollution of membrane bioreactor(MBR) is the main problem restricting its popularization and application, which shortens the service life with an important impact on the performance, thereby increasing the cost of water treatment. While membrane fouling is inevitable but can be controlled by some measures. So the study of the prevention and control measures of membrane fouling is an important content of the MBR process.With O3 and PAC combination as a means of prevention and control, the subject mainly studied the impacts of O3 and PAC for water quality membrane fouling resistance and membrane flux of Tungsten smelting wastewater. The results showed as follows:(1) The addition of PAC and O3 had a certain influence on CODcr removal,whereas,the effluent concentration of CODcr were all under 60mg/L.It also had a certain influence on NH3-N removal with the effluent concentration of NH3-N were all under 15mg/L.(2) The input of PAC can promote the growth of sludge and slow the growth rate of sludge viscosity at some degrees; The additon of O3 had no big influence on the growth of sludge, while can further reducing the sludge viscosity. Further research showed PAC can inhibit the accumulation of EPS and SMP in the reactor, and O3 had a greater impact.(3) Comparing to the average total of membrane filtration resistance(Rta) in the process of test, it can be found that the average total of membrane filtration resistance of common MBR was greater than the other three membrane reactors, for MBR > PAC-MBR > O3-MBR > O3 / PAC-MBR. Comparing to the length of water production period, it was found that: O3/PAC-MBR>O3-MBR>PAC-MBR>MBR.Thereby,all these trials showed that O3 and PAC can slow the growth rate of the total filtration resistance of membrane.(4) During the experiment, the phenomenon were same to the total filtration resistance by investigating the dominant outer membrane fouling resistance Ro. The outside membrane fouling resistance of the ordinary MBR was greater than the other three membrane reactors, for MBR> PAC-MBR> O3-MBR> O3/PAC-MBR. In terms of the form cycle of a gel layer and a cake layer, it was found that:O3/ PAC-MBR> O3-MBR> PAC-MBR> MBR. These tests proved that the addition of O3 and PAC can inhibit the formation of cake layer and gel layer, thus reducing the membrane fouling resistance of the outer membrane to control pollution.(5)In the membrane cleaning test, aeration cleaning had an unobvious effect on the recovery of membrane flux for 2h, only at about 40% of the original flux, then the continuing ultrasonic cleaning can greatly improve the membrane flux for 1h. Eventually, the membrane flux can reach 93% with 0.5%Na Cl O cleaning for 2h.(6)In the optimization experiment of O3 dosing quantity, it was found that: when pretreatment O3 concentration was between 10mg/L and 15mg/L, the treatment effect of CODcr and NH3-N for Tungsten smelting wastewater was small. When pretreatment O3 concentration was 20mg/L, the treatment effect was non-compliance while the MLSS and viscosity of sludge mixture had a big influence. Comparing to the average total filtration resistance thirty days before the test, the results showed that:Rta2 and Roa2 were mimimum.It can be explained that 15mg/L of the pretreatment O3 concentration was most optimal.