The Production And The Effect Of Extraeellular Polymeric Substances On Membrane Fouling In Membrane Bioreactor Under Different Operating Conditions

Membrane Bioreaetor, as a new teclnology for wastewater treatment using membrane filter technology,have been widely used in wastewater treatment to aehieve effulent quality. As the constant improvement of drain standard and the constant increase of cost of glebe, Membrane Bioreactor has been attached importance for its higher efficiency and less demand of glebe. But membrane fouling is one of the reasons of wide application of MBR. Although the EPS are the main components of activated sludge flocs and play significant roles in wastewater treatment process, EPS is considered a major factor in membrane fouling. Research on the impact of factors that generate EPS and EPS impact on membrane fouling can provide a theoretical basis for the stable operation of reactor and the membrane reactor to achieve efficient biological treatment.This topic obtained aerobic suspended activated sludge and biofilm sludge in different forms of EPS generation and distribution. Discussed the treatment effect of the two sludge in the MBR, including the removal efficiency of COD, NH4+-N and TN. At the same time studied the quantity of the EPS and membrane fouling. Discussed the effect of aeration, sludge concentration and temperature on the quantity of the EPS. Then analying the change of TB-EPS, LB-EPS films on the impact of membrane fouling. The experimental results show that:1 Total amounts of EPS in biofilm and suspended activated sludge were 86.5 and 83.1 mg/gVSS, respectively. Protein was the major component of EPS in biofilm sludge while polysaccharides were the dominant component of EPS in suspended activated sludge. Specific EPS productions in the supernatants followed same pattern as the total EPS. Polysaccharides were dominant.2 COD and NH4+-N removal effect were basically the same in MBR, but increased the total nitrogen removal rate.It showed that increasing filler had insignificant impact on COD and NH4+-N removal.3 As the reactor operation, the amounts of polysaccharides in the suspended activated sludge were stable. The concentrations of protein in supernatant were a relatively constant.The polysaccharide reduced after the first increased. Protein was the major component of EPS in biofilm sludge and had big change, while polysaccharides were stable. The concentrations of protein and polysaccharides in supernatant increased as a function of operating time.4 Faster membrane fouling was observed with attached growth than that with suspended growth. Both systems contained similar species and quantities protein and polysaccharide contents of soluble EPS though they were in different growth conditions. Pollution problems cound not be attributed to the soluble part.The biofilm system membrane fouling rate decreased with the sludge concentration increased. At the similar MLSS concentration, the two systems gave rise to almost the same filtration behavior.5 The value of protein, polysaccharide and p/c in TB-EPS and LB-EPS increased with the increase of sludge concentration. And With the increase of sludge concentration, the proportion of LB-EPS increased too. The LB-EPS and TB-EPS had a good linear correlation and there is a good linear correlation between the rate of membrane fouling. However, because of the structural reasons, LB-EPS made larger contribution to membrane fouling than TB-EPS.6 Comparing to membrane fouling for the different aeration MBR.In a period of beginning, the membrane fouling of the higher aeration was more serious than the lower aeration,the results were opposite in late stage. The influence of aeration on LB-EPS was important but TB-EPS was little affected by aeration. LB-EPS and protein had strong positive effect on membrane fouling, and protein was considered the major pollutants.7 With the temperature increased, the total quantity of EPS increased in range of 10-25℃. The effect of temperature was reduced on membrane flux when sludge deposited on the membrane surface and accumulation stratum thickening. The type of jamming membrane orifices was dominant when the membrane was fouled at 30℃. So the fouling types seemed to change f rom accumulation stratum to jamming membrane orifices with the temperat ure raising.