The Influence Of The MBR Operating Parameters And EPS On Membrane Fouling

China is a country that water resources are scarce, and the ownership of per capita water resources is 2250 m3/person year, less than a quarter of the world's average level. With the rapid economic development, municipal sewage and industrial wastewater increase gradually. If the waste water directly discharges without treating, it not only damages the ecological environment, but also causes the huge waste of water resources. Membrane bioreactor (MBR) as a new type of sewage treatment technology has particularly prominent advantages in the sewage advanced treatment and reuse. However, there are many problems in the practical engineering, such as the prominent membrane fouling problem. It is an main cause of the high cost and poor stability at MBR running, so researching the reasons of membrane fouling and revealing the mechanism of membrane fouling play an important role to reduce membrane fouling and promote the wide application of MBR.In this experiment, it took the synthetic wastewater which simulated domestic sewage as raw water, and respectively investigated the temperature (10,15,25 and 30?) and sludge concentration (3000,4000,6000,8000mg/L) which affected the operation situation of MBR and membrane fouling characteristics, to provide the theory basis for the optimization of MBR technology and membrane pollution control. The results were as follows:?The temperature had a great influence on the COD efficiency. With increasing temperature, the COD efficiency showed a gradual upward trend, and it was relatively low below 15?. The influence of temperature on the ammonia nitrogen removal rate was also large. With increasing temperature the biological removal rate showed a gradual upward trend, and it was under 70% belowl5?.?The LB-EPS and TB-EPS concentration in mixture-liquor declined, then increased with increasing temperature. The proportion of TB-EPS in total EPS was over 90%, which was the main component of EPS. The change tendency of protein and polysaccharide were the same as TB-EPS, and p/c ratio increased slightly, yet the trend was not obvious. The LB-EPS and TB-EPS concentration on the surface of membrane declined, then increased with increasing temperature.? The LB-EPS and TB-EPS in mixture-liquor and those on the membrane surface had well correlated with membrane fouling rate,and the LB-EPS on the membrane surface was the biggest correlation with membrane fouling rate,R2=0.92. The correlations of protein polysaccharide,p/c with membrane fouling rate were 0.89,0.90,0.99 respectively. The experimental results showed that the LB-EPS was the main material of membrane fouling, and membrane fouling rate increased with the p/c increasing.? The COD efficiency of the system increased, then declined with the increasing of sludge concentration. When the sludge concentration was below 6000 mg/L, the COD efficiency increased gradually. When it was 6000 mg/L, the COD removal rate reached maximum 96%. However, the COD efficiency would decrease to 92% when it was 8000 mg/L. The ammonia nitrogen removal rate of the system increased, then declined with the increasing of sludge concentration, and it was the same as the COD efficiency. When the sludge concentration was 6000 mg/L, the ammonia nitrogen removal rate reached maximum 96%. When it was 8000 mg/L, the ammonia nitrogen removal rate decreased to 88%.? The concentration of LB-EPS and TB-EPS in mixture-liquor increased with the increasing of sludge concentration. The proportion of TB-EPS in total EPS was over 90%, which was the main component of EPS. The Protein/polysaccharide (p/c) in LB-EPS and TB-EPS increased with the increasing of sludge concentration, but the ratio was less than 1. The concentration of LB-EPS and TB-EPS on the membrane surface increased gradually with the increasing of sludge concentration, and the proportion of LB-EPS in total EPS was 14.1%, 14.7%,15.6% and 14.1% in the different sludge concentration, which greatly increased comparing with LB-EPS in mixture-liquor.? The membrane fouling rates of the different sludge concentration were 1.6kpa/d, 1.76kpa/d,2.2kpa/d and 4.5kpa/d. The membrane fouling rate increased slightly at sludge concentration was 3000mg/L and 4000mg/L, and when sludge concentration was 8000mg/L, it rose to 4.5kpa/d which was twice that when the sludge concentration was 6000mg/L. The LB-EPS and the correlation coefficient were greater than 0.91, so the experimental result showed that protein and polysaccharide were the fouling substances 1.Through the above experiments, it could be concluded that the MBR operating temperature should be controlled within the 15?25?. The temperature which was too high or low greatly influenced the treatment effect and membrane fouling. The sludge concentration should be controlled below 6000 mg/L, because it was too high, the system removal rate would decline and the membrane fouling rate increased sharply.