| Adding additives is one of the main methods to alleviate the pollution of MBR film at the present stage. The excellent properties of rare earth metals provide the possibility for the mitigation of membrane fouling. In this experiment, a group with Lanthanum and a blank group had been set to compare their removal efficiency of organic matter and ammonia nitrogen, filtration resistance and resistance distribution of activated sludge, sludge volume index, SMP and EPS concentration under different salinity. Draw some important conclusions:From the effect of the two MBR system on the treatment of organic matter and ammonia nitrogen in the treatment of simulated domestic wastewater under different salinity, it is concluded that the removal effect of organic matter and ammonia nitrogen of the two system presented a trend of first increase and then decrease with the increasing of salinity. In the salinity of 0.5 % and 1%, the effluent COD and ammonia nitrogen of the two system were slightly lower than that of salt free conditions, both of their removal rate was higher than 95%, the removal effect of one with Lanthanum Chloride was a little better than the other. The results showed that the low salinity not only did not inhibit the activity of the sludge, but also increased the treatment effect. In the salinity of 0.5 % and 1%, the effluent COD and ammonia nitrogen of the two system began to rise. Finally, the removal rate of COD was stable at about 85%, and the removal rate of ammonia nitrogen was stable at about 70%. At higher salinity of 2%-4%, the activity of activated sludge was inhibited and the removal rate decreased, but did not cause the system to collapse, and the effect of lanthanum chloride on the promotion of microbial activity and activation of the biological enzyme has eased some of the pressure from salinity shocks, and the treatment effect is better than that of the blank group.From the Internal connection and change law of the two MBR system of filtration resistance and resistance distribution of activated sludge, sludge volume index, SMP and EPS concentration and protein/polysaccharide value in the treatment of simulated domestic wastewater under different salinity, it is concluded that the total resistance of the sludge in the two system increased with the rising of salinity. When the salinity increased to 3%, the membrane fouling of the MBR without Lanthanum began to be serious, and the sludge resistance was greatly increased, but the one with Lanthanum was still keeping a slight membrane fouling. Under the salinity of 4%, both of the two systems were almost impossible to operate, and the membrane cleaning cycle was shortened to three days or so. The resistance distribution showed that the largest proportion was sedimentary layer resistance. The SVI and the particle size of sludge decreased with the increase of salinity in both of the two system, and led to the reduce of cake layer's porosity, and the membrane fouling caused by the increase of filtration pressure. The concentration of SMP and EPS increased with the rising of salinity. The reason is that microorganisms secreted a lot of extracellular polymers in order to fight the high salt shock, led to the increase of SMP and EPS, and aggravated the membrane fouling. The P/C values of SMP and EPS also decreased with the increase of salinity, which weaken their hydrophobicity and made them easier to adhere to the surface of the membrane made by hydrophilic material. Adding lanthanum chloride could stabilize sludge particle size, reduce the SMP concentration and P/C value, improve the properties of the mixed liquid, thereby improving the membrane fouling. The results show that at 3% salinity, lanthanum chloride on the regulatory effect MBR membrane fouling is significant, and has practical application value and broad development prospects in ships, sea water for flushing and other salinity industrial wastewater treatment. |
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