Research On Operation Characteristics And Membrane Fouling Of Attapulgite-MBR Technology Under Low Temperature

Continuous development of society has greatly improved people’s living standards,Meanwhile, industrial and economic development makes environmental pollutionproblems have become increasingly prominent, water resource is the basis which humansurvival and development depends on, water pollution will directly restrict humansustainable development, research shows that China’s annual emissions of sewageshows a trend of rapid growth, but most of them is discharged to the natural water bodywithout strict water treatment, the pollution it causes is to be solved. The MBRtechnology can combine membrane technology and activated problem process, it’s nowwidely used in the field of water treatment, however, the membrane fouling problem hasgreatly limited the further application of MBR, at the same time, low temperatureconditions（10℃less） will have a significant impact on the treatment effect andmembrane fouling of MBR, attapulgite，as a cheap solid packing which has a goodadsorption performance, has been more and more used in the field of water treatment,addition of a certain amount of attapulgite into MBR will gain an important impact onthe operation of MBR.This article studies treatment of domestic sewage using MBR and attapulgite-MBRat room temperature（17.5℃～19.0℃）and under low temperature（9.0℃）, and alsothe sludge properties and membrane fouling at the same time. The result shows that theaverage COD removal rate of MBR at room temperature and low temperature is90.2%,85.5%respectively, it increases to94.4%and89.7%with attapulgite-MBR,membrane filtration contributes more to COD removal under low temperature, theaverage UV254removal rate with MBR is62.2%（room temperature） and58.8%（lowtemperature）, it also increases to73.1%and69.4%with adding attapulgite into MBR,low temperature makes great influence on the removal rate of TN, its average removalrate is53.3at room temperature and35.5%under low temperature, it increases to64.5%and49.7%respectively with adding attapulgite into MBR. This article studies the properties of sludge mixture under different conditions; thesludge activity is slightly higher at room temperature than that under low temperature,total nitrification activity is0.082mg O₂/（g MLSSï¹'min）,while it drops to0.024mgO₂（/g MLSSï¹'min） under low temperature,adding attapulgite into MBR will promotesludge activity and total nitrification activity, the activated sludge grows slowly underlow temperature, it has more large particulate matter in the cake layer on membranesurface, adding attapulgite into MBR will decreases the size of both activated sludgeand cake layer on membrane surface, the Zeta potential values is lower under lowtemperature, indicating a higher content of EPS, adding attapulgite into MBR will makeZeta potential values become higher.This article also studies membrane fouling, the membrane flux is smaller and TMPis higher under low temperature compared to the data at room temperature, but both ofthem shows the same trend whether at room temperature or under low temperature,adding attapulgite into MBR will make an negative impact on membrane foulingbecause it will cause membrane pore clogging initially，but it helps to enhancemembrane flux and lower TMP in the long run, under low temperature the content ofEPS and other microbial metabolites in the sludge mixture will rise, while some of themicrobial metabolites will be adsorbed with attapulgite added into MBR, on the otherhand, microbial metabolites will also be broken down by microorganisms with theincrease of sludge activity as attapulgite added into MBR, low-temperature conditionand attapulgite added into MBR will not change the organic matter structure of the cakelayer on the membrane surface greatly, yet the cake layer will be more loose at roomtemperature and with attapulgite added into MBR, at the same time the physical andchemical cleaning effect of membrane will be better and cleaning cycle will be longerwhich eases membrane fouling.