The Study On Release Of Soluble Microbial Products（SMP）from Activated Sludge Under Acute Shock Loading Caused By Heavy Metals

A lot of heavy metals(such as Cu²⁺、Hg²⁺、Zn²⁺、MN²⁺and so on)enter aquatic systems forming heavy metal wastewater every year,When this type of wasterwater was discharged into municipal pipe network,which could lead to unstable operation of the activated sludge process,and thus deteriorate the quality of secondary effluent water with the risk of fluctuation of the content of soluble microbial product（SMP）and the contribution to subsequent ultrafiltration membrane fouling.Therefore,we set up 4 aerobic SBRs in laboratory scale,and then sifted Cu²⁺,Ag⁺and Hg²⁺from 11 kinds of heavy metals though exploring the change of molecular weight distribution and reactive oxygen species（ROS）.We detected the change of composition,molecular weight distribution and fluorescent material of SMP caused by acute shock loading of Cu²⁺,Ag⁺and Hg²⁺,to analysis the change rule of SMP characteristics combined with the change of EPS and the activated sludge.Finally,We found that Cu²⁺,Ag⁺and Hg²⁺also have a significant impact on the activated sludge from wastewater treatment plant,which verify the necessity of carrying out this project.And we found that:1.After the shock loading of 0.16 mM Cu²⁺,Ag⁺and Hg²⁺,the quality of secondary effluent was significantly reduced,for example,the removal rate of DOC dropped from 98%to 96.5%,75.9%and 61.69%respectively.At the same time,though analyzing the change of molecular weight distribution of SMP after shock loading,we verified that the addition of Cu²⁺,Ag⁺and Hg²⁺reduced the metabolic capacity of microorganisms again.2.With the rise of the concentration of Cu²⁺,Ag⁺and Hg²⁺,the activity of the activated sludge declined obviously,while the concentration of SMP components present a rising trend.which accelerated the fouling rate of ultrafiltration membrane.3.After the shock loading of different concentrations of heavy metals,we detected the change of SMP,EPS and the activated sludge.we found that the total amount of organic matter in SMP and EPS was relatively stable,when the activated sludge was affected by the heavy metals,within the range of microorganisms’self-regulation ability.However,when the impact exceeded the capacity of the activated sludge,some microorganisms will be inactivated.4.According to the results of SEM,Cu²⁺has less damage to the structure of microorganism,but the high concentration of Cu²⁺could cause rupture of the cell membrane.while Ag⁺is mainly applied to outside of the cell,causing microbial inactivation.Hg²⁺could destroy the cell structure at a low concentration,causing irremediable damage to the microorganism.5.We found that Cu²⁺,Ag⁺and Hg²⁺also has serious effects on the activated sludge from the third wasterwater treatment plant in Xi’an.