Electrochemical Reduction Of Excess Sludge By Ti/PbO₂ Anode

Activated sludge is an inevitable product of sewage treatment,it is characterized by large yield,high moisture content,difficult dehydration and high treatment cost.With the rapid improvement of China's urban sewage treatment capacity,sludge production has also increased dramatically,and the level of harmless treatment and disposal of sludge is difficult to adapt to the current situation of rapid growth of sludge.Therefore,sludge treatment and disposal has become the main problem to be dealt with by sewage treatment plants at present.To reduce the pressure of sludge subsequent disposal,sludge reduction treatment must be carried out.Traditional methods of sludge reduction include biological method,physicochemical method and combined treatment,etc.But,these methods have disadvantages such as poor stability,high energy consumption and complicated process.In recent years,the rapid development of the power industry has greatly reduced the cost of electricity,which has greatly promoted the development of electrochemical technology.Because of its advantages such as high efficiency,cleanliness and no secondary pollution,electrochemical technology has been widely concerned by scholars in the sludge treatment industry.In this paper,electrochemical technology was used to study the pretreatment process of sludge,The research content was mainly divided into the following three parts:?1?Preparation,characterization of Ti/PbO₂ anode and the effect of reduction treatment on excess sludgeThe Ti/PbO₂ anode was prepared by thermal decomposition method and electrodeposition method.The electrochemical performance and catalytic performance of the prepared electrode were characterized and analyzed.The results showed that the prepared Ti/PbO₂ anode coating was compact,dense and regularly arranged.The removal rate of ARG chromaticity can reach 95.78%within 120 minutes,and it has high catalytic activity.At the same time,the electrode has good stability,and itsThe prepared Ti/PbO₂ anode was used for sludge reduction treatment,and MLSS?solid concentration of volatile suspension of mixed liquid?,MLVSS?solid concentration of volatile suspension of mixed liquid?and CST?capillary absorption time?were taken as indicators to measure the influence of voltage and time on the sludge treatment effect in the electrochemical process.And through the determination of DOC in the sludge supernatant on?soluble organic carbon?,N,P,DNA,particle size,and the use of LC-OCD,SEM?scanning electron microscope?respectively in the sludge supernatant molecular weight distribution and the change of microstructure of sludge before and after electrochemical treatment,to explain the mechanism of electrochemical treatment sludge.The experimental results show that the electrochemical technology can significantly destroy sludge cells.Taking the reduction effect and energy consumption as the measurement indicators,comprehensive analysis shows that with the voltage is 20 V and treatment time is 120 min,the electrochemical treatment of sludge has a better efficiency,under this condition the sludge removal rate of MLSS is 33.4%,the removal rate of MLVSS is 35.8%,and CST is increased by 33%.?2?Mechanism of electrochemical destruction of sludge cellsThe degradation of organic pollutants by Ti/PbO₂ anode mainly includes the gain and loss of electrons in the process of direct oxidation and the production of various active substances in the process of indirect oxidation.Through cyclic voltammetry,free radical shielding,and addition of chloride ions?Cl-?to explore which oxidation pathway played a role in the cell disrupt during the electrochemical sludge treatment.The experimental results show that hydroxyl radical?·OH?is the main active substance that plays a role in the lysis of sludge during electrochemical treatment.When the solution contains a certain concentration of sulfate ions?SO42-?and Cl-,it can be significantly enhanced the cell disrupt effect of electrochemical treatment of sludge,while the ozone?03?generated in the direct oxidation process and the indirect oxidation process has no obvious promotion effect on the electrochemical cell disrupt process.?3?doping modification of Ti/PbO₂ electrode and its influence on electrochemical treatment of sludgeTi/PbO₂ anode surface was modified by RGO and ACF to improve the yield of electrode·OH.The experimental results show that,when the doping concentrations of RGO and ACF were 0.05 g/L and 0.1 g/L,respectively,the yield of electrode·OH was the highest,and the oxygen evolution overpotential,surface charge transfer rate and service life were all enhanced.Finally,the PbO₂-RGO?0.05?electrode and the PbO₂-ACF?0.1?electrode were used for the pretreatment of the remaining activated sludge.The experimental results showed that PbO₂-RGO?0.05?electrode and PbO₂-ACF?0.1?electrode significantly improved the reduction,dewaterability and cell lysis efficiency of the sludge,indicating that the increase of ·OH yield could significantly enhance the treatment effect of Ti/PbO₂ electrode on the sludge.