Study On In-Situ Sludge Reduction Efficiency Using Electrode Lysis-Cryptic Growth

Due to the accelerating urbanization p rocess in China,the scale of sewage treatment is also expanding.The large amoun t of excess sludge produced in this process poses a huge challenge to existing sludge trea tment and disposal technologies.Therefore,it is necessary to reduce the output of e xcess sludge from the source.Based on the lysis-recessive growth theory,the electrochemical lysis reactor was coupled with the A/O wastewater treatment process after determining the conditions and mechanism of electrochemical lysis.Finally,the sludge reduction efficiency of the combined process in continuous operation was explored.Two kinds of electrodes(Ti/Ru O2-Ir O2 anode and Ti/Sn O2 doped anode)were identified by preliminary screening,and then the influencing factors were studied.After determining the most suitable lysis conditions,the lysis effects of the two electrodes were compared.Finally,the erbium-doped tin dioxide electrode was selected as the subsequent experimental electrode.The electrode was electrolyzed for 90 minutes under the condi tions of initial sludge concentration of 7000 mg/L,working voltage of 18 V,plat e spacing of 1 cm and initial p H of 7,the sludge dissolution rate was 25.35%,and the cel l lysis rate was 20.15%.The changes in the properties of the sludge during electroch emical lysis were analyzed.Among them,the changes in physical properties and bi ological activities included the reduction of sludge particle size and p H,the improvement of sedimentation performance,the deterioration of dewatering performance and the significant decrease of biological activity.The change of chemical composition is mainly reflected in the substantial increase of the concentration of organic substances such as COD,TN and TP in the liquid phase and the decrease of the content of protein and polysaccharide in the combined EPS.After that,the mechanism of action of electrochemical lysis was discussed in combination with the change of sludge properties.The electrochemical lysis unit is coupled with the A/O process to form an electrochemical-A/O combination process.Then,the actual sludge reduction effect and sewage treatment effect of the combined process during the operation process are explored.The experimental results show that the cumulative sludge discharge of the electrochemical-A/O process is reduced by 37.10% compared with the A/O process during 30 days of oper ation,and the apparent sludge yield is reduced by 39.07%.The combined process has consid erable sludge reduction effects.At the same time,the combined treatment process can effectively achieve the first-class A standard for the treatment of COD,NH4+-N and TN.Subject to the characteristics of the A/O process itself,th e combined process has a poor effect on the treatment of TP,and it is necessary to cooperate with enhanced chemical phosphorus removal.