Research On Fe(?)/PS Treatment Of Residual Sludge And Its Effect On Sludge Anaerobic Digestion

Since the "Thirteenth Five-Year Plan" of China,in view of the increasing sludge production of urban sewage treatment plants,China has continuously emphasized the principles of sludge reduction,harmlessness,stabilization and resource disposal.The anaerobic digestion of excess sludge as the preferred method to achieve this principle is often accompanied by problems such as hydrolysis rate limitation and low acid production efficiency.In response to these problems,the authors propose a sludge pretreatment method using a new advanced oxidation technology of Fe(?)-activated persulfate(PS).This method is used to destroy the structure of sludge microbial cell walls(membrane)and EPS.Investigate its effect on cracking effect of sludge.The response surface optimization of the single factor experiment of Fe(?)/PS pretreatment residual sludge was optimized by Design-Expert.V10.0 software,and the influence of Fe(?),PS dosage and the original pH of sludge was calculated Factor's second-order polynomial linear regression equation to get the best reaction conditions for pretreatment of remaining sludge;After the pretreatment with Fe(?)/PS,the hydrolysis performance of the remaining sludge for 21 days of anaerobic fermentation and the feasibility of converting the organic matter in the sludge into methane and SCFAs with added value through anaerobic fermentation were studied.The main conclusions are as follows:First,Fe(?)/PS pretreatment of the remaining sludge can effectively promote the dissolution of organic matter from the microbial cells of the sludge,but the amount of organic matter dissolved in the sludge does not continue to increase with the increase in the amount of Fe(?)/PS.And the pH range of this pretreatment method is very wide.It can effectively crack sludge microbial cells in the range of pH=3.0?8.5;Secondly,the second-order polynomial linear regression model simulated by re-sponse surface optimization with Fe(?),PS dosing amount,and sludge original pH as the influencing factors,and the sludge SCOD value as the response result was simulated.Significant correlation,that is,the dissolution of Fe(?)/PS pretreated residual sludge to organic substances can be calculated by mathematical models.The optimal conditions of Fe(?)/PS pretreatment residual sludge were calculated by Fe(?)dosage of 1.5mmol/gVSS,PS dosage of 1.3mmol/gVSS and initial sludge pH of 6.8.Pretreatment of the remaining sludge under this condition increased the SCOD value in the liquid phase from 112 mg/L to 1073 mg/L,the soluble protein increased from 23 mg/L to 173 mg/L,and the soluble polysaccharide increased from 17 mg/L to 110 mg/L.The CST reduction rate reached 88.6%.Third,Fe(?)/PS pretreatment of residual sludge can effectively improve the anaerobic digestion performance of residual sludge.When the amount of Fe(?)/PS was 1.5/1.3mmol/gVSS,the hydrolysis efficiency of sludge anaerobic fermentation was significantly improved,and the acid production by fermentation was significantly increased.During the fermentation process,the SCOD value reached a maximum of 2532 mg/L,which was 4.5 times that of untreated sludge.The soluble protein and polysaccharides were 366 mg/L and 156 mg/L were 6.8 and 5.6 times that of untreated sludge.The SCFAs value reached 1631mg/L is 6.4 times that of pretreated sludge;Fourthly,the optimal amount of Fe(?)/PS pretreatment for the anaerobic fermentation to produce acid and methane is different.When the dosage of Fe(?)was 1.5mmol/gVSS and the ratio of Fe(?)/PS was 15:13,the acid yield of sludge was the largest.When the Fe(?)dosage was 1.0mmol/gVSS and the Fe(?)/PS dosage ratio was 15:13,the sludge produced the largest amount of methane,with a maximum daily methane output of 94ml and a cumulative methane production of 618ml in 21 days 3.9 times the blank group;Fifth,the residual sludge pretreated by Fe(?)/PS can promote the conversion of anaerobic SCFAs to acetic acid and reduce the proportion of propionic acid,butyric acid and valeric acid.When the dosage of Fe(?)/PS was 1.5mmol/gVSS,the proportion of acetic acid in SCFAs increased from 27%to 77%,and the proportion of propionic acid decreased from 36%to 10%;Sixth,the residual sludge pretreated by Fe(?)/PS can trigger the proliferation of SRB,accelerate the consumption of interspecies hydrogen,reduce the thermodynamic obstacles of hydrogen production and acetic acid,and promote the forward movement of the hydrogen production and acetic acid reaction of the acidified substrate.