Study On The Effectiveness Of Organic Matter And Solid Content On Activated Persulfate Conditioning Sludge

Sludge,as the by-product of sewage treatment process.On the one hand,because it contains all kinds of toxic and harmful substances that harm the environment and human health.On the other hand,the high water content affects subsequent treatment and disposal and resource utilization,thus sludge conditioning and dewatering is an important part of sludge management in sewage treatment plants.In the study,a composite conditioner,Fe²⁺activated sodium persulfate(Fe²⁺/SPS)combined with phosphogypsum（PG）,was used to determine how the variability of solid content and volatile suspended-solid/total suspended solid affects optimal dose,oxidative effects and skeleton structure.The reaction difference of Fe²⁺/SPS oxidation to extracellular polymeric substances（EPS）in sludge particles and liquid phase was further studied.The difference and competition of free radical in oxidation degradation of EPS in solid and liquid phase were explained.The prediction ability of BP neural network and Self-organizing feature map networks SOFM+BP network model was compared and analyzed by constructing sludge conditioning prediction model with artificial neural network.The main research results are as follows:（1）A series of sludge with organic matter content of 34.6-43.8%and solid content of 2.8-5.9%was optimized.The response surface methodology（RSM）optimization experiment results showed that when the best conditioning was achieved,the reduction of the specific resistance to filtration of sludge with different organic matter content was stable about 98%.The reduction of specific resistance to filtration of sludge with different solids content was about 97-98%,the fluctuation of sludge dewaterability was significantly affected by solid content.The oxidation role of Fe²⁺/SPS and the skeleton builder role of PG,together,affect the conditioning,with oxidation playing a major role in conditioning.The organic content(η_SOLvalue was 0.088-0.322)affects the effectiveness of the skeleton builder more than the solid content(η_SOLvalue was0.102-0.251).Further research found that sludge with high solid content required greater Fe²⁺:SPS molar ratio,the maximum Fe²⁺:SPS molar ratio was 1.14 with solid content of5.9 wt%.After the composite conditioning,the contents of EPS and tightly bound EPS decreased by 85.18%and 89.09%,respectively.The reduction of PN and PS were90.03%and 70.05%,respectively.The sludge dewatering performance was significantly improved.（2）The degradation of organic matter in solid and liquid phase of sludge by the Fe²⁺activated SPS showed that the maximum degradation rates of PN and PS in raw sludge filtrate（RF）were 89.5%and 27.9%,respectively.The degradation kinetics of PN and PS in granular sludge（GS）was divided into fast reaction stage and slow reaction stage,and the first stage conformed to the pseudo-primary degradation process.The maximum degradation rates of PN and PS in GS were 90.1%and 79.0%,respectively.Further analysis showed that the degradation rates of PN and PS in RS were less than that of GS,the degradation rate of PN in RF was greater than that in the solid phase GS,indicating that the presence of the raw sludge filtrate in the RS would consume part of the SO₄^-·and affect the degradation of the EPS in solid phase.Further calculations showed that 22.6%of SPS was used for oxidizing organic matter of liquid phase RF,indicating that the existence of soluble organic matter in the liquid phase affected the degradation of EPS in solid phase by activated SPS.For the mass balance of PN and PS in solution,oxidation and solid phase of GS after oxidative degradation,it is found that the reduction of PN（86.7%）in solid phase（loosely bound EPS+tightly bound EPS,LB-EPS+TB-EPS）of GS was higher than that of PS（73.0%）,while the reduction of PN in solution（slime EPS,S-EPS）was 61.1%,slightly lower than that of PS（69.7%）.The reduction of PN and PS in solid phase was higher than that in solution.（3）According to the comparison of the relative error values between the predicted values and the experimental values of BP and SOFM+BP network models,the errors between the sample data were reduced and the accuracy of the model prediction was improved after the SOFM network clustering of sludge samples.At the same time,it was very necessary for sludge with different properties to cluster analysis before constructing BP neural network model.Based on the S-P composite conditioning of sludge with different properties,the effectiveness of Fe²⁺/SPS oxidation and PG skeleton builder was determined to provide a reference for the selection of the composite conditioning strategies of sludge with different properties.The prediction model of SOFM+BP network was constructed to provide a new idea for the prediction of sludge conditioning effect,which has certain theoretical guiding significance.