Experimental Study On Dewatering Conditioner Of Excess Sludge In Sewage Treatment Plant

In China,the policy on sludge treatment and disposal was late,and the phenomenon of"heavy water and light mud" has always existed,resulting in a large amount of sludge accumulation,which has adversely affected people’s normal life.According to incomplete statistics,the daily output of sludge has reached 113,000 t·d^-1,and most of the water content of sludge discharged from sewage treatment plants is more than 90%.During the "13th Five-Year Plan" period,the state formulated a series of sludge treatment and disposal policy to address these issues,which explicitly requires that "by the end of 2020,the rate of sludge decontamination in cities above the prefecture level will reach 90%,and that in other cities will reach 75%.Unstable sludge and water content greater than 60%shall not enter landfill."This shows that the task of dewatering sludge is very urgent.In recent years,many scholars have conducted research on the dewatering of sludge.One of the most commonly used methods is chemical conditioning,adding inorganic or organic agents on the sludge to improve the dewatering performance of the sludge,in order to achieve the purpose of sludge reduction.Experimental study on sludge dewatering conditioner using inorganic flocculants（PAC,FeC13,A12（SO4）3,CaO）,organic flocculants（10 million molecular weight cationic polyacrylamide,3 million molecular weight anionic polyacrylamide）and coagulants（chitosan,bentonite）.The optimum process parameters of the conditioner were determined by measuring the moisture content,solid content,dehydration rate,filtration volume,and pH of the sludge.The scanning electron microscope was used to observe the internal morphological changes of the sludge before and after conditioning,and the X-ray diffraction was used to analyze the phase changes before and after conditioning sludge reaction,the effects of single conditioner and composite conditioner on the dewatering performance of sludge were compared and analyzed,and the main research results were obtained:（1）Each conditioner can improve the dewatering efficiency of the sludge.In the single conditioner experiment,the treatment result of CPAM1000 was the best,and the optimum dosage was 210 mg·L^-1,and the measured sludge moisture content was 82.46%.（2）Based on the single conditioner experiment,CPAM1000 was used as the main conditioning conditioner,which was mixed with chitosan and bentonite.The experimental results showed that when CPAM1000,chitosan and bentonite were combined,the conditioning effect was the best.The amounts were 150 mg·L^-1,200 mg·L^-1 and 3 g,and the sludge moisture content was 79.28%.Based on this,a small laboratory test device was used to simulate pressure filtration,and the moisture content of the obtained mud cake was 74.36%.（3）The raw sludge and conditioned sludge were tested by SEM and XRD.It was found that the sludge flocs after composite conditioning were more compact and had a large number of pores,and the conditioning effect was better.There was no significant change in the phase before and after sludge conditioning.The subject uses sludge from a sewage treatment plant as a raw material to carry out an experimental study on sludge dewatering additives.The research results showed that compared with traditional conditioner such as CaO and FeCl3,the combined conditioner of chitosan,CPAM1000,and bentonite greatly improved the dewatering performance of sludge,and could achieve sludge reduction.