Research On The Dehydration Performance Of Sludge With Different Properties And The Preparation Of Sludge Adsorbent

A large amount of sludge is produced during the treatment of municipal sewage.These sludges are complex in composition and have a moisture content of 95% to 99.5%.The sludge dewaterability is poor,which hinders subsequent treatment and disposal.In this paper,excess activated sludge,thermal-treated sludge,thermal-alkaline sludge and anaerobic digestion sludge were studied.In order to achieve efficient dewatering of sludge and strengthen the resource efficiency of sludge,the factors affecting the dewaterability of sludge were studied and analyzed,and the chemical conditioning agents and methods for different sludges were screened.Correlation analysis between sludge dewaterability and various sludge properties was carried out by SPSS 22.0.The results showed that the dewaterability of sludge is affected by many factors.Sludge dewaterability was significantly negatively correlated with Zeta potential;it was significantly correlated with the molecular weight distribution of organic compounds in soluble extracellular polymeric substance(S-EPS)and loosely bound extracellular polymeric substance(LB-EPS),as well as the ratio of HA to PS(HA/PS)in LB-EPS,random coil in tightly bound extracellular polymeric substance(TB-EPS),and the fluorescence intensity of humic acid in S-EPS and LB-EPS.The optimization of chemical conditioning agent was carried out by single factor and response surface experiments.The results showed that the conditioning agent improved the dewaterability of sludge.The best improvement effect on the dewaterability of excess activated sludge,thermal-treated sludge,thermal-alkaline sludge and anaerobic digestion sludge was PAC and PFS in the single conditioning agent.Capillary suction time(CST)of the four sludges were dropped from 17.15s?87.60s?952.90s?148.80 s to 9.20s?19.25s?17.75s?15.55s(PAC)and 9.65s?19.35s?21.05s?15.00s(PFS)respectively.The three conditioning agents CPAM,PFS and CaO had the same order of influence on the four sludge CST in compounded conditioning agent,PFS>CaO>CPAM;Due to the different types of sludge,the ratio of each conditioner was different,but all greatly improved dewaterability of the sludge,CST of the four sludges were reduced to 6.70 s,8.30 s,10.70 s and 6.20 s respectively,making the sludges easy to dewatering.The sludge adsorbent was prepared by pyrolysis by using the dewatered sludge.The treatment of the reactive red dye wastewater by the adsorbent was studied,and the saturated adsorbent was recycled.The results showed that the addition of conditioning agent was beneficial to the increase of sludge adsorbent yield;the adsorption performance of the dewatered sludges conditioned by PAC,CaO,CPAM and compounded conditioning agent was greatly improved,and the removal rate of reactive red X-3B was significantly improved,the removal rate of active red X-3B was increased by 2.64%~17.58%,11.32%~20.53%,4.45%~17.74% and 3.62%~13.58%,respectively;The adsorption of reactive red X-3B by sludge adsorbent could be well fitted with the quasi-second-order kinetic equation and the Langmuir model;The mechanism of sludge adsorbent decolorization of reactive red dye wastewater includes physical adsorption,surface complexation and ion exchange.The removal effect of reactive red X-3B was better after the saturated sludge adsorbent was regenerated by alkali method,it was attributed to the cleaning of the pores and the opening of the closed pores by the alkali.