Study On The Preparation Of Unburned Ceramsite From Water Treatment Residuals-Fenton Sludge And Its Application In Wastewater Treatment

Water treatment residual is the sludge produced by coagulation and flocculation treatment of urban water,which is rich in activated iron aluminum amorphous structure,large specific surface area and high porosity.Fenton sludge is a kind of chemical sludge with high iron content produced in industrial wastewater by Fenton advanced oxidation process,which contains a large number of active hydroxyl groups.The production of these two kinds of sludge is large,the existing treatment and disposal methods have the problems of high treatment cost,easy to cause secondary pollution,and the degree of resource utilization of sludge is low.In order to broaden the way of resource utilization of water treatment residual and Fenton sludge,water treatment residual and Fenton sludge were used as the main materials in this study.Based on the study of unburned ceramsites from water treatment residuals,a new type of unburned creamsite from water treatment residual and Fenton sludge（UCFWTR）was prepared by using residual sludge and Fenton sludge in waterworks as the main raw materials.At the same time,taking the prepared UCFWTR as the core,the phosphorus removal effect of UCFWTR as adsorbent and the water purification effect of UCFWTR as biological filter material applied to biological aerated filter were investigated.The specific conclusions are as follows:（1）By XRF,XRD and FT-IR characterization of the main raw materials of water treatment residual and Fenton sludge,it is found that Fe and Al in waterworks sludge and Fenton sludge are amorphous structure,and Fenton sludge contains a large number of active-OH groups.UCFWTR was prepared by using water treatment residual and Fenton sludge.According to the disintegration rate,water absorption rate,phosphorus adsorption performance and ceramsite strength,the addition amount of Fenton sludge was determined to be 20%.UCFWTR retains the amorphous structure of raw materials,and meets the artificial ceramsite filter for water treatment（CJ/T299-2008）’standard.The addition of Fenton sludge enhanced the content of ceramsite-OH,and many fibrous network structures were generated inside UCFWTR,which made UCFWTR have large specific surface area and provided many active adsorption sites.（2）In the static adsorption experiment of phosphorus by UCFWTR,the fitting results of adsorption kinetics and adsorption isotherm showed that the fitting degree of adsorption of phosphorus by UCFWTR was higher by quasi-second-order kinetics and Langmuir isothermal adsorption model,indicating that the adsorption of phosphorus by UCFWTR was dominated by chemical adsorption of single molecular layer.The main rate-limiting step of adsorption was liquid film diffusion,and the maximum fitting adsorption amount was 1.66 mg/g.The effects of adsorption factors on phosphate removal by UCFWTR were optimized by single factor experiments.The results showed that low pH was more favorable for phosphate adsorption by UCFWTR.Considering the total phosphorus removal rate,adsorption capacity and economic practicability,the optimal solid-liquid ratio was 20 g/L;the effects of several common anions on phosphate adsorption by UCFWTR showed that Cl^-,SO₄^2-and NO₃^-had little effect on phosphate removal,but CO₃^2-had a strong inhibitory effect on phosphate adsorption by UCFWTR.The ionic strength has no effect on the adsorption of phosphate by UCFWTR,which indicates that ligand exchange is one of the main adsorption mechanisms of phosphate by UCFWTR.The phosphate content adsorbed by UCFWTR was NaOH-P>HCl-P>Res-P>BD-P>NH₄Cl-P according to the fractionation of phosphate adsorbed by UCFWTR.Stability Res-P>NaOH-P,HCl-P>NH4Cl-P,BD-P.The results show that the phosphorus adsorbed by UCFWTR is relatively stable,and the risk of re-release into water is small,which has the potential to become a stable phosphorus removal adsorbent.（3）UCFWTR and common commercial ceramsite were used in biological aerated filter to treat domestic sewage.The effluent of common commercial ceramsite biological aerated filter and UCFWTR biological aerated filter reached stability on the 8th and 7th day respectively during the start-up of biofilm formation,and the biofilm formation was successfully started within 14 days.By optimizing the operation parameters of biological aerated filter,the optimal hydraulic retention time of ordinary commercial ceramsite biological aerated filter and UCFWTR biological aerated filter were 20 h,and the optimal gas-water ratio was11:1.After stable operation under the optimized parameters,the removal rates of COD and ammonia nitrogen reached 93%and 92%respectively,and the removal rate of total phosphorus fluctuated from 78%to 89%.The removal rates of COD and NH₃-N in UCFWTR BAF reached 95%and 96%,respectively,while the removal rate of TP fluctuated between 83%and 93%.It indicated that the treatment effect of UCFWTR BAF on domestic sludge was better than that of ordinary ceramsite BAF.（4）Based on the above experimental results,it is feasible to prepare ceramsite with residual sludge from waterworks and Fenton sludge as the main raw materials by non-fired method.On the one hand,it provides a new idea for the resource utilization of these two kinds of sludge,and achieves the goal of“turning waste into treasure”.On the other hand,it can also be used as an adsorbent and biofilter in water treatment,and can achieve a better treatment effect,which implements the concept of“treating waste with waste”.