Study On Advanced Dewatering Of Sludge By Advanced Oxidation Process And Semi-Coke Compound Conditioning

The rapid increase in the amount of sludge has become one of the most critical environmental issues.The full use of sludge after deep dewatering can achieve both economic and environmental benefits.In this thesis,the advanced oxidation process and the skeleton building material semi-coke were combined to condition the sludge.The sludge specific resistance（SRF）,the moisture content of the sludge cake（W_c）and the sludge filtration time（TTF）were used as indexes to evaluate the dewatering performance,and reveal the reaction mechanism by analyzing the changes of sludge microcosmic morphology,particle size distribution,bound water content,protein and polysaccharide content in the supernatant,and calorific value after conditioning.The main research contents and conclusions are as follows:1.The effects of dosage and pH on the dewatering of semi-coke conditioned sludge were studied.The results demonstrated that semi-coke conditioning can effectively improve the dewatering performance and sedimentation performance of sludge.When the pH was 3 and the semi-coke dosage was 600mg/g DS,the dehydration effect was the best,the specific resistance reduction rate was as high as85%,and the total suction filtration time was greatly shortened.After conditioning by the semi-coke,the surface of the sludge becomes rough and irregular,a large number of pores and cracks appear,and a skeleton structure is formed;due to the adsorption and flocculation of the semi-coke,the particle size of the flocculate particles of the sludge becomes large.The content of protein and polysaccharide in the supernatant was significantly reduced,the supernatant is clearer;the hydrophobicity of the semi-coke makes the sludge floc release a large amount of surface adsorption water,the bound water content decreases;and the calorific value of the sludge after conditioning is increased from 10.12MJ/kg to 14.34MJ/kg.2.The effects of the dosages of sodium persulfate and ferrous sulfate,pH,reaction time and semi-coke dosage on the dewatering performance of the sludge were investigated.The results illustrated that the optimum conditions for the composite conditioning of Fe²⁺activated sodium persulfate and semi-coke were that the pH was not adjusted,at room temperature,and the dosages of ferrous sulfate and sodium persulfate were both 1.1mmol/g VSS and the molar ratio of Fe²⁺/S₂O₈^2-was 1,the amount of semi-coke was 600mg/g DS,and the reaction were stirred for15minutes.At this time,SRF,W_c,and TTF were 1.04×10¹²m/kg,67.34%,and 11s,respectively,and the specific resistance reduction was 89.04%.After Fe²⁺activated sodium persulfate conditioning,the surface of the sludge becomes rough and irregular from smooth layered structure,and a large number of pores and cracks appear.The EPS structure is destroyed and decomposed,releasing macromolecule organics such as proteins and polysaccharides,partially bound water is converted into free water,and the bound water content is reduced from 4.02g/g DS to 3.8g/g DS,and the particle size of the sludge colloidal particles becomes significantly smaller.After composite conditioning with the semi-coke,a skeleton structure and a water-permeable channel are formed.The sludge floc releases a large amount of surface adsorption water,and the bound water content is further reduced to 3.49g/g DS.While the semi-coke adsorbs fine particles and macromolecule organics,and the size of the colloidal particles in the sludge became larger,the content of protein and polysaccharide in the supernatant was significantly reduced,and the dehydration efficiency of the sludge was further increased.Moreover,the sedimentation performance of sludge was significantly improved,and the total suction filtration time was further reduced from 66s to 45s.The Fe²⁺activated sodium persulfate oxidized part of the organic matter,resulting in a reduction in the calorific value of the sludge from 10.12MJ/kg to 9.64MJ/kg.After the composite conditioning with the semi-coke,the calorific value of the sludge increased again to 13.82 MJ/kg.3.The effects of potassium ferrate dosage,semi-coke dosage,pH,and reaction time on the dewatering performance of sludge were studied.The results showed that the optimum conditions for the composite condition of potassium ferrate and semi-coke were PH 3,potassium ferrate potassium 45mg/g DS,and semi-coke500mg/g DS,the reaction were stirred for 15 minutes.At this time,SRF,W_c and TTF were 2.12×10¹²m/kg,67.65%and 20s.Potassium ferrate can effectively oxidize EPS and microbial cells to release macromolecule organics and partially bound water,such as proteins,polysaccharides,etc.The surface of the sludge becomes loose and porous from flat and compact,and the lamellar structure is destroyed,becoming rough and irregular.The Fe（OH）₃ generated after the reaction can flocculate the fine particles to form larger particles;the dehydration time is significantly shortened,and the sludge dewatering effect becomes better.After the composite conditioning with the semi-coke,the skeleton structure was formed,and a lot of surface adsorption water was released from the sludge floc,and the bound water content was further reduced from 3.86g/g DS to 3.33g/g DS;The adsorption of semi-coke makes the particle size of the sludge colloid particles further larger,and the content of protein and polysaccharide in the supernatant is greatly reduced;the total time of suction filtration is shortened from 3min30s to 1min20s,the sludge settling performance is significantly improved,and the dehydration efficiency is further improved.Potassium ferrate oxidize and degrade some of the organics,resulting in a slight decrease in the calorific value of the sludge.After the composite conditioning with semi-coke,the calorific value of sludge increases from 9.96MJ/kg to 14.3MJ/kg.Advanced oxidation process(Fe²⁺activated sodium persulfate and potassium ferrate)and semi-coke compound conditioning sludge can give full play to their advantages,maximize the dewatering performance of the sludge,the synergistic effect of improving sludge dewatering efficiency is obvious.It not only can achieve deep dewatering,but also can increase the calorific value of sludge,which is beneficial to the incineration disposal and resource utilization of sludge,and can also provide theoretical support and a certain reference for engineering practice applications.