Research On Dewatering Performance Of Dredged Sludge And Optimization Influenced By Advanced Oxidation System

At present, dredged sediment conventional processing technology which lead to the purpose of environment protecting could only apply to the sludge containing lower organic content and less clay content. These methods are not suitable for higher organic content and more clay content in super water retention sludge. So deep treatment processes are desiderated urgently. The advanced oxidation system is conducted with dredged sludge from Dan-chi lake and Dong-ting lake as research object. They have different physical-chemical properties. Then combinate the optimum oxidation parameters with physical conditioner is to further improve sludge dehydration and dehydration rate.In this study the enhancements of Fenton condition and O3condition were investigated. The efficiency of the treatment was evaluated on the basis of SRF and sludge cake water content. Extracellular polymeric substance(EPS) concentration, viscosity, scanning electron microscopy(SEM) and water contact angle were determined to explain the observed changes in conditioning process. Focuses were placed on pH, H2O2dosage, H2O2/Fe2+ratio, reaction temperature and time, O3dosage. To Dan-chi lake, the optimum values of pH, H2O2concentration, H2O2/Fe2+ratio, reaction temperature and time were6.2,10mg/g DS,8,25℃and10min, respectively. The SRF reduction from13.25×1012to10.41×1012could be achieved. The increased soluble polysaccharide content indicated that Fenton reagent could break EPS effectively and release bound water. The results leaded to improve the performance of sludge sedimentation and flocculation. Also the particle size became smaller and the hydrophobic performance of sludge cake had been enhanced through observing water contact angle. To Dong-ting lake, the optimum values for pH, H2O2concentration, Fe2+concentration, reaction temperature and time were6.2,50mg/g DS,6.25mg/g DS,25℃and5min, respectively, at which the SRF reduction efficiency of76.09%and filter cake water content of10.34%could be obtained. To the gel-like sludge system, the degradation of EPS leaded to the decreasing of viscosity and made large particles into small ones. The surface hydrophobic was improved by decreased polysaccharide content. Furthermore, more interstitial water and intracellular water released into dispersed phase by SEM investigation which showed the surface of conditioning sludge sample was relatively round and smooth instead of honeycomb. Two kinds of dredged sludge water quality were improved after conditioning.Besides, the optimum O3dosage was examined using Dian-chi sludge. The highest SRF reducing rate was28.91%under0.2gO3/Vg SS dosage.O3condition presented a little clearer advantages than Fenton condition, but sedimentation performance fell instead. When co-conditioned with two oxidation condition and physical conditioner, SRF was reduced greatly and the drying time was shorten significantly. Especially when the combination Fenton with QC-1, the minimum SRF was0.88X1012m/kg and the reduction efficiency was93.71%; when the combination O3condition with QC-1, the minimum SRF was0.39X1012m/kg and the reduction efficiency was97.21%.