Study On Plasma Improvement Of Sludge Dewatering Performance And Preparation Of Sludge Catalyst

Activated sludge process is widely used in urban sewage treatment plants.Under the continuous increase of sewage treatment plants and treatment capacity,the output of excess sludge,as a by-product of sewage treatment process,is gradually increasing.Reduction,harmlessness and resource utilization are the goals of excess sludge treatment and disposal.Excess sludge has the characteristics of high water content and poor dewatering performance,which leads to a substantial increase in the treatment cost of sewage treatment plants.It is a key step for proper treatment and subsequent improvement of resource utilization rate on improving sludge dewatering performance.Fenton reaction is widely used in the treatment of sewage and sludge,but there are some problems such as continuous addition of H₂O₂and Fe²⁺.Optimizing Fenton reaction and preparing H₂O₂and Fe²⁺in situ have research value and application prospect.Glow discharge is a new advanced redox technology.The materials needed for Fenton reaction are continuously provided,and a variety of strong oxidizing particles are generated for the degradation and destruction of organic matter and microorganisms.Reducing particles can be generated by changing the discharge form and discharge conditions for the reduction of metal ions.In this thesis the iron anode glow discharge plasma（GDP）was used to destroy the sludge floc structure,promote the release of intracellular bound water,and improve its dewatering performance.Reduction of Fe³⁺in iron sludge by dielectric barrier discharge（DBD）treatment,preparation of sludge catalyst,and enhanced Fenton reaction for degradation of organic pollutants in aqueous solution.The main results are as follows:（1）H₂O₂prepared in-situ by GDP reacts with Fe²⁺to produce Fenton reaction to produce excess OH,which improves the dewatering performance of sludge.Firstly,Specific resistance of filtration（SRF）was used as evaluation index.Under the initial p H value of 3.0,voltage and current of 550V and 0.1A,SRF decreased by 82.5%after GDP treatment for10min,which significantly improved the dewatering performance of sludge.The effects of discharge on the changes of dissolved organic carbon（DOC）and protein content,Zeta potential and cell membrane integrity in extracellular polymeric substances（EPS）of sludge were analyzed.The results showed that DOC and protein content in EPS of sludge decreased obviously,Zeta potential increased and cell membrane integrity was destroyed.The removal rate of hexavalent chromium ion at the initial concentration of 10mg/L in sludge reached97.8%after 2 min treatment with GDP,which indicated that GDP can reduce heavy metal ions while improving the dewatering performance of sludge.（2）Fe-containing sludge treated by DBD was used as a catalyst for Fenton reaction,and2,4-D in aqueous solution was degraded by·OH produced in situ by GDP,which provided a new method for sludge resource utilization.Catalysts prepared by H₂-DBD directly enhance the degradation of 2,4-D by Fenton reaction.Under the condition of initial p H 3.0 and catalyst dosage 1.0 g/L,the degradation efficiency of 2,4-D reached 98.3%after 20min discharge,and 100%after 25min GDP degradation.Quenching experiment and paramagnetic resonance spectroscopy confirmed that the main mechanism of 2,4-D removal was hydrogen atom reduction dechlorination and hydroxyl radical oxidation degradation.Moreover,in the GDP process,we found that the organic free radicals（R·）and hydrogen atom（·H）produced by GDP can reduce Fe³⁺increase the regeneration rate of Fe²⁺,and indirectly enhance the Fenton reaction.In summary,the DBD-prepared sludge catalyst combined with GDP can efficiently degrade 2,4-D in aqueous solution.