Effect Of Microelectrolysis-Fenton On Sludge Dewatering Performance

Sewage treatment plants will produce a large amount of excess sludge.If a large amount of sludge is not effectively treated and disposed,it will pose a great threat to the ecological environment and human health.One of the most critical factors in the sludge treatment and disposal process is the high water content,which is also a difficult point for sludge disposal.Therefore,how to improve the sludge dewatering performance has become the focus of this study.In this paper,the excess sludge was conditioned by microelectrolysis,Fenton method and the combination of the two processes.The degree of sludge disintegration(DD_SCOD),extracellularpolymericsubstances?EPS?content,the sludge moisture content and specific resistance to filtration?SRF?were investigated during the conditioning process.The effects of different treatment methods on sludge dewatering performance and the mechanism were studied,and the optimal reaction conditions were obtained.Firstly,the sludge was treated by microelectrolysis,and the effects of different iron powder dosage,Fe/C,initial pH and reaction time on sludge disintegration and dewatering performance were investigated.The results showed that microelectrolysis could effectively crack sludge flocs and EPS,and improve the dewatering performance of sludge.The optimum reaction conditions were as follows:iron powder dosage 4 g/L,reaction time 30 min,iron-carbon ratio 1:1,initial pH 2.5.At this time,the sludge moisture content was as low as 70.2%,the protein cracking rate was 41.3%,and the polysaccharide cracking rate was 24.7%.The micro-electrolysis technology has the advantages of low cost,easy operation,high degree of sludge disintegration,and improving the sludge dewatering performance under certain conditions.Secondly,the sludge was conditioned by Fenton oxidation method,and the effects of different Fe²⁺and H₂O₂ dosages,initial pH and reaction time on sludge disintegration and dewatering performance were investigated.The results showed that Fenton oxidation can effectively oxidize and destroy sludge EPS and improve the dewatering performance of sludge.The optimum reaction conditions were as follows:Fe²⁺dosage was 0.3 g/L,initial pH was 2.5,H₂O₂ dosage was3.0 g/L,and reaction time was 60 min.Under the optimal reaction conditions,the sludge moisture content was 70.5%,the protein removal rate was 68.8%,the polysaccharide removal rate was 54.5%,and the SRF was 5.296×10¹22 m/kg.Fenton oxidation has the advantages of good treatment effect and low cost.It can effectively oxidize and destroy sludge EPS and release bound water in the sludge.This technology has been studied in sludge treatment and disposal,and it has been matured in the field of sludge treatment.Finally,the sludge was conditioned by microelectrolysis-Fenton combined process,and the effects of different iron powder dosage,H₂O₂dosage and reaction time on sludge disintegration and dewatering performance were investigated.Under the optimal microelectrolysis conditions,the Fenton oxidation reaction was carried out.And the optimal reaction conditions for the combined reaction were as follows:iron powder dosage 1.2 g/L,Fenton reaction time 45 min,H₂O₂ dosage4.2 g/L.The optimum conditions for the iron powder dosage and the Fenton reaction time were reduced compared to the single conditioning process.After combined treatment,the sludge moisture content was69%,the SRF value was significantly reduced,SRF was 2.687×10¹²m/kg,and the dewatering performance was the best.The protein and polysaccharide content of the supernatant of the sludge decreased by46.8%and 20.6%,respectively,and the DD_SCODCOD increased by 10.1%compared with the original sludge.Appropriate microelectrolysis treatment is beneficial to sludge disintegration,and the generated Fe²⁺can react with H₂O₂ for Fenton to improve sludge dewatering performance.After the sludge treatment by three methods,the EPS of the sludge was destroyed,and the hydrophobic substances such as humic acid and fulvic acid in the supernatant were increased,so that the sludge dewatering performance was improved.Fenton had the strongest oxidizing power and produced more humic acid and fulvic acid.The activated carbon after microelectrolysis reaction as a skeleton building agent could enhance sludge dewatering.The microelectrolysis-Fenton combined reaction had better effect on sludge treatment than the single microelectrolysis and Fenton reaction,and the sludge cake moisture content and SRF value were more reduced,and the sludge dewatering performance was better.