Effects Of Micro-electrolysis On Textile Dyeing Sludge Disintegration And Dewaterability

As a traditional pillar industry, Textile dyeing industry is also one of the larger industry with great toxicity to environment. Textile dyeing sludge, which has complex composition, high moisture content and high content of harmful substances, should be strictly controlled in China. It is necessary to explorer an economic, rational and effective technology used in sludge treatment and reduce the volume of sludge, the cost of transport and the amount of leachate in landfill field. Nowadays, sludge dewatering is becoming one of the great challenges for the wastewater treatment plant.This study aims to investigate the effects of micro-electrolysis treatment and micro-electrolysis conjunction with Fenton on textile dyeing sludge structure and dewaterability, and to analyze the relationship between sludge disintegration and sludge dewaterability. The main findings of this study could be summarized as follows.The effects of micro-electrolysis treatment on textile dyeing sludge dewatering and its mechanisms were investigated in this study. Capillary suction time (CST) and settling velocity (SV) were used to evaluate sludge dewaterability. Extracellular polymeric substances (EPS) concentration and sludge disintegration degree (DDSCOD) were determined to explain the observed changes in sludge dewaterability. The results demonstrated that the micro-electrolysis could significantly improve sludge dewaterability by disrupting the sludge floc structure. The optimal conditions of sludge dewatering were the reaction time of 20 min, initial pH of 2.5, Fe/C mass ratio of 1/1, and the iron powder dosage of 2.50 g/L, which achieved good CST (from 34.1 to 27.8 s) and SV (from 75 to 60%) reduction efficiency. In addition, the scanning electron microscope (SEM) images revealed that the treated sludge floc clusters are broken up and that the dispersion degree is better than that of a raw sludge sample. The optimal EPS concentration and DDSCOD to obtain maximum sludge dewaterability was 43 to 46 mg/L and 4.2 to 4.9%, respectively. The destruction of EPS was one of the primary reasons for the improvement of sludge dewaterability during micro-electrolysis treatment. Sludge flocs are broken up and the floc clusters are dispersed after the micro-electrolysis treatment. By considering the integrated characteristics of micro-electrolysis (cheap material, easy operation), high dewatering efficiency and sludge disruption degree, micro-electrolysis technology has great application potential in the pretreatment of textile dyeing sludge.Extracellular polymeric substances (EPS), sludge disintegration degree (DDSCOD) and settling velocity (SV), capillary suction time (CST) were measured on textile dyeing sludge disintegration and dewaterability by micro-electrolysis treatment alone and micro-electrolysis conjunction with Fenton. The results showed that the optimal micro-electrolysis conditions of sludge disintegration were found to be reaction time 20 min, initial pH 2.5, and Fe/C mass ratio 1/1, the iron powder dosage 2.50 g/L. Under the optimal Fenton conditions (H2O2:2.00 g/L, Reaction time:40min) after micro-electrolysis treatment, polysaccharides, proteins and DDSCOD increased by 49.09%,69.20%,4.33%, respectively, compared with the raw sludge. CST, SV decreased by 70.46%,20.41% compared with the raw sludge, and 66.57%,17.89% compared with the micro-electrolysis treating sludge. Micro-electrolysis-Fenton treatment showed the advantages of stronger sludge disruption effect and better sludge dewaterability compared with single micro-electrolysis treatment.