| The operation of textile dyeing wastewater treatment process could generate a large amount of excess billogical sludge, Its moisture content reaches up to 85% after common mechanical dewatering. Thus, the reduction treatment of the textile dyeing sludge has been the key to the subsequent disposal. Previous studies have indicated that the high affinity for water of flocs structure confines the dewaterability of textile dyeing sludge significantly, and it has complex composition, containing dye, pulp, additives, etc. Its greater toxicity may cause environmental damage. This study aims to investigate the effects of electrolysis oxidation technology, and electrolysis combined CPAM treatment on textile dyeing sludge structure and dewaterability, and to analyze the relationship between sludge disintegration and sludge dewaterability, in order to reduce the volume and follow-up disposal on sludge.The study focuses on the effects of electrolysis on textile dyeing sludge dewaterability and its mechanism.Total suspended solids (TSS), volatile suspended solids (VSS), soluble chemical oxygen (SCOD), extracellular polymeric substance (EPS) concentration, viscosity, specific resistance to filtration (SRF) and capillary suction time (CST) were measured to explain the observed changes in sludge dewaterability. The results showed that the concentration of SCOD, VSS, TSS was increased as electrolysis or time increased. The optimal experimental conditions for electrolysis oxidation of the textile dyeing sludge were as follows:Concentration of SCOD, EPS, Viscosity were 165-200 mg/L,35-45 mg/L,6.2-7.5 mPa-s, respectively. As the time was constant, and the voltage was changing from 0,5, 10,15,20,25 V, it seems that the value of the CST were 79.17 s,79.57 s,78.46 s, the value of SRF were 7.48×1011 s2·g-1,7.35×1011 s2·g-1,7.56×1011 s2·g-1,respectively. It decreased by 18.65%,13.18%,41.19%,30.16%,24.56%,21.35% comparing with the raw sludge. On the other hand, As the electrolysis voltage was constant, and the electrolysis time was changing from 0,10,20,30,40,50,60 min, the value of the CST were 99.42 s,104.18s,84.69 s, the value of SRF were 6.74×1011 s2·g-1,6.88×1011 s2·g-1,6.67×10-1 s2·g-1, respectively. Compared to the raw sludge, it decreased by 18.65%,13.18%,41.19%,30.16%,24.56%, 21.35%. Thus, The optimal condition by the CST and SRF was determined to be 10-15 V with a contact time of 20-30 min, spacing between plates 3cm on textile dyeing sludge dewaterability.Based on the above test results and determined the optimum reaction parameters, and then added different doses of cationic polyacrylamide (CPAM) into the textile dyeing sludge by secondary conditioning. The results indicated that the electrolysis-CPAM could enhance the textile dyeing sludge dewaterability. It was found that the moisture of sludge cake decreased from 89.3% to 82.08% and the value of sludge’s SRP, CST and viscosity decreased by 59.4%,41.7% and 68.2%, respectively, when combined with 6.67 mg·g-1 (dry weight) of CPAM. Scanning electron microscopy (SEM) showed that the sludge flocs were damaged when electrolysis or electrolysis-CPAM treatment, and the sludge dewaterability was improved due to the weakening of the retention of bound water within the sludge as reacting at the optimal conditions. |
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