| Textile dyeing sludge is one of the large typical industrial solid wastes, and it contains high moisture and complex components. Biological gel structure existing in textile dyeing sludge also makes the dewatering difficult. Therefore, sludge dewatering is the primary bottleneck to sludge treatment. Fenton technology has often been adopted to improve sludge dewaterability. However, the practical application of Fenton technology is hindered due to the low utilization rate of H2O2and the strong acid conditions (pH≤3) required for Fenton process. Therefore, it has become an urgent issue to seek an effective treatment, like a combination of Fenton and another method, for overcoming the drawback of Fenton technology.This study aims to investigate the effects of bioleaching combined Fenton treatment and ultrasound assisted Fenton treatment 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.Bioleaching combined with Fenton oxidation was used to investigate dewaterability of textile dyeing sludge. The results showed that with the use of acidophilic Thiobacilli during sludge bioleaching, pH value decreased quickly with the increase of sulfur dosage and sludge dewaterability was enhanced to some extent by bioleaching. The optimal experimental conditions for bioleaching-Fenton oxidation of the textile dyeing sludge were as follows:reaction time2h, H2O2dosage6g/L and Fe2+dosage0.5g/L. Under these conditions, the values of total organic carbon (TOC) in the supernatant increased from20.8mg/L to356.6mg/L; and specific resistance to filtration (SRF) and moisture of sludge cake decreased from5.98×1011s2/g and88.51%to1.26×10H s2/g and82.85%, respectively. Bioleaching-Fenton oxidation showed more advantages in sludge disruption and dewaterability over single Fenton oxidation.The effect of ultrasound assisted Fenton (US/Fenton) treatment on the physicochemical properties of textile dyeing sludge was investigated. The sludge particle size, total organic carbon (TOC), extracellular polymeric substance (EPS) concentration and sludge disintegration degree (DDSCOD) were measured in an attempt to understand the observed changes in sludge physicochemical properties. The results showed that the US/Fenton-treated sludge presented obvious advantages over the Fenton treated sludge for disrupting sludge floc structure. The suitable condition for sludge disintegration was found to be0.12-0.16W/mL (ultrasonic density) and lower pH (≤3), under which the TOC in soluble phase increased obviously by releasing organic substances of sludge flocs. The changes of sludge dewaterability were dependent on sludge disintegration during US/Fenton treatment. The optimal EPS concentration and DDSCOD to obtain maximum sludge dewaterability were found to be90-100mg/L and4-6%, respectively. After10min of Fenton and US/Fenton treatment, the hydroxyl radical (·OH) was2.71μmol/L and2.90μmol/L, respectively, which confirmed that US/Fenton treatment had a synergetic effect. |
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