Effect Of Potassium Ferrate/Ultrasound Combined Treatment On Textile Dyeing Sludge Disintegration And Dewaterability

With the development of the textile dyeing industry in China, textile dyeing sludge was largely produced by the textile dyeing wastewater treatment process. It contains high moisture, heavy metals and complex components. The strong structure of biological gel lead to the difficulties in dewatering, a large amount of sludge production and high treatment cost. Therefore, it has become an urgent issue to minimize the sludge yield from the source of sewage treatment process or post treatment.During ultrasound treatment, acoustic cavitation induces different effects, including chemical reactions by radicals, pyrolysis, combustion and shearing. It can disrupt sludge flocs, then huge amounts of the cell contents and nutrients are released into the aqueous phase. Under the proper conditions, ultrasound treatment exerted a positive effect on sludge dewaterability and disintegration. Ferrate (VI) ions are reduced to Fe (Ⅲ) ions and simultaneously form a coagulant (Fe(OH)3). With a high oxidation capacity, Potassium ferrate is able to oxidize organic and inorganic materials by disrupting colloidal contaminants. Moreover, potassium ferrate is a coagulant and can be used as a transformer of fine particles into large aggregates, to promote the sludge settleability. Most studies were applied to water treatment, few have addressed the effect of potassium ferrate/ultrasound technology on the textile dyeing sludge treatment. This study aimed to investigate the effect of potassium ferrate/ultrasound treatment on sludge reduction. It broadens the application of potassium ferrate in the sludge treatment and provides reference information for sludge reduction.The effect of potassium ferrate assisted ultrasound treatment on textile dyeing sludge disintegration is discussed in this manuscript. The optimal parameters for ultrasound followed by potassium ferrate treatment were found to be a potassium ferrate treatment time of 60 min, a potassium ferrate dosage of 0.5936 g/g SS, an ultrasonic time of 15 min and an ultrasonic intensity of 0.72 W/mL. The potassium ferrate assisted ultrasound treatment synergistically enhanced the sludge solubilization and reached 668.67 mg/L SCOD, which is 31.81% greater than the additive value obtained with potassium ferrate treatment alone (215.95 mg/L) or with ultrasonic treatment alone (240 mg/L). The initial median diameter of the sludge particles was 15.24 um, and this value decreased by 35.89%. The CST was initially 59.6 s and increased by 231%, whereas the SVI was 97.78 mL/g and decreased by 25.89%. The potassium ferrate assisted ultrasound treatment presented synergistic advantages on sludge disruption compared with the potassium ferrate or ultrasound treatments alone. The potassium ferrate assisted ultrasound treatment exerted a positive effect on sludge settleability and a negative effect on sludge filterability.The ultrasound conjunction with potassium ferrate treatment was used to study the dewaterability of textile dyeing sludge. The result showed that potassium ferrate treatment alone did not have an obvious impact on sludge dewaterability. Under the proper conditions(0.45 W/mL,4 min), ultrasound treatment exerted a positive effect on sludge dewaterability, the SV30 and CST decreased by 6.3% and 16.35%, respectively. The following optimal parameters for potassium ferrate followed by ultrasound treatment were obtained:potassium ferrate dosage of 60 mg/g SS, an ultrasonic time of 4 min and an ultrasonic intensity of 0.45 W/mL. The SV30, CST and the solid content of sludge cake decreased by 18.36%,31% and 13.07%, respectively. The ultrasound conjunction with potassium ferrate treatment presented advantages over potassium ferrate treatment alone or ultrasound treatment alone on sludge dewaterability.