Effects Of Potassium Ferrate Conjunction With Microwave On Textile Dyeing Sludge Dewaterability

The sludge from textile dyeing wastewater treatment process is categorized to the special waste that should be strictly controlled in Guangdong Province. It has high moisture content and complex composition, containing dye, pulp, additives, etc. Its greater toxicity may cause environmental damage. Potential negative effects might be posed on environment during sludge production, treatment and disposal. The high water content lead to the difficulties in dewatering. Dewatering is one of the fundamental steps in sludge processing because it can reduce sludge volume and the cost of sludge transportation and disposal.Microwave has showed thermal effect and non-thermal effect. Due to the advantages of microwave, such as heat faster, control easily and sterilize effectively. It can improve the dewaterability of sludge. Potassium ferrate is a strong oxidizing agent that can oxidize organic compounds efficiently. By applying pretreatment with potassium ferrate, extracellular polymeric substances (EPS) in activated sludge are destroyed, intracellular organic substances are released. During the oxidation reation of potassium ferrate, it will product ferric hydroxide which has good flocculation and coagulant capacity. There have been lots of study about potassium ferrate, but most of them were applied to water treatment, seldom applied to industrial sludge treatment. This study explored the effect of potassium ferrate conjunction with moicrowave on textile dyeing sludge dewaterability. It broadens the application of potassium ferrate in the sludge treatment and provides reference information for fellow-up industrial sludge treatment.The main findings of this study could be summarized as following:Potassium ferrate was applied to investigate the dewaterability of textile dyeing sludge. The results showed that simple potassium ferrate pretreatment did not have an obvious impact on dyeing sludge dewaterability. Under0.2651g/gSS dosage of potassium ferrate, the settling velocity (SV30) decreased from100mL to97mL, viscosity decreased from18.83mPa-s to17.96mPa-s, capillary suction time (CST) decreased from63.3to58.8s, and the solid content of sludge cake increased from8.78%to9.03%.The effect of microwave treatment on textile dyeing sludge dewaterability was investigated. The results indicated that the sludge dewaterability was improved under proper microwave conditions. The suitable contact time, which were140s,100s and80s, was obtained at the microwave energy of2320W/L,3240W/L and4000W/L, respectively. The SV30decreased by4%,4%and5%. Specific resistance of filtration (SRF) decreased by13.62%,18.89%and20.43%. Viscosity decreased by16.57%,35.05%and36.17%. The sludge dewaterability deteriorated when the contact time exceeded a proper time. With the increase of microwave radiation power and the contact time, the values of total organic carbon (TOC) in the supernatant increased. Therefore, proper sludge disintegration can improve the dewaterability of sludge.The textile dyeing sludge dewaterability was inspected by potassium ferrate conjunction with microwave. When sludge samples were irradiated at3240W/L and100s, the optimal potassium ferrate dosage was0.1767g/g SS. The SV30, CST and viscosity decreased by13.5%,51.18%and40.79%, respectively. The solid content of sludge cake increased by14.58%. Potassium ferrate played a major role in the effects of potassium ferrate conjunction with microwave on textile dyeing sludge dewaterability. Comparing with the microwave pretreatment (3240W/L,100s), the SV30and viscosity of sludge samples which were pretreated by potassium ferrate conjunction with microwave (0.1767g/gSS dosage of potassium ferrate,3240W/L and100s of microwave irradiation) separately decreased by9.9%and8.83%. The proteins concentrations of the supernatant increased with the increase of potassium ferrate dosage. However, polysaccharides concentrations of the supernatant increased with the increase of potassium ferrate at first, and then decreased.