Effect and Mechanism of Waste-Activated Sludge Disintegration Treated by Composite Ferrate Solution

摘要

Ferrate has recently been used to reduce waste-activated sludge (WAS), but solid potassium ferrate is costly. Hence, the lower cost composite ferrate solution (CFS), which contains Fe6+, ClO-, and OH-, was prepared to disintegrate WAS in this study. Effect and mechanism of sludge disintegration treated by CFS were investigated. Results showed that CFS could effectively destroy the sludge flocs and extracellular polymeric substances, resulting in the reduction of the median particle size and the release of proteins, polysaccharides, and metal cations such as Ca2+, Mg2+, and Zn2+. Sludge cell structure had been completely disrupted, and the intracellular material released, which led to the increase in the concentrations of the soluble chemical oxygen demand, total phosphorus (TP), soluble phosphorus (SP), total nitrogen (TN), nitrate nitrogen (NO3-N), and ammonia nitrogen (NH3-N). As a result, the mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) decreased, and the sludge settleability improved. At an optimum ferrate dosage of 50 mg Fe/g SS, the MLSS and MLVSS were reduced by 59% and 73%, respectively; the sludge settleability was improved by similar to 72% setting velocity to 79% sludge volume index. TP and SP were transformed into a solid form with Fe(III) formed in situ at higher CFS dosages. During the process, part of the nitrogen escaped from the system as volatile-free ammonia.