Effects of potassium ferrate on extracellular polymeric substances (EPS) and physicochemical properties of excess activated sludge

• Published in: Journal of hazardous materials 2012-01, Vol.199, p.158-163
• Main Authors: Ye, Fenxia, Liu, Xinwen, Li, Ying
• Format: Article
• Language: English
• Subjects: Activated sludge; Capillary suction time (CST); Dewaterability; Dewatering (separation process); Dosage; EPS; Excess activated sludge; Extracellular polymeric substances (EPS); Filterability; Iron Compounds - chemistry; Polymers - chemistry; Polystyrene resins; Potassium Compounds - chemistry; Potassium ferrate; Sewage; Sludge
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2011.10.071

► Potassium ferrate pretreatment was detrimental to the filterability based on the CST results. ► Potassium ferrate pretreatment slightly enhanced the sludge settleability and dewaterability. ► LB-EPS content was increased and TB-EPS content was reduced after pretreated by potassium ferrate. ► The increased LB-EPS was the major reason for the changes in sludge settleability and filterability. ► TB-EPS and PN in TB-EPS were negatively correlated with CST. The activated sludge process of wastewater results in the generation of a considerable amount of excess activated sludge. In many wastewater treatment plants, the bottleneck of the sludge handling system is the dewatering operation. This paper investigated the effect of potassium ferrate pretreatment on the physicochemical properties of the excess activated sludge at various dosages of potassium ferrate. The particle size, extracellular polymeric substances (EPS) content and chemical components, and sludge disintegration degree were measured to explain the observed changes of physicochemical properties. It was expected that potassium ferrate could enhance the filterability and dewaterability of the sludge. However, the results showed that potassium ferrate had a negative effect on the filterability by measuring the capillary suction time (CST), but improved the settleability and dewaterability extent by determining the water content in the dewatered cake, although the flocs size reduced slightly. Loosely bound EPS (LB-EPS) content, polysaccharides (PS) and proteins (PN) contents in LB-EPS all increased with increasing the amount of potassium ferrate. However, Tightly bound EPS (TB-EPS) content, PS and PN contents in TB-EPS did not changed significantly at first, and decreased slightly under higher dosage of potassium ferrate. EPS, especially LB-EPS played more important role in the observed changes of the settleability and filterability than the sludge particle size.