Enhancing sludge dewaterability and phosphate removal through a novel chemical dosing strategy using ferric chloride and hydrogen peroxide.

In this study, we replicated full-scale centrifuge dewatering utilized in water resource recovery facilities (WRRFs) by using the Higgins modified centrifuge technique and demonstrated that analogous cake solids content and centrate suspended solids was attainable while applying a lower polymer dosage. Furthermore, we demonstrated a dramatic reduction in the concentration of phosphate (P) in anaerobically digested sludge (ADS) under various reaction conditions. H2 O2 was employed to convert embedded iron in ADS, in the form of FeS, to Fe (II) and Fe (III), which subsequently reacted to precipitate phosphate compounds, dropping the in-situ P concentration by nearly 50%. Adding ferric chloride (220 mg/L) in ADS enhanced the P-removal to more than 80%. Finally, simultaneous dosing of Fe and H2 O2 boosted P-removal efficiency to higher than 90%. The role of Fe in strengthening the flocs and increasing the dewaterability was also substantiated by demonstrating a 2% growth in the cake solids content when ADS was conditioned with Fe+H2 O2 preceding polymer treatment. The outcome of this work confirms that a deeper understanding of centrifuge operational parameters and physico-chemical properties of wastewater sludge would result in improved performance of municipal WRRFs.