Improving Dewaterability and Other Properties of Citric Acid Wastewater Treatment Sludge by Ozone and Peroxone

The efficacies of ozonation and peroxone (O₃/H₂O₂) pretreatments were compared for citric acid wastewater sludge conditioning with the objective of improving dewatering characteristics of the sludge. Treatment with 84 mg O₃/g dry solid (DS) and 12.5 mg/g DS H₂O₂ greatly enhanced the effectiveness of ozonation, providing sludge dewaterability similar to that obtained by ozonation at 250 mg O₃/g DS. Most importantly, treatment of citric acid wastewater sludge with 84 mg O₃/g DS and 12.5 mg/g DS H₂O₂ led to the preservation of the nutrient elements nitrogen, phosphorus, and potassium in the sludge with a minimal volatile suspended solids/total suspended solids reduction of 5.5%, which is much lower than that with ozonation at 250 mg O₃/g DS.