TREATMENT OF PHOSPHORIC ACID PLANT WASTEWATER USING FENTON'S REAGENT AND COAGULANTS

Abstract

The results of treatability studies viz., Fenton reaction and physico-chemical (coagulation) treatment using lime, alum, Fe salts and polyaluminium chloride (PAC) performed on wastewater generated from a unit manufacturing technical grade phosphoric acid are reported. Due to low biochemical oxygen demand (BOD) chemical oxygen demand (COD) ratio and very low pH, this wastewater is not amenable for biological treatment. The treatability studies indicated that it is possible to remove 75–80% COD using Fenton's reagent at optimum doses of 1.0 g/L FeSO₄ and 2 ml of 30% H₂O₂. Simultaneously, significant quantities of suspended solids, phosphate and fluoride are also removed. Polyaluminium chloride is found to be more effective towards suspended solids (SS), COD, phosphate and fluoride removal, when compared to other coagulants used in the present study. Addition of an anionic polyelectrolyte (Magnafloc 156) to PAC improved the performance further. A treatment scheme that consists of neutralization (pH 4) + Fenton's reagent + neutralization (pH 7.5) + PAC/Magnafloc 156 is found to be effective in treating phosphoric acid plant wastewater to meet marine discharge standards.

Keywords:

• Phosphoric acid plant
• Wastewater
• Treatment
• Fenton's reagent
• Coagulants

Acknowledgments