Innovative methods for removing phosphorus from wastewaters

Wastewater containing a mixture of hypophosphites and phosphites was treate d in order to assess the possibility of attaining high levels of phosphorus oxidation to phosphate. An initial series of tests based on chemical oxida tion by means of Fenton's reagent demonstrated the feasibility of this proc ess for solutions containing 250-750 mg/l of phosphorus. Removal yields of up to 98% were attained at pH 3.5 by using variable ratios of [H2O2]/[Fe2+] . The second series involved the electrolytic generation of Fenton's reagen t at pH 2-2.5 through cathodic oxygen reduction. This demonstrated the poss ibility of obtaining quantitative yields for solutions containing 80-160 mg /l P with a constant [H2O2]/[Fe2+] ratio of 3.94. Economic comparison of th e two processes showed that the operative cost of the electrochemical treat ment is comparable to that of the chemical process.