Phosphorous removal in batch systems using ferric chloride in the presence of activated sludges

Calculations using a chemical equilibrium model (CHEAQS) predicted that ferric phosphate precipitation should not take place if pH is higher than about 7.8. However, experimental results showed that ferric phosphate precipitation occurred even at pH 9. For this reason, a mechanistic model was proposed to predict orthophosphate concentrations as a function of Fe0:P0 at constant pH. The model can be applied to calculate the minimum Fe(III) concentration required to achieve a given discharge limit for orthophosphate as a function of its initial concentration and pH.