Effect of Ferrous Sulfate on Phosphorus and Nitrogen Removal in An Anoxic - Aerobic Configuration

Abstract

The present experiment was carried out to investigate the removal of phosphorus and nitrogen from synthetic wastewater in an anoxic-aerobic system. Phosphorus was removed through chemical precipitation. Ferrous sulfate (FeSO₄) was added into the aerobic basin. In aerobic condition, Fe²⁺ was first oxidized to Fe³⁺, and then it was precipitated with PO₄^3- to form the insoluble FePO₄, excluded from the system through waste sludge.  As a result, total phosphorus in the effluent was controlled to below 1.0 mg/L using a Fe/P molar ratio of 2.1. Nitrogen was removed biologically. The effect of FeSO₄ on nitrification and denitrification was investigated. The nitrification rate of the system was not affected during simultaneous precipitation. Denitrification was completed and not affected by the precipitation process. The nitrogen removal efficiency varied from 78% to 85%. COD removal efficiency was slightly improved after adding FeSO₄. In conclusion, the addition of FeSO₄ into an anoxic-aerobic system improved phosphorus removal. Addition of FeSO₄ also contributed to slight increase in the organic removal