Enhanced phosphorus and COD removals for retrofit of existing sewage treatment by electrocoagulation process with cylindrical aluminum electrodes

Abstract

A series of experiments were performed in a study designed to investigate the retrofit ability of removing total soluble phosphorus (sTP) and soluble chemical oxygen demand (sCODMn) from wastewater through electrocoagulation technology utilizing cylindrical aluminum electrodes in batch-operating modes (BOMs) and continuous operating modes (COMs). By varying the operating conditions and the effects of various experimental parameters such as pH, NaCl concentration, hydraulic retention times (HRT), initial phosphorus concentration, and temperature, etc, the applied electric potentials (AEPs) range between 3, 4, and 5 volts (V), with current densities from 7.04 to 16.08 A/m2 in BOM and from 7.48 to 21.69 A/m2 in COM. Electrolysis times in the limits of 1 to 20 min were tried for different types of wastewater, including synthetic wastewater and municipal wastewater. According to experimental results, it was demonstrated that superior performance in removing phosphorus from wastewater can be achieved, with experimental data indicated that more than 99% (<0.2 mgTP/L) of phosphorus, and 75% (<10mgCOD/L) of sCODMn can be removed using this method. Additionally, it was also found that TP and sCODMn removal efficiencies were also increased with the addition of more NaCl to the wastewater. It has also been determined from the data that with optimum operating conditions and electrolysis time, this method can be used in existing municipal wastewater treatment plants to enhance treatment efficiencies of phosphorus and sCODMn when properly retrofitted.