Electrocoagulation flocculation as a low-cost process for pollutants removal from urban wastewater

A combined two steps electrocoagulation-flocculation was designed to remove COD, BOD5, TSS, nitrate (NO3), nitrogen (N), phosphate (P), and fecal coliform (FC) from urban wastewater. The possibility of adding a natural flocculant extracted from plant material, Spineless Prickly Pear, Opuntia ficus Indica, juice (OFIJ), by comparing it with an industrial grade flocculant as anionic polyacrylamide (APAM), in the process of electrocoagulation-flocculation (ECF) was performed. The electrocoagulation (EC) reactor was tested in two different sequences (before and after the flocculation unit). The effect of several operational parameters, such as: current density, reaction time, flocculant dose, specific amount of dissolved electrodes and initial pH, on the removal efficiency of major pollutants was determined. The application of ECF process under optimal conditions, such as: current density (200 A/m(2)), reaction time (30 min), flocculant dose (6 ml/l), initial pH (7.4) and specific amount of dissolved electrodes (0.2 kg/m(3)) allows to achieve these promised removal efficiencies: 85%COD, 84%BOD5, 94%TSS, 63%N, 73%NO3 and 99%P. Moreover, it is of interest to note that duration of 10 min is sufficient to remove 99% of FC from the studied urban wastewater. These operating conditions of ECF led to reducing specific energy consumption from 6 kWh/kg COD and 0.6 kWh/kg P (EC process) to 5 kWh/kg COD and 0.5 kWh/kg P, respectively. A comparative operating cost analysis was also given and it was found that ECF performance requires 0.7 $/kg of COD and 0.3 $/kg of P removed vs. 0.9 $/kg COD and 0.35 $/kg P for EC process. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.