Abstract

Municipal wastewater was treated in four phases, using electrocoagulation batch reactors. In Phase I, a comparison between electrocoagulation (EC) and chemical coagulation showed enhanced effluent quality when EC is used. In Phase II, two concentrations of a conditioner were added to four-hour EC experiments at two different voltage gradients to increase conductivity and initiate electroflotation, thus improving solid-liquid separation. Complete phosphorus removal was observed in Phase II. However, the four-hour duration resulted in higher operating costs, especially given that flotation was achieved within the first 45 minutes.
Tests of Phase III were run using current densities of 10, 20 and 40 A/m2 and treatment durations of 30, 60 and 120 minutes. In each run, four 1.5 L electrokinetic reactors were operated in parallel, with continuous and intermittent exposure to DC current. Wastewater samples from two treatment plants (WWTP1 and WWTP2), with different initial characteristics, were used to evaluate the treatment efficiency.
Phosphorus was entirely removed for all runs for WWTP1 and above 90% for WWTP2. Final COD concentrations after treatment were below 40 mg/L for both wastewater samples. Intermittent exposure prevented excess dissolution of the anodes, while allowing mixing and enhancing flocculation. Operating costs of the treated samples started at the level of 16 CAD/1000m3 and depended on material and energy costs. The final phase compared flat and perforated electrodes in terms of material and energy consumption, as well as operating costs. It was demonstrated that the use of perforated anodes can reduce operating costs by 50-75%.