Characteristics of an electrocoagulation-electroflotation process in separating powdered activated carbon from urban wastewater effluent

In order to eliminate micropollutants from effluent of urban wastewater treatment plant (UWWTP), adsorption by powdered activated carbon (PAC) becomes a promising solution amongst several methods. A crucial point in this technology is the total separation of the loaded PAC from wastewater. Some separation methods, such as sedimentation, filtration, air flotation and hydrocyclone, have low efficiency or high construction cost. In this study a combined electrocoagulation-electroflotation (EC-EF) process is investigated in a bench test. Parameters of the process including zeta potential, floc-size development, separation efficiency, PAC particles size distribution and buoyant density were measured in order to analyze their significance and effect on the EC-EF process applied for the separation of PAC. It is shown that the efficiency depends strongly on charge loading and is also affected by current density and retention time. At a charge loading of 2.5 F/m(3), a current density of 100 A/m(2) and a retention time of 10 min, zeta potential was nearly zero and aggregate size grew quickly to 100 pm in D(v, 0.5). As a result, separation efficiency reached values above 95%. (C) 2014 Elsevier B.V. All rights reserved.