Effect of electrochemical treatment on the COD removal from biologically treated municipal wastewater

This investigation observed the effect of electrolytic treatment time, current density, pH and supporting electrolyte on the removal efficiency of COD of secondarily treated sewage (STS). A glass chamber of 2 litre volume was used for the experiment with two electrode plates of Al, each having an area of 125 cm2 and 2 cm distance apart from each other. The treatment showed that the removal efficiency of COD increased to 82.25% with the increase in current density (1.82–7.52 mA/cm2), time (5–40 min) and pH (4–8) of STS. The electrode and energy consumption varied from 2.52 × 10−2 to 10.51 × 10−2 kg Al/m3 and from 2.76 to 45.12 kWh/m3. Under optimal operating conditions, the operating cost was 1.56 US $/m3. The addition of 0.5 g/L NaCl as a supporting electrolyte nominally increased the removal of COD (85.8%), and later, the observation is in contrast with previously published studies claiming greatly enhanced removal of COD in the presence of supporting electrolytes.