Combined ozonation and adsorption system for the removal of heavy metals from municipal wastewater: effect of COD removal

Heavy metals like copper, chromium, cadmium, lead, and zinc are key contaminants of freshwater reservoirs because of their deadly, non-biodegradable, and persistent nature. The work involves the comparison of various single and combined processes such as ozonation (Ozo), adsorption on activated carbon (AC), adsorption on rice husk (RH), ozonation in the presence of rice husk (Ozo/RH) and ozonation in the presence of activated carbon (Ozo/AC) for the removal of chemical oxygen demand (COD) and heavy metals from the municipal wastewater. Various factors such as adsorbent dose reaction time and synchronizing effect of COD removal on the removal efficiency of heavy metals was studied. The maximum removal of both COD and heavy metals was achieved by ozonation in the presence of activated carbon (Ozo/AC) combined process. The results further reveal that COD removal efficiencies have a positive synchronizing impact on the removal efficiencies of heavy metals. It is therefore concluded that (Ozo/AC) combined process may be used for the removal of heavy metals in wastewater.