Solar treatment of sewage discharged from industrial estate for reduction of chemical oxygen demand over Degussa P-25 titania.

The aim of current investigation was to demonstrate the effectiveness of Degussa P-25 titania in the photocatalytic treatment of sewage, discharged from industrial estate, as a combined process under solar irradiation. The study was aimed to understand the role of fundamental factors including, titania load, initial COD level, and pH on the photocatalytic degradation rate. The commercially produced TiO represented a mesoporous structure, 2-30 nm, indicating the adequate activity in the COD reduction of sewages collected from the streams entreating anaerobic, aerobic, and sand filtration stages when 0.5 g L of photocatalyst was loaded. According to the obtained results, the degradation rate is accelerated with an increase in the initial COD level. Although the solar treatment of streams entering to the anaerobic, and aerobic stages indicated the higher rates, the separation of titania particles from the sludge is very difficult. Therefore, it seems that the downstream of recovery network is still the best position to assemble the photocatalytic system, as an auxiliary process to reduce COD below the standard level, and improve the recovery rate. The maximal removal efficiency, 87%, was achieved within 20 min by the solar treatment of sewage in the alkali condition with the control of pH around 8.