Photocatalytic oxidation of waste activated sludge using a backlight photocatalytic reactor

This study investigated the photocatalytic oxidation of waste activated sludge (WAS) in a backlight photocatalytic reactor. In this reactor, TiO2 nanoparticles were fixed on a Plexiglas sheet. Waste activated sludge flowed from the coated section, and a UV lamp was located on the other side of the sheet. The effect of the TiO2 nanoparticles’ concentration (40, 60, 70, and 80 g/m2) and WAS dilution (0, 2, 3, and 6 times dilution) was investigated on waste activated sludge photocatalytic oxidation. Chemical oxygen demand (COD) removal efficiency, volatile suspended solids (VSS) removal efficiency, soluble chemical oxygen demand changes, and soluble polysaccharide changes were measured after 200 min of WAS photocatalytic oxidation. The study of waste activated sludge dilution showed that the high waste activated sludge concentration (6,450 mg/L) caused no problem in COD and VSS removal. It was also revealed that the increased TiO2 concentration elevated the WAS oxidation efficiency. The highest COD and VSS removal efficiencies were 37% and 38%, respectively, which were obtained in waste activated sludge without dilution and TiO2 concentration equal to 80 g/m2. Changes in soluble polysaccharide and COD showed that waste activated sludge photocatalytic oxidation in this reactor might lead to WAS solubilization. Also, an increase in waste activated sludge dilution and a decrease in TiO2 concentration increased waste activated sludge solubilization.