Comparisons of the film peeling from the composite oxides of quartz sand filters using ozone, hydrogen peroxide and chlorine dioxide

To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone (O₃), hydrogen peroxide (H₂O₂) and chlorine dioxide (ClO₂) were examined to peel off the film from the quartz sand surface in four pilot-scale columns. An optimized oxidant dosage and oxidation time were determined by batch tests. Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33 (H₂O₂) and to 53.67 hr (ClO₂) after the oxidation treatments, and the increase of backwashing interval after treatment by O₃ was much less than for the other two treatments. Interestingly, the treatment efficiency of filters was not affected by O₃ or H₂O₂ oxidation; but after oxidation by ClO₂, the treatment efficiency was deteriorated, especially the ammonia removal (from 96.96% to 24.95%). The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Compared with the oxidation by O₃ and H₂O₂, the structures on the surface of filter sands were seriously damaged after oxidation by ClO₂. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO₂. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H₂O₂ is a suitable agent for film peeling.