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.