Effect of controlled parameters in lab-scale system of iron treatment from simulated groundwater with ozone

Dissolved ozone (O3(aq)) and residual ozone in groundwater under differently controlled parameters are two important outcomes in a lab-scale system of ferrous treatment with ozone, but they have not been well investigated yet. In this study, several preliminary parameters of ozone generation, types of diffusers, hydraulic retention time, and the pH in an ozone system of laboratory treatment were examined and evaluated statistically. The results showed that a venturi injector coupled with a bubble diffuser increased O3(aq) concentration to 9.05±0.28 mg/L corresponding to its diffusive coefficient of 0.195 min-1, 2.6 times higher than the bubble diffuser only. The O3(aq) decay constant in the presence of ferrous was 4.88 times higher than that in its absence. The mole stoichiometry of (D[O3(aq)]/D[Fe2+]) in synthetic water during ozonation was 1.21, corresponding to its mass ratio of 1.04 mg O3(aq)/mg Fe2+. The highest efficacy of ozone on ferrous removal was achieved at pH4.0, followed by that at pH6.0; the residual iron concentration at pH6.0 was 0.230±0.149 mg/L, falling below the WHO standard for drinking water. The residual ozone at pH 4.0 and 6.0 was not statistically different and may take 186 and 300 hrs. to achieve EPA and FDA regulations, respectively. The obtained results may provide a system and information of ozone conditions applied in the treatment of iron to meet the maximum standards of iron and ozone in water.