| The effect of pH and temperature on the controlling of nitrification was evaluated using rotating annular bioreactors (RABs), which were applied to simulate the drinking water distribution system. The results showed that elevated pH had little effect on nitrification occurrence at low temperature (15℃), however the pH controlling effect on nitrification was obvious at high temperature (30℃). With pH increasing from 7.5±0.22 to 9.3±0.24 at high temperature (30℃), the residual chloramines concentration increased to 0.76 mg/L, and the AOB concentration in the biofilm and bulk water reduced 0.6 lg MPN/cm2 and 1.4 lg MPN/mL respectively, the heterotrophic bacteria concentration in bulk water reduced 98 CFU/mL. With pH increasing from 7.4±0.15 to 9.3±0.26, compared with the influent nitrite concentration, the effluent nitrite concentration increased four and three times respectively at different pH levels. The effluent residual chloramines, nitrite nitrogen, ammonia nitrogen concentrations varied slightly compared with influent at low temperature (15℃), and the effluent heterotrophic bacteria concentration was also stable. |
