3.2. Ammonia oxidation
Spiked ammonia was quickly removed in all five moving bed biofilters (Fig. 2) approaching 0 mg/l at all loadings within the 6 h of sampling. The degradation was constant (substrate independent) at ammonia concentrations above 2 mg TAN/l in the bulk water. Below 1 mg TAN/l degradation rates declined exponentially with concentrations (Fig. 2). The kinetic rate constants k0a and k1a describing zero and first order degradation, respectively, are shown in Table 2. During degradation of ammonia a minor temporary peak in bulk water nitrite concentration was measured (data not shown) and nitrate concentrations increased consistently with ammonia degradation
(Fig. 2).