Abstract
Ammonia oxidation activities were compared across 5 kinds of plastic filter media and one type of earthenware ball filter medium in submerged biological filters.
With the progress of ammonia oxidation, the pH and alkalinity of the recirculating seawater decreased. Ammonia oxidation was inhibited when the pH and alkalinity reached 6.0 and 0.5 meq./l, respectively. A significant linear relationship was observed between the amount of biologically oxidized ammonia and the decrease in alkalinity. Among well-conditioned biological filters with 6 types of filter media, the filters with a net or fibriform filter media showed higher ammonia oxidation. There was no significant linear relationship between the ammonia oxidation rate in the filter and the surface area of the filter medium. Daily loading of an organic substance for 92 days reduced the ammonia oxidation rates in the filters by 28 to 52%. The maximum ammonia oxidation rate (0.55g-N/m2/day) after loading the organic substance was obtained in the filter with a net filter medium.
