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This research aimed to study the ammonia removal kinetics of nitrifying biofilter after long term usability for 3 months and 6 months. The biofilter media was porous plastic BCN-012. The kinetics parameters i.e. maximum ammonia removal rate (Vmax) and the ammonium concentration at half of the maximum ammonia removal rate (Ks) were evaluated using Monod equation and could be applied for water treatment design and calculation. The biofilter was incubated in two of 100 L plastic tanks containing ammonia concentration as 5 mg-TAN/L. The first tank was using for 3 months and another tank was for 6 months. Thereafter, 0.5 L of biofilter samples were taken out for measuring ammonia removal rate in 2 L bioreactor under batch condition. The initial ammonia concentrations in the test reactors were 1, 2, 5, 10, 20, 30 and 45 mg-TAN/L with pH and alkalinity of 7.5-8.5 and 100-150 mg/L as CaCO3, respectively. Oxygen was provided by aeration through air stone. The results showed that biofilter acclimated for 3 months had higher ammonia removal rate of 85.62 mg TAN/m2/day and half saturation constant was 11.47 mg TAN/L while the 6 month acclimated biofilter had 65.08 mg TAN/m2/day with half saturation constant of 5.55 mg TAN/L.
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