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Paller 1 S relatively constant. To minimize the influence of temporary im- balances between ammonia production and removal that result from feeding, biofilter performance (i.e., R) should be as- sessedwhen ammonia concentrations in the recycle system are at modal levels rather than at the peak levels that occur after feeding. 3. Ammonia removal is a constant percentage of the ammonia concentration, i.e., ammonia removal and the ammonia con- centration are linearly related with a y-intercept that is not sig- nificantly different from zero. These conditions will usually occur at <2.0 mg/1 total ammonia-nitrogen. Because ammo- nia removal is positively correlated with the ammonia concen- tration in the half-order range, maximum ammonia removal should occur at ammonia concentrations of approximately 2.0 mg/l. Therefore, the maximum value of C (total ammonia con- centration) in Equation 13 should not exceed 2.0 mg/I to avoid over-estimation of the carrying capacity. Values below 2.0 mg/I can be used if the predicted carrying capacity at lower ammonia concentrations is desired. 4. R is less than approximately 0.9. As R approaches 1.0, the accuracy of the model declines. S. Changes in hydraulic loading rate (F/X) do not appreciably affect the quantity or quality of bacterial biomass per unit vol- ume of biofilter medium or the transfer of dissolved materials between the water and the bacterial film. This assumption is reasonable over at least atwo-fold range of change in hydrau- lic loading rate in submerged biofilters employing biofilter beds that do not fluidize. 6. There is no (or very little) ammonia in the freshwater flush. 7. Populations of nitrifying bacteria in the biofilter are in equilib- riumwith the ammonia concentration. Measuring ammonia re- moval (R) shortly after ammonia concentrations have changed may result in erroneous results. 8. The biofilter is fully acclimated (i.e., nitrifies populations are well established).