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22 JOURNAL OF APPLIED AQUACULTURE <br />FIGURE 4. Relationship between predicted carrying capacity and flow rate in <br />biofilters of different sizes and with different ammonia removal (R) capacities. <br />200 <br />180 <br />1110 <br />rn <br />.,r <br />Y 146 <br />u 120 <br />A <br />~ 100 <br />v <br />tT ~ <br />C <br />>. ~ <br />V <br />~.. <br />~ 40 <br />U <br />20 <br />Flow rate (I/minute) <br />they result in high pumping costs without commensurate increases <br />in carrying capacity. The range of flows that will optimize perfor- <br />mance for any biofiltration system can be determined by using <br />Equation 13 to construct a curve relating carrying capacity to flow <br />rate. For example, the optimum flow range for the high ammonia <br />removal (R = 0.63) S-1 biofilter depicted in Figure 4 is in the S 1 to <br />10 I/minute range. The optimum flow range determined in tike <br />manner for a lower ammonia removal (R = 0.063} 2S-i biofilter <br />was in the 2 to 4 f/minute range. <br />Note that the previous approach does not account for the effects <br />of extremely high flow rates (and correspondingly high hydraulic <br />loading rates) on biofilm quantity and quality. Extremely high flow <br />rates would be expected to shear the biofilm from the surfaces of the <br />biofilter media, causing carrying capacity to decrease rather than to <br />reach an asymptote as predicted by the model. Similarly, extremely <br />low flow rates would reduce bacterial action by causing stagnation <br />and oxygen depletion resulting in greater reductions in performance <br />0 5 10 15 20 25 30 35 40 45 50 55 60 <br />