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Effluent diurnal SB,A profiles from three different simulated systems are shown in Figure 6. Systems with a biofilm compartment were impacted by the diurnal load to a greater extent than the suspended growth systems. This impact is an artefact of the total autotrophic nitrifying biomass in the aerobic zones, as shown in Figure 7. The simulated suspended growth process has the highest total mass of autotrophic nitrifiers, followed by the IFAS system, and the migrating Xcarrier system. The cause of the lower autotrophic nitrifier mass in the migrating Xcarrier system is a result of the increased competition between bacterial populations within the biofilm compartment. An examination of biofilm biomass in aerobic bioreactor zones of both the IFAS and migrating Xcarrier systems suggests a lesser autotrophic nitrifier concentration in the migrating Xcarrier system (autotrophic nitrifier concentration is 20% of the total biomass concentration in migrating Xcarrier system versus 30–40% in the IFAS system biofilm compartment). This is a result of the biofilm being exposed to readily biodegradable COD driven biochemical transformation processes under anoxic and aerobic conditions, which results in increased competition for space within the biofilm by ordinary heterotrophic organisms. Table 1 summarizes the average daily nutrient discharge concentrations for the systems simulated as Configuration D. Table 1 indicates improved nitrate-nitrogen concentration reduction in the migrating Xcarrier system, which may be a result of its higher ordinary heterotrophic organism concentration.
Table 1

Average daily effluent nutrient concentrations from simulated Configuration D

 ConventionalIFASMC
Ammonia, mg NH4-N/L 0.9 2.6 4.1 
Nitrate, mg NO3-N/L 10.9 14.2 13.3 
Phosphate, mg PO4-P/L 4.6 3.6 4.0 
 ConventionalIFASMC
Ammonia, mg NH4-N/L 0.9 2.6 4.1 
Nitrate, mg NO3-N/L 10.9 14.2 13.3 
Phosphate, mg PO4-P/L 4.6 3.6 4.0 
Figure 6

Diurnal profile of the bulk-liquid ammonia-nitrogen concentration for the suspended growth system , the IFAS system , and the migrating Xcarrier system .

Figure 6

Diurnal profile of the bulk-liquid ammonia-nitrogen concentration for the suspended growth system , the IFAS system , and the migrating Xcarrier system .

Figure 7

Comparison of simulated autotrophic nitrifier mass in the entire system (left) with that in the aerobic CFSTRs (right). IFAS – integrated fixed-film activated sludge; DO – dissolved oxygen; MC – mobile [biofilm] carrier.

Figure 7

Comparison of simulated autotrophic nitrifier mass in the entire system (left) with that in the aerobic CFSTRs (right). IFAS – integrated fixed-film activated sludge; DO – dissolved oxygen; MC – mobile [biofilm] carrier.

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