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OXIDATION AND DISINFECTION 10.7

nPla ~ ..... Ptan

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Section Section
Rectangular Contact Basin Circular Contact Basin
] Po{entialdead zone
FIGURE 10.3 Examples of average baffling conditions in basins. (Source: Guidance Manual.)

The detention time and contact time in reservoirs will also vary with the water level,
the depth of sludge, and whether the water level is rising or falling, so these factors must
be included in the CT calculations.
Contact Time through Filters. Filters usually have good flow distribution, so they
can be considered as having conditions similar to superior baffling. The T~ 0 for filters can
therefore be calculated by subtracting the volume of filter media, gravel, and underdrains

Plan Plan

Section
Section
Circular Contact Basin
] Potential dead zone Rectangular Contact Basin
FIGURE 10.4 Examples of superior baffling conditions in basins. (Source: Guidance Manual.)