FIG. 7.13.4 Completely mixed, combined-flow system.




Alternating Flow Diversion. The alternating-flow diversion system (see Figure 7.13.2) collects the total flow of an effluent for a time period (normally 24 hrs) while a second basin is discharging. The basins alternate between filling and discharging for successive time periods. Thorough mixing is maintained so that the discharge maintains constant pollutant levels with a constant flow. This system provides a high degree of equalization for a basin size by leveling all discharge parameters. A disadvantage of this system is the high construction cost associated with storing the waste stream volume for the time period used.

Intermittent Flow Diversion. The intermittent-flow diversion system (see Figure 7.13.3) diverts significant variance in stream parameters to an equalization basin for short durations. The diverted flow is then bled into the stream at a controlled rate. The rate at which the diverted flow is fed back to the main stream depends on the volume and variance of the diverted water, reducing downstream effects.

Completely Mixed, Combined Flow. The completely mixed, combined-flow system (see Figure 7.13.4) completely mixes multiple flows combined at the front end of the facility. This system reduces the variance in each stream by thoroughly mixing with the other flows. This system assumes that the flows are compatible and can be combined without creating additional problems.

Completely Mixed, Fixed Flow. The completely mixed, fixed-flow system (see Figure 7.13.5) is a large, completely mixed, holding basin located before the wastewater facility that levels variations of the influent stream parameters and provides a constant discharge.

Each of these systems requires different design criteria. Therefore, the first step in the selection process is to de-

FIG. 7.13.5 Completely mixed, fixed-flow system.

FIG. 7.13.5 Completely mixed, fixed-flow system.

fine the type of variability the system must equalize. Then, the facility can be designed with appropriate criteria.

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