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When the BF is surrounded by a floating 2’-deep boom, a substantial change in flow patterns occur.

Horizontal-flowing water piles up at the surface/boom interface. This creates a top-to-bottom hydraulic driving force pushing the previously-horizontal-flowing water vertically down to the bottom.

The down-flowing water bounces off the bottom and returns via a substantially diagonal curvilinear path back to the BF inlet, creating an aerobic/anoxic circulation zone (surface zone).

The returning water induces an anaerobic counter flow (sub-surface zone). The sub-surface zone is doughnut shaped surrounding the BF.

The circumferential down-flowing water creates a circular waterfall which resists cross flow into the boom-enclosed area. Water within the boomed space is contained and recirculated.

When the boom is isolated by a side curtain (or a berm), water is backed up by the resistance from the waterfall, creating a continuous stirred tank reactor (CSTR). Influent enters the CSTR at the waterfall/bottom interface on the upstream side. Effluent leaves the CSTR at the waterfall/bottom interface on the downstream side. Effluent can be "aimed" by extending the boom's vertical length from surface-to-bottom for "X" degrees of the circumference and reducing that vertical length for (360°-"X") degrees. Effluent will then exit only under the floating segment of the boom. This effect is used to cause directed-circulation in lagoons.

The sub surface and surface zones mix microbes and food. The anaerobic population grows in the sub surface zone, tripling in count. The aerobic count is unchanged, possibly the count is already high or the count is controlled by oxygen availability. DO in the surface zone in the CSTR at equilibrium is 0.3mg/l. Thus two distinct mixing zones are created in one boomed volume.