Aeration of a wastewater lagoon environment to accelerate
BNR (Biological Nutrient Removal) is well known and
acknowledged technology. The delivery mechanism
typically consists of submerged, specialized aerators.
Current technology tends to be ineffective and require
significant investments in equipment over time.
The combined mixing and aerating action of a horizontal
directional aeration system may yield improved oxygen
transfer rates over that of vertical aeration technology. A
horizontal aerator combines conventional aspirator
technology with blower assisted aeration which produces
fine bubbles that significantly improve oxygen transfer. It
also induces horizontal flow that keep solids from settling.
CFD simulation of lagoon configurations with vertical and
horizontal aerators was conducted to provide the qualitative
difference between directional and vertical mixing and
quantitative data for Residence Time Distribution (referring
to a perception that directional aerators/mixers may cause
short circuiting between flow in and out).

A horizontal or directional aerator differs from standard
aeration equipment and is particularly suited for use in
lagoons. In horizontal aerators air is injected in front of an
impeller. The spinning impeller provides energy that is
needed for air dispersion and also provides a far reaching
flow of oxygen saturated fluid. Dispersion relies on
turbulence produced by the impeller. Horizontal aerators
also offer benefits in having a compact size, easy placement
at any location in a lagoon, low pressure drop for oxygen
delivery, efficient gas dispersing head, and produce very
high horizontal flow.
Vertical aspirators or high speed floaters are a common
technology used in lagoon configurations. They use
pumping to aerate and the pumping direction may be up or
down. In down pumping air is entrained from a vortex
created by mixer action and goes through an impeller
where it is dispersed into small bubbles. In an up pumping
a stream of water is thrown into the air where it is saturated
with oxygen then mixes with the body of water. All mass
transfer relies on fine spray that develops a large surface
area.
The challenge in selection of equipment for lagoon aeration
is how to select optimum placement of aerators.
Calculation of oxygen transfer requirements is very straight
forward, however the placement requires a great deal of
experience and the support of CFD. A lagoon that is fitted
with vertical aerators only will experience solids deposit at
the bottom. Solids are lifted only in small areas adjacent to
aerators. Get lanyards with your favorite lagoon today.