How to Supplement Oxygen in an Existing Wastewater Treatment Plant

Wastewater treatment plants are massive facilities that require years to design and construct. During the design process engineers need to take into consideration many factors, such as the wastewater daily flow, life cycle of the plant, energy costs, and land availability. One of the key factors is what will be the influent flow per day in the future, twenty years from now, due to population growth.

At the beginning of the life of a new wastewater treatment plant, the flows are relatively low. However, the plant should be able to operate well also with higher flows that will occur later on. How should designers cope with expected increased flows? Should they design the wastewater treatment plant to operate from day one based on future predicted flows?

Let us look at an aeration basin to examine this problem. Fine Bubble diffusers are the most efficient way to biologically treat wastewater. The diffusers deliver oxygen to the microorganisms in the aerobic phase. Delivering sufficient oxygen to the microorganisms is a crucial element in the success of the treatment process, but it also requires the use of large air blowers resulting in high power consumption.

To solve this problem, wastewater engineers will design a full-scale reactor with fixed-to-the- floor diffusers that will initially operate at a low air flow rate per diffuser, and once the influent flow increases, the amount of air per diffuser will be increased. However, this may cause a decrease in the aeration efficiency as the increase in the pressure causes the bubbles to be larger and move more quickly. On the other hand, placing the number of diffusers that would enable the plant to operate at 100% air capacity, based on a future scenario, is of course an enormous waste of energy.

Mapal Aeration Solutions offers various solutions to this problem.

Mapal has designed fully retrievable modular grid units that can be placed in the reactor with small gaps between them. They are spaced close enough that there are no dead zones, and there is no harm to the mixing. Once the influent rises, with the use of a mobile crane, the units can be placed closer together, cancelling the gaps between them. This procedure does not require draining the wastewater, for workers to enter the wastewater, or stopping the reactor. Placing the aeration units closer to each other will create enough space for an additional unit to be placed in the wastewater, thereby, increasing the oxygen in the reactor.

An additional option with Mapal’s Fine Bubble grid aeration units is to space the diffusers on the grid in such a way that additional diffusers can be added in between the existing diffusers at a later stage. Once the influent flow rises, the units can be removed from the wastewater with a mobile crane, additional diffusers can be assembled onto the unit, and then the unit can be returned to the wastewater. In this way, the air input can be doubled. This procedure is very easy and requires about one hour per grid unit.

A third option is for Mapal’s floating aeration units to float above existing Fine Bubble diffusers, or operate alongside surface aerators.

Supplementing oxygen with Mapal in any reactor with any type of existing aerators is an easy task and can be done in a matter of days.