The principal biological methods employed in wastewater treatment for sludge stabilization are aerobic and anaerobic digestion. The former utilizes aerobic bacteria to convert organic matter and stabilize biosolids while the latter accomplishes this goal with anaerobic bacteria working without oxygen. Both processes are monitored for level within their tanks.
The gas-injection and mechanical stirring systems of anaerobic process, and the aeration systems of aerobic process, create large amounts of foam that have traditionally hampered mechanical level controls. Recent developments in radar technologies have advanced measurement accuracy despite the foam content of these digesters.