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Biogas Plants: The importance of using foaming control agents in the biological process

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Dimitris Theodoridis, Technical Director OMEX Environmental, explains the importance of using foaming control agents in biological processes and the benefits to biogas plant operations.


Foaming is a common issue that can arise from a range of causes in a biological environment. It is an occurrence associated with both the anaerobic and aerated biological treatment of wastes and wastewaters. Foaming events can have multiple operational and financial impacts to biological processes depending on the type and duration of the event and hence should be kept under monitor and control when they appear.

Foaming can occur during the start up of an aerated biological process due to the young age of the sludge and the balance between dominant cultures in the biomass. It can also form during the denitrification process when nitrogen gas is captured within masses of solids in aerated basins and clarifiers or in poorly aerated processes. Abnormal growth of aerated species can also cause foaming, especially when filamentous bacteria become the dominant process species. Operational plant parameters like variations in pH, dissolved oxygen levels and temperature can cause biological foaming.

In anaerobic digestion foaming can occur due to various causes related to the use of inadequate substrates, increases in grain-rich feedstocks or suboptimal operating conditions. Most commonly foaming in biogas plants has been observed when protein-rich feedstocks, improperly ensilaged feedstock carrying mycotoxins, filamentous bacteria carry over from aerated processes or sludges are in use. From an operational perspective, organic overloading of an anaerobic digestion plant, heavy mixing, insufficient digestate recirculation or heating can also lead to excessive foaming.

OMEX Environmental can supply a range of products to address these types of foaming events for both aerated and anaerobic biological processes. These products are aimed at minimizing the effect of an active event and, for processes with the tendency for frequent foaming, these products can offer stable and effective mitigation measures against the reappearance of foaming in the process.

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