Winter Grease Cotrol

by Aquafix Laboratories Director of Wastewater Education,
Dan McKeaton.

As cold temperatures close in, we get more and more samples coming in requesting treatment for M. parvicella foaming. But why does this filament seem to thrive in the winter?Microthrix parvicella is a relatively easy to identify filament, normally associated with foaming. It is distinctive due to its “spaghetti-like” structure, strong Gram-positive stain, and Neisser-positive granules. More information on this filament can be found in our microorganism database. This filament is known specifically to grow in cold temperatures when high levels of fats, oils, and greases are present.

So why cold temperatures? There are a number of potential reasons why this filament would be more likely to thrive inthecold. The degradation of fats is not easily performed by aerobic organisms,in any conditions,and the cold makes this processevenless efficient.

The keys to successful fats, oils, and grease degradation are:

  1. Disintegration and hydrolysis
  2. B-Oxidation of LCFAs to SCFAs
  3. Uptake of SCFAs by heterotrophic bacteria

While all metabolic processes are slowed in colder temperatures, disintegration and hydrolysis are particularly limited in fats, oils, and greases.Fats in cold temperatures harden and therefore are not making direct contact with floc-forming bacteria. Instead, filaments that float like, M. parvicella, with low-density cell walls, have an easier time making contact with fats than other cells.
M.parvicella is able to store LCFAs very efficiently within its cell structures and converts a lot of these fatty acid chains into low-density cell structures. This promotes the floatation of the filaments and requires fewer steps to degrade the fats compared to healthy activated sludge bacteria.

In addition, hydrolysis tends to occur a lot more slowly as greases will be less permeable to exo-enzymes produced by bacteria, and enzyme function will be slowed substantially due to cold conditions. This allows the grease in the system to remain for longer periods of time which provides more time for filamentous growth. Generally, filaments thrive more in slower growth rate conditions because the complexity of filamentous structures causes them to require more time for reproduction. When slower overall growth takes place, filaments have less of a disadvantage compared to other bacteria. Essentially, it isn’t that this filament grows faster in the cold, it is just less hindered than competing organisms. When considering the additional advantage M. parvicella has in conditions with fats, oils, and grease present combined with these other factors, it is no wonder M. parvicella causes so many headaches in winter wastewater systems.
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