Ponds often develop surface films often develop in warmer months. Environmental conditions promoting film formation include warm weather, low flows, and sunlight promoting algae blooms. While a slight film may cause no problems it can promote conditions for odor complaints (H2S & volatile organic acids) and be a precursor to an algae bloom. In this post I will cover what compromises the film and how it arises in the pond.
While algae is important for normal pond activity. Excessive nutrients and summer temperatures can lead to a cyanobacteria bloom. These "algae" are actually a photosynthetic bacteria. They tend to form a bright green, blue-green surface scum and increase suspended solids in the pond. Besides causing problems with effluent TSS, cyanobacteria produce chemicals that contribute to odors and off-flavors in ponds. If the bloom is substantial, cyanobacteria can also prove deadly to wildlife. In 2013, an elk herd in New Mexico drank from a pond with a cyanobacteria bloom and was found dead in the immediate vicinity.
The second source of film is less obvious from cursory visual clues. In a quiescent lagoon with anaerobic activity often forms a film containing fatty acids. Since the fatty acids are naturally hydrophobic, we get in effect a "soap scum" on the surface. This film layer prevents normal oxygen transfer which further increases the size of the anaerobic zone. As a result, the pond often produces H2S and other malodorous compounds.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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