Foaming Issues and Surface Tension Impact on Wastewater Systems

by Hydro Solutions | July 20, 2016 2:44 pm


Surface Tension is an important component of anaerobic digesters and can be used for maintenance of biosolids in anaerobic processes. Anaerobic wastewater surface tensions can run from 30 dynes/cm up to 70 dynes/cm (tap water is around 72 dynes/cm). Surfactants, volatile fatty acids, alkalinity, oil and greases, and salt are known to impact surface tension of wastewater. Foam formation is generally the first sign of surface tension changes, indicating the presence of surfactants, significant changes in alkalinity, and/or high volatile fatty acid concentrations.
Surfactants are compounds that lower the surface tension of liquids by altering the surface properties of liquids and can also cause inhibition of the biological population within wastewater systems. High volatile fatty acids, oils, and detergents and increases in alkalinity act similarly as surfactants and can decrease surface tension. These can lead to carbon dioxide and methane (released during fermentation of organic wastes) to become entrapped in the sludge, leading to poor sludge settleability and foam production. However, high salt concentrations can increase the surface tension of anaerobic digesters also leading to entrainment of air within the solids/flocs of anaerobic systems.
Surface Tension values between 40-55 dyn/cm for a high rate anaerobic digester are known to promote the growth of anaerobic granules as long as there is enough easily degradable food available for the biomass. Operation of anaerobic reactors with a low reactor surface tension can reduce biomass washout and increase granular yield. Granule Maid™ can decrease the wastewater surface tension and improve granular biomass yield by influencing the surface thermodynamics of the anaerobic microorganisms. See the blog titled “INSUFFICIENT GRANULE PRODUCTION AND LOSS OF ANAEROBIC GRANULES IN A HIGH RATE ANAEROBIC TREATMENT SYSTEM: GRANULE MAID” for more information on this product.
Here at Hydro Solutions, Inc., we measure the surface tension of wastewater using Attension’s Theta Lite Tensiometer via the Pendant Drop Method using Young-Laplace analysis and reported as dynes/cm.
For more information on Granule Maid contact us at 502-899-7107.

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