Lift-stations often have problems with grease buildup which causes problems with equipment, corrosion and odors. The "grease" is actually a mix of long chain fatty acids which result from initial decomposition of fats & oils in the collection system. Bacterial lipase splits the glycerol from the fat as an easy source of energy. This biochemical step results in three long chain fatty acids. While anaerobic decomposition occurs, the fastest way to degrade insoluble fatty acids is via aerobic beta-oxidation pathways.
Control of the FOG in lift-stations is often done using a combination of physical and chemical approaches. Water jets and vacuum trucks can loosen and collect grease deposits. Often surfactants/solvents are added to liquefy the grease for easier removal. Solvents, even natural ones such as d-limonene, emulsify grease and allow any FOG not removed by vacuum truck to pass down to the treatment plant.
Since the 1990s, many municipalities have used microbial blends for grease control in lift-stations. The microbial products are found in liquid, solid block, or dry powder form. Here is a quick run-down on what they contain:
Over the past several years, we have been evaluating ways to improve biological activity in the lift-station. We looked at using various blowers and mixers to determine:
With over a year of testing, we have noted the best approach is to combine the aeration/mixing with the microbes. The aeration/mixer can be in almost any form. The key is to mix and increase the bacteria/oil/water interface - with mixing we have enough oxygen for beta oxidation pathways. With treatment, grease does not build up into a solid cap. Any grease that accumulates is easily washed off with water spray. FOG to the treatment plant does not increase as seen with using surfactant/solvent treatments - as the fatty acids are being converted from FOG into soluble organics (BOD5) which is not a problem for most treatment plants.
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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