BIO-SYSTEMS International

CH#1138 - Anaerobic Digesters


Courtesy of Courtesy of BIO-SYSTEMS International

Waste Type: Fats, oils and grease (FOG) in Anaerobic Digesters

Problem: FOG waste poses a challenge for most municipal wastewater collection systems and treatment plants. Although fats, oils and grease will biodegrade in an anaerobic digester, high concentrations will tend to 'mat' on the sludge surface, lowering digestion efficiency.

This Midwestern municipal facility was no different. The 1.5 mgd plant pumped FOG from the scum pits directly into the digester. Over the years, build up had accumulated in the digester, decreasing digestion efficiency and methane production while increasing the amount to be wasted.

Treatment: Our BIO-SYSTEMS wastewater specialist recommended BIO-SYSTEMS B120, a dry powder, to fight the FOG grease cap. They began feeding B120 microorganisms directly into the scum pits at a rate of 4 lbs per day for the first 10 days as an initial dosage. B120 was added at a rate of 1 lb. per day thereafter as maintenance.

Results: The B120 added to the scum pits acted to liquefy and degrade the FOG being pumped into the digester. In this state, further digestion of this material in the digester occurs at a much faster rate. The B120 also helped in reducing total volatile solids in the digester.

Upon annual internal inspection, the digester looks cleaner with less buildup. Use of the BIO-SYSTEMS product has been ongoing for several years. Although performance in an anaerobic digester is difficult to measure, the operator is confident our product is working, his digester is working more efficiently - producing less sludge and more methane.

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