Using a pulsed electric field as a pretreatment for improved biosolids digestion and methanogenesis

Researchers tested using pulsed electric field (PEF) technology to enhance conversion of organic solids material in waste activated sludge (WAS) and pig manure to soluble and colloidal forms, which are more bioavailable for methane production during subsequent anaerobic digestion. Operating parameters were varied from 1.1 to 19.8 kWhr/m³ to show the influence amount of treatment has on soluble chemical oxygen demand (SCOD), small colloidal solids, and methane production via the biochemical methane potential test. When PEF treatment exceeded a threshold, which was approximately 10 kWhr/m3, focused pulsed treatment solubilized approximately 10% of the total COD, increasing SCOD from as low as 20 mg/L to more than 1000 mg/L. The process also disrupted a larger portion of the volatile suspended solids (VSS) to form small colloids not measured by the VSS assay (between 0.2 and 1.2 μm). The effects increased the biological methane potential of the samples significantly: by 80% for pig manure and 100% for WAS after 25 to 30 days. These results support the conclusion that PEF pretreatment before anaerobic digestion has the potential to significantly improve digester performance, resulting in added methane production and decreased residual biosolids.