Co-Digestion of Sewage sludge and Fat, Oil, and Grease with BioAmp Pretreatment Under Mesophilic Conditions

This study investigated the potential benefit of co-digesting sewage sludge (SS) and settled/mixed fat, oil, and grease (FOG) with BioAmp pretreatment, a bio-additive product, for a utility. BioAmp was found to increase the soluble chemical oxygen demand (SCOD)/COD ratio of FOG (from 4.19 to 4.49), consequently enhancing volatile solid (VS) reduction (from 75.9 to 84.8%). The ratio of SS and FOG for co-digestion was based on their actual daily production volume, resulting in FOG content ranging between 15 and 20% VS for co-digestion assays. Co-digestion of SS and mixed FOG waste after BioAmp pretreatment produced the highest cumulative methane yield (CMY) of 400 mL/g VSadded, which is 98% higher than that of mono-digestion of SS (202 mL/g VSadded). Kinetic analysis demonstrated a synergistic effect in co-digestion of FOG and SS with both increased CMY and degradation rate constant. For the utility, co-digestion can increase methane yield by 141%; however, 7.77% more biosolids are produced and 6% more total nitrogen will return to mainstream, a potential burden to nutrient management. Overall, the results of batch test demonstrated the benefits of co-digestion of SS and FOG with BioAmp pretreatment in terms of increased CMY, degradation rate constant, and VS reduction. The analysis of the utility showed that co-digestion can produce more biogas but also increase more biosolids and total nitrogen return.

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s13399-021-01418-9