Investigation of the Impact of Sonication on organic matter solubilization and Biomethane potential (BMP) of swine lagoon sludge

Abstract

<b><sc>Abstract.</sc></b> Lagoon sludge is a major byproduct of swine production in North Carolina, it contains undigested feed, biomass generated due to anaerobic treatment, nutrients, minerals, and residual pharmaceuticals. Sludge removal, treatment and disposal is critical to farm operations since sludge accumulation can reduce lagoon performance. Dredged sludge has limited use on farm due to limited available land for application; additionally, low dry matter content in dredged sludge (3-6%) makes hauling uneconomical over longer distance. There is a need for simple, low-cost techniques that can reduce sludge organic matter content and volume. This study investigated sonication as a potential pre-treatment for sludge. The impact of sonication on organic matter solubilization and biomethane potential was studied. At specific sonication energy of 20,400 kJ/kg_TS, an increase in soluble COD and TKN was observed, from 7.7% and 28.6% in the untreated sludge to 30.4% and 43.8%, respectively. An increase in the dissolved carbon from 446 mg/L to 1,055 mg/L was also observed. In the biomethane potential study, an increase in cumulative biogas and bio-methane yield for sonicated sludge was observed from 21.0 mL biogas/g_VS and 15.0 mL CH₄/g_VS for raw sludge to 28.4 mL biogas/g _VS and 21.3 mL CH₄/g_VS were observed (42% increase in biomethane potential). The findings suggest sonication can be implemented as organic matter reduction tool, particularly when biogas recovery is implemented.