Abstract
Lagoon sludge is a by-product of pig production in North Carolina. Sludge contains nutrients, minerals, and cellular biomass. Sustainable management of sludge is crucial to avoid accumulation impacts on lagoon performance. This study investigated sonication as a potential pre-treatment for sludge. The impact of sonication on sludge bio-methane potential and degradation kinetics was evaluated. At sonication energy dosage of 20,400 kJ.kg TS −1 , the dissolved total carbon (DOC) and soluble chemical oxygen demand (SCOD) increased from 446 to 1055 mg L −1 and from 2297 to 9239 mg O2 L −1 , respectively. In the bio-methane potential (BMP) study, cumulative biogas and bio-methane yield increased from 21.0 to 28.4 mL biogas .g VS −1 and from 15.0 to 21.3 mL CH4 .g VS −1 due to sonication. Sonicated sludge reached 95% of its experimental biomethane yield more than 10 days earlier compared to raw sludge. The first order kinetics equation showed the highest co-efficient of determination ( R 2 ) and least root mean square error ( RMSE) when fitted to raw sludge bio-methane production, while transference model was the best fit for sonicated sludge bio-methane production. The transference model substantially overestimated the maximum gas production rate for sonicated sludge. A significantly higher hydrolysis constant ( p -value < 0.05) was observed for sonicated sludge (0.6 day −1 ) in comparison to raw sludge (0.08 day −1 ). Findings suggest sonication is a promising tool to aid organic matter and nutrient fractionation, and energy recovery pathway but the high energy inputs are still a barrier. • Sludge sonication increased organic matter and nutrients in dissolved fraction. • Sonicated sludge degradation yielded higher bio-methane in shorter retention time. • First-order kinetics and transference model best explained sludge's degradation. • High energy input may challenge wider adoption of sonication treatment.
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