Sludge management in lagoons: The role of denitrification as a function of carbon biodegradation

Sludge from the bottom of an anaerobic lagoon storage system contains nutrient residues, as well as inorganic and organic matter. These wastes have polluting impacts on swine farms, and beyond the management alternatives, few studies apply economic and sustainable biological methods to reduce their effects. In this study, denitrification was proposed as an alternative sludge treatment for settling tanks (ST), biodigesters, and stabilized lagoons. The sludge sources had different deposition times and bioavailable carbon concentrations. Accordingly, the effects of agitation and carbon and nitrate concentrations were evaluated. The best removal feasibility was presented with the ST sludge, corresponding to 25% (v v−1) of the background volume, achieving higher total organic carbon (1342 mg L−1 day−1) and nitrate (279 mg L−1 day−1) removal. Furthermore, sludge management by denitrification was affected by carbon bioavailability and proven to be cost-effective, with 125 days required for processing.