ARS | Publication request: Remediation of swine slurry odor and methane using a partitioning bioreactor

Submitted to: Conference on Gastrointestinal Function
Publication Type: Abstract Only
Publication Acceptance Date: April 19, 2011
Publication Date: April 22, 2011
Citation: Cook, K.L., Loughrin, J.H., Lovanh, N.C. 2011. Remediation of swine slurry odor and methane using a partitioning bioreactor. Conference on Gastrointestinal Function. Abstract Only.

Technical Abstract: Large amounts of animal waste are generated in confined animal feeding operations that can potentially pollute air as well as ground and surface waters. Usually these wastes are treated in large earthen lagoons as a means of effecting reductions in wastewater strength before application to fields as fertilizer. More promising technologies developed to remediate volatile and semi-volatile organics from water include two phase partitioning bioreactors and permeable membranes. Here we describe a hybrid bioreactor that removes small molecules by re-circulating slurry though a permeable silicone membrane located in an aerobic tank that also contains a silicone sink that acts as a buffer for potentially toxic molecules. Mal-odorants and methane diffuse through the silicone and are degraded by microbial populations which utilize these molecules as their sole carbon source. In the anaerobic treatment tanks (TT) receiving re-circulated waste, 14.5, 0.8, 0.15 and 0.7 mg l-1 d-1 of p-cresol, p-ethylphenol, indole, and skatole, respectively were removed. On the other hand, an average of 2.8 mg l-1 d-1 more phenol was produced in these tanks than in the control tank (CT). Although the relative reduction in VFA concentrations were not as great as was the case for the aromatic malodors, acetate, propionate, 2-methylpropanoate, butyrate, and 3-methylbutyric removal rates were 1.46, 0.9, 0.8, 0.2 g l-1 d-1 and 0.01 g l-1 d-1, respectively. Microbial community composition was also effected by treatment; while both the CT and TT were dominated by common swine slurry species (Bacteroides sp. and Clostridia sp.) sequenced clones from the TT included more diverse species including Ochrobactrum sp., streptococci and iron-reducing bacteria. The system also raises slurry pH (8.0 in TT) and bicarbonate buffering (average 2,850 mg L-1 and 3,470 mg L-1 and 7,340 mg L-1 and 8,860 mg L-1 in TT), thereby lowering carbon dioxide concentrations in the slurry tank’s biogas. Therefore, even though methane production is similar in both tanks, as are concentrations of methanogenic organisms (1.25 to 2.75 X 108 cells ml-1 slurry), biogas quality in the slurry tanks is enhanced due to a favorable shift in the carbon dioxide/bicarbonate equilibrium.