Recirculating swine waste through a silicone membrane in an aerobic chamber improves biogas quality and wastewater malodors.

摘要

During the course of experiments designed to lower emission of gases and malodors from swine waste stored in subfloor deep pits, we found that carbon dioxide concentrations in the waste slurry biogas were greatly lowered, resulting in greater relative concentrations of methane. In these experiments, swine waste slurry was circulated through silicone hosing located in an aeration tank, the hose allowing for the passage of small molecules such as methane and malodors. The aeration tank employed a minimal growth medium and chopped silicone to absorb potentially toxic compounds that might slow bacterial growth. Malodors were reduced in treatments. Methane and carbon dioxide were also reduced, especially in the case of carbon dioxide, where concentrations were reduced by almost 80%. The net result of this was methane comprising about 90% of the biogas, as compared to only 70% of the biogas produced by controls. This was due to more bicarbonate buffering in treated slurries, resulting in higher slurry pH. In experiments in which the silicone rubber was omitted from aeration tanks, malodors were still removed efficiently. While carbon dioxide in treated slurry biogas was again greatly reduced, methane concentrations were not. At the end of the experiment control biogas consisted of 75% methane, while in treated biogas methane comprised 95%. In control and treated slurries, Clostridia spp. and Bacteroides spp. comprised over 50% of the total population. Clone sequences from bacterial populations in the aeration tanks grouped with the Proteobacteria and Actinobacteria, two microbial groups with representatives often associated with biodegradation and bioremediation.