Speaker
Description
The term "resource recovery facility" has replaced traditional wastewater treatment plants, reflecting the contemporary emphasis on circular economies where the recovery and recycling of water, nutrients, and energy take precedence. Anaerobic digestion (AD) is commonly employed in these facilities to manage wastewater solids or sludges. This process relies on anaerobic microorganisms to convert organic substances in sewage sludges into methane and carbon dioxide, collectively known as biogas. The AD process offers several advantages, including the stabilization of organic matter in wastewater solids, the reduction of pathogens and odors, and a decrease in the overall quantity of solids/sludge by transforming a portion of the volatile solids fraction into biogas. Ideally, the products of anaerobic digestion should yield abundant biogas, stabilized solids, and nutrients like ammonia-nitrogen and phosphorus, which can be utilized in agricultural lands. The AD process comprises hydrolysis, acidogenesis, and methanogenesis, with hydrolysis considered the rate-limiting step dictating the duration of the process and methane production. The hypothesis is that electron beam (eBeam) technology, when used as a pre-treatment for sewage sludge, can eliminate microbial pathogens, reduce sludge viscosity (improving hydrolysis), enhance biogas production (by improving acidogenesis and methanogenesis), and improve overall process efficiency by reducing digester residence times. Demonstrating the effectiveness of eBeam in enhancing methane generation can replace the use of cobalt-60 for such applications. Laboratory studies, utilizing respirometers, were conducted on 10 kGy eBeam-treated primary sludge samples from a local wastewater treatment plant to test experimental hypotheses. Optimization studies revealed that a digester seed to sludge ratio of 1:6 produced the maximum amount of methane. Sludge viscosity was reduced by up to 70%, and that digester residence time can be reduced when eBeam is used to pre-treat the sludge. Preliminary experiments with eBeam pre-treated sludge yielded 92 mL methane/gm dry sludge compared to 60 mL of methane/gm dry sludge from the untreated sample. Comparison studies with cobalt-60 are planned. Preliminary economic analyses indicate that eBeam pre-treatment of sewage sludges will be significantly more cost-effective than cobalt-60 pre-treatment without any associated security risks.
