Question

Describe the microbiology of methanogenesis and then outline how it is employed during anaerobic digestion for the treatment of sewage sludge.

Answer 1

Answer: - Methanogenesis is the biological formation of methane by microbes known as methanogens. Methanogens represent the euryarchaeota order of archaebacteria which gains energy via methane production. Methanogens gain energy by converting carbon dioxide and other bacterial waste products into methane. Methanogenesis in microbes is a form of anaerobic respiration and the terminal electron acceptor is not oxygen, but carbon. Following are the two best-described pathways of methanogenesis.

CO₂ + 4 H₂ ? CH₄ + 2 H₂O

CH₃COOH ? CH₄ + CO₂

In methanogenesis, organic matter is decomposed anaerobically into carbon dioxide, formate, and acetate and reduced to methane. This process is very important as if these organic compounds are not degraded they will accumulate in nature and pollute water sources and lead to environmental degradation.

Methanogenesis is now being exploited in sewage sludge treatment as it is a very cost-effective and efficient way to naturally degrade organic waste. Also, the methane produced in these wastewater treatment plants can be harvested and used as energy sources. As methanogens are very diverse in nature this process can be exploited in many different environments and with various types of wastewater.

Wastewater treatment plants systems utilize a series of anaerobic reactors in order to break down the organic pollutants and allow methanogenesis to occur. Example of the most common anaerobic reactor is closed digester tanks (CDT) and continuously stirred tank reactor (CSTR), another example includes Upflow Anaerobic Sludge Blanket (UASB) Reactor.