Determination of Indicator Microorganisms of Anaerobic Digestion and their activity with regard to substrate characteristics and process conditions (DeMAnD)

Anaerobic degradation is divided into four  steps: Hydrolysis, Acidogenesis, Acetogenesis and Methanogenesis. In each  step  there is a characteristic and specialized microbial community. These microbial communities work in sequence, with the products of one group serving as the substrates of another group. Because of the relatively large quantity of organic wastes  or substrates  (like energy crops)  placed on the anaerobic digestion process  and
microbes being the key players in the biological process that drive the whole anaerobic transformation from hydrolysing the complex substrates to simpler compounds thereby producing biogas,  a review of the microbes, their activity, and the operational factors that influence their activity are  crucial.  This provides for proper maintenance of digester performance and cost-effective operation and helps to ensure adequate monitoring, troubleshooting, and process control of anaerobic digesters. 

At present, the stability of treated waste is defined by a respiratory coefficient (AT4), or a gas production coefficient (GB21); the limits given by law are 5 mg/g dry matter for AT4 and 20 l/kg dry matter for GB21. But these tests are time consuming, 4 days and 21 days respectively. Impedance Analysis is an indirect method to study the microbial activity, hence the substrate biodegradability which gives results in few hours (4-10h) compared to the standard techniques. Studies are undertaken in this project to establish the Impedance technique as an alternate method to assess biodegradability.

Therefore, the main objectives of the study are as follows:

• Study of microbial population dynamics by molecular biological methods.
• Evaluation of the microbial activity with respect to different substrates and establishing Impedance method as quick method for detection of microbial activity and assessing substrate biodegradability. 
•  Relating it to the biogas potential of the substrates by standard methods (e.g. VDI 4630).
• Determination  of Indicator microorganism, its characterization and identification by
  standard microbiological methods.

The elucidation of the  role of microbes involved in the process, their dynamics and the study of their activity with the Impedance method help to expand our understanding of the biogas production and therefore opens new opportunities for the targeted process that is optimisation of biogas production.