Bioaugmentation for recovery of anaerobic digesters subjected to a toxicant
Abstract
Traditionally, practitioners have considered anaerobic methanogenic cultures as "black boxes" and have not paid considerable attention to the microorganisms. However, the methanogenic community is important because different populations may behave differently in terms of methane production rate or stability during process upset. The research presented in this dissertation explored the diversity of Bacteria and Archaea communities in various methanogenic enrichment cultures. With the help of molecular techniques (PCR, cloning, restriction digests, and sequencing), Bacteria and Archaea clone libraries were constructed for four enrichment cultures herein referred to as C1, C2, C3, C4. The enrichment conditions differed based upon substrates and oxygen fed, and were as follows: C1-H2 :CO2 , C2-H2 :CO2 + glucose, C3-H2 /:CO 2 + air, and C4-H2 :CO2 + glucose and air. It was hypothesized that the varied conditions would have an effect on microbial community diversity. When comparing the enrichment cultures that received air versus those that did not, a shift in methanogen community occurred. In C1 and C2, Methanosaeta was the most dominant genus. On the other hand, Methanosaeta was not dominant in C4 and not found in any sequences in C3. Methanospirillum was the most common methanogen genus in C3. These results indicate that addition of air had an effect on the methanogen community. Bioaugmentation, the addition of a specific microorganism or mixed culture to enhance a desired activity (e.g. methane production or COD reduction), can potentially be used to increase the recovery rate of anaerobic wastewater treatment facilities after exposure to toxicants. In the work describe herein, cultures C2 and C4 were used to bioaugment upset anaerobic digesters. The bioaugmentation investigations successfully demonstrated the ability of the bioaugmentation culture to increase methane production and recovery rate of a stressed digester exposed to the toxicant, oxygen. Methane production increased an average of 47% in the bioaugmentation digesters as compared to the controls, which were not bioaugmented. Also, SCOD concentrations in the bioaugmented digesters decreased below 2,000 mg/L 83 days sooner than the controls. Bioaugmentation is a promising approach to help decrease the recovery time of anaerobic digesters exposed to a toxicant.
This paper has been withdrawn.