Specialist Group on ANAEROBIC DIGESTION Newsletter - IWA

Bioaugmentation for recovery of anaerobic digesters subjected to a toxicant
by Anne E. Schauer-Giménez
Institution:
Marquette University, December 2008
New PhD Contact:
Post-doctoral Fellow
Marquette University
Water Quality Center
Milwaukee, WI (USA)
Supervisor:
Dr. Daniel H. Zitome
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 – H 2 :CO 2 , C2 –
H 2 :CO 2 + glucose, C3 – H 2 :CO 2 + air, and C4 – H 2 :CO 2 + 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.
IWA <strong>Specialist</strong> <strong>Group</strong> on Anaerobic Digestion
26 June 2009 Newsletter