Ordering Information:
ORDER NUMBER:  2996
DATE AVAILABLE: Winter 2007/2008

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PRINCIPAL INVESTIGATORS:
Daniel Hoefel, Gayle Newcombe, Paul Monis, Alexandra Keegan, and Christopher Saint

OBJECTIVES:
The objectives of this project were to (1) assess the biological removal of methyl isoborneol (MIB) and geosmin through sand filter column experiments; (2) detach the biofilm from sand filter columns and subsequently enrich for the degraders; (3) isolate bacteria capable of degrading MIB and geosmin; (4) use molecular techniques to elucidate the genes involved in the degradation of the taste and odor compounds; and (5) assess the feasibility for the development of whole cell biosensors for the analysis of MIB and geosmin.

BACKGROUND:
Taste and odor compounds in water are a frequent cause of customer complaints. There is a need for reliable, low cost methods to detect and remove these problematic compounds. Biological filtration is a possible treatment option but has not been fully explored for MIB and geosmin. Characterization of the organisms responsible for biological removal will improve understanding of biological filtration and may lead to the development of either gene-based or enzyme-based biosensors for these compounds.

HIGHLIGHTS:

1. Sand from filter beds degraded both MIB and geosmin from source waters.
2. The cam gene, responsible for camphor degradation, does not appear to degrade MIB.
3. The genes responsible for cyclohexanol degradation do not appear to be involved ion geosmin degradation.
4. Bacteria reported by others to degrade either MIB or geosmin were unable to degrade these compounds in this study.
5. Geosmin degrading bacteria were isolated from sand filter biofilms.
6. Degradation of geosmin only occurred in the presence of a consortium of bacteria.
7. No MIB degrading bacteria were isolated from the sand filter columns.

APPROACH:
Laboratory-scale sand filter experiments, using sand from the filter of a water treatment plant, were conducted to determine if MIB and geosmin were being removed. Biofilm was removed from the sand and degraders were enriched using culture techniques. Biodegradation experiments monitoring bacterial community composition analysis were used to identify bacteria associated with the degradation of geosmin. Biodegradation experiments were conducted to confirm the ability of putative degraders to remove geosmin. Due to the requirement of a consortium of bacteria to degrade geosmin, differential display experiments were conducted in an attempt to identify gene expression associated with geosmin degradation.

RESULTS/FINDINGS:
Bacteria from biologically active sand filters were shown to degrade MIB and geosmin at ng l ^-1 to mg l ^-1 concentrations in the absence of the solid support. Bacteria reported by other researchers to degrade MIB and geosmin were not found to do so in this study. Bacteria capable of degrading camphor could not degrade MIB, suggesting that different enzymes are involved in camphor and MIB degradation. Bacteria capable of degrading geosmin did not possess the genes involving cyclohexanol degradation, suggesting different degradation processes for these two compounds. Methods were developed within the laboratory for the enrichment of the degrading bacteria, which led to the discovery that Gram-negative bacteria may work as a consortium for the degradation of geosmin. Two different consortia that degrade geosmin, one comprising three species, the other comprising two species, were isolated. Although the original biofilm bacteria were capable of degrading MIB, attempts to isolate or enrich for the bacteria responsible for MIB degradation were not successful. Differential-display methods have been optimized for the identification of genes responsible for the degradation of the taste and odor compounds.

IMPACT:
This study has made significant advancements towards the understanding of biological filtration of MIB and geosmin. Isolation of degraders allows for the possibe seeding of WTP sand filters with these bacteria to enhance the biological degradation of geosmin.This project represents an important step towards the elucidation of the genes involved in the degradation of MIB and geosmin, which in turn provides a significant advancement towards the development of biosensors for the analysis of MIB and geosmin.

PARTICIPANTS:

• CRC for Water Quality and Treatment
• Australian Water Quality Centre
• South Australian Water Corporation
• United Water International