Microbial degradation of chemicals used in coal seam gas activities

This project established microbial and chemical baselines in aquifer waters, surface waters and soil samples in sites in and around the Narrabri Gas Project area, and assessed the capacity of these microbial communities to degrade a range of ‘higher hazard’ chemicals likely to be used in coal seam gas activities.

This study has provided the most comprehensive baseline dataset on soil and surface water microbiology in the region and extends existing groundwater data south and east of Narrabri. It also provides the first insights into the fungal diversity in non-vertosolic/non-cropping soils and surface waters.

Over 50 sites were studied, including 14 groundwater, 16 surface water and 32 soil locations, with most samples collected in November 2022 and June 2023.

For its investigation into chemical degradation, this project focused on chemicals of ‘higher hazard potential’ with regard to their hazards to human or environmental health. Surfactants and biocides were prioritised due to their known activity against cell membranes and living organisms.

The chemicals studied were:

• alcohol ethoxylates mixtures (surfactant; used as detergents, cleaning agents, emulsifiers and wetting agents in industrial processes)
• hydrocarbon mixtures (surfactant; used in well workovers)
• monoethanolamine (surfactant; used in personal care products and detergents, textile and pharmaceutical applications, and in gas treatment processes to remove acidic gases such as carbon dioxide and hydrogen sulphide)  
• Dazomet (biocide; used as a soil fumigant in horticulture, golf courses, garden nurseries and turf businesses).
• Glutaraldehyde (biocide; mostly used in hospitals and other medical settings to sterilize surgical instruments).
• 3’3’-methylenebis(5-methyloxazolidine) (biocide; used to preserve water-based paints and cooling lubricants, and as a hydrogen sulphide ‘scavenger’ in oil and gas processing).

Using soil and water samples collected from the Narrabri region, the chemicals were incubated in soil microcosms for four weeks and in surface water and groundwater microcosms for three months.

Results demonstrate that most chemicals tested degraded completely in groundwaters, surface waters and soils of the region. As previously observed in other studies, faster degradation occurred in soils than in groundwaters, though significant amounts of the alcohol ethoxylates mixtures persisted in the groundwaters and trace amounts of these same compounds persisted in soils.

Finally, this study identified numerous microorganisms in groundwaters, surface waters and soils that are likely capable of degrading chemicals in the environment; and conversely a number of taxa were identified that were sensitive to chemical additions in these environments. Such taxa may be useful targets for environmental monitoring programs.