EAPSI:Depth Limitations of Biofilm Extraction From Groundwater Wells Using Sonication

Huynh Kimberly T, Chicago IL

Investigators

Abstract

Groundwater microbial communities are traditionally analyzed through extracting water samples from monitoring wells. It is well known that most of the microbial biomass in groundwater exists as surface-attached organisms (biofilm); however, this fraction is often underrepresented in groundwater analysis. Biofilm assessment can be improved through creating conditions to physically detach microorganisms from sediment surface. Sonication with low-frequency acoustic waves, for example, creates a pressure change in the sediment that loosens and detaches the biofilm. The efficacy of this treatment decreases with increased distance from the sonicator. Currently, pre-treatment efficacy at depths greater than 1 m below the water table is unknown. Through collaboration with Murray Close of the Institute of Environmental Science and Research (ESR), this research will examine the extraction quality of in-situ sonication at varying depths. This may shed light on the limits of in-situ sonication and improve microbial assessment in groundwater. Accurate assessment is important because microorganisms play key roles in nutrient cycles and contaminant degradation. Using established sites in Canterbury, New Zealand, groundwater samples will be retrieved from two monitoring wells before and after application of a low frequency sonicator. The sonicator will be used at increasing depths (e.g. 1 m, 4 m, and 7 m) below the water table for each trial and three sonication pulses at 1.6 kW at 50 minute intervals will be induced each time. The biomass of aquifer microorganisms will be determined for each sample using assays available at ESR. Biofilm extraction quality will be assessed by comparing this biomass against (1) the microbial biomass collected from established sediment cores in the wells (biofilm) and (2) the microbial biomass collected from the well before sonication (suspended microorganisms). This research is funded in collaboration with the Royal Society of New Zealand.