Desalination Technology Waste Streams: Impact of pH and Brine on Bacterial Metabolism Among Natural Marine Assemblages
2008
Montgomery, M. T. | Boyd, T. J. | Osburn, C. L. | Plummer, R. E. | Coffin, R. B.
Hydrate formation-based techniques have been proposed as desalination technologies for transforming seawater into potable water. Marine Desalination Systems (MDS) is currently developing new technology in gas hydrate formation to supply potable water using hydrocarbon gas-based hydrate crystals (Kubota et al. 1984). The MDS technology might change the natural bacterial assemblage in primarily two ways: metabolic rate (secondary production) and assemblage composition. This influence on the microbial assemblage can affect ecosystem health with a disruption of the microbial growth efficiency and changes to key elemental cycles. This report focuses on the effect of salinity and pH changes on the rates of bacterial metabolism among natural marine assemblages. When the marine bacterial assemblage is exposed to salinity and pH conditions similar to those expected in MDS system waste streams, heterotrophic production is significantly reduced. However, in the case of salinity, these impacts on overall heterotrophic bacterial metabolism may be transient. Bacterial production inhibition due to decrease in pH is dramatic and appears much less reversible based on the production recovery only after 24 hours. It should be noted that the pH change was three orders of magnitude compared with the two-fold maximum salinity change. The inhibitory effect of 1.5 pH units (from pH 8.0 to 6.5) at 33 PSU was approximately equal to increasing the salinity 27 PSU (from 33 to 60 PSU) at pH 8.0.
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