Most common waste water bacteria function well from low Total Dissolved Solids and/or chlorides up to 3.5% (or near the concentration of salinity in the ocean). Once you go above this point, the microbial population makeup begins to change to favor more halotolerant microbes. This region like similar inflection points in temperature and pH can be difficult to develop a stable biomass. Often our commonly studied wastewater microbes cease growth around 4.5% chlorides and switch to halotolerant strains is mandatory.
At Aster Bio, I have been working with wastewaters having chlorides up to 5% even after chloride reduction. Additionally, microbial enhanced oil recovery often has oil reservoirs with chlorides above 7 - 10%. In effort to address these difficult wastewaters, we have been evaluating a number of halotolerant strains that thrive above 4% chlorides.
Interestingly, we have found some halotolerant strains isolated from desert environments that have evolved a resistance to chlorides and other common dissolved ions that can stress many common organisms. Current screening has shown excellent growth at various chloride concentrations.
From the research on these strains, I have developed a chart on chloride tolerance of various microbes in Aster Bio's catalog:
- Most waste water Bacillus sp. - growth up to 4.5%some strains grew as high as 5.5%
- Pseudomonas sp. - growth up to 4% - with some strains reportedly going higher in literature
- Rhodococcus sp - growth tested up to 4.5% with some strains needing testing for greater tolerance
- New desert Bacillus strains - growth up to 8.2% chlorides with excellent growth at 7%.