One of the major limitations for bioremediation of chlorinated ethenes in aquifers with a pH of approximately 6 and below is the perceived need to adjust the pH to the circumneutral range. This is based on numerous studies with Dehalococcoides and mixed cultures containing Dehalococcoides that indicate a steep reduction or cessation in cDCE and VC reduction to ethene at pH levels below 6.
Nevertheless, field evidence from several locations indicates that complete reductive dechlorination does occur under low pH conditions. We have been working with samples from three such sites in an attempt to develop an enrichment culture that could be used for bioaugmentation of low pH aquifers, thereby reducing the need for raising the aquifer pH. Results suggest that low pH-tolerant Dehalococcoides can be enriched, although their rates of dechlorination activity are not as high as strains that grow at neutral pH. The potential for field applications will be discussed.