A site in the eastern US had low levels of PCE (10 - 120 ug/l) with lesser amounts of TCE and DCE, and no vinyl chloride. In many eastern states, the MCL for cis-DCE is 70 ug/l (EPA MCL), considerably higher than the MCL for PCE or TCE (5 ug/l). Because of the mass loss of 42% in converting PCE to cis-DCE and the higher MCL for cis-DCE, converting all PCE concentrations lower than 120 ug/l to cis-DCE results in attainment of MCLs for cis-DCE. The PCE --> DCE reaction is simple to achieve, often occurring naturally, and stalling after that reaction step.
A low level of electron donor was added and bioaugmentation was not needed. PCE concentrations dropped below 5 ug/l in targeted wells and cis-DCE did not exceed 70 ug/l. Vinyl chloride was only observed in one well and was well below the MCL of 2 ug/l. VOCs have not rebounded after 7 years. The 1st 2 photos are of me salmon fishing with friends since I have so little work to do at the site.
