Successful Remediaiton Case for GW with Chromium IV
Successful Remediaiton Case for GW with Chromium IV
(OP)
Is there any successful case of remediation project for groundwater contamination with metals primary with chromium (Cr VI)?
Thanks for all feed back!
nschuang@itri.org.tw
Thanks for all feed back!
nschuang@itri.org.tw





RE: Successful Remediaiton Case for GW with Chromium IV
Both ’pump and treat’ and in situ methods are in use at Superfund and other sites.
’Pump and treat’ methods utilize the same procedures as the metal finishing industry uses for Cr+6 wastewaters: Ion exchange, chemical reduction, and electrochemical reduction (e.g., electrocoagulation), plus precipitation of Cr+3 hydroxide. Not sure whether electrocoagulation is actually in use at any major site, but have seen it demonstrated, and it has the advantage of simultaneously treating other metals and organics.
In situ methods can only be used if it is considered sufficient to convert the Cr+6 to the less hazardous Cr+3, which has a solubility < 1 ppm at pH 6.5-8.5.
http://www.finishing.com/Library/metalpH.html
Either a PBR Permeable Reactive Barrier or injection of a sodium hydrosulfite (dithionite) solution can be used. See ‘Metals and Inorganics’ at
http://www.rtdf.org/public/permbarr/prbsumms/
The Hanford listing describes the use of rows of dithionite injection wells to create a chemical barrier.
I haven’t reviewed all of the listings, but one PRB site in Denmark utilizing Fe0 as the chemical reducing agent is being re-worked due to exhaustion of the Fe0 in areas of higher than expected Cr+6 concentrations. Some PBR designs allow for reactant replenishment, and of course it is not a problem when using a virtual PBR (series of injections wells, as at Hanford).
RE: Successful Remediaiton Case for GW with Chromium IV
good luck.