Molasses Injection Questions 3

[cgoddard]

We're looking to change our remedial approach at a PCE plume site from dual-phase extraction to molasses injection. We've completed a pilot-test and have seen the begining of successful dechlorination of TCE to 1,2-DCE (and a little 1,2-DCE to VC). We're going full-scale but I haven't found much info on the appropriate dilution or dosage of molasses? Any ideas? If I knew the hydrogen yield from molasses I could probably do it.
Thanks

 

[RStanford]

Doing a web search for 'molasses bioremediation' brings up a lot of examples. Perhaps the best are the case studies done by USEPA through the Federal Remediation Technology Roundtable (FRTR -

http://www.frtr.gov).

For example, see:

http://costperformance.org/profile.cfm?ID=2&CaseID=2

and

http://costperformance.org/profile.cfm?ID=14&CaseID=14

. The USEPA Project Manager was the same person for both studies (Eugene Dennis at EPA Region 3 - E-mail: dennis.eugene@epa.gov). The Emeryville, CA study used a 5:1 solution of molasses:water, but the PA study used 'varying' concentrations. For some reason, Arcadis seems to think that this is a proprietary technology.

The Air Force has done some studies using molasses (again, with Arcadis as the consultant). See:

http://www.estcp.org/projects/cleanup/199920o.cfm

. The page gives the Air Force project officer, so you can contact him for information.

Hope all this helps.
Rick

 

[4tuna]

Be careful with this approach cgoddard. When using molasses, the process can slow considerably or stall out at cis 1,2 DCE. This is because molasses contains sulfate, and encourages the growth of sulphinators - bacteria that while very effective for reductive dechlorination of PCE and TCE are very inefficient/slow at breakdown of DCE and cant degrade VC at all. Better solutions are sodium lactate or the hydrogen release compound (HRC)commercially available through Regenesis, which is a polylactate ester for slow release of lactic acid on contact with water.

 

[1ddt]

This is true about the daughter products being'spawned' and the chance for the reductive dehalogenations 'stalling'. Arcadis was the originator of the blackstrap molasses technic for injection of a carbon source; however, as 4tuna interjected, one way to eliminate this would be to consider the use of potassium permanganate - which eliminates the intermediaries. This can also release free iron to the aquifer thereby decreasing permeabilities via iron fouling. Good luck! ddt

 

[agsgeophysics]

This is a great thread and brings up some interesting points. I'm going through some of these issues myself - a lack of info for molasses injection as far as appropriate dilution, volumes necessary, # of injection points, etc.

I know Regenesis has calcs for their HRC product (HRC is quite expensive). Does anyone know if this can be used as a starting point for designing a molasses injection system?

4tuna makes some great points. Typically you would expect reductive dechlorination to stop at VC - VC degrades aerobically, not anaerobically like the other chlorinated hydrocarbons. I have seen some case studies where they've gotten lucky and achieved complete mineralization with molasses injection. And yes, ARCADIS Geraghty Miller is very tight lipped with the details (Hard to think of something as simple as molasses injection is proprietary but they are trying to keep their competitive edge)

 

[dangnm]

Very interesting thread... I was wondering if anyone has done studies on the VOC content in the molasses after it has been injected (if possible). I would think that PCE and the daughter products would partition into the molasses or does the molasses fully metabolize. Also, it seems that potassium permanganate would be quicker and/or less expensive than molasses or HRC.

Has anyone done life-cycle cost comparisons between molasses, permanganate, and HRC?

I appreciate thoughts on the subject. Thanks