Edible Oil Substrate (EOS) for In-Situ Injection

[Guest]

I am currently reviewing a facility that wants to use this food grade vegetable oil for injecting into the subsurface to accelerate the reductive dechlorination of a chlorinated solvent plume. I just recently read that my state conducted two independent trials to verify the target constituents of the EOS product that would exceed groundwater criteria but found that each time, metals sampled under EPA Method 6010 showed RCRA Metal(s) that would exceed the state's criteria.

I don't know which metals have shown up exceeding groundwater criteria, but I am wondering why would metals even show up in the first place? Does anyone have an idea?

I suggested to my administrator that the EOS product may have been purchased from China but that only produced an ever-so-brief smirk and a suggestion to try to find out what is going on. The only other thing I can come up with is that the vegetables that are cultivated to make the oil have somehow taken up these metals and accumulated them in a manner that yields a significant concentration by mass once the plants are cultivated, dried, and processed to make the oil.

Any other thoughts or ideas are welcomed!

JR

 

[Dleg]

I can't imagine any reason that metals should be present in vegetable oil, unless it was mixed with some other waste oils. Maybe they're jsut picking up metals that were in the groundwater, or could the oil somehow be leaching metals from the soil? I can't see how that would happen, but I'm not an expert in remediation.

At any rate, what substances do you normally inject to help break down a chlorinated solvent? Is the vegetable oil a new thing?

 

[Guest]

At any rate, what substances do you normally inject to help break down a chlorinated solvent? Is the vegetable oil a new thing?

There are a number of different ways to address the chlorinated solvent plumes. Some people try to use strong oxidizers like Hydrogen Peroxide (>50% v/v) or potassium permanganate. Others try to promote the natural indigenous biological organisms like Dehalococcides ethenogenes to enhance the natural degradation of those solvents. Right now, the current thinking is that if you can create a biofilm that serves as a pore volume of enhanced reductive activity that you can achieve a more complete, cost-effective solution that way.

The purpose of the edible oil substrate (EOS) is to provide an easy, readily acceptable carbon source for the microbial community. While the substrate provides an excess of what would be considered a limiting food source, the problem is that the EOS is non-specific - it isn't going to target the Dehalococcides specifically as much as it is promoting any bacteria.

The other limitation present is electron-donors. Often-times, your dehalogenators find themselves competing with lower energy donors like (SO4), (NO3) and of course they prefer the lower energy donors because it is easier to pluck thier electrons. I am not up-to-date with the intricate measures taken to promote dechlorination above the lower-energy electron donors, but I am a believe it when I see it sort of guy when it comes to these technologies. In the case of this pilot study, I am requiring strict controls, constraints, and measurements for evaluating the performance so as to ensure that the contamination isn't simply displaced by the injected substrates.

It's good stuff under the right conditions and could serve as a cost-effective way to remediate chlorinated solvent plumes but as they say ... the proof is in the pudding. I do a lot of chlorinated solvent plume remediation - I can add more case studies/projects/etc. if you or anyone else is interested.

JR

 

[Dleg]

We've had a couple of TCE plumes that got remediated during my time here, but I wasn't directly involved. Both were pump & treat with GAC. My only real involvement was having to decide whether or not to let the remediation firm dispose of the GAC cartridges in the landfill, and even on that I deferred to USEPA for technical advice. As I recall, we told them NO - send it back to the states for proper treatment & disposal.

 

[snickerd3]

I just approved a pilot study Work Plan here in Illinois using EOS for a TCE plume. They did a lab study using first using site groundwater and soil to determine which injection chemicals they wanted to use and EOS won out in the lab...they even spiked one of the samples with TCE and they were able to get done to non-detect...even the vinyl chloride...quite impressive. They just added the culture to the pilot study area (to speed things up) about a month ago...performance monitoring should begin soon. I'll have to see if I can get there lab study scanned.

One of my other sites wants to use sodium persulfate for basically the same thing...except they have benzene in the plume too, which they claim will cause EOS not to work. They refused to do a lab study, and their field tests indicate total oxidant demand results were very high and dissolved oxygen levels really low. They would have to inject large quantities of chemicals to overcome the metals(mostly iron they think) demand on the oxidant in the soil/groundwater. Since that would be cost prohibitive, they want to try air sparging the area first to neutralize the metals, hoping to raise dissolved oxygen and lower the oxidant demand. I'm doubtful though.

 

[Guest]

One of my other sites wants to use sodium persulfate for basically the same thing...except they have benzene in the plume too, which they claim will cause EOS not to work.

I am going to go the author of the letter to find out a little more about these metals. I can provide you a copy of that letter if you like - it calls out specifically RCRA Metals as a concern.

Sodium persulfate is actually a MUCH stronger oxidizer that potassium permanganate or hydrogen peroxide. The problem is that you don't get the full effect of the oxidation potential unless you add heat as a catalyst. As I recall, the optimal temperature for oxidation was something on the order of 60 C - pretty warm by most standards, but I am sure especially in Illinois. I have some white papers on sodium persulfate if you are interested. Also - I discussed this technology with Scott Hueling at US EPA Ada Oklahoma Laboratory a year ago. He still characterized this remedy as not-proven in a field-scale application. In other words, most of the encouraging results were based on bench-scale laboratory analyses. That was a year ago - things may have changed, but at least worth noting.

Feel free to PM me if you would like to discuss further.

JR

 

[Guest]

[SIZE=12pt]^^^ UPDATE[/SIZE]

I spoke with the author of the letter calling into question the issue of RCRA metals as a potential chemical constituent of concern and received a better answer. Apparently, there have been 'urban legends' circulating about the purity of food grade lactate. There have been critics who have suggested (without analytical data) that the lactate can contain concentrations of RCRA metals that would exceed RCRA metals - specifically aresenic.

My Department has conducted an intensive survey of the EOS product but due to matrix interference of the lactate (especially calcium) in the EPA Method 6010 analyticals - results have not been produced below method detection limit (MDL) qualifiers. So, the issue becomes a method detection limitation/quantification issue rather than a disclosure issue. As I understand it, EOS is pursuing other avenues to back up its' disclosures of potential chemicals of concern that could exceed groundwater criteria but that the primary issue pertains to the limitation of the analytical method and not a concern of trace contaminants in the formulation.

JR