Contributed by Keith Pyron, Principal, PPM Consultants
Several years ago, I attended a Brownfields Symposium in southwest Florida sponsored by the Florida Department of Environmental Protection (FDEP). The symposium consisted of many different speakers giving presentations on different approaches and technologies concerning the assessment and cleanup of contaminated properties. While I found some of the presentations interesting and others not, there was one presentation that really grabbed my attention above the rest. The presentation was about remediating petroleum-contaminated sites using a type of bioremediation process called Biovation™.
It was strange that I became so captivated by a bioremediation presentation. I confess I have never been impressed with any type of bioremediation method in my 35-plus years of experience as an environmental consultant. Frankly, I’ve never seen a bioremediation technology that produced any great results, or even mediocre results for that matter. However, the speaker of this presentation really caught my attention because he began to share how they were able to clean up site after site using their technology in six months or less. Yes, I did say six months or less.
I’m listening to this guy thinking that he is either a little crazy, seriously stretching the truth, snake-oil salesman (but I repeat myself), or maybe he is just presenting only the success stories. I mean, nobody gets up to speak at one of these conferences and talks about their failures, right? What really got me taking him seriously is when he began openly offering this remediation method on a pay-for-performance (PFP) basis to anyone willing to give him a site to try. Where I come from, this means he was putting his money where his mouth is. Most consultants will avoid PFP projects like the plague, simply because of the risk too many things can go wrong.
I was compelled to learn more about this technology. After his presentation, I began grilling him one-on-one with one question after another. I questioned him about how many of these remediations had they completed? How long was his average cleanup? What was the longest period of time they took to clean up a site? He told me they had cleaned up dozens of sites with this process, the average cleanup time was less than three months, and they never had a remediation take longer than a year.
By now, you are probably asking what is the bioremediation technology that can clean up petroleum contaminated sites in less than three months average. Let me give you a brief overview of how this system works. Groundwater is extracted through recovery wells and pumped into a tank located inside a trailer mounted remediation system. Inside the tank, microorganisms and oxygen are introduced into the tank and then the mixture is pumped back into the subsurface through injection wells. The treated groundwater infiltrates down through the contaminated soil into the water table then migrates through the groundwater plume, thereby treating contamination in both the vadose and saturated zones. Down-gradient extraction wells then recapture and recirculate groundwater back into the mixing tank again. Sounds pretty much like another pump and treat system doesn’t it? So, there are a few things that are different that makes this system work so well.
The first thing that sets this technology apart is that the microorganisms are harvested from actual petroleum releases as opposed those grown in a lab. Since they are all naturally occurring, they have a much greater probability of survival when they are injected back into the ground. Only the most aggressive strains of bacteria are harvested and cultivated. These microorganisms strongly prefer aerobic conditions, so they are mixed with oxygen-rich water before they are injected into the subsurface to help keep them alive.
Another major distinction between this technology and others is the recirculation method. It is not simply pumped into the ground and then hope it reaches the contaminants it needs to. The continuous cycle of injecting the oxygen and nutrient–rich water from the trailer then pumping it back out via recovery wells and reinjecting it again forces the microorganism to travel throughout the entire zone of impacted soil and groundwater. Typically, microorganisms that are cultivated for this purpose have to feed or they die off. That’s what happens a lot with other bioremediation technologies. The microorganisms are simply injected and left to feast or starve on the available petroleum hydrocarbons and oxygen immediately around the injection point. That is the major reason the microorganisms suffer a mass extinction. In the Biovation™ technology, the bacteria and oxygen enriched water is pushed and pulled throughout the formation so it is both enriched and can get to more contaminants to consume.
The more I learned about this technology, the more I became interested. I decided I had to give it a try at one of the sites we were remediating for a client. The first site selected was in Panama City, Florida. The site had been undergoing remediation efforts using vacuum events for about 6 months. This Panama City site seemed to have the right geologic environment for using the Biovation™ process, so it was proposed to the FDEP and accepted. Petroleum hydrocarbon concentrations were reported to be less than 20 parts per billion at the startup of the remediation using Biovation™ . There were a few twists and turns that occurred in getting the system up and running such as a car chase with the local police that ended up with a car crash into the remediation trailer. However, once the system was turned on, the site was cleanup in less than two months of runtime.
There are some factors to consider, This remediation technology, it is not applicable to all sites. It must have the right geologic environment, which it needs groundwater that can be pumped out of single wells at the rate of at least one gallon per minute. Basically, the formation needs to have enough silt, sand and gravel to move water through the formation so predominantly clayey soils won’t provide the groundwater yields needed and distance that the plume has travelled is not an issue.
Cost is also factor to be considered. If you need a remediation system that will run at a low monthly cost, this may not be the technology for you. The cost of adding the harvested micro-organisms is not cheap. However, when you compare the overall cost of capital, operations, and maintenance for less than a year to technologies that take years to complete, this technology is often much more cost-effective.
In addition, this technology should not be used on sites with free product or with extremely high concentrations in the groundwater. These conditions are too high for the mico-organisms to handle and they will die off. However, this technology can be used in immediately following the use of other technologies that can rapidly eliminate free product and reduce very high concentrations such as the case with dual-phase vacuum extraction.
The bottom line is that if you have the right conditions, this could be the most cost-effective technology you may ever use. For more information, feel free to contact me a 251-990-9000 or keith.pyron@ppmco.com