FAQs

We have pre- and post-application monitoring recommendations in the attached document and also available on our website: https://petrofix.com/wp-content/uploads/2020/10/PetroFix-Monitoring-Parameters.pdf. If you take our recommended monitoring parameters you should be covered to be able to track effectiveness of the technology. For example, VOC reductions give us direct evidence of treatment effectiveness, EC acts as a secondary tracer to help us track PetroFix distribution, and methane and CO2 are used to track remedial progress and that end products are still forming. There are other “optional” monitoring parameters that you can take such as QuantArray Petro that help show microbial response if that level of data and support is needed to document remedial progress. The required groundwater sampling parameters issued by the state often cover much of the geochemistry that we also look for PetroFix (i.e. pH, DO, sulfate, nitrate, etc.).

Yes, PetroFix does increase the degradation rates of both soil and groundwater. Part of this is because PetroFix is very effective at driving groundwater concentrations down which helps drive soil remediation by improving the rate of dissolution for the soil mass and we do account for some soil mass in our calculations. However, PetroFix is by-and-large a groundwater treatment technology that can also handle sorbed contamination resulting from groundwater contamination passing through the area, not necessary high soil contamination from a direct release. If your primary goal is treatment and reduction of high soil mass evident at your site then we would recommend other forms of soil treatment and not PetroFix. Some options for high soil mass treatment are typically a surgical excavation or ISCO and both of which could be a prelude to PetroFix polishing.

We anticipate that if PetroFix is stored under recommended temperature ranges that PetroFix can be stored for at least 6 months with no expected problems. We do have a cold/hot weather storage memo that gives our recommended storage requirements: https://petrofix.com/wp-content/uploads/2020/07/PetroFix-Freezing-and-Hot-Weather-Handling-Technical-Memorandum-20200701.pdf

Yes, the EA blend should be dissolved completely before injection. The EA blend dissolved very quickly and usually only a few minutes are needed to fully dissolve the electron acceptors salts (sodium nitrate and ammonium sulfate). There is some calcium sulfate dihydrate in the actual PetroFix remedial fluid that serves as a longer-term source of sulfate.

We don’t have a basis or refence table to provide for you on our carbon isotherms. PetroFix estimates normally use groundwater concentrations as the starting point to estimate PetroFix activated carbon demand and then estimate sorbed mass under equilibrium conditions. As groundwater contaminants are degraded this causes an equilibrium shift of contaminants to move from soil to groundwater which then causes treatment of previously sorbed contamination. This hydrophobically sorbed contamination can be visualized as a thin layer of contaminant that is retained by clear aquifer materials when they come into contact with dissolved contaminant flow. The mass of contaminant sorbed to the aquifer matrix is a function of the bulk density of the aquifer matrix, the fraction of organic carbon in the matrix (Foc), and the contaminant-partitioning coefficient (Koc). Input values for the soil, the bulk density, and the fraction of organic carbon are estimated based on soil type used in the PetroFix software. To that end, PetroFix is not designed to handle highly concentrated soil mass where high soil mass cleanup goals are what is needed. We find that its not always necessary to treat 100% soil mass as long as we have enough carbon and sufficient biodegradation rates handle all incoming flux. John Wilson, formerly of EPA, discusses this topic of treating flux versus total hydrocarbon mass in a 2019 PetroFix webinar: https://petrofix.com/defining-cleanup-success-for-groundwater-remediation/.

For any treatments into a lithology that is roughly 75% or greater coarse material, including sand of any size, gravel, fill, and cobbles, we recommend spacing of a 6.5 ft grid. While even site is going to be slightly different we generally expect ROIs of at least 4 ft in most sandy sites.

An important best practice is taping the threads of your injection tooling. It doesn’t take long for the DPT tooling to wear a little on the threads and no longer be water tight. We encourage the use of Teflon tape, or electrical tape on the threads and wrench tighten each rod. This has a huge effect at limiting surfacing, especially on tooling that’s not brand new. We’ve also seen caution tape used this way for slightly lower success.

“Preclearing” refers to any augmentation to the ground surface prior to advancing tooling for direct push injections. This includes hand auguring, cement coring, air knifing, etc. in this. Each of these cause some level of disruption to the settled surface and can make surfacing more likely. This is usually from two things. The first, which can be helped by taping tooling as described above, is the seam between two DPT rods leaking and that seam being closer to ground surface the leak is now noticeable. This is something that bentonite can help limit and control, but the best solution is to prevent it by taping the tooling and wrenching them tight. The other reason that preclearing can cause surfacing is that the disruption of native soils loosens the native compaction and creates vertical preferential pathways that are comparably easier to travel through than the native horizontal conditions. This can be very difficult to handle and is best controlled by bentonite and lower injection rates if preclearing cannot be prevented.

Cement coring, the removal of a cement layer that is too think to drill through, is going to be the least disturbing, because you aren’t removing any native soils, and you are typically not going deeper than a foot (usually less). Cement coring usually only results in the first form of surfacing from leaking tooling. For that reason cement core requires the least bentonite, but we still encourage the application of some bentonite. Here the bentonite is more of a preemptive quality of life measure as if surfacing does occur around the tooling it can be difficult to get your hand in the coring hole and around the tooling to apply and pack bentonite. For this reason, just a few inches are appropriate, enough to make it easier on yourself if surfacing was to occur.

Hand auguring, because you are removing native soil is more disruptive and therefore requires more effort to prevent surfacing. The amount of bentonite depends on how much deeper than the bottom of the clearing is the top of your injection interval. If you have more than 10 feet between the bottom of the hand clearing and the top of your injection interval, then nothing more than filling the hole with the previously removed soil is needed. That remaining 10+ feet of native soil should be sufficient in holding your injectate in the ground. If you are injecting within 5 feet of the bottom of you clearing, then something like two feet of well hydrated bentonite at the bottom of your clearing with the native soils to the surface, should be effective at preventing surfacing. If you are injecting only a foot or two from the bottom of your clearing, then we recommend adding more like three or four feet of slightly hydrated bentonite. One thing that seems to help is using the drill probe to press down and compact that slightly hydrate bentonite and soil before advancing tooling.

Air knifing/vac trucking is the most destructive, and really loosens everything up, making surfacing very hard. If at all possible, we recommend avoiding air knifing unless you are injecting 10+ feet below the bottom of the air knife. If you do have to use air knife, we recommend mixing a some grout and bentonite and filling the clearing entirely with that at least a day before injecting that location. Not a lot of grout, a little bit that will help make it more solid than bentonite alone, but you can still advance tooling through.

Avoid a situation where your preclearing and injection intervals overlap. People have had success preclearing several locations over an area, but actually injecting at a point that is 6 inches to a foot offset from those preclearings. That defeats the purpose of preclearing, so we would recommend avoiding DPT and use injection wells in those cases.

PetroFix aptly treats any dissolved hydrocarbons emanating from NSFO/heavy viscous POL plumes (dissolved concentrations are typically low) and there are no other chemicals needed for long-term treatment. PetroFix is very effective at driving groundwater concentrations down which helps drive soil remediation by improving the rate of dissolution for the soil mass and we do account for some soil mass in our calculations. However, I do want to stress that PetroFix is by-and-large a groundwater treatment technology that can also handle some light soil contamination versus high soil contamination from a direct release. If your primary goal is treatment and reduction of high soil mass then we would recommend other forms of soil treatment first before PetroFix. Some options for high soil mass treatment are typically a surgical excavation or ISCO followed by PetroFix polishing.

During injection into the subsurface PetroFix may flow into nearby monitoring wells as evidenced by finding black well water. This occurrence is common and desired so that we know that we are attaining distribution. Like a contaminant, PetroFix is simply flowing out into the natural flux zones of the subsurface. This is in comparison to high pressure fracturing of PAC or GAC that results in the permanent occlusion of carbon mass directly in well pack, well screen, or settled in thick layers on the bottom of the well itself. When this happens, the wells cannot be rehabilitated. In contrast, PetroFix freely flows into and out of a well and isn’t deleterious to their function.

Some practitioners like to perform a clear water flush post injection to evacuate PetroFix from monitoring wells. We see this step as optional because eventually the PetroFix attaches to soil evenly and the groundwater clarifies. We have specific instructions on how to flush a well (including an excel calculator) as well as sampling guidance documents. We recommend that groundwater not be sampled if PetroFix is >100 mg/L in concentration (difficult to see through a 40 ml VOA). Each PetroFix shipment comes with one (1) simple, colorimetric field test kit taped to the top of a tote or drum to help assess field concentrations. Here is a link to more information: https://petrofix.com/resources/?_categories=technical-bulletins.

While we have applied PetroFix at 100ft bgs and in weathered bedrock, PetroFix is not usually going to be the limiting factor on depth. Direct push is the recommended method of application, and will reach depth on most sites, however, several site conditions may make DPT unrealistic. We recommend the use of direct push for application for serval reasons; the ability to apply over small discreet injection areas helps ensure even vertical distribution, and the low cost of a single injection location allows for the application of many injection locations, helping to achieve an even horizontal distribution. As PetroFix is a contact sport, both of these are required. PetroFix can successfully and has successfully been applied through injection wells. PetroFix is roughly the size of a single bacterium so will not result in any clogging of wells. If using wells to apply PetroFix, it is important to keep in mind that even poorly graded sands with a highly diluted solution you should not expect PetroFix to evenly travel in the subsurface greater than about 8 ft. PetroFix will bind to native soils as it travels in the subsurface, those limiting the maximum ROIs that can be expected. For this reason, we generally apply PetroFix on fairly tightly spaced grids making injection wells often too costly of a method. One exception of this is weathered bedrock. Due to the nature of weathered bedrock we have seen PetroFix consistently travel over 30 ft.

There is no incompatibility using ORC Advanced with PetroFix. The only limitation to this approach would be the additional cost for ORC Advanced and the need to inject the material in separate injection points because they are incompatible to be injected together. However, once injected through separate grid injection points the combination of ORC Advanced plus PetroFix with provided nitrate and sulfate electron acceptors would be a very aggressive and effective remediation approach because the stimulation and growth of aerobic bacteria would happen quickly as well as subsequent aerobic oxidation of a broad range of fuel hydrocarbons. As oxygen is the preferred natural electron acceptor for hydrocarbon bioremediation based on the standard free energy available for oxidation it would be used preferentially and nitrate and sulfate use would be suppressed until oxygen was depleted. Following depletion of oxygen, nitrate and sulfate would be utilized. The combined use oxygen followed by nitrate and sulfate electron acceptors would be expected to improve syntrophic processes under anaerobic conditions because you have increased the total electron acceptor capacity and are bio-stimulating a more diverse range of bacteria capable of handling the more recalcitrant VOCs such as benzene. We do want to emphasize that while we would be highly confident on the combined use of ORC Advanced with nitrate and sulfate, we still believe that for most sites the provided nitrate and sulfate are sufficient for stimulating fuel biodegradation.

We agree with your question and statement in theory, but in practice we find that oxygen replenishment to aquifers from the atmosphere or surface water infiltration are insufficient to stimulate aerobic biodegradation in the time frames needed. If your aquifer already is anaerobic then we believe the use of the provided nitrate and sulfate a wise choice. However, if you evaluate the levels of dissolved oxygen and
oxidation/reduction potential (ORP) of your aquifer and find that it is indeed well oxygenated and aerobic then injecting PetroFix would still be beneficial by allowing the PetroFix to sorb and remove dissolved phase contamination while having the naturally high oxygen concentrations stimulate aerobic biodegradation of sorbed contaminants. The use of the additional electron acceptors provided in separate white buckets is optional.

In short, it comes down to chemical equilibrium and when the overall syntrophic process is thermodynamically favorable. As fermentation end-products (acetate, H2) accumulate, the entire process yields less energy for the microbes. As long as these intermediates are being removed by sulfate reducers and/or methanogens and the pH doesn’t increase too much (which can slow things down) the process remains energetically favorable.

From lab studies we know hydrocarbons, and specifically benzene is biodegraded by doing full-bottle extractions on batch experiments. After incubating with benzene, activated carbon, soil and water, an entire bottle is extracted with another solvent and we see all benzene is gone. In control experiments like this (killed/sterile bottles) the benzene can be recovered from the activated carbon at very high recovery percentages, showing biodegradation is the removal process. REGENESIS PlumeStop technical bulletin 3.1 is available on regenesis.com showing a post-sorption contaminant biodegradation lab study with benzene
that documents benzene biodegradation on the activated carbon (PlumeStop and PetroFix use the same diameter carbon and this lab study is representative for PetroFix as well). In the field, we rely on multiple lines of evidence to show ongoing biodegradation after adsorption. The utilization of added nitrate and sulfate in the right pattern (nitrate first, sulfate second) is the first line.

Temperature will certainly affect the expected rate of biodegradation. At 4ºC biodegradation will beslower, but still occurring. Many deep lakes in cold climates have sediments at this temperature, yet still experience natural methane emissions from organic carbon being biodegraded. The effect is loosely comparable to how
quickly food would spoil inside vs. outside of a refrigerator. Despite this, PetroFix would still be a viable treatment option at low temperatures.

We have plenty of lab data confirming biodegradation is occurring, and did not see the need to use isotopic tests as a part of initial field product testing. With that said, when using PetroFix compound specific isotope analysis (CSIA) has limited field use because groundwater contaminant levels commonly drop to ND after treatment. Stable isotope probing (SIP) is a method offered by Microbial Insights where a labelled compound is placed on a bio trap (activated carbon beads) and its removal, as well as incorporation into microbial biomass, can be followed.

It is true that microbes must uptake TPH rather than rely on extracellular enzymes, but there are other potential ways for microbes to actively uptake TPH, including biofilm and/or biosurfactant production. While the exact mechanisms are not clear, we conclusively know (see answer 13) adsorbed compounds can be degraded.

The formulation of PlumeStop is proprietary, but the point is the polymer is a source of carbon for the microbes much the same as the hydrocarbons are. The added organic polymer must be biodegraded along with the PHCs and this process will consume electron acceptors.

Yes, the issue is bulk floating petroleum. We believe using a rule-of-thumb that the presence of continuously measured floating LNAPL is an indicator of high mass that usually results in an exceedance of the desired performance range of PetroFix. High amounts of LNAPL could both overwhelm sorption sites on the PetroFix carbon and the rates of anaerobic degradation. Our goal for PetroFix is to provide sustained multiple-order of magnitude reductions of BTEX and TPH and to let our customers know of site conditions where we think attaining this goal would be challenged. If uncertain, we advise that you order a single drum of PetroFix and pilot test at your site.

The particle size of PetroFix is 1 to 2 μm in diameters which is below the pore-throat size of fine sands and silts. However, PetroFix cannot be injected into tight clay without high-pressure fracturing which we try and avoid. We realize that sorbed LNAPL often is present as a source in clay and PetroFix is not designed to directly remediate LNAPL bound in clay. Instead, PetroFix is designed to infiltrate all permeable transport zones above, below, or interbedded in clays that lead from a source to downgradient receptors. By focusing on liquid delivery in these zones you will stop migration of contaminants, particularly by mitigating the impact of contaminant back diffusion into these zones, and reduce site risk which opens up possibilities for closing sites by this method alone or in conjunction with other source treatment approaches.

PetroFix is specifically formulated for hydrocarbon plumes and while it could sorb both solvents and petroleum, its formulation will not promote anaerobic destruction of chlorinated products. In fact, PetroFix injected with its electron acceptors in an area targeted for reductive dechlorination treatment of solvents would be expected to repress reductive dechlorination until they are depleted and this would negatively delay solvent treatment. What we advise is that if you are concerned about overlap that you contact Regenesis for design assistance to evaluate an optimal treatment scenario.

It is true water soluble electron acceptors can flush out of a system, while PetroFix will remain positionally stable. We see this as an issue for a minority, not majority of projects and keep in mind that there will be some co-migration of contaminants with electron acceptors, albeit at different rates. For nitrate, its utilization is so fast that we predict it will not migrate significantly before it is utilized in most aquifers.
Sulfate utilization is slower and generally dependent on nitrate being depleted first and may move out of the system in high velocity groundwater environments. If you are concerned about washout it may be possible to replenish the aquifer with additional soluble electron acceptors through further injections, drip system, etc. One option is to co-inject ORC Advanced within or upgradient of the PetroFix application to supply continuous oxygen (ORC Advanced material doesn’t migrate with groundwater).

We don’t see an issue with using soil once treated with PetroFix as long as treatment concentrations have achieved acceptable use concentrations. Aesthetically, treated soil will be black which might be a consideration on their use.

Yes, PetroFix will work well with treating dissolved phase contamination in those ranges. For readers who may not be familiar with Canadian F1 to F4 ranges they are: F1 (C6-C10); F2 (>C10-C16); F3 (>C16-C34), and F4 (>34). The Indiana case study we showed presented both TPH-GRO (C6-C10, or F1 fractions) and TPH-DRO (C10-C28; or F2 and partial F3 ranges) ranges each having reductions of +2 OOM and +1 OOM reductions, respectively. We don’t have direct experience stimulating the biodegradation of F4 fractions at this point, but know that both the susceptibility and biodegradation potential are related to respective solubility of hydrocarbons. Components for F3 or F4 that are water soluble and mobile would be expected to be sorbed and treated by PetroFix using our mixed electron acceptor approach.

When treating hydrocarbon sites we hope to achieve one or more order-of-magnitude (OOM) reductions of contaminants sustained, if not better, for BTEX and TPH ranges. Reductions will happen quickly upon contact with hydrocarbon followed by biodegradation. The Indiana case study we presented was a challenging site that performed well at high concentrations and we will continue to monitor for performance. We believe that upper limits depending on soil type is probably in the 30 to 50 mg/L range total hydrocarbons before you might need to consider future, supplemental electron acceptor injections. Keep in mind that we believe that a single injection of PetroFix is probably suitable for most sites and any additional rebound can be addressed with the injection of desired electron acceptor and/or nutrient blends. The caveat to this is if you suspect that aquifer distribution was not achieved and that might warrant supplemental PetroFix injections to fill in the gaps.

We believe that PetroFix is compatible with RegenOx and PersulfOx® chemistry and could be co-injected in the same areas as these products. However, these material should not be injected simultaneously in the same hole. Other constraints to consider would be the ability to get total volumes from both ISCO products and PetroFix in the ground simultaneously since both require high volumes and high effective pore space filled. We see PetroFix as a very strong option for post ISCO polishing as either a second subsequent injection or possibly simultaneous injection during a single mobilization. The practitioner would need to determine the optimal timing when PetroFix should be injected to coincide with the mass reduction goals of the ISCO injections and at which injection event PetroFix should be paired. Regenesis is happy to discuss such options and make recommendations.

Yes, this product can be applied in deep aquifers as long as injection wells were designed for that purpose. Achieving distribution would have to take into consideration the limited ROI and distribution potential for pressure injection of PetroFix or consider pump-and-pull well arrangements if the aquifer were highly permeable to enhanced distribution. Please also see question 21.

Under most circumstances there is no need to add anything besides what is delivered with PetroFix. If needed or desired, small amounts of other nutrients like diammonium phosphate can be added to PetroFix for injection as it is water soluble and doesn’t interfere with the chemistry.

We have had a project where PetroFix was distributed in a bedrock aquifer and distribution was better than expected because effective pore space is less than in soil. As long as fractures are interconnected and the aperture sizes of those fractures are large enough you would expect to be able to push PetroFix into the formation, potentially using larger ROI’s than what we normally estimate for direct push. In a fractured bedrock site with sufficient interconnectivity you also have the option to use a pump-pull arrangement using different wells to facilitate distribution in different directions. We would recommend a small pilot test using a drum of material to verify the deliverability of the product and validation of ROI.

We advise caution and proper design in these situations since we are trying to avoid uncontrolled or partial placement of PetroFix in an aquifer. PetroFix as shipped and undiluted would possibly meet density/viscosity requirement as a frack fluid and possibly could be paired with a sand proppant. Hence, PetroFix fracturing could be performed and it’s also entirely feasible that PetroFix fractures could be replenished with additional electron acceptor blends if they were connected to re-injection wells. We also have evidence to believe that PetroFix may also diffuse into clays beyond the fracture. Furthermore, the amount of carbon and electron
acceptors in PetroFix would probably be insufficient for direct remediation of LNAPL in clay. The ideal application of PetroFix is in the high flux zones where the material can control future back diffusion from clays into permeable zones to control risk. It is worth considering that many sites, despite having tightly bound contamination in clay, may achieve closure simply by injecting PetroFix into conductive zones to reduce off-site flux to levels sufficient to protect human health and environment. We leave it up to the practitioner to determine the specific need for source treatment in clay and perspectives on answering such a question was covered recently by Dr. John Wilson in a webinar entitled “Defining Cleanup Success for Groundwater Remediation” which can be accessed at regenesis.com.