Petroleum Hydrocarbon Remediation

Remediation of Petroleum Hydrocarbons

Petroleum sites usually come to us as one of two problems: an oxygen problem or an oxidant problem. Either the bacteria that eat fuel are there and starving, or the source zone is too concentrated to wait on biology and needs to be oxidized. Most real programs end up doing both, in sequence — and this page is about deciding which, where, and with what.

Petroleum hydrocarbon treatment technologies are designed to break the carbon–hydrogen bonds that make up the contaminant. Hydrocarbons range from a single carbon with multiple hydrogens (methane, CH₄) to more complex compounds such as benzene (C₆H₆) — and the more complex the compound, the more difficult it is to fully remediate. The technologies Hepure supplies are primarily in situ: treatment occurs within the aquifer or soil matrix without removing water or soil, which has proven effective at reducing both the time and the cost of petroleum remediation.

One requirement follows from the chemistry: in situ treatment of petroleum-contaminated soil requires the soil to be saturated with water, because chemical and biological reactions only take place with the contaminant in solution. That is accomplished either by injecting the amendment with water or by soil mixing with water added.

Site Conditions That Drive the Design

Choosing a petroleum remediation technology starts with site conditions, typically collected and documented in a detailed site assessment covering soil and groundwater conditions, the contaminants present, and the likely sources of the release:

• Type of aquifer — perched, non-drinking groundwater, or drinking water
• Geology — clay, silt, sand, or fractured bedrock
• Type of contaminant — BTEX, gasoline, diesel, or heavier oils (and PAHs where present)
• Concentration — parts per million or parts per billion
• Remedial goals — polishing, or drinking water standards
• Groundwater chemistry — pH, redox, minerals, hardness

Enhanced Aerobic Bioremediation

Oxygen is typically the most limiting factor in the biodegradation of petroleum hydrocarbons — a plume exhausts the aquifer’s dissolved oxygen quickly, and recharge can’t keep pace. Two oxygen sources cover the range: calcium peroxide releases oxygen slowly over months (about 0.6 pounds of oxygen per pound of CaO₂), while hydrogen peroxide delivers it fast (each part of H₂O₂ yields about half a part of oxygen). A typical program pairs the long-lasting oxygen source with a hydrocarbon-degrading bacterial culture: many in situ applications rely on naturally occurring bacteria, but adding a strain establishes a hydrocarbon-degrading population faster — advisable given the finite release life of calcium peroxide. See the bioremediation amendments line, including the bacterial supplement.

Where aerobic conditions can’t be established, some petroleum hydrocarbons also degrade anaerobically; emulsified vegetable oil and sodium lactate support that pathway, more slowly.

Chemical Oxidation

For source zones and hot spots, in situ chemical oxidation destroys mass faster than biology can. The petroleum oxidants are activated persulfate — effective on BTEX, MTBE, TPH (GRO and DRO), and PAHs, with days-to-weeks persistence — and catalyzed hydrogen peroxide (Fenton’s chemistry, with ferrous sulfate as the catalyst), whose heat also helps desorb LNAPL that would otherwise sit out of reach. Permanganate, the workhorse for chlorinated solvents, is weak on benzene and fuels and is rarely the right choice here. The common pattern: an oxidant pass on the source, then oxygen and bacteria on the dissolved plume. Compare the options on our chemical oxidants page.

Delivery: Soil Mixing

Soil mixing can be effective for hydrocarbon-contaminated soils with either bioaugmentation or chemical oxidation, provided the soils are shallow enough to mix (up to about 20 feet below ground surface) and enough water can be added to saturate them. Mixing can be done with an excavator bucket — not considered complete mixing — or with a rotary tool attached to an excavator. Mixing needs to be far more complete for chemical oxidation than for biological treatment, because oxidation depends on full contact; bioaugmentation is more forgiving, since the amendment has time to diffuse through the saturated soil matrix.

Delivery: Injection

Injection treatment is performed with drilling or direct-push equipment: a casing or hollow rod is advanced into the contaminated zone, and treatment chemicals and water are injected under pressure to ensure full contact and saturation of the soils. It reaches depths soil mixing can’t and is the standard delivery for dissolved-phase plumes; see in situ groundwater remediation and soil remediation for how it fits the wider toolkit.

Common Questions

Calcium peroxide or hydrogen peroxide for a fuel plume? Both, often. Peroxide for a fast pulse and source-zone oxidation; calcium peroxide for months of sustained oxygen on the dissolved plume.

Can permanganate treat gasoline? Not well — benzene resists it. Persulfate or catalyzed peroxide are the petroleum oxidants; permanganate belongs on chlorinated solvent sites.

How deep can soil mixing go? Roughly 20 feet with excavator-mounted tools. Deeper than that, inject.

Send us the site assessment and we’ll help select the chemistry and estimate quantities — call 866-727-4776 (Pat Randall x1, West; Bob Kelley, Ph.D. x2, East) or request more information.