Oil Eating Bacteria Compared: 73% Heavy C37-40 Reduction in 15 Days

Soil taken from a petroleum contaminated site in China came into the lab with a strong hydrocarbon odor and 33,570 ppm of total petroleum hydrocarbons across the three fractions heavy enough to quantify: 16,800 ppm of C15-28, 15,300 ppm of C29-36 and 1,470 ppm of C37-40. A fourth fraction, C10-14, measured 110 ppm and sat close to the 50 ppm reporting limit.

Almost the entire load is mid chain and long chain, and that shape matters more than the total. Light fractions weather off and biodegrade quickly, so they rarely control a cleanup schedule. The heavy end does. Longer carbon chains are waxy, poorly soluble in water and less available to the bacteria that have to digest them, which is why C37-40 is the fraction that stalls at the tail of a remediation project and keeps a site out of compliance after the easy numbers have already come down.

The second problem has nothing to do with the soil. A site owner or remediation contractor comparing microbial products has almost nothing to go on. Every product sheet claims a high CFU count, a broad strain list and fast hydrocarbon degradation, and none of that predicts what happens in a specific soil. The only way to separate them is to run them on the same material at the same time.

Petroleum Treat (PT) and two competing oil eating bacteria products were applied to the same contaminated soil under matched conditions, and TPH was measured by carbon fraction on day 15.

Soil from the contaminated site was sampled and analyzed for total petroleum hydrocarbons by carbon fraction. Those are the day 0 numbers. The soil was then split and treated three ways: Petroleum Treat (PT), a high-CFU blend of petroleum degrading bacteria, and two competing microbial products, all under matched conditions. Odor was tracked through the run, and TPH was re-analyzed by fraction on day 15.

Petroleum Treat works by feeding on the hydrocarbons rather than moving them somewhere else. The blend produces biosurfactants and broad spectrum enzymes that make oil more available to the bacteria, which matters most on the heavy fractions, where low solubility is the thing holding degradation back.

Day 0 is a baseline, not an untreated control. No untreated soil was carried alongside the three treatments, so the trial shows which product moved the soil furthest in 15 days, not how much of the reduction would have happened without any product at all. The two competing products are the closest thing here to a reference point.

The source record also does not state the soil volume, the application rate, the temperature or the moisture content of the test. Those affect degradation rate in any soil program, and none of them are documented here, so the percentages should be read as a head to head ranking under one shared set of conditions rather than as a rate you can transfer to a different site.

C37-40, the fraction that normally sets the length of a cleanup, fell from 1,470 ppm to 390 ppm under Petroleum Treat in 15 days, a 73% reduction. Competitor A brought the same fraction to 660 ppm, a 55% reduction. Competitor B reached 890 ppm, 39%.

The mid chain fractions followed the same order. C29-36 dropped from 15,300 ppm to 6,260 ppm with PT, 59% lower, against 9,640 ppm for Competitor A (37%) and 11,700 ppm for Competitor B (24%). C15-28 went from 16,800 ppm to 7,420 ppm, 56% lower, against 10,500 ppm (38%) and 11,000 ppm (35%). C10-14 started at 110 ppm and finished below the 50 ppm reporting limit under all three products, so no removal rate could be calculated for it.

Adding the three quantified fractions together, the soil went from 33,570 ppm TPH to 14,070 ppm under Petroleum Treat, a 58% reduction in 15 days. Competitor A finished at 20,800 ppm and Competitor B at 23,590 ppm, 38% and 30%. Those combined figures are summed from the per fraction lab results rather than reported directly.

PT led on every fraction that could be quantified, and the gap widened as the chains got longer. On C29-36 it removed 59% where the better competitor removed 37%. On C37-40 it removed 73% against 55%. Products that look similar on a light or mid range hydrocarbon can separate sharply on the heavy fractions.

Eight days after Petroleum Treat was applied, the pungent hydrocarbon smell was gone. Odor is not a compliance metric and it was not tracked for the two competing products, so it belongs in the record as an observation about PT and nothing more.

What this trial does not establish is an endpoint. Fifteen days is a short window, the run stopped there, and 14,070 ppm of TPH is still a contaminated soil. What it does establish is comparative. On one batch of heavily contaminated soil, under one shared set of conditions, three microbial products separated clearly, and the separation was widest on the hydrocarbons that are hardest to degrade.

For what the same product does over a longer run, the on-site windrow program on 20,000 ppm soil cut TPH 97% and returned the treated soil to the site, and a municipal oil water separator went from 22,940 to 79 mg/L over 120 days.