Hydrocarbons, VOCS and Mineral Oil in water

Question

I'm a reporter in Charlottesville, Virginia, USA. I've been covering a water crisis in one of our outer counties. Orange County, Va had a water crisis in Aug 2024.
The water supply was contaminated with what authorities now claim came from 2-3 gallons of mineral oil due to a failed pump at the water treatment plant.
I'm curious if anyone has any knowledge about the threshold for mineral oil infecting an entire public water supply? Benzene and hydrocarbons were discovered in the first day of the event. The water still smelled and tasted like petroleum 4 days after the crisis started and authorities told residents to start using and then start drinking the water- all while it was still brown and smelled and tasted of gasoline.
How could 2-3 gallons of mineral oil cause this big a problem? It affected 13,000 residents and closed schools and businesses for days.
Any help you can offer is greatly appreciated. I've reached out to Virginia Tech and Michigan State and neither one can answer these questions for me.
Thank you, Heather Price Ives- The Daily Progress  hives@dailyprogress.com
Orange County's water crisis remains unresolved (dailyprogress.com)

Water Network Research · Answer

Here is what AI CHAT GPT has to say about this: 
The situation you're describing in Orange County, Virginia , raises serious questions about how even a relatively small amount of mineral oil could contaminate a public water supply affecting 13,000 residents . Here’s a deeper look into how and why this might happen.
1. Mineral Oil in Water Supplies :
Mineral oil is a byproduct of petroleum distillation and consists of hydrocarbons , which can be toxic at certain levels. Even a small quantity of mineral oil can have a disproportionate effect on a water supply because of its properties: Low dilution : Mineral oil is hydrophobic (does not mix well with water), so it can form a layer or disperse in small droplets, contaminating large volumes of water. Contaminants like benzene : Mineral oil and other hydrocarbons can contain volatile organic compounds (VOCs) like benzene , which is a known carcinogen. These compounds have very low safe exposure thresholds, and even minute amounts can cause water to smell or taste like gasoline.
2. Small Amounts, Big Impact :
2-3 gallons of mineral oil contaminating an entire water supply may seem unlikely, but the following factors explain why it could cause such widespread issues: Water system design : Water treatment and distribution systems are designed to carry water efficiently across large areas. If mineral oil entered through a critical point like a failed pump , it could spread quickly through the system. Sensitivity to VOCs : Hydrocarbons, like those in mineral oil, are detectable by humans at very low concentrations (parts per billion). The smell and taste thresholds for hydrocarbons are much lower than the concentrations that can make people sick. This means even a tiny amount of contamination can cause noticeable sensory effects like the taste and smell of gasoline. Stubborn contaminants : Hydrocarbons like those in mineral oil can be difficult to remove from water supplies because they are non-polar , which makes them resistant to standard water treatments like filtration and chlorination. They can also bind to pipes and other infrastructure, continuing to leach out long after the initial contamination.
3. Benzene and Hydrocarbons :
The discovery of benzene on the first day is a red flag. Benzene is a toxic and carcinogenic hydrocarbon , often associated with petroleum products, including mineral oil. The EPA’s Maximum Contaminant Level (MCL) for benzene in drinking water is 0.005 mg/L (5 ppb) , which is a very low threshold. This indicates that even small amounts of contamination could result in unsafe levels of benzene. Petroleum-like smell and taste : These are strong indicators of hydrocarbon contamination . Hydrocarbons, particularly aromatic compounds like benzene, toluene, and xylene, have distinct, pungent odors and can impart a gasoline-like taste even at very low concentrations.
4. Why It Persisted for Days :
Infrastructure contamination : Hydrocarbons can persist in the water system, especially in the piping or reservoirs, if they adhere to surfaces or form films. This can cause the smell and taste to remain even after flushing and treatment attempts. Delayed remediation : The response timeline you describe, where authorities cleared the water for use while it still smelled and tasted of gasoline, raises questions about the effectiveness of the cleanup measures. It's possible that inadequate flushing or incomplete removal of hydrocarbons left residual contamination.
5. Precedents and Similar Cases :
Contamination of this scale isn't unique. There have been other cases in the U.S. where small amounts of petroleum products, such as fuel or oil, caused widespread water supply contamination. For instance: In Charleston, West Virginia in 2014, a chemical spill contaminated the water supply of 300,000 people. The contamination involved crude MCHM , and even though the quantities were relatively small, it took days to resolve the issue, with water still having an odor. Camp Lejeune, North Carolina had long-term contamination of its water supply with benzene and other VOCs due to improper disposal of industrial chemicals.
6. Potential Solutions and Future Prevention :
Regular monitoring and maintenance of critical water infrastructure (like pumps) is crucial to prevent contamination. Enhanced detection systems : Using more sensitive equipment to detect hydrocarbons and other contaminants early in the process could help in future incidents. Improved emergency response : Ensuring that water systems are thoroughly flushed and tested after contamination is essential before allowing the public to resume using the water.
Recommendations:
You may want to reach out to experts in environmental toxicology or water treatment engineering , as they could provide more specific insights into how hydrocarbons behave in water systems and why this particular contamination was so widespread. Agencies like the Environmental Protection Agency (EPA) or state-level Department of Environmental Quality (DEQ) could also offer detailed thresholds for specific contaminants like benzene, as well as protocols for dealing with oil-based contaminants in water systems.
In conclusion, while 2-3 gallons of mineral oil may seem like a small quantity, the presence of hydrocarbons like benzene and their ability to spread and persist in water infrastructure can explain how this contamination affected thousands of people and lingered for days.

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