Vinyl Chloride

About Vinyl Chloride Contamination

Vinyl chloride (VC) is a regulated contaminant classified as a known human carcinogen by the EPA. It commonly occurs as a daughter product from the incomplete reductive dechlorination of chlorinated solvents such as PCE and TCE. When parent compounds are only partially degraded through sequential pathways (PCE → TCE → cis-DCE → VC), vinyl chloride can accumulate in groundwater at concentrations that exceed regulatory standards.

Avoiding Vinyl Chloride Accumulation

One of the key advantages of Hepure’s Ferox zero valent iron products is that ZVI treats chlorinated solvents abiotically, avoiding the stepwise production of harmful daughter products like dichloroethene (DCE) and vinyl chloride. This is particularly important at sites where incomplete biological reductive dechlorination has caused VC accumulation.

Treating Existing VC Contamination

Hepure’s Ferox ZVI products can directly treat vinyl chloride through abiotic reduction pathways. For sites where biological treatment is appropriate, Hepure’s emulsified vegetable oil (EVO) and sodium lactate support complete anaerobic dechlorination to ethene and ethane. Dehalococcoides bacteria can fully degrade vinyl chloride when provided with appropriate electron donors and geochemical conditions.

Ferox Plus emulsified ZVI combines both approaches — providing ZVI for direct abiotic treatment alongside vegetable oil to support continued microbial activity.

Why Plumes Stall at Vinyl Chloride

Sequential reductive dechlorination gets harder at each step: PCE and TCE give up chlorine atoms relatively readily, but the final step — vinyl chloride to ethene — is the slowest and most demanding. Completing it biologically requires specific Dehalococcoides populations carrying the right enzymes and a sustained supply of electron donor. When the donor runs out, geochemical conditions drift, or the needed organisms are absent, the sequence stalls — parent compounds decline while vinyl chloride accumulates. That is why a site can show “progress” on PCE and TCE while its regulatory problem is getting worse: VC is more toxic and more strictly regulated than the parents it came from.

Sources and Regulatory Standards

Beyond its role as a degradation daughter product, vinyl chloride is used industrially in PVC production, and historic releases occur near manufacturing and disposal sites. The federal drinking water MCL for vinyl chloride is 2 parts per billion (0.002 mg/L) — among the strictest for chlorinated compounds, reflecting its classification as a known human carcinogen. Many states apply comparable or stricter groundwater standards, which is why VC frequently drives site cleanup requirements even where parent-compound concentrations have fallen.

Treatment Options for Vinyl Chloride

Zero valent iron (abiotic reduction). ZVI degrades chlorinated ethenes through abiotic pathways that largely bypass the sequential daughter-product chain — treating VC directly and preventing new VC from forming. Delivered as injectable powders, in permeable reactive barriers with granular Ferox PRB, or combined with electron donor as Ferox Plus (eZVI). See the full list of contaminants ZVI treats and a field case study of a ZVI barrier stopping a cDCE/VC plume.

Chemical oxidation (ISCO). Permanganate oxidizes chlorinated ethenes — including vinyl chloride — quickly and without generating daughter products, making it well suited to VC source zones and hot spots where fast mass destruction is the goal.

Enhanced anaerobic bioremediation. Where biology is the right tool, the fix for a stalled plume is usually restoring the drivers: sufficient electron donor via emulsified vegetable oil or sodium lactate, appropriate geochemistry, and — where needed — bioaugmentation. Hepure’s bioremediation amendments support driving dechlorination all the way to ethene rather than parking at VC.

Plume control while treatment proceeds. Colloidal activated carbon barriers can arrest VC migration toward receptors while source treatment does its work.

Common Questions

Why is vinyl chloride rising while PCE and TCE decline? That pattern usually means reductive dechlorination is running but incomplete — the chain is stalling at the VC step. Check electron donor supply and dechlorinating population before assuming the remedy is failing.

What’s the fastest way to address a VC exceedance? For source zones, permanganate ISCO or ZVI injection destroy VC directly. For dissolved plumes threatening a receptor, a ZVI or carbon barrier intercepts migration while upgradient treatment continues.

Related contaminants: PCE, TCE, and the broader chlorinated solvent (CVOC) family.