PVC and Vinyl Chloride Manufacturing Wastewater: Chlorinated Hydrocarbons and Mercury

PVC plants run one of two routes, and they produce quite different water. The ethylene route feeds EDC and VCM with chlorinated hydrocarbons as the main concern. The carbide acetylene route, still common in China, adds mercury from the catalyst used to hydrochlorinate acetylene — which turns a treatment problem into a much more serious compliance one. Establishing which route you have, and whether both run on the same site, changes the design fundamentally.

Two Routes, Two Problems

The ethylene route chlorinates ethylene to EDC, cracks it to VCM, then polymerises. Wastewater carries dissolved EDC, VCM and other chlorinated organics, plus suspended PVC resin fines from reactor cleaning and recovery systems. Suspension polymerisation adds dispersants and initiator residues.

The carbide route reacts calcium carbide with water to generate acetylene, then hydrochlorinates it over a mercuric chloride catalyst. Wastewater from this route carries mercury — in spent catalyst, in scrubber liquor, and adsorbed onto carbide slag fines. It also carries sulphide and phosphide from the acetylene generation step, since technical-grade carbide is rarely pure.

Many sites run both. If yours does, keep the streams separate. Mercury-bearing water has no business being diluted into the general sewer, both for treatment reasons and for the sludge classification consequences that follow.

Chlorinated hydrocarbons are volatile, recoverable, and toxic to the biology you would otherwise rely on. Removing them by stripping ahead of biological treatment is standard and should be the first step, not an afterthought.

Air or steam stripping in a packed tower removes EDC and VCM efficiently. Recovered vapour goes back to the process or to a destruction unit — do not vent it. Stripping also protects downstream workers from exposure and reduces the odour complaints that otherwise arrive with any chlorinated solvent release.

Suspended PVC fines need removal first, or they foul the stripper packing. Hydrocyclones or dissolved air flotation ahead of stripping handle them, and recovered resin has value if it is not too degraded.

Mercury: Treat It as a Separate Project

Where mercury is present, it dominates everything else. Limits are extremely low — typically measured in tens of micrograms per litre or less — and the analytics are specialised and expensive.

Treatment routes that work: sulphide precipitation to very low solubility, ion exchange or specialised chelating resin for polishing, activated carbon or metal-specific adsorbent media, and membrane rejection. Most plants need two of these in sequence rather than one.

Critically, mercury partitions to solids. Your sludge, your spent carbon and your spent resin are all potentially mercury-bearing wastes. Classify them, and confirm a disposal route, before you commission. This is the same lesson as with any metal-bearing sludge, except here the consequences of getting it wrong are considerably worse. If your site also runs this kind of duty, Landfill Leachate Membrane Concentration and Evaporation system covers the cost side of the decision in more depth.

Mercury also volatilises. Enclosed treatment units with managed vent gas are worth the cost, and operators need appropriate exposure monitoring.

Biological Treatment on Chlorinated Streams

Once the recoverable solvents are stripped, the remaining dissolved load is treatable, but salinity is usually the binding constraint. Chloride concentrations from the chlorination and cracking steps are high, and conventional biomass struggles above roughly 10,000 to 15,000 mg/L chloride.

Acclimatised biomass handles substantially more than a municipal seed would, which is why slow ramp-up with a halotolerant seed is worth specifying. Membrane bioreactors help by holding inventory at long sludge ages, letting you keep the slower-growing adapted organisms.

What Our Project Data Actually Shows

Across 42 commissioned plants where we hold complete COD records, influent COD ranged from 200 to 172,000 mg/L and treated effluent from 50 to 5,000 mg/L. Average removal across that set is 87.1% — not a marketing figure, but the measured mean.

That average is worth pausing on. It sits well below the 95%-plus numbers most suppliers quote, because the set includes genuinely difficult streams. On some electroplating and municipal duties the installed configuration only reaches about half the influent COD, and saying that up front is more use to you than a number the plant will never hold.

Anaerobic treatment deserves consideration — chlorinated compounds are often amenable to reductive dechlorination under anaerobic conditions, which can make otherwise recalcitrant molecules treatable. Pilot first. Reductive dechlorination is also slow, and intermediate products such as vinyl chloride are more concerning than the parent compound.

Where biological treatment is marginal, advanced oxidation or wet air oxidation on the concentrate is a credible route. Both are expensive per cubic metre, which is an argument for keeping the concentrated streams small.

Practical Priorities

Segregate aggressively. Mercury-bearing, high-chloride and clean cooling streams each want separate handling, and blending them produces a large volume that is harder to treat than any of the parts.

Recover resin fines and strip solvents before anything else. Both reduce load more cheaply than any treatment stage. Much of this mirrors the situation set out in brewery and winery wastewater treatment.

Finally, get the analytical capability sorted early. If your laboratory cannot measure mercury at the consent limit reliably, you have no way of knowing whether the plant works. Much of this mirrors the situation set out in Toxic Organics, Auxiliary Chemicals and ZLD.

Where This Fits in the Wider Plant

If your site also runs this kind of duty, Paint Booth Wastewater Treatment covers the cost side of the decision in more depth. Most facilities do not run a single clean stream, and a shared equalisation and biological stage is usually the economical answer once the streams are chemically compatible.

Why Choose Baihuipu as Your Manufacturer

Picking a supplier for this kind of plant is mostly about who carries the risk when something goes wrong. We have built this equipment for more than twenty years, and we are the ones who fabricated it, programmed the controls and will still answer the phone three years from now.

Manufacturing Base in Guangdong

Owned production lines mean we control tolerances, materials and delivery. Standard modular units and bespoke skids are both built by our own people, so schedule commitments are ours to keep.

Experience Built the Hard Way

Since the early 2000s we have commissioned plants for food and beverage processors, chemical works, electroplaters, textile mills, mines and municipalities. The lessons that stick are scaling, fouling and sludge handling — those inform every design we issue.

Documentation You Can Actually Audit

Each system ships with as-built drawings, material certificates, welding records and a functional specification. If a client's own consultant wants to review the process calculation basis, we hand it over rather than treating it as proprietary.

Certification and Export Practice

CE marking is standard and we work to ISO 9001 procedures. Where a project calls for specific material grades, pressure vessel certification or ATEX-rated equipment, we build to that standard and ship the full documentation pack.

We Engineer the Whole Train

Screening, equalisation, biological or chemical treatment, membranes, evaporation, brine handling — the complete line comes from one organisation. Process design, mechanical, electrical and PLC programming sit under the same roof, so there is no gap for finger-pointing at handover.

Twenty-Plus Export Markets

We have shipped to the United States, Canada, Russia, Indonesia, India, Nigeria and Vietnam among others. Crating, export documentation and certificates are handled in-house, which keeps customs surprises to a minimum.

Spare Parts and After-Sales Support

We carry membranes, pumps, blowers, diffusers and instruments for every system we supply. Remote support through the PLC is standard on most builds, and on-site service covers commissioning, training and urgent callouts.

Let's Look at Your Numbers

Share your water analysis and site constraints and we will give you a straight assessment of the process route and the realistic operating cost before you commit to anything. Contact our engineers at WhatsApp: +86 13631765076, or find us at hkbhp.com.

WhatsApp: +86 13631765076

Frequently Asked Questions

What does it cost to run, per cubic metre?

Energy dominates, then chemicals, then sludge disposal. We give you a per-cubic-metre breakdown during proposal so you can compare it against your sewer charge — treating too aggressively is a common and expensive mistake.

What spare parts should we hold on site?

Critical spares are pumps, dosing valves, instrumentation sensors and any specialty media. We ship a recommended spares kit with the plant and hold stock for everything we supply, so lead times on replacements stay short.

How long does a PVC vinyl chloride system take to deliver?

Standard units ship in about 9 to 10 weeks. Custom trains with strip before you treat included run longer — plan for 16 to 21 weeks once detailed engineering starts. Site installation and wet commissioning add another few weeks.