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Skid-mounted membrane module trains at a brine concentration plant.

VMD · Technology

Vacuum Membrane Distillation

Vacuum membrane distillation drives separation with a vapor pressure gradient instead of a hydraulic one. A vacuum on the permeate side pulls water vapor through a hydrophobic membrane, leaving everything that is not volatile behind. The result: 85 to 90%+ total feedwater recovery on feeds that defeat reverse osmosis, and about 95% overall when it treats the reject of an RO plant, using less electricity (26 against 43 kWh/m³) and fewer utilities (129 against 300 kWh/m³) than an evaporator and crystallizer on Petro Sep's AQUA-SEP® data sheet.

Send a fluid sampleRequest spec sheet

What it solves

Performance you can size against.

What the process delivers. Every number is testable on your own feed.

Maximum feed TDS
Up to 250,000 mg/L
Far beyond the 60,000 to 80,000 mg/L practical limit of reverse osmosis.
Total feedwater recovery
85 to 90%+
Per the AQUA-SEP® brochure; about 95% overall when AQUA-SEP® treats RO reject.
Operating temperature
60 to 80°C
Low-grade heat works, including waste heat from upstream processes.
Footprint, 100 m³/day plant
2 skids
5.5 × 5.5 × 5 m and 6.5 × 2.5 × 5 m, per the AQUA-SEP® brochure.

How it works

The working principle.

A hot, salty feed flows through the lumen of hydrophobic hollow-fiber or flat-sheet membranes. Vacuum on the shell side drops the vapor pressure, drawing water vapor through the membrane pores while liquid water and dissolved solids are blocked by the membrane's hydrophobicity. Vapor condenses downstream as clean distillate. Salts, metals, organics, and suspended solids stay in the brine, which can be cycled back through the loop until the desired concentration is reached.

Guide

Performance envelope

Specs and operating range.

For preliminary sizing only. Production sizing is always validated against your specific feed.

Recovery
85 to 90+%About 95% overall when AQUA-SEP® treats RO reject.
Maximum feed TDS
250,000mg/L
Permeate quality
<10mg/L TDS
Operating temperature
60 to 80°C
Specific energy
26 + 129kWh/m³ electricity + utilitiesAQUA-SEP® Energy Comparison data sheet (100 GPM unit): 26 kWh/m³ of electricity and 129 kWh/m³ of utilities, against 43 and 300 kWh/m³ for an evaporator and crystallizer.
Footprint, 100 m³/day plant
2 skids5.5 × 5.5 × 5 m and 6.5 × 2.5 × 5 m

How we compare

VMD vs the alternatives.

Where Vacuum Membrane Distillation wins, where it does not, and where the alternatives are honestly the better fit.

Maximum feed TDS

VMD

Up to 250,000 mg/L

Reverse Osmosis

60,000 to 80,000 mg/L

Mechanical Vapor Recompression

Up to 350,000 mg/L

Specific energy

VMD

26 kWh/m³ electricity plus 129 kWh/m³ utilities (AQUA-SEP® data sheet, 100 GPM unit)

Reverse Osmosis

3 to 8 kWh electrical/m³ (low TDS only)

Mechanical Vapor Recompression

20 to 35 kWh electrical/m³

Tolerance to fouling

VMD

High; hydrophobic membrane resists organic fouling

Reverse Osmosis

Low; pretreatment cascade required

Mechanical Vapor Recompression

Moderate; scale management critical

Capex per m³/day capacity

VMD

Mid-range

Reverse Osmosis

Low (when feed permits)

Mechanical Vapor Recompression

High

Best fit

VMD

High-salinity, high-organic, ZLD-bound feeds

Reverse Osmosis

Low-TDS feeds with stable composition

Mechanical Vapor Recompression

Concentrated brines ahead of crystallization

Where this technology applies

Industries that use this process.

Vacuum Membrane Distillation fits some sectors better than others.

Oil, Gas & Energy

Process equipment, packaged plants, and patented separation for upstream, midstream, downstream, and energy.

Learn more

Mining

Process plants and patented separation for tailings, brines, lithium, and ZLD.

Learn more

Industrial Manufacturing & Environmental

Process equipment, packaged plants, and patented recovery for manufacturing, water reuse, and emissions control.

Learn more

Engineering FAQ

Questions engineers ask.

The questions we hear weekly. If you have a different one, send it with your consultation request and we will answer it directly.

Can VMD handle silica?
Yes. Hydrophobic membranes are far less sensitive to silica scaling than RO, and AQUA-SEP® uses high-velocity hollow fibres that keep scale and fouling off the membrane surface without chemical descalants.
What about feeds with hydrocarbons or oil?
Oily wastewater is one of the applications VMD serves, but oil and surface-active compounds can wet a hydrophobic membrane, so these feeds need pretreatment, as every AQUA-SEP® feed does. We pilot every feed before sizing the production system.
How does VMD compare to reverse osmosis on cost?
On low-TDS feeds, RO is cheaper to operate. As TDS climbs above 60,000 mg/L, RO recovery drops sharply and pretreatment cost rises. Above 80,000 mg/L, VMD is usually cheaper on lifetime cost. Above 100,000 mg/L, RO is not an option.
Can the system run on waste heat?
Yes, and many do. VMD operates at 60 to 80°C. Waste heat from compressors, boilers, and process streams in that range can run the system at marginal energy cost.
How are membranes replaced?
Module by module, not the full system. AQUA-SEP® membrane modules are easy to replace without shutting the system down, so plants stay online during replacement.

Have a feed that VMD
might fit?

We will pilot before we promise. Send us a sample and a target outcome. If the technology fits, we will tell you what to expect; if it does not, we will tell you that too.

Request a quote