MD · Technology
Membrane Distillation
Membrane distillation is the thermal cousin of VMD. A temperature gradient across a hydrophobic membrane drives water vapor from a hot feed to a cooler permeate side. No vacuum required. Used where waste heat is plentiful and the feed cannot tolerate the energy of true evaporation.
What it solves
Performance you can size against.
The outcomes below come from commissioned systems and verified pilots, not theoretical limits. Every number is independently testable on your own feed.
- Thermally driven, no vacuum
- Suits sites with available waste heat and tight space envelopes.
- Recovery on high-TDS feeds
- Up to 95%
- Comparable to VMD on most feeds.
- Operating temperature
- 60 to 90°C
- Pairs with low-grade heat sources.
- Distillate quality
- <10 mg/L TDS
- Boiler-quality water from highly impaired feeds.
How it works
The working principle.
Hot feed flows on one side of a hydrophobic membrane. Cool distillate flows on the other side. The temperature differential creates a vapor pressure gradient that drives water vapor through the membrane pores. The membrane stays liquid-tight; only vapor crosses. Distillate condenses on the cool side and is collected.
Performance envelope
Specs and operating range.
For preliminary sizing only. Production sizing is always validated against your specific feed.
- Recovery
- 85 to 95%
- Maximum feed TDS
- 200,000mg/L
- Distillate quality
- <10mg/L TDS
- Hot side temperature
- 60 to 90°C
- Cold side temperature
- 20 to 40°C
- Specific thermal energy
- 300 to 600kWh thermal/m³Drops sharply when waste heat is available.
- Membrane life (typical)
- 3 to 5years
- Footprint per m³/day
- 1.5 to 3m²
How we compare
MD vs the alternatives.
Where Membrane Distillation wins, where it does not, and where the alternatives are honestly the better fit.
| Trait | MD | VMD | Multi-Effect Evaporation |
|---|---|---|---|
| Driving force | Temperature gradient across the membrane | Vacuum-induced vapor pressure gradient | Direct boiling, multi-stage |
| Operating temperature | 60 to 90°C | 60 to 80°C | 100 to 120°C across stages |
| Energy source | Thermal (waste heat ideal) | Mostly electrical (vacuum pump) | Steam, electrical for compression |
| Specific energy | 300 to 600 kWh thermal/m³ | 150 to 250 kWh/m³ total | 250 to 600 kWh thermal/m³ (evaporator; ~429 kWh/m³ total with crystallizer per the AQUA-SEP comparison) |
| Best fit | Sites with abundant low-grade waste heat | Sites with electrical capacity, high recovery targets | Centralized, very-high-volume facilities |
Driving force
MD
Temperature gradient across the membrane
VMD
Vacuum-induced vapor pressure gradient
Multi-Effect Evaporation
Direct boiling, multi-stage
Operating temperature
MD
60 to 90°C
VMD
60 to 80°C
Multi-Effect Evaporation
100 to 120°C across stages
Energy source
MD
Thermal (waste heat ideal)
VMD
Mostly electrical (vacuum pump)
Multi-Effect Evaporation
Steam, electrical for compression
Specific energy
MD
300 to 600 kWh thermal/m³
VMD
150 to 250 kWh/m³ total
Multi-Effect Evaporation
250 to 600 kWh thermal/m³ (evaporator; ~429 kWh/m³ total with crystallizer per the AQUA-SEP comparison)
Best fit
MD
Sites with abundant low-grade waste heat
VMD
Sites with electrical capacity, high recovery targets
Multi-Effect Evaporation
Centralized, very-high-volume facilities
Where it's deployed
Industries that use this process.
Membrane Distillation fits some sectors better than others. The industries below are where we have shipped multiple systems.
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.
When should I pick MD over VMD?
What about feed temperature limits?
Can MD handle scaling-prone feeds?
Direct contact vs air gap vs vacuum: which configuration?
Have a feed that MD
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.