VSEP Industries

Glycol Recovery

Recover Glycol. Cut Disposal Costs. Hit Discharge Limits.

Boost plant efficiency with membrane‑first glycol recovery engineered for the toughest industrial wastewater, from ethylene oxide scrubbers to PET condensate, TEG dehydration, and airport de‑icing systems. VSEP® (Vibratory Shear Enhanced Process) delivers high‑flux RO concentration, superior fouling resistance, and dramatic reductions in thermal load, helping you cut COD/BOD, recover valuable glycol, and meet stringent discharge limits with confidence.

Why recover glycol instead of “treating for discharge”?

  • High COD/BOD liability: Ethylene/propylene glycols drive COD/BOD and oxygen depletion; airport runoff studies show BOD often in the 100–1,300 mg/L range with COD 200–2,100 mg/L, largely from propylene glycol—directly translating to higher permit and treatment burdens.
  • Value in the waste: EG/PG/TEG are water‑soluble and non‑volatile relative to water, so membranes can concentrate them efficiently for reuse or sale, while permeate is polished to meet discharge or reuse specs. (Industry references below describe how these glycols are created in each process.)
  • Lower thermal energy: By pushing most of the water removal onto VSEP® RO, any downstream evaporator/distillation step is right‑sized and lowers steam/electric demand compared with thermal‑only recovery.
  • Regulatory fit: For airports, EPA’s deicing effluent program and NPDES permits increasingly expect collection and treatment of ADFs; membrane concentration simplifies compliance and lowers haul‑off. Membrane treatment also allows for recovery and reuse of the glycol instead of disposal.

The VSEP® Process (designed for fouling‑prone, high‑COD feeds)

  1. UF (optional) – Inline ultrafiltration when TSS, waxes, or oligomers are present (e.g., PET fines, oil carryover from TEG units).
  2. VSEP RO (primary concentration) – Vibratory shear turns “RO‑unfriendly” feeds into stable high flux, removing water and concentrating glycol to 10–20 wt%.
  3. Thermal finishing (as needed) – If higher concentration or product‑grade glycol is required, a small evaporator or distillation step takes over after VSEP. Because most water is already removed, thermal load is minimized.
  4. Polishing of permeate – A second‑stage spiral‑wound RO on VSEP permeate reduces residual COD for discharge or reuse.

Outcome: Reduced volume (and cost) to thermal or off‑site treatment, recovered glycol for internal reuse, and permeate that meets internal recycle or permit targets.

Applications for Glycol Recovery with VSEP

Below, we detail how each process generates glycol-bearing effluent, what you typically see in that effluent, and why a membrane‑first flowsheet pays back.

Applications for VSEP for glycol recovery systems.

1) Ethylene Oxide (EO) & Ethylene Glycol (EG/DEG/TEG) Plants

Where glycol comes from:

  • EO wet scrubbing: EO is absorbed into water then hydrolyzes to ethylene glycol; acid catalysis (e.g., sulfuric acid) is often used to accelerate conversion. Recirculating scrubbing solutions are periodically purged as “spent solution” rich in EG.
  • Integrated EO/EG circuits: Modern flowsheets use EO absorbers/strippers and re‑absorbers to route EO either to purification or to a glycol reactor; dilute EO–water absorbates and clean‑up bleeds are common side streams that ultimately form glycols upon contact with water.

Typical glycol strength you’ll encounter:

  • Indicative range: dilute to low‑wt% EG in scrubber/absorber purges, often operated until a “spent” threshold is reached for purge/recharge (site‑specific to loading and scrubber design). Vendor and process literature consistently document hydrolysis to EG and purging of EG‑bearing solutions, though exact purge setpoints vary by facility.

Why VSEP® first:

  • Organics & fouling tolerance: EO scrubber liquids and absorber bleeds contain EG plus acids and trace organics, VSEP’s high shear resists fouling better than conventional RO, letting you concentrate the glycol to 10–20 wt% before any thermal step.
  • Energy & OPEX: With most water removed by RO, evaporator/dryer duty drops, lowering steam and carbon per ton of recovered EG.

2) PET Resin & Fiber Manufacturing (MEG recovery)

Where glycol comes from:

  • PET is produced from EG + PTA/DMT; overheads from esterification/polycondensation and vacuum system waters often carry unreacted EG and low‑MW oligomers, and cleaning/wash waters mobilize additional EG.

Typical glycol strength you’ll encounter:

  • Indicative range: ppm‑level up to low‑wt% EG, depending on unit operation (e.g., polymerization condensate vs. equipment wash‑outs). References cite EG‑bearing “spent glycol” and condensates but plant‑specific process controls dictate the actual range.

Why VSEP® first:

  • Handles oligomers/fines: UF→VSEP tackles oligomer fines and BHET fragments that quickly foul spiral RO, while concentrating recoverable MEG.
  • Higher reuse value: Concentrated MEG can be routed to your internal MEG reclaim step; permeate goes to a polishing RO to hit process‑water specs.

3) Natural Gas Dehydration (TEG systems)

Where glycol comes from:

  • TEG units absorb water from gas; side waters (flash/KO pots, regenerator overheads/condensates, blowdowns) carry dissolved TEG and contaminants (BTEX traces, salts, oils).

Typical glycol strength you’ll encounter:

  • Indicative range: trace to low‑% TEG in wastewater, highly dependent on carryover and housekeeping. The process is designed for very low TEG volatility and losses, but contamination/upsets drive variability. (Industry guidance highlights TEG’s low vapor pressure, typical lean concentrations ~98.5–99.5 wt% in the loop, and efforts to minimize losses.)

Why VSEP® first:

  • Hydrocarbon/solids tolerance: VSEP UF removes oils/solids; VSEP RO concentrates TEG for return to reclaim or thermal finishing, cutting haul‑off and lowering COD load.
  • Polish for discharge/reuse: A spiral RO on VSEP permeate reduces COD to meet permits or utility‑water targets.

4) Airport De‑icing (Aircraft & Pavement)

Where glycol comes from:

  • Aircraft de‑icing/anti‑icing fluids (ADFs) are typically ~50% glycol (EG or PG depending on spec); during operations, fluid is collected on pads but significant fractions are lost during taxi/takeoff, generating stormwater with high BOD/COD.

Typical glycol strength you’ll encounter:

  • Runoff strength is highly variable with weather and collection efficiency; monitoring at major airports shows BOD ~100–1,300 mg/L and COD ~200–2,100 mg/L, with propylene glycol responsible for at least half of oxygen demand at monitored outfalls. Hot‑spots near pads can reach percent‑level glycol during intense events.

Why VSEP® first:

  • Variability ready: VSEP handles swings from dilute snowmelt to concentrated first‑flush, concentrating PG/EG to 10–20 wt% for off‑site recycling or on‑site thermal finishing, while permeate is polished to meet airport stormwater permits.

Airplane going through deicing.

How VSEP Works

VSEP® (Vibratory Shear Enhanced Processing) uses a vibrating membrane module to create intense shear at the membrane surface. This shear keeps solids, oils, polymers, and organic molecules from forming a fouling layer, allowing RO and NF membranes to operate on streams that would instantly plug conventional spiral‑wound systems.

A Membrane‑First Flowsheet Engineers Can Act On

Feed conditioning

  • UF (as needed): remove TSS/oligomers/oils to make RO robust (common at PET and TEG sites).

Primary concentration

  • VSEP RO: concentrate glycol to 10–20 wt%, remove the majority of water at low specific energy vs. evaporation.

Product finishing (optional)

  • Evaporator or distillation: reach product specs or higher concentrations; energy dramatically reduced because VSEP already removed most water.

Permeate polishing

  • 2nd‑stage spiral RO: trim COD and ions to discharge/reuse spec (cooling tower makeup, wash water, or boiler feed prep depending on site).

What you can expect from a VSEP® design package

  • Projected flux & recovery on your actual effluent, including UF pretreatment if needed.
  • Energy & mass balance that quantifies thermal load reduction vs. evaporator‑only or hauling.
  • Integration details for EG/PG/TEG recovery and permeate polishing (e.g., EO/EG absorber purge handling; PET condensate segregation; TEG reclaim; airport pad collection equalization).
  • Compliance mapping to NPDES/airport stormwater limits or internal reuse specs.

Ready to evaluate your stream?

Whether you’re bleeding EO scrubbers, managing PET condensate, minimizing TEG losses, or upgrading an ADF collection system, we’ll model UF → VSEP RO → Thermal (optional) → Polishing RO on your data and deliver a site‑specific business case.

Let’s run a quick sizing and energy comparison on your current disposal vs. recovery options.

Get a Site‑Specific Cost & Performance Analysis

VSEP® performance depends on feedstock, membrane selection, and recovery targets.

For a no cost custom performance projection, contact a VSEP engineer:  info@vsep.com

Learn More

New Logic Research has been deploying VSEP® membrane systems industrial applications since 1987. Our engineers have conducted dozens of pilot trials for glycol and commissioned commercial systems across North America, South America, and Europe