Desalter Effluent Treatment with VSEP Ultrafiltration
Prevent Rag‑Layer Upsets and Protect Your Refinery Wastewater Plant with VSEP® Ultrafiltration
Desalters processing today’s variable crude oil, especially opportunity crudes, generate highly unstable effluent for desalter effluent treatment. Rag‑layer blowdown and mud‑wash events release emulsified oil, fine solids, and brine that routinely overload refinery wastewater treatment systems, causing compliance risk, process interruptions, and lost oil.
The VSEP® vibrating membrane system applies high‑shear ultrafiltration to separate suspended oil and solids directly at the desalter. VSEP treats either the full effluent stream or just the rag‑layer blowdown, producing a clean permeate for the WWTP and a concentrated oily sludge suitable for coker feed. The result is a more stable desalter, reduced WWTP load, and increased flexibility to run challenging crude slates without process upsets.
The Problem: Desalter Upsets Propagate to Wastewater
Desalting is the first step in crude oil processing and a common bottleneck. As feedstock quality and operating conditions vary, rag layer discharge (undercarry) and mud washing events release emulsified oil, solids (rust, clay, silt), and brine into wastewater. This can:
- Overload the refinery WWTP (primary source of oil carryover).
- Increase corrosion/fouling risk downstream.
- Force conservative desalter operation that degrades desalted crude quality.
- Limit flexibility to run opportunity crudes.
Typical ranges and contributors include:
- Wash water: ~2–6% of crude for extraction of salts/sediment.
- Effluent generation: ~2–2.5 gal/bbl crude to WWTP.
- Contaminants: salts (chlorides, carbonates), emulsified oil, suspended solids, metals, H₂S, ammonia, and phenolics (feed dependent).
- Operating variables: mixing intensity, demulsifier dosing, pH control (acid/caustic), electrostatic coalescence, and periodic mud washing that entrains rag layer emulsions.
Result: Even well-run desalters can intermittently send difficult emulsions and solids to the WWTP, increasing risk of noncompliance.
Treatment Improvements Possible
- Remove suspended oil and solids from desalter effluent, especially the rag layer blowdown, to avoid WWTP upsets.
- Dewater oily sludges to reduce haulage and enable coker feedstock utilization where permitted.
- Provide redundancy so the refinery can continue operating through variability, maintenance, or WWTP constraints.
- Improve desalted crude quality and increase feed flexibility (opportunity crudes) by decoupling blowdown risk from WWTP performance.
VSEP® Technology Overview
VSEP (Vibratory Shear Enhanced Processing) uses torsional membrane vibration to generate extremely high shear at the membrane surface, preventing fouling and enabling separation of viscous, high-solids refinery streams that defeat conventional filtration systems.
Key mechanics:
- Vibration: 50–55 Hz, ~1/2″ peak‑to‑peak displacement in torsional oscillation.
- Shear intensification: 5–15× higher filtration rates vs. conventional crossflow due to sinusoidal shear waves at the membrane surface.
- Module design: Parallel membrane disks with gaskets inside an FRP cylinder; pumped flow path maintains gentle bulk flow while vibration handles boundary layer control.
- Drive: AC motor with VFD; eccentric mass excites the filter stack at resonance for energy‑efficient operation.
Membrane flexibility: >200 membrane options from microfiltration to reverse osmosis. Selection is application‑specific (e.g., target removal of free/suspended oil and fines for WWTP protection, or tighter cut for discharge quality).
VSEP Refinery Installation – Long Beach, CA
Process Configurations for Desalter Effluent
Option A — Treat the entire desalter effluent
- Operate the desalter with continuous mud wash to smooth solids loading.
- VSEP permeate → existing WWTP (or to discharge if using tighter membranes meeting limits).
- VSEP concentrate (oily sludge) → coker feed (subject to site limits/specs), reducing hazardous waste liabilities and recovering hydrocarbons.
Option B — Treat rag layer blowdown only (event‑based)
- Automated valves route normal salty water to WWTP.
- Prior to mud wash/blowdown, valves switch to VSEP; post‑event, revert to WWTP.
- Removes the upset driver (emulsions/solids) from the WWTP, preserving biological stability and primary treatment capacity.
Control philosophy: VSEP is installed sidestream and starts on demand based on tank level or programmed events. It can be fully bypassed at any time to maintain refinery operations.
Using VSEP Concentrate as Coker Feedstock
Refineries with coking capacity can typically consume small quantities of oil‑bearing sludges (including VSEP concentrate) without impacting coke specifications, within site‑specific limits. This approach:
- Reduces offsite disposal of hazardous sludges.
- Recovers hydrocarbons from emulsions and rag layer blowdown.
- Complements existing practice (e.g., exchanger bundle sludge, tank‑cleaning filter cakes, slop emulsions).
Note: Maximum allowable rates are constrained by coke product specs and unit limits; engineering review required.
Technical Benefits (Operations-Focused)
- Redundancy & risk control
- Sidestream installation with full bypass capability.
- Modular units allow N+1 parallelization.
- Operator burden reduction
- Decouples WWTP performance from rag layer events.
- Less dependence on perfect demulsifier tuning during feed variability.
- Debottlenecking
- Mitigates the desalter as a rate‑limiting step; supports continuous refinery throughput.
- WWTP load reduction
- Removes the primary oil source to WWTP during blowdown events.
- Option to treat full effluent further reduces oil and solids reaching the plant.
- Improved desalted crude quality
- With VSEP capturing oil in blowdown, operators can lean into contaminant removal without risking WWTP upsets.
- Opportunity crude flexibility
- Reduces desalter upset risk associated with “opportunity crude” (lower assay, higher contaminants/water), expanding feed envelope.
Expected Outcomes (Application-Dependent)
- Permeate: Suspended oil/solids removal suitable for routing to the existing WWTP; with tighter membranes, potential for direct discharge (site‑specific, permit‑driven).
- Concentrate: Dewatered oily sludge with reduced volume; suitable for coker co‑processing (where allowed).
- Operations: Fewer WWTP upsets tied to rag layer events; smoother primary treatment loading; more stable compliance margin.
Note: Exact flux, rejection, and energy performance are site‑specific and depend on crude slate, chemistry, and control strategies. New Logic Research recommends treatability testing to finalize membrane choice and duty.
FAQs
Q1. How does VSEP handle emulsified oil from rag layer blowdown?
A. The vibrating membrane stack generates high shear at the membrane surface, disrupting boundary layers that stabilize emulsions in crossflow systems. This enables consistent removal of suspended/emulsified oil and fines while limiting fouling, even during mud wash events.
Q2. Can VSEP permeate bypass the WWTP?
A. Yes—if a tighter membrane is selected and site‑specific discharge criteria are met. Otherwise, permeate typically feeds the WWTP with significantly reduced oil/solids loading.
Q3. What happens to the concentrate?
A. It becomes a dewatered oily sludge. Many refineries co‑process small quantities as coker feedstock within coke spec limits; otherwise, concentrate volume is minimized for alternative management.
Q4. How is VSEP operated during desalter mud washing?
A. In event‑based mode, automated valves route blowdown to VSEP only during mud wash and rag layer discharge. In full‑flow mode, continuous operation smooths variability and reduces WWTP load at all times.
Q5. Does VSEP require high crossflow velocity?
A. No. VSEP relies on vibration‑induced shear, not high bulk velocity, allowing treatment of viscous, high‑solids refinery streams that challenge conventional crossflow systems.
Q6. Will VSEP reduce desalter bottleneck risk?
A. Yes. By decoupling rag layer events from WWTP limits and stabilizing effluent quality, VSEP reduces the likelihood that desalter behavior constrains refinery throughput.
Case Study – Whiting Indiana
New Logic provided demonstration VSEP equipment to filter mud wash brine using a PVDF UF membrane. The mud wash contained 3% oil and 0.4% TSS. The system operated at 70ºC and was able to recover 95% of the volume as filtrate with very low oil and TSS to send to the WWTP.
| % Solids | Conductivity | pH | Volume | |
| Initial Feed | 1.25% | 2900 µS | 8.16 | 100% |
| Final Permeate | 0.07% | 4650 µS | 8.43 | 95% |
| Final Concentrate | 26.62% | n/a | 7.83 | 5% |
Case Study – Illinois Desalter
Concerns were raised about refinery effluent discharging to Lake Michigan. An industry organization Petroleum Environmental Research Forum (PERF) organized a VSEP pilot trial and a Midwest refinery processing heavy crude. The VSEP, using a 5 kDa PES UF membrane was able to process the rag layer discharge by itself attaining 25 gfd flux rate. The system was also run on the mud wash brine and performed at a slightly higher flux rate.
The Purdue University Calumet Water Institute evaluating this and other VSEP desalter projects concluded: “One technology to remove solids and oil carryover for the control of brine upsets from desalting is showing success in pilot tests and the VSEP membrane system is of great interest.”
PERF Rage Layer Samples Before/After VSEP
VSEP® Design Considerations
- Recovery limited by material rheology and viscosity
- Performance is site‑specific
- Throughput depends on temperature, type of membrane, concentration level
- Prescreening >100 microns required
Design note: Actual performance is site‑specific. We pilot test to select membrane type, flux, recovery, and pretreatment options. Chemistry varies for each refinery. Final system sizing, membrane selection, and performance projections are only provided after pilot testing validation.
VSEP® systems are designed to support NPDES discharge, sewer discharge, and reuse permits, subject to site‑specific regulatory approval.
Request a No‑Cost VSEP® Mud Wash Assessment
With decades of experience treating some of the most challenging industrial wastewaters, VSEP® provides proven desalter effluent treatment solutions.
Your assessment includes:
- Contaminant characterization (Oil, TSS, ammonia, metals, TDS)
- Pilot testing options using your actual effluent
- Treatment configuration and implementation roadmap
- CAPEX and OPEX estimates
Talk to a VSEP refinery expert today.
+1‑775‑783‑7600
info@vsep.com
Pilot Testing: https://www.vsep.com/technology/pilot-testing/
VSEP® Technology: https://www.vsep.com/technology/
Read the full case study: https://www.vsep.com/pdf/DesalterCaseStudy.pdf
Summary: Key Benefits of Using VSEP for Desalter Effluent
- Stabilizes refinery wastewater treatmentby removing the main source of oil and solids upsets—rag‑layer blowdown and mud‑wash emulsions.
- Improves desalter reliabilityby decoupling effluent quality from variable crude slates, demulsifier performance, and operator timing during blowdown events.
- Recovers valuable hydrocarbonsby capturing oil in the blowdown and returning it as concentrated sludge suitable for coker feedstock.
- Reduces WWTP load and expands capacity, enabling higher throughput or accommodating future regulatory requirements.
- Mitigates refinery bottlenecksby preventing desalter-related process interruptions, allowing more stable crude unit operation.
- Enhances desalted crude qualityby giving operators freedom to optimize contaminant removal without risking WWTP overload.
- Expands ability to process opportunity crudes, lowering feedstock cost while reducing the risk of desalter upsets associated with high‑contaminant crude oils.
- Provides operational redundancythrough modular, sidestream installation with full bypass capability and automated event‑based control.
- Handles viscous, high‑solids streamsthat defeat conventional crossflow membranes due to VSEP’s high‑shear vibrating filtration mechanism.