Above-Ground Oil-Water Separators
OPERATING TIER
Above-ground oil-water separators in the 50–100 GPM range are often selected for applications where wastewater volumes appear modest, but operating realities quickly expose weak separator designs.
At this flow range, separators do not fail because gravity separation “doesn’t work.” They fail because internal components foul, access for inspection is limited, and systems are selected by nameplate flow rather than real wastewater behavior.
Mercer’s 50–100 GPM separators are engineered for wastewater that includes free oil, suspended solids, temperature variation, and fluctuating flow conditions—not idealized influent assumptions. These systems are designed for continuous or high-frequency operation where uptime, serviceability, and predictable performance matter.
Built To Scale
This product family follows a compact, low-flow footprint philosophy, with internal volume and coalescer sizing adjusted by flow range and application requirements.
Please Note: Exact materials, dimensions, and configurations vary by application. Carbon steel construction is typically introduced at higher flow ranges where structural requirements dictate.
FIELD-PROVEN SYSTEMS
At this scale, experience is visible—or it isn’t.
The installations shown represent Mercer systems operating in the 50–100 GPM range, deployed in facilities where solids loading, oil variability, and maintenance access are part of daily operation.
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
Above Ground
400 GPM
TRUSTED BY INDUSTRY LEADERS
A small sampling of companies with Mercer separators.
ENGINEERED TO SOLVE
Flow rate is a label. Operating scale is the reality.
CORE TECHNOLOGY
A tank provides residence time.
Separation performance is determined by what happens inside the coalescer.
Mercer’s Multi-Pack™ coalescer is a purpose-engineered separation system designed to remain effective, adjustable, and serviceable even in compact separators operating under sustained solids loading.
Flat, steep-angled plates promote predictable oil rise while allowing solids to shed cleanly from plate surfaces. This geometry eliminates dead zones that trap solids and accelerate fouling in conventional media designs.
Plate spacing can be adjusted to match actual wastewater conditions, including oil type, temperature, viscosity, and solids behavior. Performance is tuned to the application rather than assumed.
Plates are arranged in a herringbone configuration that deliberately separates rising oil from settling solids, stabilizing internal hydraulics even as operating conditions fluctuate.
As oil droplets coalesce and solids shed from plate surfaces, they enter baffled, low-velocity Chimney Zones™ where oils rise and solids settle without re-entrainment.
The Multi-Pack™ is fully removable as a single assembly. Operators can visually inspect, clean, and return the coalescer to service without dismantling internal components.
There has never been a Multi-Pack™ removed from a Mercer separator where operators could not see through to the opposite side before cleaning begins. Surface films may be present. Clogged pockets are not.
Failures in the 50–100 GPM range seldom announce themselves. Instead, they sneak up on operators—through progressive fouling, reduced oil removal efficiency, rising maintenance effort, and increasing doubt about whether the system is still functioning as intended. In many installations, separators remain in operation well after their internal components have ceased to perform effectively.
The Multi-Pack™ is designed to avoid this slow decline. Its ability to release solids consistently, maintain stable internal flow conditions, and allow complete visual inspection and cleaning ensures that separation performance can be confirmed, recovered, and trusted over time—rather than taken for granted.
All at no cost to you.
We walk your site, capture real influent data if needed, engineer a custom separator from your worst-case scenario, and validate performance before fabrication. Only after the data confirms it do we issue a written guarantee. That’s how risk is removed.
PROVEN LONGEVITY
Built to Stay in Service
Many Mercer systems in this flow range were installed years ago and remain in continuous operation today. These are not retired units—they are active separators still managing oil and solids under real operating conditions.
Longevity at this scale reflects internal designs that can be inspected, cleaned, and maintained over time rather than replaced.
Above Ground
400 GPM
year: 2003
Above Ground
400 GPM
year: 2003
Above Ground
400 GPM
year: 2003
Above Ground
400 GPM
year: 2003
Above Ground
400 GPM
year: 2003
Above Ground
400 GPM
year: 2003
INDUSTRY APPLICATIONS
Above-ground oil-water separators in the 400–600 GPM range are deployed in operations where wastewater treatment is continuous, not intermittent, and where solids loading, oil characteristics, and maintenance access determine long-term performance more than nominal flow rate.
Food processing operations—including bagel, potato chip, sugar, fragrance, and flavor production—generate wastewater containing fats, oils, grease, organics, and suspended solids. Mercer separators are used where washdown cycles, temperature variation, and solids require non-fouling internals and consistent long-term performance.
Oil and gas water management (frac, flowback, and produced water), chemical manufacturing, tank farm cleaning, fuel handling, and spill recovery introduce wide variability in oil types, solids loading, and temperature. Mercer systems are selected in these environments for predictable separation, “next to nothing” maintenance, and internals that can be inspected and maintained under demanding conditions.
Utility yards, basement sumps, pump-and-treat systems, and consultant-designed treatment trains rely on oil water separators that operate reliably with minimal oversight. Mercer systems are incorporated where compliance, uptime, and long-term maintainability are required across varied operating conditions.
Airline wash-down facilities, truck washing operations, fleet maintenance areas, and transportation support facilities produce oil-laden wastewater with detergents and intermittent flow patterns. Mercer systems are deployed where cycling flows, solids carryover, and serviceability are critical to maintaining compliance.
Garbage collection sites, transfer stations, junkyards, and scrap operations generate heavily contaminated runoff with grit, debris, and hydrocarbons. Mercer separators are applied where robust solids handling and maintainable internals prevent gradual fouling and performance loss.
At 50–100 GPM, separators stop being a line item and start being a liability if misapplied.
Mercer engineers evaluate flow variability, solids behavior, and operating constraints to confirm that the separator will perform in real conditions, not just on paper.Talk to Mercer before finalizing equipment selection to reduce operational risk and protect long-term compliance.
At this scale, performance is rarely limited by coalescing media alone. Inlet energy control, flow distribution, and residence time determine whether the plates see uniform loading or spend their life fighting turbulence and channeling. This is why Mercer treats these systems as hydraulic devices, not tanks with plates dropped inside.
As flow increases, so does the consequence of unmanaged solids. Sludge buildup changes effective volume, disrupts flow paths, and quietly degrades separation efficiency. Mercer systems are designed to make solids visible, accessible, and removable so performance does not erode between maintenance intervals.
Yes. Systems in this range are often subject to inspections, audits, or discharge verification. Mercer designs for post-installation validation, including stable sampling conditions, predictable hydraulics, and repeatable performance rather than one-time acceptance testing.
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