Smarter Separation for Refineries and Process Facilities
Mercer’s enhanced gravity separators replace outdated concrete API tanks and corrugated units with those that provide automated, compliance-ready solutions for refinery wastewater and process drainage.
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INDUSTRY INSIGHT
In refinery and petrochemical operations, oily wastewater is a constant byproduct from desalters and washdowns to stormwater containment and equipment drainage. Many refineries still rely on concrete API separators where chain-and-flight skimmers never worked as intended, or were removed years ago. Without functional removal systems, these basins slowly choke with floating oil, sludge mats, and accumulated solids. Operators are left hand-cranking skimmers, dealing with collapsed water columns, and fighting constant TOG/TSS carryover into the WWTP.
Mercer replaces that entire failure cycle. Our systems deliver automatic oil recovery, timer-controlled solids purging, and stable, full-volume hydraulic performance. Vapor containment and odor reduction are built in, and the Multi-Pack™ coalescer captures oil droplets up to three times smaller than legacy technology can touch. The result: dependable, automated primary separation that finally gives downstream treatment a fighting chance — and restores the performance that refineries have been missing for decades.
Mercer International’s Compliance Master™ separator, equipped with the Multi-Pack™ coalescer system, is engineered for high-efficiency removal of free and dispersed hydrocarbons across all refinery drainage points. These systems deliver API 421-level performance in a smaller, automated, and low-maintenance footprint, giving operators confidence in compliance and reliability.
Mercer’s downstream solutions bridge the gap between environmental responsibility and process uptime, ensuring cleaner water discharge, recovered oil revenue, and longer downstream treatment system life.
Challenges
Many refineries still rely on oversized concrete API separators that occupy valuable real estate. With many units dating back to the 50s tank viability alone is a major issue.
Most refineries turning to us have long since removed their aggravating merry go round removal systems. For those that are still keeping up the fight, this nightmare requires constant troubleshooting and replacement.
Slotted pipes and hand cranked manual skimmers? Good luck with that. With solids particulate creating a cottage cheese textured oil layers, the oil just sits and seeps. Getting oils to rise is only valuable if you can quickly remove it. The longer it sits, and the more time it has to comingle with solids, the quicker it will sink. Now you have weighted oily sludge at the bottom that likely doesn’t get cleaned until an outage. Little by little that oil will seep out and carry through the unit
Millions of dollars are thrown away calling in pumper trucks and men with shovels every 2 years to haul away oily solids that have no way out.
With many of these concrete tanks being open to the air, they have been difficult to bring into air quality compliance as regulators have pivoted. Floating covers or even concrete tops have been implemented, serving as the critical sealing point that preserves proper hydraulics and prevents the oil and solids carryover issues outlined above.
Solutions
Mercer’s Compliance Master™ and Multi-Pack™ coalescer technologies replace traditional API and CPI separators with true enhanced-gravity performance engineered for refinery conditions.
Delivers the same or better separation in one-quarter of the footprint while capturing oil droplets three times smaller than legacy systems. The result: predictable, dependable uptime, even when process conditions shift.
Mercer units can be equipped with electromechanical skimming to remove recovered product the moment it rises. We aren’t just coalescing the oil, we’re capturing it instantly. With a secondary decanting stage, recovered oils consistently test at <1% BS&W, reducing disposal hassles and improving product quality.
Mercer systems automatically evacuate solids using level-based monitoring and timed actuation of multiple sludge valves along the hopper bottom. Imagine eliminating the recurring cost of cleaning out sludge from that API concrete tank, that savings alone pays for the upgrade ten times over.
Multi-Pack™ modules easily tie into existing API basins, vaults, sumps, or process drains, upgrading performance without major civil modifications.
Purpose-built for refinery environments with durable fabrication and chemical-resistant linings that stand up to decades of service. Airtight covers with premium gasketing ensure VOC/BTEX constituents do not weep from the tank, protecting operators and maintaining compliance.
Applications
Recover oil and protect biological treatment systems downstream.
Capture oily runoff from secondary containment and stormwater events.
Remove trace oils and particulates before discharge or reuse.
Treat oily wastewater at the source to reduce central system load.
Automate treatment and discharge control for compliance with NPDES permits.
MERCER ADVANTAGE
Mercer designs every refinery solution with one core mandate: reliable oil and solids removal paired with airtight emissions control. In today’s O&G environment, emission collection, suppression, and elimination are no longer optional—they’re operational requirements. We build for that reality.
Controls handle skimming, sludge purging, and vapor sealing—cutting labor, downtime, and VOC/BTEX escape.
Eliminate massive civil structures while achieving superior separation performance.
Reduce labor, eliminate confined space entry, and integrate with plant control systems.
Durable construction, long cleaning intervals, and recoverable oil improve ROI.
Built and tested to align with API 421 intent with proven real performance, not just paperwork.
Cleaner effluent, recovered oil, and reduced waste hauling support sustainability and ESG reporting.
Yes. Mercer’s systems are designed for retrofit or full replacement, offering equivalent or better performance in a smaller footprint.
Absolutely. Materials and coatings are selected based on exposure, including hydrocarbons, acids, and surfactants to prevent corrosion and fouling.
No. Mercer systems allow bypass operation or skid-mounted swap-out options for continuous uptime.
Each unit includes automated oil skimming and discharge, minimizing operator involvement.
Yes. Systems can include SCADA/PLC connectivity, oil-level alarms, and remote monitoring capabilities.
