How it Works: Highland Tank Oil Water Separators

By Peter Smyth
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Highland Tank oil water separators (OWS) combine state-of-the art technology with time-tested materials, making their OWSs the strongest and most reliable high-performance separators in the industry. Their OWSs help many industrial, commercial, and retail facilities with vehicle storage, maintenance, fueling, and washing areas comply with the Federal, Provincial and Local discharge and spill regulations.

Highland OWSs are designed for the removal of free-floating oil, grease, and settleable oily coated solids from oil/water mixtures associated with many types of petroleum, industrial, commercial, military, and municipal facilities. They can be installed below or above grade to help these facilities comply with tough spill and discharge regulations.

All Highland separators are constructed to American Petroleum Institute (API) and Underwriters Laboratories, Inc. (UL) specifications and equipped with their patented Corella® technology with secondary Petro Screen coalescers to provide effluent quality down to 10PPM or less of free oil. The coalescers combine the features of both a flat plate coalescer and a corrugated plate coalescer into a new “self-cleaning” design that performs better than traditional plate separators. Corella® accelerates the separation process and greatly reduces the level of oil and oily coated solids discharged into municipal sewer systems.

Diffusion Baffle

The velocity head diffusion baffle, located near the inlet of the separator, is designed to serve four basic functions: 

  1. Dissipate the velocity head, improving the overall hydraulic characteristics. 
  2. Direct incoming flow downward and outward maximizing the use of the separator volume. 
  3. Reduces flow turbulence and distributes the flow evenly over the separator’s cross-sectional area.
  4. Isolates inlet turbulence from the rest of the separator. 

Internal Chambers

In the sediment chamber, heavy solids settle out, and concentrated oil rises to the surface. The oily water then passes through the Corella® coalescer, an inclined arrangement of stacked parallel flat and corrugated plates.

The corrugated underside of the Corella® plates causes the oil to coalesce into sheets. The oil globules then rises to the surface of the separation chamber, where the separated oil accumulates. 

Any remaining solids sink to the top of the plates and slide off of the plates to the solids collection are. The effluent flows downward to the outlet downcomer, where it is discharged by gravity displacement from the lower regions of the separator.

Monitoring Systems

For easy and efficient operation and maintenance, electronic oil level controls sound an alarm at high oil levels so that waste oil can be removed from the separator. Double-walled separators are monitored with electronic leak detection systems for the interstitial space. Additional monitoring equipment is available for oil or water level sensing, alarm, and pump out control.

Oil/Water Separator Operation and Maintenance

Although an oil/water separator is designed for long-term trouble-free operation, maintenance is required as needed or in accordance with the specific facilities maintenance schedule.

  • The oil/water separator should be filled with water at all times for proper operation.
  • Periodically inspect the floor and trench drains and sand and grit interceptors which are installed upstream of the oil/water separator. The amount of debris permitted to enter the oil/water separator must be minimized for maximum effectiveness.
  • Periodically inspect the oil/water separator for sludge and oil level. oil/water separators should be maintained as free of accumulated sludge and oil as possible.
  • Regularly inspect the effluent in accordance with local codes and permits.
  • Detergents and solvents should not be discharged into the oil/water separator. Use of non-emulsifying, biodegradable cleaners is recommended.
  • Waste water containing untreated sanitary sewage must be excluded from the oil/water separator.
  • Waste oils should not be intentionally drained into the oil/water separator.
  • Cleaning the oil/water separator internals with high pressure cleaning equipment from above is the procedure of choice. This prevents a confined space entry and the possibility of discharging hazardous material at grade during cleaning. Persons servicing the oil/water separator must employ all mandated safety precautions.