How to Size an Oil Water Separator

If you are looking for a gravity oil water separator, here is a rule of thumb to determine the size. Multiply your estimated flow rate times 10 and that will be the minimum tank size. For example, if your flow rate is around 30 gallons per minute (gpm) you will want an oil water separator with a separation tank that is at least 300 gallons. This will give the oily water a 10 minute retention time in the separation tank. 10 minutes is usually enough time for gravity separation. If you want to be sure, collect a sample of your ... » Read More

Separating Emulsified Oils in Water

Separating Emulsified Oils in Water Oil can become emulsified in water by mechanical agitation and by chemical emulsification or both. Mechanical Emulsification of Oil in Water Centrifugal pumps often will cause mechanical emulsification. Also, any influent piping that is elevated above the surface of the oily water that is splashing into the tank will also cause emulsification and possible foaming. Oil that is mechanically emulsified will usually separate given enough time. Oil coalescing grids will also assist in separating the emulsified oils. Chemical Emulsification of Oil in Water Degreasers and soaps can chemically emulsify oil in water. Most degreasers and ... » Read More

What Do Oil Removal Claims Really Mean?

When you see a manufacturer claim that his oil water separator will remove oil and grease to below 200 mg/l or some other number, keep in mind what he really saying. They are usually basing their claim using pure water, at 65 to 70 degrees,  with some amount of clean SAE 30 weight motor oil straight from the can. Ask the vendor exactly what they are basing their oil removal claims on. Ask what percent oil was added, ask for exact SAE weight or viscosity and ask the temperature. Bench scale testing of your oily water is usually a good ... » Read More

My Wastewater Stinks Like Rotten Eggs

We received a call last week from a company complaining that the wastewater in the collection pit of their wash bay stunk so bad the workers were not wanting to work. They complained that the wash water in the collection pit smelled like rotten eggs. Hydrogen Sulfide Stinks That rotten egg smell is Hydrogen Sulfide gas (H2S).  This gas is produced by what are called anaerobic (no oxygen) bacteria. Anaerobic bacteria can live in the sludge that settles to the bottom of your collection pit. You can often see small bubbles of this gas coming to the top of the ... » Read More

Wash bay design mistake

Don’t Make this Wash Bay Design Mistake

An all too common wash bay design mistake I was recently working at an oil field service company in Houston and needed to walk out in the wash bay. It was a brand new wash bay, everything looked great. But I couldn’t believe it, the floor was slippery as an ice rink. I could barely walk across the floor. The construction contractor had put a smooth polished concrete finish on the wash bay floor. Add water, soap and the grease from the parts being washed and the floor turned into a slippery mess. The entire wash bay was a gigantic ... » Read More

Wash Bay Odor Problems?

Does the water in your wash bay have a strong offensive odor? Is it especially noticeable after a period of inactivity such as Monday morning? What causes Wash bay Odor problems? Odor is usually from bacteria in the water under what is called anaerobic conditions (no oxygen). When those conditions exist the anaerobic bacteria produce Hydrogen Sulfide gas, and that gas smells like rotten eggs. This is usually most notable in the summer time when its warm or after a weekend when the water sits and becomes stagnate. How Do I Control Wash Bay Odor Problems? Manual Odor Controls: Visit your ... » Read More

Selecting the Right Wash Bay Wastewater Treatment Equipment

Getting Started First review your local city and county regulations for the limits set on fat, oil, and grease that can be discharged. Take a sample of your wastewater and have it analyzed for the list of parameters in your local sewer regulations. Compare your sample results with the local limits, you may not need any treatment at all. Keep your analytical data on hand just in case you need it and resample annually or at the frequency required in your local regulations. Wastewater that doesn’t meet your local limits for fat, oil, grease or any other parameter cannot be ... » Read More