Earth Day 2022: Why Oily Wastes are a Big Problem for Water Treatment

Earth Day is a chance to show appreciation for our planet’s natural resources. This Earth Day we are highlighting clean water resources and wastewater treatment methods.

What is HEM?

An important part of protecting clean water resources is the removal of oil and grease from wastewater. If these fatty compounds are not extracted before the water is discharged in the environment, the residues can be harmful to aquatic life and lead to pollution (1). Removal and testing of oil and grease, also called total n-hexane extractable material (HEM), is included in US EPA Method 1664 B. HEM is used to measure pollution from chemicals including benzene, toluene, hydrocarbons, aliphatics, and fatty acids (2). Wastewater testing can also use HEM to ensure that facilities are operating well and free of clogs from oil or grease.

How do you extract oil and grease?

Water and oils don’t mix, but oil and grease extraction is challenging without the right equipment. PVC vacuum manifolds are a lightweight and portable solution for HEM. In approved method EPA 1664, hexane is used to extract fatty materials from an acidified sample. Then the hexane is evaporated, leaving behind a solid residue of hexane extractable materials (3). Here are some basic steps to the method (4):

  1. Assemble a vacuum manifold and connect to vacuum pump
  2. Prepare water sample
  3. Condition extraction cartridge
  4. Load sample to cartridge
  5. Elute sample dissolved in hexane
  6. Dry the extract to recover HEM

You can help reduce HEM

Fat, oil, and grease do not dissolve in water, leading to big problems for wastewater treatment. Clogs of fatty materials cause drain blocks and sewer back-ups that leak harmful materials into the environment. A large percentage of fats that lead to these clogs are food waste from vegetable oils, meats, and dairy products. This Earth Day you can reduce HEM in wastewater by disposing of fatty food wastes in the garbage or by taking it to an oil certified collection center.

References:

  1. Oil and Grease Analysis. Caltest Analytical Laboratory. Retrieved from https://caltestlabs.com/analytical-services/oilgreaseanalyses/
  2. Modern Hexane-Extractable Material (Oil and Grease) Analysis in Wastewater Samples. Chromatography Online. Retrieved from https://www.chromatographyonline.com/view/modern-hexane-extractable-material-oil-and-grease-analysis-wastewater-samples
  3. Understanding Oil and Grease. Cole-Parmer. Retrieved from https://www.coleparmer.com/tech-article/understanding-oil-and-grease-method
  4. EPA Method 1664B: n-Hexane Extractable Material. Unitedchem.com. Retrieved from https://www.unitedchem.com/media/at_assets/tech_doc_info/EPA_Method_1664B_1.pdf