If you are unfamiliar with terms like “fatberg” and “FOG,” you might not realize the significance and environmental ramifications of this phenomenon. Your perspective will change if you look through recent news articles where fatbergs have blocked and damaged sewer systems in major cities.
Photo credit: Thames Water
In its most severe form, fatbergs physically block and break sewer pipes, forcing rain runoff, drainage water and raw sewage onto our sidewalks, streets and front lawns. The compounds necessary to form fatbergs are contributed by multiple sources; most notably, from us. When some of us pour fats, soaps, waxes, greases and oils down our drains and others of us flush random objects down our toilets (baby wipes, for example), all of those components meet up in a sewage pipe as they travel to the nearest wastewater treatment plant. The resulting product is a dense, insoluble solid which grows as other trash objects and oil and grease components travel by.
In its less severe form, this phenomenon creates a potential health hazard, and a challenge for wastewater treatment plants who must constantly monitor and treat this water before we consume it, bathe in it and cook with it.
On the surface (no pun intended!), testing this water seems relatively straightforward. Analytical instrumentation has advanced to become more sensitive, easier to use and more robust to handle more challenging sample matrices. Quantifying hydrocarbons that are coming from fats, soaps, waxes, greases and oils that people pour down their drains is well-within the capabilities of these instruments. However, proper extraction and separation of these components is key to the success of these analyses.
The current approach to this application involves the use of n-hexane to extract these compounds – which are appropriately referred to as Hexane Extractable Materials, or HEMs. The hexane solutions are then evaporated to dryness and a simple gravimetric measurement provides a quantitative oil and grease result. The use of hexane with an automated extraction and evaporation workflow, is safer, more efficient and more environmentally friendly than alternative approaches which require the use of chlorofluorocarbon solvents. It’s also compliant with EPA Method 1664B – a key aspect to keep in mind when evaluating a new system or laboratory workflow.
How do you perform your oil and grease measurements? What the keys to the success of your analyses? Let me know in the comments!