Wastewater professionals who are either enforcing industrial effluent standards or trying to keep their industry from exceeding the limits for fats, oil and grease (FOG) must perform numerous gravimetric tests or spend a considerable amount of money with a contracted testing laboratory. Infrared (IR) analysis provides an alternative testing method which will significantly reduce costs and save time in the following ways:
1. 90% less hexane required for solvent extraction.
When using EPA Method 1664, a liter (1000 ml) sample requires 100 ml of hexane for the extraction. The amount of solvent cannot be reduced with this method as the weight of the residual oil would be so low that it would be less accurate for lower levels of oil and grease. With the hexane/infrared extraction method, only 50 microliters of extract are required for analysis so the sample size can be reduced to 100 ml. This 100 ml sample volume requires only 10 ml of hexane for the extraction versus 100 ml of hexane for the 1664 method. In addition to a cost savings, reduced solvent usage means less exposure to solvent fumes for the operator and less volatile fumes as a potential fire hazard. The option is also available to use pentane as the IR extraction solvent which is less toxic than hexane.
2. 10 minutes versus 2 hours for analysis.
The hexane/gravimetric method is time consuming — taking up to 2 hours before a final result – as well as labor intensive. The hexane/infrared method takes less than ten minutes. This means quick sample turnaround and less personnel time.
- Add hexane to the sample and shake for 2 minutes
- Allow sample to partition
- Take 50 microliters from the top layer of hexane extract and deposit on sample plate
- Press the “run” button on the analyzer. After the timer countdown, the measurement result is displayed
Fixed filter infrared analyzers, such as the Wilks InfraCal TOG/TPH Analyzer – Model HATR-T2, are compact (less than 6” square), light weight (less than 5 lbs) and be operated from a battery pack or a 12 volt power from a vehicle. This means wastewater effluent testing can be done at the site.
On-site operation allows pretreatment operators at an industrial site to quickly check how their system is performing under different loading conditions. Those on the regulation side of the testing can sample right at an industry’s outflow making it easier to catch high oil and grease offenders. By screening for out-of-compliance effluent discharges, the number of samples collected, transported and ultimately tested in the laboratory can be reduced.
The same can apply for in-laboratory testing of FOG. Samples can be quickly screened to determine which samples are over the regulatory limit. Those that are can then be tested by the regulatory method (in the US– EPA 1664). Pre-screening samples will ultimately save time, solvent, and labor costs.
4. Less glassware to clean (or break!).
In the field, bottles with milliliter markings on them (as pictured above) can be used to collect the sample, add the solvent, shake the sample and take the 50 microliters of extract from the top for measurement. In this case, only one piece of glassware is used for analysis—requiring less solvent for cleaning and avoiding bulky separatory funnels with an easily breakable tip. If you have not broken a separatory funnel yet, you haven’t done enough extractions!
Infrared analyzers provide wastewater professionals with a quick and cost reducing way to measure FOG levels. The highly regulated petroleum industry has been using IR analysis for oil in produced water testing for over 45 years.