Wastewater professionals enforcing industrial effluent standards for fats, oil and grease (FOG) usually must either perform a number of gravimetric tests or spend a significant amount of money with a contracted testing laboratory.
Infrared analysis offers an alternative that will considerably bring down costs and save time in the following ways:
90% Less Hexane Needed for Solvent Extraction
While using EPA method 1664, a liter sample requires 100ml hexane for extraction. The solvent quantity cannot be reduced with this method as the residual oil weight will be so low that it will be less precise for lower levels of oil and grease.
With the infrared/hexane extraction method, only 50µm of extract is needed for analysis and the sample size can be reduced to 100ml for a fairly well mixed waste stream. The 100ml volume requires 10ml of hexane for the extraction. Further to a monetary saving, reduced solvent usage means less exposure to solvent fumes for the operator and less volatile fumes as a potential fire hazard.
10 Minutes versus 2 hours for Analysis
The hexane/gravimetric method is time consuming and labor intensive, taking up to two hours before a final result is produced. The hexane/infrared method takes less than 10 minutes. This means a quick sample turnaround and less laboratory technician time.
The hexane/infrared method is easy and the following steps are followed:
- Add hexane to the sample and shake for 2 minutes
- Allow sample to partition
- Take 50 µm from the top layer of hexane extract and deposit on sample plate
- Press the “run” button on the analyzer, after the timer countdown of 5 minutes the measurement result is displayed
Fixed filter infrared analyzers, such as the InfraCal TOG/TPH Analyzer – Model HATR- T2, are compact (less than 6” square), light weight (less than 5 lbs) and be operated from a 12V power supply enabling them to be operated from a vehicle.
This means that wastewater effluent testing can be done at the site, helping in catching high oil and grease offenders. Screening for out-of-compliance effluent discharges enables collection, transportation and ultimately testing in the laboratory can be reduced.
The same can apply for in-laboratory testing. Samples can be quickly screened and the effluent samples that are over the oil and grease limit can be tested by the EPA 1664 method—saving time, solvent, and labor costs.
Less Glassware to Clean
In the field, bottles having milliliter marking on them can be used for collecting the sample, adding the hexane, shaking the sample and take the 50µm 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.
This kind of measurement is not new, as infrared measurement of oil and grease levels in produced water has been used in the petroleum industry worldwide on highly regulated off-shore and on-shore oil platforms for well over 30 years. Most of the analyzers being used for this measurement are the InfraCal TOG/TPH Analyzer – Model HATR-T2.
This information has been sourced, reviewed and adapted from materials provided by AMETEK Spectro Scientific.
For more information on this source, please visit AMETEK Spectro Scientific.