Lab testing of waste: Knowing what to ask for

Do you send samples of waste for laboratory analysis? Do you understand the menu of options for analysis? Do you know what tests will give you the data you need? Do you understand the results that the lab provides? If you answered no to any of the above, then read on.

It is my experience that many samples of waste sent to laboratories for testing are resulting in inappropriate and often inadequate data being collected. Since this exercise is costly both in time and money it is important that this is done correctly.

Often, it can be a straightforward task, for example when you are testing a waste against a certain set of parameters, say on permit or other consent. You know what you need to test for and can compare your results with a list of limits. However, often this is not the case and you will need to decide what the lab should test for and then have an assessment carried out on the results. This is typically the case when testing waste, for example soil and trommel fines.

According to Waste Classification Technical Guidance WM3 all waste is classified as either hazardous or non-hazardous. To classify waste you need to know what hazardous properties the waste has and this will depend on the chemical substances that are present. There is no set list of chemicals to test for to be able to complete a robust hazardous waste assessment, this will always depend on what you expect the waste to contain.

All laboratories can provide a price for their ‘environmental suite’. This will typically include metals, non-metals, metalloids, total/speciated petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAH) etc. While this is a good place to start, it may not be adequate in some instances.

In the course of my work as an Environmental Consultant I see a lot of laboratory data on which I am requested to carry out a hazardous waste assessment. I can assess whatever data I am provided but if the data set is inadequate so too will be the assessment. Here are some of the common mistakes I see:

• Just a spreadsheet of the lab results is not adequate. The actual laboratory report is required as evidence within the hazardous waste assessment report.
• Too few metals being reported on. It actually costs very little more to get results on a good long list of metals.
• Total petroleum hydrocarbons being reported for C5 to C35. This should be C6 to C40 to comply with WM3.
• Leachate test data only being provided (known as WAC tests). A hazardous waste assessment cannot be carried out on WAC data alone. WAC tests should only be carried out on waste samples that have already been classified a hazardous or non-hazardous and are going to landfill. WAC data is of little use for waste being sent for recycling, so don’t waste your money on this.

Since you get what you ask for from a lab give this some consideration, even talk to the lab staff. You will find they have a wealth of knowledge and are keen to help. If you send the lab a sample of say soil and ask for a WAC test, that is what they will do for you whether it is appropriate or not in your circumstances. To classify waste (assign the correct waste code) you need to obtain ‘total content analysis’ results – this means the lab tests for what is in the waste and not what leaches off it, as in the WAC test.

While variability of results between samples of waste causes problems so too does the variability of results from different labs. Not all laboratories will handle samples in the same way, and this can affect the reported results. Not all laboratories analyse for substances in the same way, and this can affect the reported results. This does not make the results wrong but means that details of sample handling (details of sample clean-up etc.) and how the test was completed does need to be accounted for in the assessment of the results.

Testing waste samples can often throw up some unexpected results. This can be due to interference from other substances in the waste affecting results. The most common example of this is with total petroleum hydrocarbons (TPH). Other organic materials in the sample can cause a false high result. However, if requested, the laboratory can perform a clean up technique on the sample to avoid this. The more accurate, lower TPH result may make the difference between the waste being classified as hazardous or not.

Laboratories can also perform tests that look for the presence of hazardous properties in waste. These can be especially useful when a waste has been assessed as having a hazardous property, but you have reasons to suspect that it does not. For example, flammability. The presence of flammable substances may cause a waste to be assessed as flammable and therefore hazardous. However, a flammability test may confirm it is not flammable, which may change the classification of the waste.

The enforcement of ‘classification of waste’ requirements by environmental regulators will undoubtedly lead to more sampling and testing of waste being carried out. The cost of this to waste operators is likely to be significant so this process needs to be as efficient and effective as possible.

To help waste site operators understand more about lab testing of waste, watch our free video - Testing Your Waste: What to Ask For here.