The Sampling Protocol and Measurement of Micro-constituents Recent Learnings

Over the last fifteen to twenty years in Europe, North America, and elsewhere, there has been growing interest and concern about the potential impact of micro-constituents on the health of the local and regional environment A number of jurisdictions in North America and Europe have undertaken studies to determine the concentrations and quantities of these constituents, and the ability of wastewater systems to remove these compounds, as well as their impact on human health and the local ecosystem. What is often overlooked and poorly understood are the sampling and analytical tools used to measure these parameters and the subsequent level of uncertainty that must be applied to the results used by wastewater facility design and operations personnel. This aspect has significant implications for regulators and for the owners and operators of wastewater treatment systems.Some recent findings in this area suggest there is an urgent need for enhanced communication and education between the data generators (typically chemists and environmental technologists) and the data users (typically engineers and operators) of analytical data. This involves a critique of existing sampling and analytical methods and the subsequent pitfalls that can be created by an inadequate exchange of information between researchers and practitioners, which can lead to the inappropriate interpretation of analytical results by wastewater practitioners.As with many analytical parameters the location, type, and timing of sample collection is critical to the values derived from the sample analysis. Furthermore, there are concerns related to the type of sample container used which impacts sample integrity, degradation, adsorption, volatilization, photo-degradation, as well as other physical actions that may impact each micro-constituent differently. For example the sample handling, storage temperature (i.e. freezing) and holding time can have a significant impact on transformation mechanisms that may occur. The container material and surface to volume ratio can influence concentration levels in the final result. In addition, the analytical methods matrix effect, the holding time, uncertainty level and recovery rate associated with the particular instrument, method, and analyst will have a significant impact on the final result. Furthermore, the level of data validation and proficiency testing (both of which seldom apply to analytical tests undertaken for these compounds) need to be considered when using the published laboratory data. The practitioner needs to factor in these aspects when evaluating the analytical results. Mistaken conclusions can ultimately cost utility owners and operators millions of dollars which in turn can undermine their credibility with staff and customers, or in the case of consulting firms, their clients. This paper addresses the stewardship of micro-constituent analytical data from the collection source to the production of the analytical result, and level of diligence required to ensure a result, that even so, carries with it a high degree of uncertainty.