Potable water quality and reporting
The importance of pure water in the laboratory cannot be overstated. From general lab procedures to highly sensitive analytical techniques, such as inductively-coupled plasma mass spectrometry (ICP-MS) or high performance liquid chromatography (HPLC), the quality of the water used can positively or negatively affect the outcome of the your laboratory’s results. With the goal of planning for the level of water filtration equipment your lab needs, you’ll need to know as much as possible about the quality of your feed water. To better understand how potable water is further filtered and refined, we must start at the source.
In the United States, water quality standards are defined by state agencies and change depending on the body of water. Many of these regulations stem from the Clean Water Act (CWA) and Safe Drinking Water Act (SDWA) which require governing bodies to provide annual reports on water quality. Also known as the 303(d) and 305(b) reports, these documents can provide a wide-ranging body of information about the water sample collected. Once these reports are submitted, the Environmental Protection Agency reviews and takes any necessary action based on the information contained in the report.
Contaminate Testing
Common contaminates that are tested and monitored are classified into six different categories. The first category is microorganisms. The microorganisms category is comprised of cryptosporidium, giardia lamblia, heterotrophic plate count (HPC), legionella, total coliforms, turbidity, and enteric viruses. Microorganism contaminate sources in potable water often come from human/animal feces or soil runoff. The next categories of contaminants are the disinfectants and disinfection byproducts. The disinfectants and disinfection byproducts consist of chloramines (as Cl₂), chlorine (as Cl₂), chlorine dioxide (as ClO₂), bromate, chlorite, haloacetic acids (HAA5) and total trihalomethanes (TTHMs). These various contaminants are present in the potable water because they are used to control microbial growth or as by product of water disinfection process. The largest category of water contaminants are the organics. This category consists of 52 contaminants. These range from acrylamide to xylenes. Inorganic contaminants are the second largest category. This category consists of 16 contaminates ranging from arsenic to thallium.
Organic and inorganic contaminants can be present in potable water for a variety of reasons, including but not limited to runoff from fertilizer use, discharge from refineries and factories, or erosion of natural deposits near water sources. The final category of contaminants are the radionuclides. This category consists of alpha particles, beta particles and photon emitters, radium 226/228, and uranium. These contaminants are found in water through the natural decay of deposits of certain minerals.
Getting the Right Source Water
With so many contaminates being tested for and monitored, establishing clear and safe measures is important for producing safe potable water. For each of the contaminants previously listed there are several established levels or thresholds. The maximum contaminant level (MCL) value is the established upper limit that should be present in your potable water. For example, chloramine has an MCL of 4 and your source water has a tested value of 1 it is safe to say that source water has no known or expected risk to an individual’s health. There is a special limit set for monitoring residual levels of disinfectants known as the maximum residual disinfectant level (MRDL). The MRDL is the highest level of a disinfectant allowed in your potable water. Values at or below the established MRDL pose no known or expected risk to an individual’s health. The last established limit of measure is something known as the treatment technique (TT). TT is a required process intended to reduce the level of a contaminant in drinking water. Often this paired with coliform or organic contaminates. Maximum contaminant level goal (MCLG) and maximum residual disinfectant level goal (MRDLG) are additional limits set for water contaminants that may or may not differ from the MCL, MRDL, or TT.
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