Testing Drinking Water - An Overview of National & International Regulations

Introduction

Contaminated water is a threat to human health and the environment. As a result, national and international regulatory agencies like the U.S. Environmental Protection Agency (USEPA), World Health Organization (WHO), EU, and other regulators have set official drinking water testing methods and wastewater testing methods. For the analysis of drinking water, these methods must be used to assure a certain quality of the results and to ensure a benchmark of health and safety.

While a quality standard must always be maintained, regulations have increasingly allowed for more method flexibility in recent years. For example, the USEPA criteria for the recognition of slightly modified methods were pioneers in terms of simplifications. This paved the way to use test kits with the same chemistry like in official water testing methods. The revisions of the EU drinking water directives are also pursuing a similar approach. In the latest update of December 2020 [EU Directive 2020/2184], the measurement of uncertainty in conjunction with the limit of detection was defined as the criteria for method applicability. This means that any method can now be used in principle for the analysis, provided it meets the criteria. This also applies to the use of alternative methods like rapid tests.

To provide more convenient, while still reliable methods for users, rapid test methods following recognized standards (ISO, USEPA, and others) were developed. Respective certifications like ISO accordance or equivalency to EPA methods assure users that the ready-to-use test kits deliver comparable results so they can be used to comply with national regulations. These methods offer several additional benefits. One notable advantage is the reduced use of chemicals and sample volumes, resulting in decreased waste generation and enhanced user safety.

What do WHO, USEPA, and the EU say?

WHO Drinking Water Limits and Methods¹

The WHO declares access to safe drinking water to be a basic human right, essential to human health, and an element of an effective policy for health protection.

There are drinking water guidelines published for the maximum allowable levels of many parameters and detailed information on individual parameters can be found in the subchapters of the guidelines.

In addition to imposing limits on parameters, the WHO is also clear on its guidelines for drinking water analysis methods. While it is not essential to use standard methods, it is crucial to ensure that the chosen methods are appropriately validated and that their precision and accuracy are determined before making any significant decisions based on the obtained results.

It is therefore necessary to ascertain that a given method has sufficient precision and accuracy, with an auditable quality control and quality assurance procedure to ensure credible results.

USEPA Drinking Water Limits and Methods

The USEPA states on its Groundwater and Drinking Water web page: “The National Primary Drinking Water Regulations (NPDWR) are legally enforceable primary standards and treatment techniques that apply to public water systems. Primary standards and treatment techniques protect public health by limiting the levels of contaminants in drinking water.”²

In 1974, the Safe Drinking Water Act (SDWA)³ was enacted to protect and regulate public water supplies in the US. The SDWA authorized the USEPA to set enforceable standards for contaminants in drinking water in the interest of public health. Most approved analysis methods come from either the USEPA, the American Public Health Association (APHA), or the American Society for Testing and Materials (ASTM).

Additionally, there are allowances for modified methods with strict guidelines in terms of how alternatives are implemented and categorized.⁴ USEPA-equivalent methods may differ significantly from approved methods but must meet the criteria set out for procedural changes to be considered USEPA-compliant.

We received our first USEPA equivalency certificate in 1999 for a Spectroquant^® photometric test kit and since then we continue to work closely with consultants to have more equivalent methods for a range of testing parameters certified. To date, we provide equivalent methods to those in the Safe Drinking Water Act for the following parameters:

• Ammonium
• Chlorine
• COD
• ortho- and total Phosphate

For wastewater analysis, several equivalent methods to those in the Clean Water Act are available:

• Ammonium
• Chlorine
• Chromium (VI)
• COD
• Cyanide
• Nitrate
• Nitrite
• ortho- and total Phosphate
• Sulfate

For more detailed information, including approvals/equivalency documents, visit SigmaAldrich.com/usepa

EU Drinking Water Directive

The EU Drinking Water Directive (2020/2184 of Dec 16th, 2020)⁵ established the legal framework to protect human health from the adverse effects of drinking water contamination, providing clear regulations for all member states. Like both WHO guidelines and USEPA regulations, limits on various water parameters were implemented in order to protect human health. In its most recent update in December 2020, an important change was included in terms of analytical quality assurance such that the performance characteristics required of a measurement were clearly defined. Any method that fulfills the requirements for Limit of Quantification (LOQ) and Uncertainty (k=2) of the measurement as a minimum can be used.

Annex III, Part B of the directive has the chemical and indicator parameters for which such performance characteristics are specified, including a table defining the minimum performance characteristic ‘uncertainty of measurement’.

A comprehensive list of photometric ready-to-use test kits that meet these criteria can be found in our catalog which can be downloaded at SigmaAldrich.com/wfa-catalog

A general overview of drinking water testing with links to different focus topics can be found on SigmaAldrich.com/water-testing