Water Quality Exercises-Part 1: A Survey of EPA Water Quality Criteria
Earth Science Extras
by Russ Colson
A lot of rural water around the world is still derived from ground water via wells, like in the case of the kitchen faucet in the picture above. This water might be filtered, or run through a water softener, or sometimes treated for bacteria, but is generally not given more complicated chemical treatment.
Introduction
In this lesson, you will:
- Become aware of the EPA Water Quality Standards Handbook
- Consider some of the legal implications of the EPA water quality criteria
- Consider different water uses and the water quality criteria for each
- Think about biomagnification, bioaccumulation, and bioconcentration
- Consider different types of toxicants such as pathogens, herbicides and pesticides, inorganic elements, and others
- Compare toxicity of different toxins and categories of toxins
- Consider the effects of environmental factors such as salinity, oxidation state, and water hardness on toxicity
- Pay attention to units of concentration and unit conversions
- Calculate volumes of surface or ground water that could be contaminated by given amounts of a toxicant
- Think about water quality criteria under two different laws: The Clean Water Act and the Safe Drinking Water Act
Understanding EPAs Guidelines for Acceptable Pollutant Concentrations
The Water Quality Standards Handbook | US EPA is a valuable resource for understanding how water quality is evaluated and how the limits on pollutant levels are set. Take a look at this document and follow some of the links. The amount of reading to get through this document is quite extensive, but feel free to read as much as you can!
For an even more involved exploration of the detailed methodology, concepts, and approaches to evaluating and treating surface and groundwater, you can check out the following publication:
EPA publication EPA/600/6-85/002a, Water Quality Assessment: A screening procedure for toxic and conventional pollutants in surface and ground water, Revised 1985. Parts 1 and II.
This is the document (particularly part I) that I used to figure out water quality science as a young geologist, and, although it's getting on the old side, it still has concepts and ideas that are valuable to understand. Again, this is a lot to read through, a sort of "Bible" for calculating and figuring out many problems in water contamination, remediation, surface flooding, ground water issues and others, but you should look through it to get a sense of the kinds of approaches that might be possible when you need to solve a problem in water quality science.
However, trying to swallow all of the material above in one big gulp is a bit more than we are going to attempt in this lesson. Instead, we are going to focus on one particular chapter of the Water Quality Standards Handbook, that is, Chapter 3: Water Quality Criteria. ( U.S. Environmental Protection Agency (EPA). 2017. Water Quality Standards Handbook: Chapter 3: Water Quality Criteria. EPA-823-B-17-001. EPA Office of Water, Office of Science and Technology, Washington, DC. Accessed November 2018. https://www.epa.gov/sites/production/files/2014-10/documents/handbook-chapter3.pdf )
This is the chapter that deals specifically with the criteria for concentrations of pollutants in water that achieve the goals of the Clean Water Act. It addresses the "acceptable levels" of a variety of different pollutants in water, and includes several different categories of water.
For example, we can evaluate water quality according to different water uses such as recreational use, use for fishing/drinking, or use as a natural area. Recreational use might involve extensive body contact with the water with incidental consumption, whereas use for fishing would involve intentional consumption of water, fish, or shellfish. Use as a natural environment would emphasize preserving the vitality of the creatures living in the ecosystem. Each of these different uses of water corresponds to different criteria for acceptable pollutant levels.
There can be complexities to how the criteria are defined. For example, the human health considerations in the case using water for consumption, including consumption of fish, depend on whether a pollutant/toxicant easily partitions into air or water, or whether it tends to concentrate in living things (toxicants that concentrate in living things are said to bioaccumulate). Other factors can also affect our assessment of what constitutes an acceptable level of a pollutant or toxicant, such as oxidation state of the pollutant or the hardness of the water (hardness refers to the amount of dissolved ions in the water). Other conditions of the water might also be important to consider: artificial changes to the temperature of the water might constitute a type of 'pollution' for organism that require a particular temperature range.
Guidelines and standards governing pollutant levels in natural surface waters are governed primarily by the Clean Water Act (CWA). In contrast, drinking water (and consequently groundwater which is the source of drinking water for many rural populations) are mostly governed by a different law, the Safe Drinking Water Act (SDWA). The levels of toxicants that are acceptable in drinking water will (unsurprisingly) be different from those acceptable in surface waters. An interesting note: the guidelines for specific private rural water wells used for drinking water falls under the auspices of yet another organization, the Food and Drug Administration (FDA).
The exercises in the first part of this lesson are mainly intended to give you a sense of the variability in the acceptable levels for various pollutants/toxicants and an awareness that there are a variety of considerations in avoiding water quality problems, in determining a problem exists, and in remediating a problem.
Understanding the EPA water quality criteria in Chapter 3
The introduction to the online Water Quality Standards Handbook includes the following statement (as of 3/5/2022):
The Water Quality Standards Handbook is a compilation of EPA's water quality standards (WQS) program guidance including recommendations for states, authorized tribes, and territories in reviewing, revising, and implementing WQS. The guidance in this handbook supports EPA's WQS regulations at 40 CFR Part 131 .
Also, the online introduction to Chapter 3: Water Quality Criteria, includes the following statement (as of 3/5/2022)
The WQS Handbook does not impose legally binding requirements on the EPA, states, tribes or the regulated community, nor does it confer legal rights or impose legal obligations upon any member of the public. The Clean Water Act (CWA) provisions and the EPA regulations described in this document contain legally binding requirements. This document does not constitute a regulation, nor does it change or substitute for any CWA provision or the EPA regulations.
Did you notice the reference to "protect the designated use" in the EPA document cited in the feedback for the question above? There are different uses for water, and each use can have different health or environmental risks and therefore different criteria for acceptable levels of a pollutant or toxicant. Chapter 3 is organized to some extent according to different uses--take note of those uses in your reading of the chapter.
The first water use criteria that we are going to look at are the Human Health Criteria:
National Recommended Water Quality Criteria - Human Health Criteria Table | US EPA
Or to ensure that you use the same data that I am using for the exercises, you can look at
You need to open the Human Health Criteria table in another window and look carefully through the data to answer the questions below.
The Human Health Criteria give guidance for how much of a pollutant can be in fish and shellfish that people might eat. Since fishing can also be considered as a recreational activity, this usage of water could be folded into the category of "recreational usage", another category in the Water Quality Standards Handbook, as discussed in Chapter 3. In fact, some states, in developing their standards, do consider this as a recreational usage. However, whereas recreational use criteria focus more on bacterial elements in the water (significant if there is lots of body contact with the water and incidental ingestion), the Human Health Criteria are concerned with a wider range of pollutants and toxicants.
The Human Health Criteria table shows the concentrations below which there is expected to be little health impact for typical consumption rates. Both organism-only and organism + water criteria are shown. In listing both of these values together, the Human Health Criteria must take into account how pollutants can become concentrated in aquatic organisms that people eat (called bioaccumulation). There is a relationship between the concentration in the water and the concentration in fish that live in the water because pollutants will partition into organisms as the organisms 'breath' and 'drink' the water (this is referred to as bioconcentration). However, the relationship is made more complex because some types of pollutants, particularly those that are not volatile (that is, not easily evaporated) and do not readily partition into water, can become more highly concentrated in the organisms than might otherwise be expected. This might happen for example when a pollutant tends to stay in organisms long-term and when one organism eats another, and then other organisms eat that one, toxicants becomes bioaccumulated up the food chain (this is called biomagnification). When a pollutant becomes biomagnified, its limiting criteria concentration in the organism alone will be lower (or rather a smaller amount higher) relative to water, because by eating the organism, we humans can biomagnify a bigger dose of the pollutant into ourselves, and thus the tolerable concentration of the toxicant in the organisms that we eat will be lower.
Side discussion:
The pesticide DDT, mentioned in the question above, has a significant place in the history of the environmental movement. In the 1960s, DDT was biomagnifying (that is, becoming increasingly 'magnified' in living things as it moved up the food chain) and became a serious problem for some top-of-food-chain predators such as the bald eagle. In fact, the bald eagle, an important symbol of the United States of America, was threatened with extinction. Take a few minutes to think about how the symbolic importance of the bald eagle may have contributed to the acceptance of the dangers of DDT use, and, by proxy, use of other chemicals, Sometimes, moral rightness and logical clarity may not be particularly persuasive in convincing people of something they are not inclined to believe. Tying the argument to something that they truly care about might be more persuasive. However, if one abandons too completely the moral and logical foundations for an argument, and tries too much to make it simply an argument about what people want for themselves, the argument can lose its integrity and seem merely 'political' (in the negative sense of the word) and manipulative.
Spend some time thinking about a current environmental issue that you care about. Jot down some of the moral and scientific reasons for your stance on the issue. Then think of one or two reasons that someone not inclined to your viewpoint might become interested in the issue and more sympathetic to your perspective on it. Remember, the arguments that have convinced you have probably already not worked for the other person (and yelling the same arguments even more loudly or calling opponents stupid for not agreeing with you almost never works!), and it may be something else entirely that they find persuasive.
The second water use criteria we are going to look at are the Criteria for Aquatic Life
National Recommended Water Quality Criteria - Aquatic Life Criteria Table | US EPA
Or to ensure that you use the same data that I am using for the exercises, you can look at
National Recommended Water Quality Criteria - Aquatic Life Criteria Table _ US EPA-captured 3-3-2022
This table gives the concentration level below which the pollutant is not expected to significantly impact aquatic life communities. It gives values for the maximum 'spike' in concentrations that are acceptable as well as the acceptable continuous concentration averaged over some period of time. Since the toxicity of various pollutants depends on the conditions of the water, the table also shows values for both fresh water and salt water. It also, at the end, provides a means to estimate how the hardness of water (that is, the amount of dissolved minerals) affects the toxicity.
As before, you need to open the Aquatic Life Criteria table in another window and look carefully through the data in order to answer the questions below.
The third water use criteria we are going to look at are the Criteria for Drinking Water
National Primary Drinking Water Regulations | US EPA
Or to ensure that you use the same data that I am using for the exercises, you can look at
National Primary Drinking Water Regulations _ US EPA-captured 3-3-2022
This table gives the maximum concentrations that are allowable in drinking water, along with a maximum concentration goal. In contrast to the criteria we examined above which are governed by the Clean Water Act (CWA), drinking water criteria and regulations fall under the auspices of the Safe Drinking Water Act (SDWA), so the legal implications and implementation of these criteria are somewhat different than for the aquatic waters criteria. Be sure to read through the footnotes to the table, which tells you what the different terms and acronyms mean and what units are being used.
Did you notice the allowable level (MCL) for dioxin--one of the lowest numbers in the table? There is quite a story about dioxin. An entire town in Missouri had to be permanently abandoned in 1983 due to dioxin contamination. This was just four years before I moved to St Louis, just 17 miles away. How did this happen? In the 1960's the herbicide Agent Orange, used in the Vietnam War, was manufactured in Missouri (Agent Orange is 2,4,5T, a now-banned herbicide that you can find in the Drinking Water Criteria Table). Dioxin was a byproduct of the manufacture of Agent Orange. In the early 1970s, a waste hauler was hired to get rid of the dioxin held in tanks, and his choice was to mix it with oil and then spray it on dirt roads and racetracks to suppress dust, which he did throughout Missouri, including in the little town of Times Beach. Horses, pets, and children became terribly sick or died, birth defects became common, and the EPA traced the problem to the dioxins. In 1982, a flood of the Merrimac River spread the dioxins near Times Beach throughout the town. In 1983, the EPA used Superfund money to buy out the town permanently. This became one of the first of the Superfund sites, superfund being the common name for projects that fell under the CERCLA law (Comprehensive Environmental Response, Compensation, and Liability Act, first passed in 1980).
Back in the 1970s, a phrase became popular in the environmental remediation field: "Dilution is the solution to pollution." To some extent this is true, and this phrase might have influenced the choice made by waste hauler who 'diluted and distributed' the dioxin in Missouri. However, as is clear from the Missouri case, indiscriminate dilution is not a solution. One needs to be aware of the level of dilution that is necessary, and that is one contribution of the EPA water quality criteria.
In Part 2 of this lesson, we will consider a real-world case in which the EPA criteria have been used to develop water quality standards in the state of Minnesota and applied in the monitoring of the ground and surface water quality near a county landfill.
last updated 3/9/2022. Text and pictures are the property of Russ Colson, except for text and data from the US EPA.