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1.2: Water Chemistry and Standards

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    Learning Objectives

    After reading the chapter the student should be able to identify:

    • Matter, elements, and compounds
    • Public water systems: community and non-community
    • Primary and secondary standards
    • Water treatment violations
    • Volume math problems

    Water treatment is a complex process that involves parts that the human eye cannot see. In this chapter, you will learn about the basic scientific principals related to the water treatment. We will also discuss drinking water standards in the United States and different community standards.

    Matter, Elements, and Compounds


    The smallest parts of an element are comprised of particles known as atoms. Even though they are so small, atoms still retain the characteristics of the element. Even with technological advancements, microscopes are still unable to capture atoms. The multiple arrangements of atoms make each element unique. The atom ever so small, is comprised of three particles known as the proton, neutron, and electron. Each particle is associated by different charges.

    • Proton-positive
    • Neutron-no charge
    • Electron- Negative charge
    Carbon from the periodic table
    Carbon atom
    Figure \(\PageIndex{1}\): (left) Carbon by Science Activism is licensed under CC BY 2.0. Figure \(\PageIndex{2}\): (right) Carbon atom by Alejandro Porto is licensed under CC BY-SA 3.0

    The defining characteristic of an atom is identified by the proton. The proton, located in the nucleus, has a distinctive number. For example, carbon has six protons located in the nucleus. No other element has six protons in the nucleus. The number of protons is represented as the atomic number. The atomic weight is the number of protons and neutrons. The number of protons that exist for a given element is always the same, but the number of neutrons can vary. When there is a varying number of neutrons of a given element, it is known as an isotope. When an atom has a difference in electrons, it is called an ion. When the charges of the atom are not balanced, they become unstable. An atom that has more protons than neutrons is called a cation. An atom that has more electrons than protons is called an anion.

    Most common elements in the water treatment profession:

    • Aluminum (Al)
    • Antimony (Sb)
    • Arsenic (As)
    • Barium (Ba)
    • Beryllium (Be)
    • Boron (B)
    • Bromine (Br)
    • Cadmium (Cd)
    • Calcium (Ca)
    • Carbon (C)
    • Chlorine (Cl)
    • Chromium (Cr)
    • Copper (Cu)
    • Fluorine (F)
    • Hydrogen (H)
    • Iodine (I)
    • Iron (I)
    • Lead (Pb)
    • Magnesium (Mg)
    • Manganese (Mn)
    • Mercury (Mn)
    • Nickel (Ni)
    • Nitrogen (N)
    • Oxygen (O)
    • Phosphorus (P)
    • Potassium (K)
    • Radium (Ra)
    • Selenium (Se)
    • Silicon (Si)
    • Silver (Ag)
    • Sodium (Na)
    • Strontium (Sr)
    • Sulfur (S)
    • Thallium (Tl)

    There are elements that are pure in form, such as oxygen. Since elements are unstable, they often combine with other elements to form compounds. Water (H2O), for example, is a compound. It is a combination of two hydrogen atoms and one oxygen atom. A compound is two or more elements that are bonded together due to their attraction by reverse charges. The combining elements form a molecule. When two chemicals are mixed together without a chemical reaction it is called a mixture. The difference between a mixture and a compound is bonded together by a chemical reaction. A good example of a mixture is saltwater. The salt can be removed from the water through distillation. Water chemistry will be covered in greater detail in the Water Quality text and course.

    Drinking Water Standards

    The first drinking water standards created in the United States occurred in 1974 and were called the Safe Drinking Water Act (SDWA). The US EPA sets drinking Water Standards that all Water Municipalities must adhere to. Although States are able to come up with their own Standards, they must meet the minimum requirements set forth by the federal EPA. In California, drinking water standards are much more stringent than the federal requirements and therefore have primacy. As of 2014, the State regulatory group responsible for drinking water is the State Water Resources Control Board. Revisions to the safe drinking water act include approval techniques for treatment plants, specifying criteria for filtration of public water supplies, distinguishing different treatment techniques for surface and groundwater, and prohibiting lead products in drinking water systems. There are two sets of drinking water Standards identified as primary standards and secondary standards. Primary Standards affect human health and are mandated with Maximum Contaminant Levels (MCL). The MCL is the official safe level at which a human can consume the given contaminant without adverse health effects. Secondary Standards do not affect human health and are controlled with Maximum Contaminant Level Goals (MCLG). When a contaminant is reported, there is no such thing as zero. Levels are set to protect human health but are also set based on the best available technology. As technology improves MCL’s may be reexamined. Instrumentation to measure contaminant levels are not always capable of reading to absolute zero. Because of this, a Detection level for reporting is required.

    Public Water Systems

    There are three different categories of public water systems:

    • Community Public Water System: A community public water system has 15 or more service connections and serves at least 25 or more people year-round. These would include municipalities, mobile home parks, condos, and apartment buildings.
    • Nontransient, NonCommunity System: A nontransient, NonCommunity public water system owns its own system and serves an average of 25 people for at least six months. Schools, hospitals, and office buildings are included in this category.
    • Transient, NonCommunity System: A transient, NonCommunity public water system owns their own water system and serves an average of 25 people per day. In this category people consume the water for a short period of time. This category includes churches, parks, restaurants, and motels.
    Public Water System
    Figure \(\PageIndex{2}\): Image by the CDC is in the public domain

    Primary Drinking Water Standards are split into five categories. The categories include Inorganics, Organics, Turbidity, Microbiological, and Radiological.

    • Inorganics: Metals, Nitrate, and Fluoride
    • Organics: Pesticides, solvents, and Disinfectant byproducts (DBP’s)⁠—The combination of Chlorine and natural organic material. This topic will be discussed in greater detail later in the text.
    • Turbidity: The cloudiness of the water. Turbidity has the ability to shield microbiological material.
    • Microbiological: Coliform testing (This will be covered in greater detail later in the text. Water operators do not test for specific microbiological agents. We test for the indicator organism coliform. They colonize in greater numbers so if a sample comes back positive there is a greater likelihood of fecal contamination.)
    • Radiological: Gross alpha, beta, and radon

    Secondary drinking water standards are solely based on the aesthetic quality of drinking water. The main focus of secondary standards is taste, odor, and color. A glass of water that smells like fish and is orange in color may be “safe” to drink but wouldn’t be well received or readily consumed. California, as well as some other states, has endorsable secondary standards.

    Table 2.1: Recommended Levels for Contaminants and Characteristics


    Recommended level


    0.05 to 0.2 mg/L


    250 mg/L


    15 color units


    1 mg/L




    2 mg/L

    Foaming agents

    0.5 mg/L


    0.3 mg/L


    0.05 mg/L


    3 threshold odor number


    6.5 to 8.5


    0.10 mg/L


    250 mg/L

    Total dissolved solids

    500 mg/L


    5 mg/L

    Source: Graph by the EPA is in the public domain

    Public Notification

    In the event that a treatment plant does not meet requirements of the SDWA, the public must be notified. There are three different tiers of notification with tier I being the worst of violations and tier III being the least. The EPA provides very specific language for public notifications in the event of a violation. Violating a SDWA compliance is bad enough, but failing to report violations brings even stiffer penalties and fines. In 2014 in Flint Michigan 15 people were criminally charged due to their negligence in the water treatment profession. It all started when the city of Flint changed their source water without properly testing. Officials knew the water was not safe to drink and numerous violations had been made. The public was not properly informed of these violations which resulted in 10 deaths and 77 others becoming severely ill. It is something that is rarely discussed because people in industrialized countries never really worry about the quality of their drinking water. The most important thing you can do as an operator is say something if there appears to be a problem with the quality of the drinking water. Otherwise, you may end up in jail. Notification options include radio or television announcements, newspapers, hand delivery, posting in public places, loudspeakers, texting, and reverse 911. The notification will vary based on the severity of the violation.


    Tier I

    • Any positive fecal coliform positive test and failure to sample after an initial positive test
    • Nitrate or Nitrite violation
    • Chlorine Dioxide Maximum residual disinfection limit
    • Exceed treatment plants allowable turbidity level. Can be a tier II if the primacy agency does not elevate violation.
    • Waterborne emergency or outbreak of waterborne illness

    Tier II

    • MCL, MRDL and, Treatment Technique (TT) violations if treatment plant does not perform corrective actions to fix issues in treatment plant or fails to inform public.
    • Water quality monitoring violation⁠—not taking required water quality samples. Can also be a tier III violation but can be elevated for gross negligence
    • Noncompliance of a variance or an exemption

    Tier III

    • Water testing and monitoring violation
    • Any time the treatment system is running under a variance or exception. Primacy agency may give a treatment plant a variance or exemption for a short period of time. The public notification is to inform the public that a water agency is not running in accordance with an approved treatment technique. It doesn’t mean the water is unsafe to drink, but the operating manuals are very specific.

    Water Quality monitoring

    Continuous monitoring of drinking water ensures quality; reliable drinking water is being delivered to the public. The number of samples taken, frequency of sampling, sampling location, testing procedures, and requirements for record-keeping are all specified by state and federal requirements. If sampling requirements are not met, it can lead to public notification. The tier violation is based on the contaminant and whether or not the contaminant causes acute health effects.

    The type of monitoring is based on the source of the water, the treatment technique, and the size of the system. Reporting and record keeping is based on the primacy agency’s regulations. The state regulations must meet federal requirements at a minimum but may be more stringent as is the case in California.

    Record Keeping

    Below is a list of records that must be kept and the amount of time the records must be retained on file.

    • Bacteriological and Turbidity⁠—5 years
    • Chemical analysis⁠—10 years
    • Corrective actions from violations⁠—3 years
    • Sanitary surveys⁠—10 years
    • Exemptions⁠—5 years after expiration

    Variances and Exemptions

    In the event a water system is unable to meet a MCL because of the source water, a primacy agency can grant a variance or exemption. The variance is only given when the agency has incorporated the best available technology and there is zero risk to public health. In the case of Flint Michigan, the new source water was not properly tested before it was used in the system. Flint Water plant was unable to properly treat the source water which had elevated levels of lead and the City was not using the best available technology. Even if the City of Flint would have applied for a variance or exemption, it would not have been granted because the lead levels in the water create a significant risk to public health.

    In future chapters of the text, we will examine regulations added to the SDWA. Several changes and enhancements have been made since the exception of the original legislation. We will discuss in greater detail the Total Coliform Rule, Surface Treatment Water Rule, Long Term 2 Enhanced Surface Water Treatment Rule, Lead and Copper Rule, Ground Water Rule, and Stage 1 &2 Disinfectant Bi-Product Rule.


    Volume calculations will become very common for water treatment operators. Operators use volume calculations to solve math questions with circles, triangles, and rectangles. If you look around a water treatment facility, it is full of geometric shapes. Tanks can be cylindrical or rectangular in nature. Settling ponds may have a triangular nature to them. The basic volume questions will become more involved later on in the text as you may have to solve a volume question first, and then solve a flow-related question.


    Cylinder with diameter and height (or depth) labeled

    Volume = 0.785 × D2 × H


    Rectangle with length, width, and height (or depth) labeled

    Volume = L × W × H


    Trapezoid with base 1, base 2, length, and height (or depth) labeled

    Volume = 34Iyq_G5SzFNgXo_jfzalFEARJc8--6onH-fM1zS-5LNv4P9awxXNnNmZEStIrnFjkc82OMjk7eUdxhqq43uT_BVb3a9rQuxP0NRIfs3Gn9jrKPpXv5Wd9X_ephCcIkM5zhGtos × H × L

    Example \(\PageIndex{1}\)

    What is the volume of a cubed tank that is 10 feet high? (Remember cubes have the same unit of length on all three sides. This is the easiest problem to solve.)

    Cube with length, width, and height all measuring 10 feet

    Volume = Length × Width × Height

    Volume (ft3) = 10ft × 10ft × 10ft

    Answer is 1,000 ft3

    Example \(\PageIndex{1}\)

    What is the volume of a rectangular tank that is 20 ft. high, 10 ft wide, and 7ft in length?

    Rectangular tank that is 20 feet high, 10 feet wide, and 7 feet in length

    Volume= Length × Width × Height

    Volume= 7ft × 10ft × 20ft

    Answer is 1,400ft3

    There are two different ways to solve cylindrical math problems. The easiest formula to use is volume= .785 d2 H. This formula is easiest because in water math we are generally looking at the diameter of a cylindrical shape and not the radius. The radius of a circle is half the diameter. It is a straight line measured from the center of the circle to the edge of the circle. The diameter is a straight line that passes through the center of the circle with endpoints on the circle.

    Example \(\PageIndex{2}\)

    What is the volume of a storage tank that measures 40 ft. in diameter and is 20 ft. deep?

    Storage tank that measures 40 feet in diameter and is 20 feet deep

    Volume= .785 × d2 × H

    Volume= .785× 40ft × 40ft × 20ft

    Answer is 25,120ft3

    Often the water math word problems will require multiple steps to solve. Typically, we want to know how many gallons a given tank will hold. Once we find the volume of the tank in cubic feet, we will then convert the cubic feet into gallons.

    Example \(\PageIndex{3}\)

    Convert the answer from Example \(\PageIndex{3}\) into gallons.

    25,120 ft³ x 17.48 gal x 1 ft³ = 187,898 gal x 1

    Answer: 187,898 gallons

    Example \(\PageIndex{4}\)

    A rectangular water tank is full. The dimensions are 30ft high 12ft wide and a length of 10 ft. Convert to gallons.

    A rectangular water tank that is 30 feet high, 12 feet wide, and has a length of 10 feet

    Volume= 10ft x 12ft x 30 ft

    Volume= 3,600ft3

    3,600 ft³ x 17.48 gal x 1 ft³ = 26,928 gal x 1

    Answer: 26,928 gallons

    Example \(\PageIndex{5}\)

    A cylindrical storage tank has a diameter of 50ft and a height of 30ft. The tank is half full. How many gallons are in the tank?

    A cylindrical storage tank with a diameter of 50 feet and a height of 30 feet

    Volume= .785 x 50ft x 50ft x 15ft

    Volume= 29,437.5 rounded to 29,438ft3

    29,438 ft³ x 17.48 gal x 1 ft³ = 220,196 gal x 1

    Answer: 220,196 gallons

    Chapter Review

    1. The smallest part of an element is known as ___________.
      1. Proton
      2. Neutron
      3. Atom
      4. Nucleus
    2. The atomic weight is comprised of ___________.
      1. Neutrons and electrons
      2. Protons and neutrons
      3. Nucleus and neutrons
      4. Atom and nucleus
    3. An atom with a negative charge is known as ___________.
      1. Proton
      2. Neutron
      3. Nucleus
      4. Electron
    4. What does the symbol mg/L stand for?
      1. Micrograms per liter
      2. Milligrams per/L
      3. parts per million
      4. Both 2 and 3
    5. What does the acronym MCL stand for?
      1. Minimum contaminant level
      2. Micron contaminant level
      3. Maximum contaminant Level
      4. Milligrams counted last
    6. How long do sanitary surveys have to be retained for records?
      1. 3 years
      2. 5 years
      3. 7 years
      4. 10 years
    7. The most severe water system violation that requires the fastest public notification is ___________.
      1. Tier I
      2. Tier II
      3. Tier III
      4. Tier IV
    8. The primacy agency may grant a variance or exemption as long as ___________.
      1. The agency is using the Best Available Technology
      2. There is no threat to public health
      3. There is never a scenario for a variance or exemption
      4. Both 1 and 2
    9. A public water system that serves at least 25 people six months out of the year is known as ___________.
      1. Nontransient noncommunity
      2. Transient noncommunity
      3. Community public water system
      4. None of the above
    10. Regulations based on the aesthetic quality of drinking water are known as ___________.
      1. Primary Standards
      2. Secondary Standards
      3. Microbiological Standards
      4. Radiological Standards
    11. The lowest reportable limit for a water sample is ___________.
      1. 0.5 mg/L
      2. Zero
      3. Public health goal
      4. Detection Level for reporting
    12. Primary Standards are based on ___________
      1. Color and Taste
      2. Aesthetic quality
      3. Public Health
      4. Odor
    13. A circular clearwell is 150 feet in diameter and 40 feet tall. The Clearwell has an overflow at 35 feet. What is the maximum amount of water the clearwell can hold in Million gallons rounded to the nearest hundredth?
      1. MG
      2. 4.62 MG
      3. 18.50 MG
      4. 7.50 MG
    14. A sedimentation basin is 400 feet length, 50 feet in width, and 15 feet deep. What is the volume expressed in cubic feet?
      1. 100,000 ft³
      2. 200,000 ft³
      3. 300,000 ft³
      4. 400,000 ft³
    15. A clearwell holds 314,000 ft³ of water. It is 100 ft in diameter. What is the height of the clearwell?
      1. 25 ft
      2. 30 ft
      3. 35 ft
      4. 40 ft

    1.2: Water Chemistry and Standards is shared under a CC BY license and was authored, remixed, and/or curated by LibreTexts.

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