Vocabulary List

• Organisms: an individual animal, plant, or single-celled life form
  
  
• Species: a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding
  
  
• Conductivity: the degree to which a specified material conducts electricity, calculated as the ratio of the current density in the material to the electric field that causes the flow of current
  
  
• Optical: relating to sight, especially in relation to the physical action of light
  
  
• Opaque: not able to be seen through; not transparent
  
  
• Velocities: the speed of something in a given direction
  
  
• Ecological: relating to the relation of living organisms to one another and to their physical surroundings
  
  
• Waterborne: conveyed by, traveling on, or involving travel or transportation on water
  
  
• Dissolved: to become incorporated into a liquid so as to form a solution
  
  
• Corrode: destroy or damage (metal, stone, or other materials) slowly by chemical action
  
  
• Indicator: an animal or plant species that can be used to infer conditions in a particular habitat
  
  
• Soluble: able to be dissolved, especially in water

Case Example

Jim and Pam were hiking in the mountains near their home when they discovered a spring of water. The water looked crystal clear and the temperature was cold. Since the water looked safe, they decided to take a drink. It tasted amazing, so they filled their bottles and took the water home with them. About one week later, both Jim and Pam started experiencing watery diarrhea, stomach pains, and dehydration. A visit to the doctor revealed that they had been exposed to cryptosporidium from the clear water. They learned the lesson that you cannot always judge the quality of water by its looks.

Introduction

Water Quality Characteristics

Water qualities can be broken down into three areas: physical, chemical, and biological. This unit will not discuss everything that affects water quality, but it will review some of the most important factors.

Physical

Temperature: Temperature has a major influence on biological activity and growth. Temperature governs the kinds of organisms that can live in rivers and lakes. For example, fish, insects, plankton, and other aquatic species all have a preferred temperature range. As temperatures get too far above or below this preferred range, the number of individuals of the species decreases until there aren’t any left. Temperature is also important because of its influence on water chemistry. The rate of chemical reactions generally increases at higher temperatures. Water, particularly groundwater, with higher temperatures can dissolve more minerals from the surrounding rock and will have a higher electrical conductivity. It is the opposite when considering a gas, such as oxygen, dissolved in water. Warm stream water can affect the aquatic life in the stream. Warm water holds less dissolved oxygen than cool water and may not contain enough dissolved oxygen for the survival of different species of aquatic life (USGS, 2018c).

Turbidity: Turbidity is not the amount of turbids in the water. Turbidity is the measure of the relative clarity of a liquid. It is an optical characteristic of water and is a measurement of the amount of light that is scattered by material in the water when a light is shined through the water sample. The higher the intensity of scattered light, the higher the turbidity. Materials that cause water to be turbid include clay, silt, tiny inorganic and organic matter, algae, dissolved colored organic compounds, and plankton and other microscopic organisms.

Turbidity makes water cloudy or opaque. During periods of low flow (base flow), many rivers are a clear green color, and turbidites are low, usually less than 10 NTU. During a rainstorm, particles from the surrounding land are washed into the river, making the water a muddy brown color and indicating that the water has higher turbidity values. Also, during high flows, water velocities are faster and water volumes are higher, which can more easily stir up and suspend material from the stream bed, causing higher turbidity. High concentrations of particulate matter affect light penetration, ecological productivity, recreational values, and habitat quality, and cause lakes to fill in faster. In streams, increased sedimentation and siltation can occur, which can result in harm to habitat areas for fish and other aquatic life. Particles also provide attachment places for other pollutants, notably metals and bacteria. For this reason, turbidity readings can be used as an indicator of potential pollution in a body of water.

High turbidity, or cloudiness, in drinking water does not look good and may also represent a health concern. Turbidity can provide food and shelter for pathogens. If not removed, the causes of high turbidity can promote regrowth of pathogens in the water, leading to waterborne disease outbreaks, which have caused significant cases of intestinal sickness throughout the world (USGS, 2018d).

Total Dissolved Solids (TDS): TDS represents the total concentration of dissolved substances in water. TDS is made up of inorganic salts, as well as a small amount of organic matter. Common inorganic salts that can be found in water include calcium, magnesium, potassium, sodium, carbonates, nitrates, bicarbonates, chlorides, and sulfates. These minerals can originate from a number of sources, both natural and human. Mineral springs contain water with high levels of dissolved solids because the water has flowed through a region where the rocks have a high salt content.

Some minerals can also come from human activities. Agricultural and urban runoff can carry excess minerals into water sources, as can wastewater discharges, industrial wastewater and salt that is used to deice roads. Alone, a high concentration of dissolved solids is usually not a health hazard. In fact, many people buy mineral water, which has naturally elevated levels of dissolved solids. After all, a very low concentration of TDS has been found to give water a flat taste, which is undesirable to many people. Increased concentrations of dissolved solids can also have technical effects. Dissolved solids can produce hard water, stain household fixtures, corrode pipes, and have a metallic taste (SDWF).

Chemical

Salinity: The term salinity refers to the amount of dissolved salts that are present in water. Sodium and chloride are the predominant ions in seawater, and the concentrations of magnesium, calcium, and sulfate ions are also substantial. Naturally occurring waters vary in salinity from the almost pure water, which don’t have salts in snowmelt, to the saturated solutions in salt lakes such as the Dead Sea (Britannica). Salinity helps determine many aspects of the chemistry of natural waters and the biological processes within them. Salts can be toxic to freshwater plants and animals and can make the water unsafe for drinking, irrigation, and livestock watering. Excess salinity can occur in areas where evaporation is high and made worse by repeated use of water for irrigation (EPA, 2022). While freshwater can contain up to 0.1% of salt, some examples of salinity levels include the oceans at around 3.5%, the Great Salt Lake in Utah that ranges from 5 to 27%, the Dead Sea at 33.7% and Don Juan Pond in the Antarctic comes in at 44% (World Atlas, 2019).

Hardness: The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, mainly calcium and magnesium. Hardness is a property of water that is not a health concern, but it can be irritating. Hard water can cause mineral buildup in plumbing, fixtures, and water heaters; lower the performance of soaps and detergents; and even shorten the life of fabrics and clothes. But hard water has some benefits, too. Humans need minerals to stay healthy, and the World Health Organization states that drinking water may be a contributor of calcium and magnesium in the diet and could be important for those who are deficient in calcium and magnesium intake. Water systems that use groundwater as a source are concerned with water hardness, since as water moves through soil and rock it dissolves small amounts of naturally occurring minerals and carries them into the groundwater supply (USGS, 2018e).

pH: pH is a measure of how acidic or basic water is. The range goes from 0 to 14, with 7 being neutral. A pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates a base. The pH of water is a very important measurement concerning water quality. For instance, not only does the pH of a stream affect organisms living in the water, but a changing pH in a stream can also be an indicator of increasing pollution or some other environmental factor. Pollution can change a water's pH, which in turn can harm animals and plants living in the water. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at a lower pH level because they are more soluble. A high or low pH can be detrimental for the use of water. High pH causes a bitter taste, water pipes and water-using appliances become encrusted with deposits, and it lowers the effectiveness of the disinfection of chlorine, thereby causing the need for additional chlorine when pH is high. Low pH water will corrode or dissolve metals and other substances (USGS, 2019).

Dissolved Oxygen (DO): Dissolved Oxygen (DO) is a measure of how much oxygen is dissolved in the water and the amount of oxygen that is available to living aquatic organisms. The amount of dissolved oxygen in a stream or lake can tell us a lot about its water quality. Although water molecules contain an oxygen atom, this oxygen is not what is needed by aquatic organisms living in natural waters. A small amount of oxygen, up to about ten molecules of oxygen per million of water, is actually dissolved in water. This dissolved oxygen is breathed by fish and zooplankton and is needed by them to survive. Rapidly moving water, such as in a mountain stream or large river, tends to contain a lot of dissolved oxygen, whereas still water contains less. Aquatic life can have a hard time in still water with a lot of rotting, organic material, especially when dissolved-oxygen levels are at a seasonal low. Conditions may become especially serious during a period of hot, calm weather, resulting in the loss of many fish (USGS, 2018b).

Biochemical Oxygen Demand (BOD): Biochemical oxygen demand (BOD) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter at a specified temperature. In other words, it is the rate at which dissolved oxygen is consumed. BOD is often tested at wastewater treatment facilities as an index of the degree of organic pollution in water (USGS, 2018a).

Metals: Metals are elements present in all water bodies, with natural concentrations corresponding to local geology. Types of metals found in water bodies may include aluminum, arsenic, copper, lead, manganese, mercury, nickel, selenium, and zinc.

Metals occur naturally and are released into water bodies when flowing water erodes rocks, minerals, and soil particles. Because different rock types contain different metals, and some rock types are more susceptible to erosion and erode more quickly, the types and amounts of metals deposited in water bodies depend on the local geology. There are also many human-caused sources of metals in water bodies, including mines and smelters, firing ranges, coal-burning power plants, and wastewater treatment effluent (EPA, 2021).

Nitrates: Nitrates are a chemical that can make you sick if it is in your tap water at unsafe levels. Nitrate and nitrite are naturally present in soils, water, air, and plants. The use of fertilizers and waste from animals adds to the amount of nitrate in the environment. Nitrate and nitrite dissolve easily in water and will therefore move quickly through the soil into surface water and groundwater. Drinking water from wells containing nitrate from sources such as animal waste and/or fertilizer runoff and eating plants grown in contaminated soil will increase your exposure to these chemicals. Some people who ate food or drank fluids that contained unusually high levels of nitrite experienced a decreased ability for the blood to carry oxygen to tissues. This condition in children is also known as blue baby syndrome, where children under six years old who drank formula that was made from water with higher than the recommended nitrate levels began to turn blue from lack of oxygen in the blood. Other symptoms include decreased blood pressure, increased heart rate, headaches, abdominal cramps, and vomiting (ATSDR, 2017).

Biological

Infectious diseases caused by pathogenic bacteria, viruses, and protozoa are the most common and widespread health risks that are associated with drinking water (WHO, 2008). The presence of bacteria, viruses, and protozoa can affect water quality and since they are generally small and microscopic, they are often difficult to detect in water.

Bacteria: Bacteria are everywhere in our environment, including surface waters and groundwater. Some of these disease-causing bacteria can be harmful to human health and make you sick (Minnesota, 2022). Most bacterial pathogens potentially transmitted by water infect the gastrointestinal tract and are excreted in the feces of infected humans and other animals (WHO, 2008). Some of the principal bacterial pathogens that have been shown to cause human intestinal disease associated with drinking water are Salmonella typhi, Typhoid fever, Shigella dysenteriae, Vibrio cholerae, leptospirosis, Yersinia enterocolitica, and Escherichia coli (Mecklenberg, ).

Viruses: Viruses associated with waterborne transmission are predominantly those that can infect the gastrointestinal tract and are excreted in the feces of infected humans. Water transmitted viral pathogens that are classified as having moderate to high health significance by the World Health Organization (WHO) include adenovirus, astrovirus, hepatitis A and E viruses, rotavirus, norovirus enteroviruses (WHO, 2008). Sources of viruses in drinking water come from human and animal fecal waste (CDC, 2022).

Protozoa: Protozoa are among the most common causes of infection and disease in humans and other animals. Water plays an important role in the transmission of some of these pathogens. The control of waterborne transmission presents real challenges because most of the pathogens produce cysts, oocysts, or eggs that are resistant to processes generally used for the disinfection of water and in some cases can be difficult to remove by filtration processes. Two of the most important protozoa are Cryptosporidium and Giardia (WHO, 2008). Both Cryptosporidium and Giardia cause gastrointestinal illnesses such as diarrhea, vomiting, and cramps and are found in human and animal fecal waste (CDC, 2022).

References

ATSDR. (2017). ToxFAQs™ for Nitrate and Nitrite. Retrieved Jan 30, 2023, from https://books.byui.edu/-Dqfz

Britannica.Salinity. Retrieved Jan 30, 2023, from https://books.byui.edu/-hqGB

CDC. (2022). A Guide to Drinking Water Treatment and Sanitation for Backcountry and Travel Use. Retrieved Jan 30, 2023, from https://books.byui.edu/-LmxL

EPA. (2021). FACTSHEET ON WATER QUALITY PARAMETERS -Metals. Retrieved Jan 30, 2023, from https://books.byui.edu/-dZQY

EPA. (2022). Indicators: Salinity . Retrieved Jan 30, 2023, from https://books.byui.edu/-goSZ

Mecklenberg, H. D. Microorganisms That May Be Found In Drinking Water

Print . Retrieved Jan 30, 2023, from https://books.byui.edu/-zfTn

Minnesota, D. H. (2022). Bacteria, Viruses, and Parasites in Drinking Water. https://books.byui.edu/-eGGX

SDWF.TDS and pH. Retrieved JAN 30, 2023, from https://books.byui.edu/-gaXq

USGS. (2018a). Biological Oxygen Demand (BOD) and Water . Retrieved Jan 30 2023, from https://books.byui.edu/-EILr

USGS. (2018b). Dissolved Oxygen and Water . Retrieved Jan 30, 2023, from https://books.byui.edu/-EILr

USGS. (2018c). Temperature and Water. Retrieved Jan 30, 2023, from https://books.byui.edu/-eGy

USGS. (2018d). Turbidity and Water . Retrieved Jan 30, 2023, from https://books.byui.edu/-aqki

USGS. (2018e). Water Hardness. Retrieved Jan 30, 2023, from https://books.byui.edu/-FSig

USGS. (2019). pH and Water. Retrieved Jan 30, 2023, from https://books.byui.edu/-PQQq

WHO. (2008). Guidelines for Drinking-water Quality. Retrieved Jan 30, 2023, from https://books.byui.edu/-JLEo

World Atlas. (2019). The World's Saltiest Bodies of Water. Retrieved Jan 30, 2023, from https://books.byui.edu/-fPaC