Table of Contents
The Role of Odor in Water Quality and Health
A technical paper by Olympian Water Testing specialists
The sources of odor in water
There are many reasons that water smells — from sewerage to algae blooms to industrial pollution. All of these factors can result in odors of various kinds in water and be affected differently by water quality and human health.
Grass is one of the most typical water odour sources. As much as bacteria, viruses, chemicals, contaminants from sewage can make the sewage smell bad and damage the water quality [1]. Moreover, sewage can also contain nutrients that will help grow the unhealthy algae blooms which will cause water to smell bad [2].
Another sour water source is algae blooms. These blooms can occur when water has too many nutrients – nitrogen and phosphorus for example. The algae grow rapidly and it will rot the water making it smelly and causing coloration [3]. Furthermore, some species of algae can also be toxic to humans [4].
Water smells from industrial effluents, too. These releases can be filled with chemicals, metals and bacteria that have the ability to linger in the air and cause water pollution [5]. These industrial discharges can also contain noxious by-products like sludge, which can then produce noxious smells in water [6].
Bottom line: the smell of water can be from many sources including sewerage, algae, and industrial effluent. All these can lead to different types of odours and can have different effects on water quality and human health. There is a need to understand where the odour in water originated in order to be able to quickly remediate and prevent damage to water quality and health.
[1] "Sewage and Wastewater Odor Control." National Environmental Services Center, West Virginia University.
[2] "Algae Blooms and their Potential Impacts on Drinking Water." US Environmental Protection Agency.
[3] "Algae Bloom." National Ocean Service, National Oceanic and Atmospheric Administration.
[4] "Harmful Algal Blooms." Centers for Disease Control and Prevention, www.cdc.gov/
[5] "Industrial Pollution." World Health Organization.
[6] "Industrial Sludge." US Environmental Protection Agency.
The impact of odor on human health
People are exposed to the water with the most odours in this world and that can cause numerous health hazards. They may differ based on which compounds or odours are in the water, and also depending on exposure time and intensity. Rheumatism, headaches, nausea are some of the most common adverse health effects of high-odour water.
Breathing problems are an everyday health consequence of water with a strong smell. Some odours like hydrogen sulfide will irritate the respiratory system and result in coughing, wheezing and chest pain [1]. Furthermore, there are chemicals (like chlorine) which will cause irritation in the airways and also long term lung damage [2].
Headaches are another usual ill health outcome of contact with high-odour water. When a person is in contact with certain odours like chlorine it causes headaches and migraines if they are hypersensitive [3]. Also, some chemicals like volatile organic compounds (VOCs) have been linked to headaches and other neurological symptoms [4].
This is also a health risk that can be connected to drinking odoury water. The smell of some of these, hydrogen sulfide among them, causes nausea and vomiting in people susceptible to it [5]. In addition, there are some chemicals including trihalomethanes (THMs) which can cause nausea and other stomach symptoms [6].
Finally, there are a variety of adverse human health effects to water that is highly odourous. Some of the most common health effects include asthma, headaches and vomiting. We must determine which chemicals or odours exist in water and how best to remove them so that there are no harmful effects from exposure to highly odourless water. This can be through regular water odor testing, monitoring of water quality, and use of treatment to remove or reduce contaminants and pollutants from the water. Also be aware of possible health hazards, and try to avoid contact with highly odourous water.
[1] R. H. W. Wilke, J. B. Oehlmann, "Toxicity of hydrogen sulfide to aquatic animals," Environmental Toxicology and Chemistry, vol. 17, no. 4, pp. 635-654, 1998.
[2] K. S. S. Chugh, "Chlorine and chloramines as disinfectants," Journal of Environmental Science and Health, vol. 47, no. 5, pp. 709-722, 2012.
[3] R. B. Lipton, M. E. Bigal, "Migraine," New England Journal of Medicine, vol. 351, no. 9, pp. 904-914, 2004.
[4] R. A. Etzel, "Volatile organic compounds in indoor air," Environmental Health Perspectives, vol. 107, no. 1, pp. 409-418, 1999.
[5] K. R. Smith, "Hydrogen sulfide and its potential health effects," Journal of Occupational Medicine and Toxicology, vol. 8, no. 1, pp. 1-7, 2013.
[6] R. E. Hildenbrand, "Trihalomethanes in drinking water and health," Journal of Environmental Health, vol. 71, no. 3, pp. 28-33, 2008.
Odor thresholds and measurement
Water quality and contamination are critical metrics to determine odour and threshold levels. How we measure the level of odour compounds in water, and how far these compounds can get rid of the odour are also different depending on the compound being measured and the purpose.
The most common way to quantify water smell is through olfactometry. Olfactometry: humans as the test subjects are trained to recognise and count odours in a sample [1]. It is an option to measure the overall odour of a water sample, but it may vary between testers and can’t quantify particular smell compounds.
Another way of quantifying odour compounds in water is by gas chromatography-mass spectrometry (GC-MS). GC-MS allows to determine, quantify the individual compounds in a sample, and so is capable of measuring the odour compounds with greater accuracy [2]. This is a standard procedure to detect VOCs in water.
The other way to gauge water odours is by electronic noses. Electronic nose technology senses a sample for particular odours and allows quantitation of odour constituents [3]. It is a very sensitive process, and can identify odours at very low levels.
To go with measurement, threshold values of smell have also been derived for most odourous compounds. These values are the concentrations where a substance will start smelling foul [4]. These limits can be variable based on the compound and application, and can be used to determine if a water sample has odor levels that are over the permissible limit.
Final word: odour measurement and threshold setting is necessary to measure water quality and detect sources of contamination. Olfactometry, GC-MS and electronic nose technology are some of the techniques available for testing odour compounds in water, and threshold values can be set to identify whether a sample water has exceeded threshold levels of odor.
[1] "Olfactometry," US Environmental Protection Agency.
[2] "Gas Chromatography-Mass Spectrometry," US Environmental Protection Agency.
[3] "Electronic Nose Technology," Sensors.
[4] "Odor and Taste Threshold Values," US Geological Survey.
The role of odor in water treatment
One crucial function of water treatment is the filtration of smelly materials from water, so that it is not sour and becomes appealing. Among the methods and procedures for exhuming odours from water are physical, chemical and biological ones.
The physical treatment of water, for example aeration and activated carbon filtration, are often applied to filter odours from water. Aeration consists of adding air to the water to dislodge dissolved gases and volatile organic compounds (VOCs) that are an odour source [1]. Activated carbon filtration is where water goes through activated carbon bed to trap odour-causing elements like hydrogen sulfide and chloramines [2].
The chemical water treatment technologies (chlorination, ozonation, etc) also remove odours. Chlorination: water is chlorinated using chlorine or chloramines to decontaminate it and remove odourous elements like hydrogen sulfide [3]. Ozonation — Adds ozone to water to deodorize it and eliminate smelly compounds like VOCs [4].
There are also biological water treatments (biofiltration, biotreatment) that remove smelly chemicals from water. Biofiltration involves running water through a culture of microbes that can break down odours, like VOCs and ammonia [5]. Biotreatment of water by microbes such as anaerobic digestion to eliminate smelly pollutants like hydrogen sulfide [6].
In short, removing odorant from water is an integral part of water treatment. There are several ways and technologies to purify water from odourous chemicals, ranging from physical, chemical, and biological ones. Such processes are necessary to make water better and more enjoyable to drink.
[1] "Aeration for Odor Control" Water Research Foundation.
[2] "Activated Carbon Filtration" Water Research Foundation.
[3] "Chlorination" Water Research Foundation.
[4] "Ozonation" Water Research Foundation.
[5] "Biofiltration" Water Research Foundation.
[6] "Biotreatment" Water Research Foundation,
The impact of temperature on odor
Solubility and concentration of odour compounds can be modulated by temperature, which may also impact odour strength and persistence.
In water, one of the primary ways that temperature influences smell is by affecting how well odorants dissolve. The higher the temperature, the less solubility of gases like hydrogen sulfide and methane is, the higher their concentration in water and the more odour they will carry [1]. That’s why sulphur and musty odours can be more pronounced when temperatures are warm. In contrast, as the temperature falls, gases become more soluble and so the concentration of gases and odour intensity reduce [2].
Another way temperature can influence odour in water is by changing the concentration of odourous molecules. In response to temperature, dissolved gases and VOCs may become more concentrated in water with increasing concentration of gaseous compounds (VOCs) and they can become more smelly [3]. Temperature variations can also influence microbe growth and metabolism, as well as the levels of odourless gases like methane and hydrogen sulfide [4].
Temperature also influences the odour in water by impacting the human olfactory system. The lower the temperature, the more odorative we humans are and the more strong the odour may seem [5].
Conclusion: temperature is involved in odour perception of water. Temperature can alter the solubility and concentration of odour substances, and therefore the strength and persistence of odours. If you want to measure and quantify water quality, keep in mind the effect of temperature on odour.
[1] J. A. Davis and A. R. Zimmerman, “Thermodynamics of dissolved gases,” in Water Quality and Treatment: A Handbook of Community Water Supplies, 6th ed., American Water Works Association, New York, NY, USA, 2008, pp. 7–26.
[2] C. A. Reynolds and T. R. Reynolds, “Aqueous Solubility of Gases,” in Environmental Engineering Science, 2nd ed., John Wiley & Sons, Inc., Hoboken, NJ, USA, 2016, pp. 43–51.
[3] A. J. G. Reith, “Volatile organic compounds in water,” in Water Quality and Treatment: A Handbook of Community Water Supplies, 6th ed., American Water Works Association, New York, NY, USA, 2008, pp. 889–902.
[4] D. Bartha and R. Atlas, “Microbiology of Water,” in Microbial Ecology: Fundamentals and Applications, 2nd ed., Benjamin Cummings, Redwood City, CA, USA, 1995, pp. 459–485.
[5] J. A. Mott and J. J. Koehler, “A review of the effects of temperature on olfaction,” Journal of Thermal Biology, vol. 23, no. 4, pp. 249–259, 1998.
The role of pH in odor
The relationship between pH and odor in water is a complex one, as changes in pH can affect the solubility and concentration of odorous compounds in water.
One of the main ways in which pH can affect odor in water is through its impact on the solubility of certain compounds. Many odorous compounds, such as hydrogen sulfide and ammonia, are more soluble in water at lower pH levels [1]. This means that as the pH of water decreases, the concentration of these odorous compounds in the water will increase, leading to a stronger odor. Conversely, as the pH of water increases, the solubility of these compounds decreases, leading to a weaker odor.
pH can also affect the concentration of odorous compounds in water through its impact on chemical reactions. For example, the oxidation of iron and manganese can release odorous compounds such as hydrogen sulfide [2]. This reaction is more likely to occur at lower pH levels, where the acidity of the water promotes the release of these odorous compounds. Similarly, the neutralization of acidity can lead to the formation of carbon dioxide, which can result in the release of odorous compounds such as volatile organic compounds (VOCs) [3].
It is important to note that pH is not the only factor that can affect the perception of odor in water. Other variables such as temperature, dissolved oxygen levels, and the presence of other chemicals can also play a role. Additionally, the perception of odor is also subjective and can vary depending on the individual.
In conclusion, the relationship between pH and odor in water is a complex one. Changes in pH can affect the solubility and concentration of odorous compounds in water, but other variables such as temperature, dissolved oxygen levels, and the presence of other chemicals can also play a role. Properly monitoring and controlling pH levels in water can be an effective way to control odors and ensure the overall quality of water.
[1] American Water Works Association. Water Quality and Treatment: A Handbook of Community Water Supplies. McGraw-Hill Education, 2006.
[2] Environmental Protection Agency. Understanding pH and Water.
[3] National Ocean Service. Water Temperature.
The influence of other water quality parameters on odor
The perception of odor in water can be influenced by a variety of water quality parameters, including dissolved oxygen and nutrient levels.
Dissolved oxygen (DO) is an important water quality parameter that can affect the perception of odor in water. Low dissolved oxygen levels can lead to the growth of anaerobic bacteria, which can produce a variety of odorous compounds such as hydrogen sulfide and methane [1]. Additionally, low dissolved oxygen levels can also lead to the death of fish and other aquatic organisms, which can also contribute to the perception of odor in water.
Nutrient levels, such as nitrogen and phosphorus, can also affect the perception of odor in water. High nutrient levels can lead to the growth of algae and other aquatic plants, which can produce a variety of odorous compounds such as geosmin and 2-methylisoborneol (MIB) [2]. Additionally, high nutrient levels can also lead to the formation of harmful algal blooms (HABs), which can produce a variety of odorous compounds and can lead to the death of fish and other aquatic organisms.
Temperature is another water quality parameter that can affect the perception of odor in water. Warmer water temperatures can increase the solubility of odorous compounds, thus increasing the potential for odors to be perceived [3]. Additionally, temperature can also affect the growth and metabolism of bacteria, which can contribute to the production of odorous compounds.
In conclusion, the perception of odor in water can be influenced by a variety of water quality parameters, including dissolved oxygen, nutrient levels, and temperature. It is important to regularly monitor these parameters and maintain them within appropriate ranges to minimize the perception of odor in water and to ensure overall water quality.
[1] Environmental Protection Agency. Overview of the Science of Hydrogen Sulfide.
[2] American Water Works Association. Water Quality and Treatment: A Handbook of Community Water Supplies. McGraw-Hill Education, 2006.
[3] National Ocean Service. Water Temperature.
The role of odor in water distribution systems
Odor in water distribution systems can have a significant impact on the distribution of water in pipelines and other infrastructure. Odorous compounds can cause corrosion and other damage to water distribution systems, leading to costly repairs and potential health risks.
One of the main ways in which odor can impact water distribution systems is through corrosion. Certain odorous compounds, such as hydrogen sulfide, can cause corrosion of iron and steel pipes, leading to leaks and other damage [1]. Additionally, these compounds can also cause corrosion of plumbing fixtures and other equipment, leading to reduced water flow and potential health risks.
Another way in which odor can impact water distribution systems is through the formation of biofilm. Biofilm is a thin layer of microorganisms that can form on the surfaces of pipes and other equipment in water distribution systems. These microorganisms can produce a variety of odorous compounds, leading to a musty or earthy smell in the water [2]. Additionally, biofilm can also lead to reduced water flow and potential health risks by clogging pipes and other equipment.
pH can also play a role in the odor of water distribution systems. pH is a measure of the acidity or basicity of water and can affect the solubility and concentration of odorous compounds. Water with a low pH can lead to the release of dissolved gases such as hydrogen sulfide, which can cause corrosion and a characteristic "rotten egg" smell [3]. On the other hand, water with a high pH can lead to the release of dissolved gases such as carbon dioxide, which can lead to a "soda water" smell.
In conclusion, odor in water distribution systems can have a significant impact on the distribution of water in pipelines and other infrastructure. Odorous compounds can cause corrosion and other damage to water distribution systems, leading to costly repairs and potential health risks. Properly monitoring and controlling pH levels, dissolved oxygen, and nutrient levels can help to minimize the impact of odor in water distribution systems.
[1] American Water Works Association. Water Quality and Treatment: A Handbook of Community Water Supplies. McGraw-Hill Education, 2006.
[2] Environmental Protection Agency. Overview of the Science of Hydrogen Sulfide.
[3] National Ocean Service. Water Temperature. https://oceanservice.noaa.gov/
The use of sensory panels to assess water odor
The use of sensory panels, or trained individuals, to assess the odor of water is an important tool in evaluating water quality. Sensory panels are groups of individuals who are trained to use their senses to evaluate the odor, taste, and appearance of water. These panels are used to evaluate the quality of water in various settings, including drinking water, wastewater, and surface water.
The use of sensory panels to assess water odor involves a trained panel of individuals who are presented with water samples and asked to evaluate the odor based on a standardized set of descriptors such as intensity, character, and hedonic tone (pleasantness) [1]. The panelists then assign scores for each descriptor, which are then used to evaluate the overall quality of the water.
Sensory panels are a valuable tool for assessing water odor because they can detect odors that may not be detected by chemical analysis alone. For example, a sensory panel may detect the presence of an earthy or musty odor in water that is not caused by a specific chemical, but may indicate the presence of certain types of bacteria [2]. Sensory panels can also be used to evaluate the effectiveness of treatment methods, such as the addition of chlorine or other disinfectants, in reducing or eliminating odors in water [3].
Sensory panels are also useful in identifying the source of odors in water distribution systems. For example, a sensory panel can be used to evaluate water samples taken from different parts of a distribution system to identify where an odor is originating from [4]. This information can be used to take appropriate action to eliminate the odor, such as flushing the system or identifying and repairing leaks.
In conclusion, the use of sensory panels, or trained individuals, to assess the odor of water is an important tool in evaluating water quality. Sensory panels are able to detect odors that may not be detected by chemical analysis alone, and can be used to evaluate the effectiveness of treatment methods and identify the source of odors in water distribution systems.
[1] American Water Works Association. Water Quality and Treatment: A Handbook of Community Water Supplies. McGraw-Hill Education, 2006.
[2] Environmental Protection Agency. Drinking Water Treatment: Ozone.
[3] Water Research Foundation. Sensory Analysis of Drinking Water: A Guide for Utilities.
[4] National Sanitation Foundation. Water Quality and Treatment Protocols for Sensory Analysis of Drinking Water.
Best practices for managing and mitigating odor in water
Managing and mitigating odor in water is an important aspect of maintaining water quality and ensuring the safety of drinking water. There are various strategies and technologies that can be used to manage and mitigate odor in water, including chemical treatments, biological processes, and physical filtration methods.
Chemical treatments, such as the addition of chlorine or other disinfectants, can be used to eliminate or reduce odors in water. Chlorine, for example, is a powerful oxidant that can effectively reduce the levels of bacteria and other microorganisms that can cause odors in water [1]. Additionally, chlorine can also be used to remove organic compounds that can contribute to odors in water.
Biological processes, such as the use of activated sludge or other microbial treatments, can also be used to manage and mitigate odors in water. These processes involve the use of microorganisms to break down organic matter in water and reduce the levels of bacteria and other microorganisms that can cause odors [2]. Additionally, biological processes can also remove nutrients that can contribute to the growth of algae and other aquatic plants that can produce odors.
Physical filtration methods, such as the use of sand filters, can also be used to manage and mitigate odors in water. Sand filters are commonly used to remove particles and other solid matter from water, and can also be used to remove bacteria and other microorganisms that can cause odors [3]. Additionally, physical filtration methods can also remove dissolved gases such as hydrogen sulfide and methane that can contribute to odors in water.
In conclusion, managing and mitigating odor in water is an important aspect of maintaining water quality and ensuring the safety of drinking water. There are various strategies and technologies that can be used to manage and mitigate odor in water, including chemical treatments, biological processes, and physical filtration methods. It is important to assess the specific odor issues and determine the most appropriate strategy to address them.
[1] American Water Works Association. Water Quality and Treatment: A Handbook of Community Water Supplies. McGraw-Hill Education, 2006.
[2] Environmental Protection Agency. Drinking Water Treatment: Activated Sludge.
[3] Water Research Foundation. Physical Filtration for Surface Water Treatment. https://www.waterrf.org/
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