Glossary of Technical Terms Used in Environmental Health & Safety: threshold odor number (TON)

threshold odor number (TON)

The Nose Knows: Understanding Threshold Odor Number (TON) in Water Treatment

In the pursuit of clean and palatable water, the importance of odor control cannot be overstated. While water quality is often assessed through chemical and biological parameters, odor plays a crucial role in public perception and acceptance. This is where the concept of Threshold Odor Number (TON) comes into play.

What is TON?

Threshold Odor Number (TON) is a measure of the odor intensity of a water sample. It quantifies the minimum dilution required to eliminate a detectable odor in a given volume of water. Simply put, it tells us how many times we need to dilute a water sample with odor-free water before the odor becomes undetectable by the human nose.

How is TON Determined?

TON is determined through a sensory test called odor threshold testing. This process involves trained individuals, known as odor panelists, who sniff and assess water samples diluted to varying degrees. The panelists are asked to identify the lowest dilution level at which the odor is no longer perceptible.

The Significance of TON in Water Treatment:

TON is a vital tool for:

  • Identifying odor sources: TON can help pinpoint the specific compounds responsible for the odor, allowing for targeted treatment strategies.
  • Evaluating treatment effectiveness: Monitoring changes in TON over time can indicate the success of odor control measures.
  • Setting treatment goals: A specific TON value can be set as a target to ensure odor-free water.
  • Maintaining public acceptance: Low TON values contribute to the overall acceptability of treated water.

Factors Influencing TON:

  • Chemical composition: The type and concentration of odor-causing compounds in the water.
  • Water temperature: Odor intensity often increases with higher temperatures.
  • pH: Changes in pH can alter the volatility and odor intensity of some compounds.
  • Interference: The presence of other volatile compounds can mask or enhance the odor.

Applications of TON:

  • Drinking water treatment: Ensuring the odor-free nature of tap water.
  • Wastewater treatment: Controlling odors from sewage treatment plants.
  • Industrial wastewater treatment: Managing odor emissions from industrial processes.
  • Environmental monitoring: Assessing the impact of pollutants on water bodies.

TON: A Vital Tool for Odor Control:

By providing a quantitative measure of odor intensity, TON plays a crucial role in ensuring the quality and acceptability of treated water. By understanding and managing TON, water treatment professionals can effectively control odor, contributing to a positive perception of water quality and public health.


Test Your Knowledge

Quiz: The Nose Knows: Understanding Threshold Odor Number (TON)

Instructions: Choose the best answer for each question.

1. What does Threshold Odor Number (TON) measure?

a) The total number of odor-causing compounds in water b) The concentration of a specific odor-causing compound c) The minimum dilution required to eliminate a detectable odor d) The intensity of a specific odor

Answer

c) The minimum dilution required to eliminate a detectable odor

2. How is TON determined?

a) Chemical analysis of water samples b) Sensory testing by trained odor panelists c) Measuring the volume of air released from a water sample d) Observing the color change of a specific indicator

Answer

b) Sensory testing by trained odor panelists

3. Which of the following is NOT a factor influencing TON?

a) Chemical composition of the water b) Water temperature c) Air pressure d) pH

Answer

c) Air pressure

4. Why is TON important in water treatment?

a) It helps determine the effectiveness of treatment methods b) It provides information on the source of the odor c) It allows for setting treatment goals for odor control d) All of the above

Answer

d) All of the above

5. What is a potential application of TON in environmental monitoring?

a) Assessing the impact of pollutants on water bodies b) Monitoring the effectiveness of wastewater treatment plants c) Determining the source of odor in a specific area d) All of the above

Answer

d) All of the above

Exercise: TON Calculation

Scenario: You are a water treatment plant operator and you need to determine the TON of a water sample that exhibits a strong chlorine odor. After conducting odor threshold testing, you find that the odor is no longer perceptible at a dilution of 1:1000 (1 part water sample to 1000 parts odor-free water).

Task: Calculate the TON of this water sample.

Exercice Correction

The TON of the water sample is 1000. This is because the odor was eliminated at a dilution of 1:1000, meaning the water sample had to be diluted 1000 times to become odor-free.


Books

  • Water Quality and Treatment: A Handbook of Public Water Systems by American Water Works Association (AWWA) - This comprehensive handbook covers various aspects of water treatment, including odor control, and provides detailed information on TON and its significance.
  • Standard Methods for the Examination of Water and Wastewater by American Public Health Association (APHA), American Water Works Association (AWWA), and Water Environment Federation (WEF) - This standard reference book offers specific procedures for determining TON and other odor-related parameters.
  • Handbook of Water and Wastewater Treatment Technologies by David T. O'Connor and William E. K. Warford - This handbook provides a practical guide to water treatment processes, including odor control strategies, and discusses the role of TON in evaluating odor removal efficiency.

Articles

  • "Determination of Threshold Odor Number (TON) of Water Samples" by C.A. Burlingame and G.E. Welcher - This article describes a detailed methodology for conducting odor threshold testing and calculating TON.
  • "Odor Control in Drinking Water Treatment" by D.M. Adams - This article explores the significance of odor control in drinking water treatment and highlights the importance of TON in evaluating the effectiveness of odor removal techniques.
  • "The Use of Threshold Odor Number (TON) in Wastewater Treatment" by J.H. Parker - This article discusses the application of TON in monitoring and managing odor emissions from wastewater treatment plants.

Online Resources

  • American Water Works Association (AWWA) - AWWA provides a wealth of resources on water treatment, including odor control, and offers various standards and guidelines related to TON.
  • Water Environment Federation (WEF) - WEF offers resources on wastewater treatment and odor control, including articles, training materials, and best practices.
  • EPA Office of Water - EPA provides information on water quality standards, guidelines, and regulations related to odor control and TON.

Search Tips

  • "Threshold Odor Number (TON) definition" - This will return results explaining the concept and significance of TON.
  • "Threshold Odor Number (TON) testing method" - This will provide information on the procedure used for determining TON.
  • "Threshold Odor Number (TON) in drinking water treatment" - This will show articles and resources specifically focused on the use of TON in drinking water treatment.
  • "Threshold Odor Number (TON) in wastewater treatment" - This will display relevant information on the application of TON in managing odor emissions from wastewater treatment facilities.
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