TDS measurement

Introduction

Total Dissolved Solids (TDS) is a crucial parameter in assessing water quality. Whether for drinking water, industrial applications, or environmental monitoring, understanding TDS measurement can help in making informed decisions regarding water treatment and usage. In this blog, we will explore the background, technical knowledge, and importance of measuring TDS, supported by research findings.

What is TDS?

Total Dissolved Solids (TDS) refer to the combined content of all inorganic and organic substances dissolved in water. These include minerals, salts, metals, and ions that contribute to the water's conductivity and overall quality. The primary sources of TDS in water include:

  • Natural sources like mineral springs and soil runoff
  • Agricultural and urban runoff
  • Industrial wastewater and sewage
  • Water treatment chemicals

TDS is measured in parts per million (ppm) or milligrams per liter (mg/L).

How is TDS Measured?

There are two primary methods of measuring TDS:

1. Electrical Conductivity (EC) Method

Since dissolved solids increase the water’s conductivity, TDS meters measure electrical conductivity (EC) and convert it into a TDS value using a predefined conversion factor (typically between 0.5 and 0.7, depending on the water source).

The process follows these steps:

  1. A probe with electrodes is placed in the water sample.
  2. A voltage is applied, and the current flow is measured.
  3. The EC value is converted into a TDS reading using the specific conversion factor.

This method is widely used because it is fast, inexpensive, and practical for field measurements. However, it does not directly measure non-ionic substances like organic pollutants.

2. Gravimetric Method (Laboratory Standard)

The gravimetric method involves evaporating a water sample and weighing the residual solids. This provides a direct measurement of TDS and is considered the most accurate method, though it is time-consuming and requires specialized laboratory equipment.

Why is Measuring TDS Important?

Understanding the TDS level in water is critical for various reasons:

1. Drinking Water Quality

According to the World Health Organization (WHO) and the Environmental Protection Agency (EPA), TDS levels in drinking water should ideally be below 500 ppm. High TDS levels may indicate contamination by heavy metals, salts, or other pollutants, affecting taste and safety.

Low TDS (<50 ppm): Ultra-pure water, often demineralized or reverse osmosis (RO) treated.

  • 50–150 ppm: Ideal for drinking, retains essential minerals.
  • 150–500 ppm: Acceptable, but taste and quality may vary.
  • 500–1000 ppm: May affect taste and cause scaling in appliances.
  • >1000 ppm: Generally unsuitable for consumption without treatment.
  • 2. Industrial Applications

Industries such as pharmaceuticals, food processing, and electronics manufacturing require specific TDS levels to ensure process efficiency and product quality. High TDS in boiler feed water, for instance, can lead to scaling and corrosion, reducing equipment lifespan.

3. Aquaculture and Agriculture

  • In aquaponics and fish farming, maintaining a balanced TDS level is crucial for aquatic life.
  • In agriculture, excessive TDS can lead to soil salinity, affecting crop yields.

4. Reverse Osmosis (RO) and Water Treatment

Monitoring TDS is essential for assessing the efficiency of water purification systems. RO systems typically reduce TDS by 90-99%, improving water quality for drinking and industrial use.

Scientific Research on TDS and Health

Several studies highlight the significance of TDS monitoring:

  • A study published in the Journal of Water and Health found that high TDS levels (>600 ppm) in drinking water were linked to an increased risk of kidney stones and cardiovascular diseases.
  • Research from the National Institute of Environmental Health Sciences (NIEHS) indicates that certain dissolved solids, like lead and arsenic, can pose serious health risks even at low concentrations.
  • The American Water Works Association (AWWA) has emphasized the need for regular TDS monitoring to prevent infrastructure damage due to corrosion and scaling.

Conclusion

TDS measurement is a fundamental aspect of water quality assessment. Whether for drinking, industrial, or agricultural purposes, understanding TDS levels helps ensure safe and efficient water use. By utilizing accurate measurement techniques and adhering to recommended guidelines, we can maintain water safety and sustainability.

Would you like to learn how to test TDS at home? Stay tuned for our next article!