Ensuring QA/QC in Water Testing Laboratories for Public Safety


Water plays an essential role in our daily activities, be it household or industrial. Specialists assess the health of the water and carry out regular tests to determine and maintain its quality as it is important for public safety.

Why is Water Testing Essential?

It is important to conduct proper testing of water so that it is safe for various purposes such as drinking, bathing, fishing, watering crops, and other routine purposes. Many water testing laboratories have been established across the world to test water quality.

What are the Different Types of Water Tests?

A water testing laboratory is equipped with the latest range of analytical instruments to conduct various tests on water samples. There is a wide range of water quality tests performed to determine if specific contaminants are present in a water body. Some common types of tests performed by water testing laboratories are below.

1. Bacteria Tests

E. coli is one of the most potential bacterial contaminants that can plague water which comes from fecal matter exposure and can result in serious health implications when consumed. Bacteria testing is essential to determine if the water is safe for drinking or exposing to your skin.

2. Mineral Tests

There exists a wide range of mineral tests, such as tests for determining the presence of chlorine and chloride, nitrate and nitrite, lead, copper, iron, zinc, potassium, and sodium in water. The water in different regions or areas may differ in its composition of certain types of minerals. Mineral testing determines the water quality and helps decide the kind of mineral treatments needed to make the water fit for use.

3. Temperature Tests

The water temperature determines the maximum dissolved oxygen concentration in water, the types of aquatic organisms living in a water body, and whether a water body is suitable for human consumption and use. It is essential to test the temperature of water to determine how capable it is to hold oxygen. Water at very high temperatures cannot hold oxygen and decrease organisms’ capacity to resist pollutants.

4. Chloride Tests

Industrial pollution can lead to changes in the levels of chloride present in the water. Chlorides can contaminate freshwater bodies. Hence, a chloride test is important to determine if the chloride level is within the permissible limit.

5. Salinity Tests

This test is usually performed to test the presence of non-carbonate salts in water.

6. Turbidity Tests

Turbidity influences the taste and odour of drinking water. Turbidity deteriorates the water quality because the particles that cause turbidity may lead to the growth of pathogens. This test is performed to check the clarity of the water.

7. Nitrate & Phosphate Tests

Nitrates and phosphates are essential nutrients for plants. However, the excess addition of artificial fertilizers containing these nutrients could be equally harmful. High levels of nitrogen and phosphorus are associated with agricultural pollution from fertilizers and animal or human waste. Nitrogen is contributed by sewage and industrial pollution, making the water unhealthy for drinking or cooking purposes.

8. Pesticide Tests

This test is performed to estimate the concentration of pesticides in the water. High concentrations of pesticides in the water meant for public use may lead to acute toxicity, cancer, genetic mutations, and can even be fatal.

9. Redox Tests

The redox test is useful for determining microbial contamination, both qualitative and quantitative. This test determines the reduction-oxidation potential of a water body. The growth of microorganisms is inversely proportional to the redox potential of the medium or water body.

10. Electrical Conductivity Tests

Electrical conductivity tests are performed to determine the amount of solids dissolved in the water.

11. Heavy Metal Tests

Human activities such as mining, processing of minerals, use of metals as containers can introduce heavy metals such as Aluminum, Copper, Cadmium, Tin, Nickel in water bodies. These heavy metals are known to harm human organs such as the kidney, liver, reproductive organs, brain, joints, and nervous system.

12. pH Tests

pH testing measures the concentration of hydrogen ions in water. More hydrogen ions mean more acidic water which is unhealthy to drink.

What is Water Sampling and Why is it Important?

Water sampling is the process of taking a small portion of water that represents a water body (for example, a lake) as a whole. It helps in determining the quality and the hydrodynamic properties of the water. Every laboratory may have its own set of sampling standard operating procedures (SOP). Few common best practices for collecting samples include:

1. Containers for Sample Collection

It is essential to be prepared with proper containers/bottles, field equipment, and preservatives before collecting samples. Different testing methods require different types of bottles. For example, samples for the analysis of metals require plastic bottles, volatile organics and pesticides are collected in glass containers, and bottles used to store samples for determining bacteria should be well sterilized. Additionally, amber-coloured bottles are used for analytes that break-down in sunlight, which prevents contaminants from breaking down in the laboratory.

2. Preservatives

Different analysis methods require different preservations. For example, Sodium Thiosulfate is a common preservative used for bacteria analysis. The analysis of volatile organics also requires hydrochloric acid as a preservative to reduce any microbial activity that could reduce the contaminants while in transit to a water testing laboratory. Another most important preservation method is low temperature as most analysis demands the samples to be kept cool.

3. Holding Time

Holding time refers to the length of time from collection to the time when the analysis begins. Temperature is the most important factor to be considered when collecting, storing, or shipping samples. Holding time plays an important role when it comes to temperature control. It becomes critical to manage the temperature of samples during the summer. Samples are required to be packed in ice and gel packs to maintain the required temperature.

4. Sample Collection Techniques

When collecting water samples, it is important to allow sufficient water to flow. A good way to determine if you have run the water enough is to use onsite measurements such as pH, temperature, and conductivity. It is recommended to record the required parameters every two to three minutes. Once three consistent measurements are recorded in a row, you are ready to collect samples.

5. Toolkit

It is always better to maintain a sampling toolkit. A good sample kit must include supplies such as gloves and alcohol swabs, equipment to run onsite analysis such as meters to measure pH, temperature and conductivity, standard solutions to properly calibrate equipment, a wrench for removing difficult aerators, screwdrivers, and flashlights.

6. Sampling Points

Sampling points depends on the type and objective of the analysis. It is recommended to collect samples from different sources through which water is supplied to the public so that potential points of contamination such as loops and low-pressure zones could be identified.

QA/QC in Water Testing Laboratories

Although it is very crucial to maintain the quality of water, we could still find several poorly-functioning water testing laboratories. The reason for this could be a failure to follow standardized procedures, maintain certification, and perform routine checks for quality assurance and quality control (QA/QC) processes. These may lead to compromises in water safety. A water testing laboratory must have a robust Quality Assurance/Quality Control program which eventually needs reliable positive and negative controls. A good QC program must be based on the guidelines of the Environmental Protection Agency (EPA) NELAP and ISO/IEC 17025:2017 recommendations. Water testing laboratories must record data generated from QA/QC processes and analyze trends across a set of QC samples to identify variation in analytical results. Furthermore, they must have a system to flag samples that have out-of-specification results or do not meet the regulatory limit of various contaminants.

Role of a LIMS in Water Testing Laboratories

Water testing laboratories must have a Laboratory Information Management System (LIMS) to assure the validity and reliability of test results. The rise in water pollution has increased the need for testing new contaminants in the water. This increasing demand for water testing cannot be managed with some form of paper-based data management system. A LIMS can help in the following ways:

  • Manage samples, sample sources, and test results.
  • Meet quality standards by streamlining QA/QC processes.
  • Integrate with analytical instruments so that data is efficiently captured, stored, and then distributed to anyone who needs it.
  • Automatically flag out-of-specification results.
  • Meet compliance requirements.


Water for public use must be of an established quality for the economic, health, and social well-being of the people. Monitoring the quality of water would eliminate the potential health risks related to water contamination. Water testing laboratories play a crucial role in determining the water quality by conducting various tests to ensure the safety of water consumed. Before performing these tests, it is important for water testing laboratories to manage all collected samples and determine tests to be performed on the samples. The management, collection, and distribution of these samples and test results could be easily done through a software solution such as LIMS. A LIMS also helps water testing laboratories in maintaining a proper quality check by meeting regulatory requirements.