Water quality is measured in different ways.
Continuous water quality monitoring
Continuous monitoring is in situ. Continuous monitoring is beneficial for many purposes. Examples include for long-term analysis or for use in making operational changes. In situ water quality monitoring uses probes (also known as sensors) immersed in water. Water quality monitored at sites by continuous monitoring currently includes:
- dissolved oxygen (DO)
- pH
- salinity as electrical conductivity (EC)
- turbidity
- water temperature
- chlorophyll-a
Various probe types are used. This includes a combination of single and multiprobes. Multiprobes measure multiple parameters. All monitoring sites use optical DO sensors, which measure DO via light scatter. pH sensors measure pH using electrochemical methods. All monitoring sites use EC sensors combined with concurrent temperature measurement. These two measurements then give a salinity level. Turbidity sensors measure the amount of light passing through the water. Chlorophyll-a is measured using optical sensors.
Spot water quality monitoring
Spot water quality is collected and measured in situ. Spot water quality monitoring is used for verification of continuous monitoring equipment. Calibrated handheld devices measure spot water quality. Spot water quality parameters include:
- DO
- EC
- pH
- temperature (air and water)
- turbidity
Sampling and laboratory analysis water quality monitoring
Water samples are collected, stored, and transported to a laboratory for ex situ analysis. Standard methods are used for collection of samples. Sample bottles are appropriate for the required future analysis. Samples are transported in appropriate packaging to the laboratory. Transport must be in a timely manner to ensure analysis is conducted within any analysis time limitation. Appropriate quality control is conducted, which includes collection of blanks and duplicates.
Laboratory analysis
Laboratory analysis of water quality includes analysis of general chemistry parameters, nutrients, metals, organic compounds, and microbes. Analytical methods include:
- ion chromatography for anions
- inductively coupled plasma atomic emission spectrometry for cations
- direct analysis for nutrients
- gas chromatography flame ionisation detector (GC-FID) for hydrocarbons
- inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma oxygen releasing compounds (ICP ORC) for metals
- plate counts for coliforms
Reviewed 22 July 2024