Background
Water quality monitoring systems can provide researchers, operators, and engineers with vital data for laboratory research, quality control, and hydraulic model calibration by tracking changes in water source quality over time. Water quality sensors can be the eyes and ears of system operators, providing real-time actionable data that can be used to protect water quality in a water distribution system. Water quality assessments can also alert organizations like the Centers for Disease Control, helping prevent public health disasters. Water quality sensor information is often used to make decisions on a wide range of management issues, including meeting regulatory water quality requirements, identifying non-regulated water quality for key users, validating water quality models and applying pollution early warning systems.
The chemical, biological and physical conditions of water resources indicate their quality in several ways. Even small changes in characteristics such as pH measurement can affect those who depend on water sources.
To maintain water quality, water quality assessments should track parameters such as conductivity, dissolved oxygen, pH, salinity, temperature and turbidity, which are critical. For the same reason, water quality sensors have become standard in many systems.
What are the common water quality sensors?
There are many types of water quality sensors currently in use. Below is a short list of the most commonly used sensors.
Chlorine sensor
Measuring residual chlorine in water treatment centers and water distribution systems is critical to the safe treatment of water and has been important as long as chlorine has been used for water disinfection.
These water quality sensors assess the levels of free chlorine, monochloramine, and total chlorine in water sources. The main application is drinking water disinfection, although total chlorine is also often assessed when treating wastewater.
Turbidity sensor
Turbidity sensors typically measure suspended solids in water by determining the amount of light that is able to pass through the water. These water quality sensors are used in river and stream testing, wastewater measurement, drinking water treatment operations, sedimentation tank management, sediment transport studies and laboratory testing.
Conductivity sensor
Conductivity tests are often performed in industrial settings to obtain data on the total ion concentration in aqueous solutions, such as the amount of dissolved compounds. Common applications include water purification, clean-in-place (CIP) control, and measuring concentrations in solutions.
Standard conductivity sensors can be in-line sensors that plug in directly, or they can be water quality sensors in an enclosure connected by a cable to a transmitter that sends a signal to processing and/or recording equipment.
pH sensor
The pH (acidic or basic) of a solution is the primary indicator of water quality. A pH sensor is usually a single electrode, usually made of glass, which is very delicate. The electrodes are usually connected to an analyzer that has interfaces for water quality data collection, calibration and alarms.
ORP sensor
The ORP sensor measures the oxygen reduction potential of the water source. Used in conjunction with a pH sensor, ORP measurement can provide insight into the extent of oxidation/reduction reactions occurring in a solution. ORP sensors should be connected to efficient interfaces and software to collect data.