Water Sensors Toolbox | US EPA

This toolkit is a collection of resources and information related to EPA research that uses, evaluates, and/or develops water sensors―including remote sensors and related data management technology. These resources may be useful to students, researchers, citizen scientists, water quality decision makers, or others interested in collecting data on water quality with the use of water sensors.

Water sensors can be used both for drinking water and environmental applications. Because those applications often overlap, they are presented together in this toolkit. Where the distinction is important, it has been noted.

Uses and Applications

Uses for Water Sensors

• Monitoring water quality

• Detecting contaminants

• Monitoring septic systems for discharges

• Measuring levels of nutrients in surface waters

• Detecting chlorophyll a, which can in turn be used for predictions (e.g., harmful algal blooms and/or cyanotoxins in watersheds)

• Measuring the use and effectiveness of wastewater and drinking water treatment

• Monitoring distribution systems

Applications of Water Sensors

• Measuring water quality parameters, such as pH, water temperature, conductivity, dissolved oxygen, and turbidity.
• Monitoring for contaminants, such as cyanobacteria and cyanotoxins, chlorophyll and algae, nutrients (i.e., nitrogen and phosphorus) and nutrient species (e.g., ammonia, nitrite, nitrate, orthophosphate, total nitrogen, total phosphorous), arsenic, bromine, calcium, magnesium, and chloride.
• Help with describing physical characteristics of water, such as water presence/absence, water level, and discharge.

​Development to Evaluation​

Water Sensor Development

• While EPA’s focus is on using available sensors, there is some work aimed at developing sensors for specific contaminants, such as for arsenic detection. (Report: A disposable acetylcholine esterase sensor for As(iii) determination in groundwater matrix based on 4-acetoxyphenol hydrolysis. Analytical Methods.)
• EPA encourages inventors and entrepreneurs to develop needed sensors through Challenges. A recent example includes the development of nutrient sensors. View a complete list of EPA Challenges.

Interpreting and Evaluating Water Sensor Data

As the number of water sensors increase, EPA is working to better understand the capabilities and limitations of water sensors. Below are documents and information on water sensors and their use:

• Online Water Quality Monitoring Resources. Online instruments for real-time water quality measurement in source waters and/or distribution systems. These resources can help utilities optimize treatment processes, improve distribution system operations, and detect contamination incidents.
• Smart Data Infrastructure for Wet Weather Control and Decision Support. Wet weather (i.e., rain and snowmelt) can significantly increase flows at wastewater treatment facilities, creating challenges to treatment efficiency, reliability, and control of treatment units. This EPA document is a guide on how local governments and treatment facilities can use advanced monitoring data to support wet weather control and decision-making in real time or near real time.

Supporting Technology and Data Management of Water Sensors

The supporting technologies needed for water sensors are similar to those used for air sensors since the underlying technology, after the initial detector, is basically the same. There are a small number of projects on these technologies, such as those aim to improve managing the data produced by sensors. For example, EPA’s CANARY system gathers sensor data from distribution systems to develop algorithms that indicate when a system may be out of balance. Given the large amount of data anticipated as sensor use becomes more common, this area of research will become more important over time.

Water Sensors Performance Evaluations

The evaluation of the sensitivity, precision, and reliability is a critical need for sensors. Below are some highlighted efforts for evaluating sensors:

• EPA’s Homeland Security Research Program. Developed a suite of models, tools and applications for securing and sustaining water systems. Among these tools is CANARY, a software-based contamination warning system that uses uses statistical and mathematical algorithms on standard water quality data to identify the onset of periods of anomalous water quality.
• Alliance for Coastal Technologies. ​​Conducts sensor evaluations and EPA scientists are involved in the effort.
• Distribution System Water Quality Monitoring: Sensor Technology Evaluation Methodology and Results. This 2009 EPA report gives EPA’s results from investigating water quality monitoring sensor technologies that could have been part of a real-time contamination warning system (CWS).

How EPA is Using Water Sensors

Water sensors are used to provide data for several EPA-supported efforts, such as those listed below. For many of these efforts, EPA scientists are working in collaboration with other federal agencies, including the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), the U.S. Geological Survey (USGS), and the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID). In addition, EPA often works with states, tribes, and local governments on these efforts.

Research Publications and Presentations

Publication Highlights

Presentation Highlights

Additional Resources

Frequently Asked Questions About Water Sensors

Answers to commonly asked questions about water sensors are provided to inform those interested in using the technology.

What is a water sensor?

Water sensors are devices that can be used to collect information from a targeted body of water. At EPA, researchers are particularly interested in water sensors that collect information about pollutants and other factors that impact water quality.

Water sensors currently on the market measure a wide variety of pollutants and other water quality parameters. Examples include the following:

• Blue-Green Algae (phycocyanin, or phycoerythrin pigments)
• Chemical Oxygen Demand
• Chlorophyll
• Color
• Conductivity
• Chlorine
• Depth
• Dissolved Oxygen
• Flow Rate
• Nitrogen (either as ammonia, nitrate, and/or nitrite, or without distinguishing
• Oxygen Reduction Potential
• pH
• Presence or Absence of Water
• Pressure
• Salinity
• Surface sheen
• Temperature
• Turbidity
• Other parameters may be available

How is water sensor technology being used?

Potential uses for water sensor technologies include the following:

• Science education
• Supplementing regulatory water quality measurements
• Conducting research
• Measuring local water quality to better understand sources of pollution

• Locating leaks at industrial facilities

• Emergency response

Can water sensor data be used to help identify water quality problems?

Yes. Several of the water sensor activities included in the toolbox are designed to identify water quality problems. A few EPA examples are listed below:

What are the common challenges experienced by users of water sensors?

• Business case – Some sensors work very well but are difficult to integrate into a research or operational plan.  There should be a clear path to using the data that is being generated by any sensor prior to procurement and installation.
• Biofouling of sensors – This is a problem for multiple sensors. Users need to know how often to clean sensors. Copper coated sensors tend to reduce fouling but, in some cases, leaching of copper ions may affect other detection analyses.
• Sensor placement – Placing a water sensor at the right location is key to accurate sensor readings. For example, flooding in a stream or any kind of water fluctuation can affect placement of sensor and thus can affect readings. Birds and other animal interferences have been notorious for affecting sensor readings!
• Data logging, transfer, and warehousing – There can be different challenges depending on the type of data. Things to consider are firewalls, data ownership, and mechanisms for transferring data. The more remote you are the more difficult it is to transfer data. Cost of data storage and transfer should be considered. Some software for transmitting data behind firewalls can be expensive.
• Data compatibility – Sensors from multiple vendors can have varying data on the same parameters. For example, there is a lot of variability with different sensors in detecting pH.
• Data analysis – Data processing for large volumes of data are difficult without data scientists to analyze data. There should be conversations on how to standardize data analysis across multiple projects.
• Maintenance cost – Routine maintenance of a sensor should be considered. For example, Ion Selective Electrodes have membranes that need to be replaced frequently
• Standardization of data based on calibrations – There are no standards on pre-data and post-data calibration of instruments. For example, calibrations can vary depending on the type of media for calibration (e.g., distilled water or buffered water).
• Life cycle cost – Depending on type of sensor, the expense of a sensor can vary significantly. Therefore, knowing the life span of a sensor and cost analysis of maintenance of sensor should be considered.
• Site specific concerns – power, availability of light for photovoltaic cells, cellular connectivity, human activity, animal activity, weather, extreme high or low water conditions, sedimentation, highly corrosive waters, and earth movements, among others.
• Clocks on sensors – Variation can exist between sensor on time logging. This should be considered when linking time with sampling analyses.

Why is EPA involved in the advancement of water sensors?

The demand for more frequent, lower cost monitoring approaches for water is increasing and will be important as the EPA works to respond to existing and new challenges in managing water quality. As such, sensors are playing an increasing important role in the monitoring of water quality. In EPA’s Office of Research and Development, we have several efforts aimed at the development and use of sensors. These efforts are all aimed at providing data and tools to support utilities and water quality managers.

Can EPA make recommendations on water sensors to help guide me in my selection?

As a federal agency, EPA cannot make recommendations to the public on the use of particular commercial water sensors for their projects, nor can EPA endorse commercial products.