Overview
By the 1960s, water pollution was prevalent in many parts of the United States with rivers, lakes, estuaries and coastal waters rapidly degrading. The United States Environmental Protection Agency (USEPA) was formed in 1970 and the Clean Water Act (CWA) was introduced into law in 1972. The CWA has since been extended with additional regulations and amendments, including: Storm Water Discharge, Industrial Pretreatment, and Nonpoint Source Pollution.
Focus on estuaries, coastal waters, and wetlands along with assessment and enforcement have kept Americas water quality in check these past few decades. However, stresses on our water resources continue to grow. Population growth and redistribution, climate change, water for energy, and an aging water supply infrastructure contribute to tension on the water resources.
Water quality monitoring is essential to understanding the impact humans have on the environment. Clean water is important to the health of plants and animals and the quality of life for all people. Water quality professionals routinely monitor: temperature, dissolved oxygen, pH, conductivity, salinity, and turbidity.
Selecting a Sensor
There are many water quality sensors on the market. Common sensor manufacturers include NexSens, YSI, In-Situ, Hydrolab, and Turner Designs. The popular multi-parameter water quality sondes offer the ability to simultaneously measure multiple parameters in a single, compact sonde. Available sensors include temperature, conductivity, dissolved oxygen, pH, turbidity, chlorophyll A, and blue-green algae.
Most water quality sensors output a digital or analog signal that interfaces with NexSens iSIC or SDL data loggers. Common interfaces include RS-485, SDI-12, 1-wire temp string, 0-2.5 VDC, 4-20mA, and more.
Data Logging and Telemetry
At the heart of the water quality monitoring system is a NexSens iSIC or SDL data logger. The data logger can be pole mounted, housed in a secondary enclosure, or outfitted on a floating buoy platform. Options are available for solar or AC power. When configured with telemetry, data can be transmitted in real-time from the monitoring site to a project computer, eliminating the need for periodic site visits to upload data.
Two factors help determine the best telemetry method - site conditions and distance to the project computer. When the project computer can be located within a few miles (line-of-site) or few hundred feet (non-line-of-site), license free spread spectrum radio telemetry is the best choice. If the project site is remotely located relative to the project computer, cellular telemetry becomes the best option. Options are also available for landline phone or Ethernet telemetry if the site has access to a landline or Ethernet hub.
Selecting a Location
The location of water quality monitoring stations depends largely on site conditions. PVC deployment pipes can be mounted along the bank or seawall in stream and river applications. The PVC pipe should have perforations at the bottom to allow fresh sample to pass over the face of the sensors. A stainless steel bottom-pin should also be installed at the bottom of the pipe to keep the sensor in a fixed position.
Oftentimes, site conditions make it difficult or impossible to mount the monitoring equipment along the shore. When this is the case, buoy-based systems offer the most cost-effective solution. NexSens MB-300 and MB-500 data buoys are ideal for deploying temperature strings, multi-parameter sondes and other monitoring instruments in small reservoirs, lakes, rivers, streams, and protected coastal waters. The buoy-based systems are solar-charged and offer options for wireless radio or cellular telemetry.
Alarm Notification
NexSens Water Quality Monitoring systems offer two types of alarms; software and data logger. Software alarms are used to notify persons via SMS text messaging or email of parameters exceeding pre-defined parameter limits. NexSens iChart Software sends the alarm when it receives data from the data logger. Data logger alarms are used to change the functionality of the data logger based on parameter inputs, such as changing sample and log intervals based on a particular logged reading.
Once the water quality alarm limits are determined, the values are entered into NexSens iChart Software. When the water quality exceeds this pre-defined range, a text message or email is automatically sent to a pre-defined list of contacts to take appropriate actions. Typically, this involves notifying nearby water plants of the alarm condition.
Managing Data
Once the Water Quality Monitoring Systems are setup, data is logged at a user-defined interval (minimum 1 minute). The user also sets the interval at which data is transmitted via radio or cellular telemetry. A typical monitoring system logs water quality data every 10 minutes and transmits every 30 minutes.
Data is transmitted to a nearby (or remote) computer running iChart Software. iChart is a user-friendly software package that serves as the centralized interface and database for all incoming data. All data and sensor configuration settings are also stored in a single iChart database.
The software offers a unique historical report creation tool that can generate customized reports with data from all sensors in an iChart database. When creating a report, users can include specific information about the monitoring site, location, sensors, and project. After creation, reports can be converted to PDF, exported to Microsoft Excel, sent to interested parties via e-mail, uploaded to a web server, and more. The report template can also be saved and automatically generated, further automating the reporting process.
The NexSens WQData web datacenter is an optional service that automatically generates an online graphical interface for viewing, analyzing, and downloading data in real-time. This datacenter allows project members and stakeholders to remotely experience the project information and data in order to monitor lake water quality as it occurs.
Rental Equipment and On-Site Services
While it often makes sense to purchase systems outright, there are many short-term water quality measurement projects that make it cost-prohibitive. NexSens Technology offers real-time Water Quality Monitoring Systems with weekly and monthly rental rates to meet project requirements.
To ensure that customers can begin using their Water Quality Monitoring Systems as quickly and efficiently as possible, our application engineers are available for training and technical support, both by phone and in person. Our company offers both extensive field experience and a wide array of deployment hardware to facilitate seamless implementation of the project. Contact our application engineering team for your next water quality monitoring project.
