Description

Rhodamine WT (RWT) dye is a bright, non-toxic, fluorescent red tracer commonly used in hydrology and water quality studies. Unlike naturally occurring pigments, RWT is an artificial dye that is highly detectable at very low concentrations. Its unique fluorescent properties make it an ideal tool for tracking water flow, dispersion, and mixing patterns in various aquatic environments.

Why is Rhodamine WT Dye used in Monitoring?

Rhodamine WT dye can be crucial for specific hydrological and environmental investigations:

• Flow and Transit Time Studies: RWT is widely used to determine how quickly water travels through rivers, streams, pipes, or treatment plants, providing vital data for understanding flow dynamics and predicting pollutant transport.
• Dispersion and Mixing Analysis: By observing how the dye plume spreads, researchers can assess how well pollutants or discharged effluents mix with the ambient water, which is critical for compliance and impact assessments.
• Leak Detection: In infrastructure like pipelines, wastewater collection systems, or septic tanks, RWT can be introduced to pinpoint sources of leaks or cross-connections, helping to located the source of contamination.
• Groundwater Tracing: The dye can be used to track groundwater flow paths and interconnections between surface water and groundwater, aiding in contaminant transport modeling.
• Storm water Runoff Studies: RWT helps characterise the movement and impact of storm water runoff, identifying pathways for pollutants entering waterways.
• Calibration of Sensors: In some cases, RWT is used as a standard for calibrating fluorescence-based sensors that measure other parameters, such as chlorophyll or phycocyanin, due to its stable and well-understood fluorescent properties.

How Rhodamine WT dye Sensor Work

A Rhodamine sensor measures the concentration of Rhodamine dye based on its fluorescence properties. It operates by emitting a specific wavelength of light, typically in the green spectrum (e.g., around 500-560nm), into the water. This light excites the Rhodamine WT dye molecules present, causing them to re-emit light at a different, longer wavelength (e.g., 570-590nm) – a process known as fluorescence. A dedicated detector then measures the intensity of this emitted fluorescence, which is directly proportional to the amount of chlorophyll present in the water, providing an accurate and real-time measurement.

To use Aquaread’s Rhodamine WT sensor, first install it into the AP-6000 or AP-7000 probe. The probe use an excitation at 520nm and then detects the resultant fluorescence above 575nm.

When to use the sensor

Rhodamine WT dye monitoring is an indispensable technique for highly specific hydrological and environmental investigations where understanding water movement is key. It is particularly valuable for:

• Hydrological Tracer Studies: Ideal for mapping flow paths, determining stream velocity, calculating discharge rates, and understanding residence times in rivers, lakes, and coastal areas.
• Wastewater and Stormwater Infrastructure Assessment: Crucial for identifying illicit discharges, tracking combined sewer overflows, and evaluating the effectiveness of wastewater treatment plant mixing zones.
• Pollutant Transport Modeling: Providing empirical data on dispersion and dilution, which is vital for calibrating and validating numerical models used to predict the movement of contaminants.
• Industrial Discharge Permitting: Used to ensure that industrial effluents mix adequately with receiving waters, meeting regulatory standards for dispersion.
• Septic System and Leach Field Evaluation: Assessing the performance of onsite wastewater treatment systems and identifying potential failures leading to groundwater contamination.
• Source Water Protection: Tracing potential contamination pathways to drinking water sources.

7000-RHOD Electrode

The 7000-RHOD electrode is a Rhodamine WT Dye sensor designed for connection with the AP-6000 or AP-7000 water quality probe from Aquaread. It is a fixed response fluorometer, meaning it excites the Rhodamine Dye in the water at a fixed wavelength (520nm) and then measures the subsequent emitted fluorescence (575nm). The electrode induces the Rhodamine molecules to fluoresce, then measures the longer wavelength light which is emitted as a result of the fluorescence process.

Automatic Cleaning Mechanisms on AquaProbe

Both the AP-6000 and AP-7000 AquaProbes include automatic cleaning mechanisms which are incredibly beneficial for any optical sensor. The brush and wipers are critical because they:

• Prevent Biofouling Build-up: By periodically wiping the optical surfaces, they physically remove algae, biofilm, and other organic matter before it can significantly impact readings. This is especially crucial for long-term deployments.
• Dislodge Air Bubbles: The wiping action effectively dislodges any trapped air bubbles that might cling to the sensor’s surface, ensuring a clear path for light transmission and reception. Air bubbles are a common issue in turbulent waters or when probes are initially deployed.
• Maintain Accuracy: By keeping the optical windows clean, the cleaning mechanism ensures the sensor’s readings remain accurate and reliable over extended periods, reducing the need for frequent manual cleaning and site visits.