Understanding COD Sensors: The Multi-Parameter Solution for Water Quality Monitoring
Chemical Oxygen Demand (COD) sensors, often referred to as multi-parameter water quality sensors, are essential tools for assessing organic pollution in water. Today, we will explore COD sensors from four key perspectives: definition, working principle, features, and measurement methods.
What is a COD Sensor?
A COD sensor measures the amount of oxygen required to oxidize soluble and particulate organic matter in water. Expressed in milligrams per liter (mg/L), it indicates the concentration of reducing substances present in a water sample. This parameter serves as a critical indicator of organic pollution and is widely used as a comprehensive measure of organic content in water.
How Does a COD Sensor Work?
Most water-soluble organic compounds absorb ultraviolet (UV) light at 254 nm. COD sensors leverage this property by measuring the absorption of UV light at 254 nm to determine the total organic pollutant levels. Advanced COD sensors utilize a dual-light path design: one path employs 254 nm UV light, while the other uses 850 nm infrared light to compensate for turbidity and optical path attenuation. This ensures stable and reliable measurements.
Key Features of COD Sensors
- Reagent-Free Operation: No additional chemicals are required, making it an eco-friendly and cost-effective solution.
- Compact and Easy to Install: Designed for seamless online and continuous water quality monitoring.
- Multi-Parameter Measurement: Capable of simultaneously measuring COD, turbidity, and temperature.
- Automatic Turbidity Compensation: Effectively minimizes interference from turbidity for accurate results.
- Integrated Cleaning Brush: Prevents biofilm and microbial fouling.
- High Accuracy and Fast Response: Delivers reliable measurements with minimal drift.
- Long-Term Stability: Maintains consistent performance over extended periods.
- Low Maintenance and Operational Costs: Requires minimal upkeep and offers extended service life.
- Digital Sensor with RS-485 Interface: Supports Modbus/RTU protocol for easy integration.
- Low-Power and Anti-Interference Design: Ensures reliable operation in challenging environments.
Measurement Methods for COD
COD is typically measured using oxidants such as potassium permanganate or potassium dichromate. The choice of oxidant affects the results, so it is essential to specify the method used. Standardized testing protocols ensure comparability across measurements.
- Potassium Dichromate Method: Commonly referred to as Chemical Oxygen Demand (COD).
- Potassium Permanganate Method: Often called Oxygen Consumption (OC) or the permanganate index.
Water Quality Standards for COD
COD levels are a key metric in water quality classification:
- Class I & II Water: COD ≤ 15 mg/L
- Class III Water: COD ≤ 20 mg/L
- Class IV Water: COD ≤ 30 mg/L
- Class V Water: COD ≤ 40 mg/L
Higher COD values indicate more severe organic pollution.
Maintenance Tips for COD Sensors
Regular calibration is crucial for ensuring accurate COD sensor readings. When replenishing or replacing reagents, calibrate the sensor using pure water and compare the results against reference data. For best practices, set the sensor to manual analysis mode during calibration. If your water quality monitoring device does not support this feature, increase the frequency of calibration checks.
Investing in a reliable COD sensor not only enhances water quality monitoring but also supports sustainable and efficient environmental management. Choose a multi-parameter water quality sensor for precise, real-time insights into organic pollution levels.
