Types of sensor
Galvanic Sensor
Polarographic Sensor
Galvanic Sensors- It consists of a biological cathode and an anode, which generate electrical current in the presence of oxygen.
Polarographic Sensors- It consists of a platinum cathode and a silver anode, which measure electrical current.
Process of sensor (how it works)
i. Exposure to oxygen-The electrodes of the sensor come in contact with oxygen dissolved in water.
ii. Electrochemical reaction-On coming in contact with oxygen, an electrochemical reaction occurs, which is converted into an electrical signal.
iii. Measurement of signal-The concentration of DO is reported in specific units (mg/L) by measuring the generated signal.
Merits of sensor
1. High Accuracy
2. Fast reading
3. Automatic Measurements
4. Continuous Monitoring
5. Minimum maintenance
Demerits of sensor
Limitations of the sensor life
Ecological factors (Temperature, PH level effect)
High cost
Defective Sample
Pollution
Importance of measuring DO
The essential reasons for measuring Dissolved Oxygen (DO) are as follows:
Protection of Aquatic Life:
1. Lack of oxygen affects aquatic life.
2. Oxygen is necessary for the survival of fish and other aquatic organisms.
3. Helps maintain the diversity and balance of aquatic life.
Aiding in Water Pollution Control:
1. DO levels help detect water pollution.
2. Assists in preventing water pollution from industrial and domestic waste.
3. DO levels are important in water purification and management.
Assisting in Water Health Assessment:
1. DO levels are used to evaluate water quality.
2. Determines the health and safety of the water.
3. Helps in determining whether the water is safe or unsafe for use.
Environmental Protection:
1. DO levels are important for the protection of water sources.
2. Helps in preventing climate change and water crises.
3. The quality of water is crucial for environmental protection.
Ensuring Human Health Safety:
1. Determines if the water is safe for drinking and other uses.
2. Helps in preventing waterborne diseases.
3. The quality of water is important for human health.
For these reasons, measuring DO is essential to ensure the safety of aquatic life, control water pollution, assess water health, protect the environment, and safeguard human health.
Problems in DO (Dissolved Oxygen) Analysis
Various issues can arise in DO analysis that can affect the accuracy and reliability of the measurements. The following problems are commonly observed in DO analysis:
1. Contact with Oxygen During Sampling: If the sample comes into contact with atmospheric oxygen during collection and transportation, the DO levels may change.
2. Contact with Contaminants: If unknown chemicals or pollutants are introduced into the sample during collection, it can affect the accuracy of the DO measurement. These contaminants may interfere with chemical reactions, leading to incorrect results.
3. Technical Issues (Sensor Malfunction)
Factors such as faulty electrochemical sensors, lack of calibration, or changes in sensor sensitivity can affect accuracy. If the sensor is not properly maintained, it can produce incorrect results.
4. Lack of Maintenance
Regular maintenance of equipment and methods is essential. If proper care of the instruments is neglected, the measurements may become inconsistent and incorrect data may be obtained.
5. Human Errors
Human errors during laboratory measurements, such as incorrect readings or recording, can cause inaccuracies in DO levels.
6. Environmental Factors (Temperature and pH Changes)
Temperature changes: Water temperature has a direct impact on DO levels. As temperature increases, water’s ability to retain oxygen decreases. If there is a temperature change during the measurement, the DO level might be inaccurately measured.
pH changes: Variations in water pH can also affect DO measurement. Different pH levels can alter chemical reactions, leading to incorrect DO readings.
Conclusion:
To ensure accuracy in DO analysis, attention must be paid to solving these issues.
Solutions to the Problems:
1. Contact with Oxygen During Sampling:
Solution: During sample collection, fill the sample bottle completely with water and tightly seal the lid to avoid air contact. Bring the samples to the lab for analysis as soon as possible and avoid extreme temperatures during transportation.
2. Contact with Contaminants:
Solution: Use clean and sterile equipment during sample collection and keep the collection site free from contaminants. Store samples in conditions that are free from pollution.
3. Technical Issues (Sensor Malfunction):
Solution: Regularly calibrate electrochemical sensors or other instruments. Maintain the sensors according to the manual, and if any fault is found, replace or repair the sensor immediately.
4. Lack of Maintenance:
Solution: Inspect and maintain equipment regularly. Fix any defects or inaccuracies in the instruments immediately. Periodically evaluate measurement methods and procedures to ensure the equipment performs at its best.
5. Human Errors:
Solution: Provide proper training to laboratory staff to prevent mistakes during the measurement process. Develop detailed guidelines and checklists for measurement techniques. Exercise caution and attention while recording measurements, and double-check procedures.
6. Environmental Factors (Temperature and pH Changes):
Temperature Changes:
Solution: Measure the water temperature before and after the test, and apply temperature correction for DO measurement. Try to keep the temperature stable during the DO measurement, or adjust the measurement accordingly if the temperature changes.
pH Changes:
Solution: Measure the pH levels, and if there is any significant variation, include it in the DO measurement. Take proper steps to stabilize the water pH before DO measurement, such as keeping the water clean and stable.
Conclusion:
By ensuring proper sample collection, regular maintenance of equipment, appropriate training, and adjustment for environmental factors, errors in DO measurement can be minimized, leading to more reliable and accurate results.
.png)
