How to Use a Portable COD Testing Device Effectively?

Having a portable COD testing device means that you can now measure chemical oxygen demand at any location. You can now do testing without needing to wait for results from a lab. You also do not need to transport samples to a lab. You can do testing on site to get results almost immediately, allowing you the ability to make actions based on the results you get. Using a portable cod testing device can also allow you to test on the location or site you need to do testing for. However, using the device to get the data you need to make changes or decisions is not as simple as just using the device. To get data you can trust to make changes or actions based on the results, there are a few steps to take to get the right info.

Portable COD testing devices can be used to monitor wastewater treatment plants, check for industrial discharge, and do field work for environmental studies. The reliability of such devices depends on the user's ability to implement some best practices.

Start with the right preparation

Taking some time to get ready is the first step. Portable devices are supposed to be simple to use, however, that does not mean you should skip any steps that are involved in setting it up. Before even leaving the lab or even the office, the first step to take is to check that the portable cod testing device is functioning properly and is calibrated. You should do the calibrating if it is needed prior to leaving, because even the best device will produce results that are wrong if it is not calibrated.

Also, consider the reagents. Portable COD testing usually uses predetermined dosages in separate reagent vials. Verify that you have enough reagents for the number of tests you want to conduct. Look for reagents that are nearing expiry. Expired reagents can yield inaccurate results. Finally, ensure the vials are clean and undamaged. Scratches and chips on vials can impact the reading.

When testing, be certain to check that the device has enough battery. There is nothing more annoying than trying to conduct a test and the battery dies. Make sure you charge the device and remember to bring a spare battery or a portable charger to help you complete the test.

Collect a representative sample

It is important to remember that the quality of your results is dependent on the quality of the sample. If the sample is not representative, the results you obtain will not be of much value. When thinking of what to measure, consider the source of the water and the COD level you are testing for.

When taking a sample from a flowing stream or discharge pipe, ensure to position the sampling point to reflect the average condition. Avoid the edges where stagnant water can collect. Tank or lagoon samples may also require sampling from multiple locations if the contents are poorly mixed. In this case, multiple samples may be taken from different levels of the tank or lagoon.

To collect a sample, use a clean, unused container. Before your sample is taken, rinse the container to remove any contaminants. Sediment disturbance during sampling should be minimized; samples should be transferred with extreme care. If the sample to be taken contains solids that have to be measured, ensure that the sample is adequately mixed before transferring it to the reagent vial. A sample that is adequately mixed is defined as homogeneous.

Follow the reagent vial procedure

With regard to the reagent vial, it should be noted that most portable COD devices use pre dosed reagent vials that contain everything needed for the digestion step. Although the procedure may be relatively simple, it is the attention to the details that matters.

Carefully open the vial. Some vials come with a protective cap that will need to be removed. Using a pipette or a syringe, add your sample to the vial. Be exact about the volume. Adding too much or too little sample alters the chemistry and skews the result. Most systems require a small sample volume, usually two milliliters or less. Use the pipette that came with your system or a pipette that is known to be accurate and calibrated for your volume.

Once the sample is added, cap the vial securely. Invert it several times to mix the contents. Do not shake the vial vigorously. A few gentle inversions should be sufficient to mix the sample with the chemicals.

Run the digestion step

The digestion step is where the chemical transformation happens. A typical portable cod testing device has a heating block that heats vials to the required temperature. Place the vials into the heating block and start the digestion. Portable systems have a digestion time of about 20 minutes. Unlike traditional methods, this is much faster, but you will have to let it run the entire time.

Please do not interrupt the digestion cycle. Opening the block prematurely, or a drop in temperature, may affect the reaction. You may continue with your other preparations while the vials are heating, but please watch the timer.

After the digestion cycle, the vials must cool prior to measurement. Some systems have built in cooling racks or may have a designated cooling period. Measuring a hot vial can damage the instrument or give an inaccurate reading. It generally takes about ten minutes for the vials to cool down. During that time, you should prepare your instrument for the measurement.

Measure the sample accurately

First, wait for the vials to cool down, and once they do, you are ready to take the measurement. Place the vial in the measurement chamber of the portable cod testing device. Please ensure the vial is clean. Remove any fingerprints, smudges, and other marks that may obstruct the optical reading. If the vial is not clean, use a clean, lint free cloth to wipe it.

Now, close the chamber and begin measurement. The apparatus will shine a beam of light through your sample and record the amount of light that is absorbed. This measurement is then converted into a value for COD. The majority of portable devices will give you a result in a few seconds, displayed in milligrams per liter.

Do not assume an unexpected result is an incorrect result. Check through your steps. Did you measure out the correct sample volume? Did you thoroughly mix the vial? Is the device calibrated? Do not discard an unexpected result; it may reveal something important about your water. If you believe it to be incorrect, then you should test it again. Duplicate testing is an effective technique for confirming results.

Record your results

If you do not record the result, it is like it never happened. Remember to save the results. If your testing device has a way of saving results, like with a time and date stamp, then be sure to use it. Each result should also be noted in a field notebook with the location, time, and test conditions to keep track of results, especially if your device does not save results.

Good record keeping helps you track trends, prove compliance, and troubleshoot problems. A record will let you see the exact time of an occurrence if the values in your work happen to shift abruptly.

Clean up properly

Your work area and testing equipment need to be cleaned after testing. If any liquids have spilled, be sure to clean the measurement chamber. Do not pour reagents or digested samples down the sink, as they are classified as hazardous waste. Consult your workplace's procedures for the disposal of chemicals. Many reagent vials can be disposed of as solid waste after they have been cooled and sealed, but check the manufacturer's instructions to be sure.

Store your portable cod testing device in a place that is dry and clean. A well cared for device will give you reliable results for years.

Calibrate and maintain regularly

Regular maintenance is required for even the most portable COD testing device. The guidelines set by the manufacturer should be followed. Calibration should be done on a regular schedule. A device that is used regularly but never calibrated will eventually drift out of accuracy.

Be sure to check the battery consistently. A battery that is running low can hinder the heating block and optical system's performance. If your device has a rechargeable battery, keep the battery charged. If the device uses replaceable batteries, keep extras on hand.

Look for wear on the device. Look for dirt and scratches in the measurement chamber. Check the heating block to see if there are any signs of residue. Follow the device manufacturer's instructions to clean the device. A little maintenance goes a long way in helping you achieve reliable results.

Know your device's limits

A portable cod testing device is an extremely useful tool. However, every device has its limits. Most portable systems are designed for a specific measurement range. If your sample has a COD level outside that range, you may need to dilute it before testing. Check the specifications for your device. If you frequently test samples with very high or very low COD, make sure your device is suited for that.

Understand that portable devices are meant to be taken out into the field but can be easily damaged. Give the device care in order to keep it in good working order.

Conclusion

Using a portable cod testing device effectively begins with preparation, moves on to careful sampling and handling, and ends with proper recording and maintenance. Each step requires attention. Following best practices gives results that can be relied upon. When results can be relied upon, decisions can be made with confidence about water quality, treatment processes, and regulatory compliance.

A portable COD tester puts the capabilities of a state of the art laboratory in your hands. Treat it with the respect it deserves, and it will serve you reliably for years.