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Latest in Field Instruments: Applications for Water Testing

Matthew Sullivan, an environmental specialist in the Field Operations section of the Bureau of Environmental Services for the city of Portland, Oregon, talks to contributing editor Tanuja Koppal, Ph.D., about how field testing, particularly for water analysis, has changed over the years. The testing equipment is now better suited for field analysis, in terms of its size, compactness, and robustness. The newer instruments have also allowed for sampling and testing to be done remotely and in an automated fashion. Overall, field instrumentation is striving to provide faster, cheaper, more robust, and more real-time measurements for routine analysis.

Q: Can you describe your team and the types of field testing they do?

A: We have a team of nine people with backgrounds in chemistry, biology, environmental sciences, and engineering. Our bureau is in charge of the wastewater collection and treatment for the city of Portland, and we are responsible for sampling and monitoring the streams and rivers. We perform a broad variety of field sampling and testing of streams, rivers, and the groundwater. We also collect samples and monitor industries that discharge waste into the city’s sewage treatment plants and collection systems.

We do a lot of long-term in situ monitoring with field instruments, where the field meters are left to collect data on various parameters for months at a time. For temperature readings, the meters are sometimes left for a year. In situ testing is ideal for most parameters and used whenever possible, because parameters such as pH, temperature, dissolved oxygen, conductivity, turbidity, and oxidation- reduction potential start to change dramatically over time. Metals, on the other hand, do not disintegrate, so we collect the sample and bring it back to the laboratory and have it analyzed. However, if we are interested in the portion that is dissolved versus in the solid phase, we do field filtering to test the dissolved portion.

Q: How do you carry out the testing?

A: We have a few different types of vehicles and each one is geared for a specific type of monitoring. We work off of a boat outfitted with equipment to collect samples from large rivers. We have mobile vans for testing industrial discharges that are being released into the city’s sewage treatment plants and we make sure that they stay within their permitted limits. We have vehicles to collect samples from confined spaces, such as sewer lines or from the storm water collection system, for source tracing of contaminants.

Q: What has changed in field testing in recent years?

Optical Dissolved Oxygen SensorAn optical dissolved oxygen sensor on a multiparameter water quality meter that is configured for logging dissolved oxygen, pH, conductivity, and temperature. (Source: Matthew Sullivan)A: I have been doing field testing for just under 20 years now, and within the last five years there have been a number of technological advances in testing. There is a new optical technology for measuring dissolved oxygen. Previously we used a galvanic cell with a fragile membrane that required frequent changing. The new optical method is more durable and less prone to biofouling. We have installed these units for continuous monitoring of dissolved oxygen and doing so has enabled us to go from weeks between maintenance cycles to about a month. There are also new ion selective electrodes that are installed on long-term monitoring devices to test nutrients like nitrates and ammonia; metals like copper, silver, and lead; and other elements like chloride, fluoride, and new electrodes that continue to be introduced every day.

We also now have a lot more remote access to field equipment. Instead of having to drive out to check a piece of equipment, you can use cell phone technology to dial in and communicate with the equipment. You can set certain thresholds, prompting the device to call you or send a text or e-mail if the parameter being tested drops below a set level. We do a lot of automated sampling, where we remotely set conditions to have a flow or level meter collect samples once a certain water level is reached. You don’t have to go out there in the middle of the night to collect the samples.

Laser Particle AnalyzerA laser particle analyzer to determine the concentration and particle size distribution suspended in water (Source: Matthew Sullivan)Q: Is the equipment also getting faster, cheaper, and smaller?

A: Yes, of course. Temperature loggers are now less than $100 apiece and we have them located in streams throughout the city. They are robust and can withstand floods and rocks. As long as you can find them, you can always pull the data from them. They also use so little power that they can last a whole year without any input from us. One interesting piece of equipment that we have just started to use is the laser particle analyzer. It’s identical to the one being used in the lab, but now we have one designed specifically for rugged field use. Previously we would collect the water sample and submit it to the lab for particle size analysis and get the data back two weeks later. Now, with this instrument in the field, within a few seconds we have data on what the particle size distribution is within a given volume of water. We are currently renting the laser particle analyzers, since they are so expensive, but we hope to own a few some day.

Today equipment manufacturers are definitely making instruments that are designed specifically for field use. Previously, the instrument for measuring dissolved oxygen in the field was identical to the one being used in the lab, except it had a handle on it. We now have ones that are small, handheld, waterproof, and well suited for field use. 

Q: Do you have to undergo any specialized training for carrying out the types of testing you do?

A: We all need to have an understanding of general chemical and biological principles to be able to interpret the data obtained in the field and to make decisions on the fly. Knowing what the accepted values are for the parameters you are looking at is critical, especially to know if the instrument is malfunctioning or if there is a problem. We are trained in the operation of each piece of equipment and have learned to use the software program associated with each device. Some of the places where we collect samples can be hazardous. So we have to undergo safety training for working on a boat or in confined places such as in a storm water pipe or at tricky locations at an industrial site.

Q: What challenges do you face and what improvements can you recommend?

A: It rains a lot in Portland and it is unavoidable in fieldwork for equipment to get wet or dropped in the water. Hence, we are always purchasing equipment that is as waterproof as possible. Another challenge, especially in longterm field monitoring, is biofouling caused by algal or bacterial growth on the equipment sensor. That can throw off the readings and we have to look out for that, since the problem is not always obvious. We have made improvements in technology, such as with the dissolved oxygen meter, where instead of the fragile membrane, there is now a robust optical sensor with wipers integrated into it so it goes much longer before it gets fouled. Copper components that have antimicrobial properties are also being used in monitoring equipment to prevent bacteria or algae from growing. It’s still a challenge knowing how long you can expect to record the data before you have to go out and clean and recalibrate the device.

Q: Do you see any radical changes taking place in field testing going forward?

A: It does seem like every year there are more and more types of analyses that can be done with field meters and without the need for lab analysis. We can collect so much data, so fast. We can watch how a creek responds to a storm event with a laser particle analyzer logging data over the course of the storm. We can record all the particle sizes without having anyone on-site in the storm, waiting all night to collect samples to turn in to the lab. So there is a lot of labor savings.

More and more things can be done remotely and in an automated fashion. 

Matthew SullivanMatthew Sullivan is an environmental specialist in the Field Operations section of the Bureau of Environmental Services in lovely but rainy Portland, Oregon. He has spent the past 17 years utilizing a variety of field instrumentation and specialized sample collection techniques to gather environmental and water-quality data. This data is used to fulfill regulatory requirements associated with Portland’s storm water and wastewater collection and treatment, and to support the objectives of improving the water quality in Portland’s rivers and streams, reducing storm water runoff and its associated pollution, and improving the habitat for fish and wildlife. He has witnessed an increased range of analytes that can be measured using field instruments, as well as continual improvements in the ease of use, durability, and water-resistance of such instruments. Matthew has a B.S. in biology from Colby College in Waterville, Maine.