The goal of every monitoring program is to gain a better understanding of an environment. That deeper understanding can lead to better water management tactics or better decision making. Ultimately, to better understand water – we simply need more data – and the more the better.
To tell the full story of what is happening in a river, lake, stream, estuary – high resolution data is critical.
Some organizations only have the resources to monitor on a weekly basis with handheld water quality sampling equipment, and while that is a great first step to collect water quality data, a more robust monitoring schedule of even daily sampling can shed light on events occurring there.
Ultimately, however, we can’t be at the site 24/7, 365 days a year to maintain the high resolution dataset we need via handheld instrumentation. That’s why sondes are critical to building a global water quality data set.
For those of you who are new to water quality monitoring, a sonde (EXO) is a piece of instrumentation that can autonomously record water quality data in-situ for weeks or months at a time. This equipment can be installed throughout a watershed to capture basic parameters on the health of a waterbody.
Rain or snow, day or night, sondes continually collect data until they’re pulled from the water or run out of power.
When sondes were initially developed by various manufacturers nearly thirty years ago, the primary limitation on how long they could be deployed into the field was battery life. Sensors were power hungry and the internal hardware components weren’t nearly as power efficient as they are today.
A long deployment period for a sonde was a couple of days or even a week if you were lucky.
It wasn’t long before the power limitations of this type of equipment were resolved, and instrumentation could autonomously collect data for months at a time.
The only problem was the quality of the heaps and mounds of data we were collecting. In many environments, within a week (or in some cases even within a day), the deployed sensors were coated in sediment, biofilms, or even barnacles. Data was skewed and near worthless.
Maintaining equipment at that pace made continuous data seem unrealistic from a logistics standpoint. Sending technicians to service instruments every few days was both time consuming and expensive.
Everything starts to add up financially. The cost of the technicians’ time, the expenses to get out into the field, the supplies used each time to go out to the site, and the opportunity cost of the resources spent... The cost per data point is extreme when your sonde can’t keep its sensors clean of debris.
It was at this point when sensor manufacturers and developers understood the true enemy of high resolution data sets. It wasn’t battery life. It was the volley of algae, silt, and microorganisms that harsh aquatic environments throw at you and your equipment.
It was sensor fouling. It was biofouling.
Over the course of the next few weeks, we will provide you with blog posts full of tips on how to fight fouling and how to collect the highest quality data over the course of a long-term sonde deployment period. Using a combination of our suggestions, you’ll be able to significantly reduce the frequency at which your team must travel to field sites to clean and maintain sondes and water quality sensors.
If you’ve been using sondes for a while you may be familiar with copper based anti-fouling paint.
This is what was commonly used when we first started thinking about extending deployment times.
The paint was borrowed from the marine industry where it is used to cover hulls of ships and effectively prevented barnacles and other marine organisms from growing and reducing the ship’s performance. Similarly a sonde can be painted with this anti-fouling paint to achieve the same affect.
Without getting too technical, most anti-fouling paints consist of a copper component like copper oxide and a variety of aromatic hydrocarbons like benzene or toluene for example. For this reason you would want to be sure to take every necessary safety precaution recommended by the paint manufacturer when applying anti-fouling paint. This would consist of gloves, eye protection, a respirator, etc. and of course making sure you are in a well ventilated area.
A number of manufacturers produce anti-fouling paints that are suitable for YSI sensors. Two products that we have had good success with are Petit Paint’s “Trinidad SR”, and Interlux “ACT BottomKote” . Black paint must be used. Both are readily available at marine supply stores or online. A gallon of this paint will cost about $100.
There are no long term effects to using these paints on the instrumentation but be sure to not get any of this paint on the sonde or sensor connectors. Also note this paint will likely flake off over time where the old paint will likely need to be removed and a new coat should be applied.
So a sonde painted with copper-based paint will provide quality data for longer periods in the field and require fewer visits for cleaning and maintenance. Organisms have trouble getting a good foothold on the painted surfaces and are more easily cleaned off as well.
Each sensor can be removed and painted separately along with each part of the sonde including the guard. Paint is applied in thin coats and allowed to dry and then reapplied for maximum effect. This process needs to be repeated periodically as the paint flakes off or is removed with cleanings over time. And although an effective way to prevent fouling, the painting process is time consuming and there are increasing concerns over long term toxic effects. So the use of copper based paints may take a little extra time and effort but it will help prevent organisms from growing on your instrumentation and help extend your deployment times.
Next, Tip #2 – Use Copper Components on Your Instrument to Prevent Biofouling
A huge thank you to YSI Product Manager, Brandon Smith, YSI Marketing Specialist, Patrick Beatty, YSI Technical Support Team Lead, Tom Moeggenberg and YSI Application Engineer, Tiffany Shirmer for providing the information found in this post.
Additional Blog Posts of Interest:
Extend Your Water Quality Sonde Deployment Times with Wiped Sensors [Case Study]
The EXO Wiped Conductivity & Temperature Sensor Helps Eliminate Biofouling
The Evolution of Water Quality Monitoring [Free eBook]
Water Quality Monitoring Challenges [Series]