Mollusks can be used to monitor the quality of water around industrial sites in real time — an inexpensive solution with unmatched reliability. Total Exploration & Production's R&D teams joined forces with the French National Center for Scientific Research (CNRS) to observe and better understand these bivalves. This is the story of how something very small contributes to something very big.
When animals talk
Bivalve mollusks live in freshwater or saltwater. Their flat body is made of a two-part hinged shell. The most well-known types are oysters, mussels and scallops, which feed by filtering the water they live in to capture nutrients. They are extremely sensitive to the quality of their environment. When they detect any chemical, physical or acoustic stress or change in water turbidity1, their behavior changes.
Valvometry, or How Small Mollusks Make a Big Difference
These features drew the attention of Total Exploration & Production's R&D teams, who are working on finding an optimally reliable method to monitor, in real time and in situ, the environment around the company's facilities. As a responsible operator, Total is committed to efficient water use, which means reducing withdrawals and consumption and maintaining its quality. "As regulatory and community pressures concerning our activities' environmental footprint grow, we must show that they do not have a harmful impact. The animal and other species that live in the immediate environment, especially aquatic, are the most reliable indicators of its quality," says Laurent Cazes, who manages environmental and CSR R&D projects at Total. Right now, there is no device that can provide a continuous water analysis as quickly. Nature knows best! At the beginning of the decade, the R&D team met with researchers at the CNRS marine biology laboratory at the Arcachon marine station in France and the University of Bordeaux, who have been studying the respiratory physiology of these mollusks for the past twenty years. "Our aim is to interpret and understand what these animals can tell us."
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Sixteen small mollusks, millions of data
The principle of high-frequency, non-invasive (HFNI) valvometry involves observing the mollusks' natural gaping cycle — or valve opening and closing — and noting when this cycle is disturbed, for example if it stops or speeds up. To do this, electromagnets are attached to both parts of the shell (valves) so that the quantity and quality of gaping activity can be recorded. The data collected is then analyzed. "Quite simple in theory, but in practice we had to solve a few technological challenges," notes Laurent Cazes. "For example, we had to make sure the electromagnet didn't disturb them. Studies showed that it didn't; the mollusks continued to reproduce, for instance. We miniaturized the electromagnets and made them lighter so that we could avoid bothering them." Just sixteen mollusks in a net less than a meter long can generate and send more than 2.5 million data daily over long periods — at least two or three years — and continuously. Because bivalves are extremely sensitive to hydrocarbons, even the slightest disturbance to their environment causes a reaction. "Ultimately, the aim is to limit human intervention and automate everything," adds Laurent Cazes.
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A minor revolution in monitoring
Biomonitoring also breaks with the traditional ways of approaching measurement. In the past, to evaluate adverse changes to the environment, you had to look for a specific substance, measure its concentration and compare it to the applicable standards. Using bivalves means the overall quality of an environment can be assessed by determining whether its ecosystem is healthy. "Total aims to be a responsible operator and back up its claims. With this tool, we can do that in real time, and in a verifiable manner," says Laurent Cazes.
Bivalves can be used in extremely harsh environments. In Russia, valvometers were submerged in the Barents Sea, an extremely cold environment where companies avoids sending personnel to conduct maintenance. In the United Arab Emirates, a completely different, very hot climate, pearl oysters — an emblematic local species — were used for over a year to monitor water quality around one of Total ABK's offshore platforms. There's no need to import potentially invasive species; local species already adapted to the environment can be used. "We've shown that valvometry works in warm waters, cold waters, freshwater and saltwater," says Laurent Cazes. "We now need to see if it is effective in estuaries, where saltwater and freshwater mix."
All of this comes in significantly cheaper than the techniques currently used. A year of continuous valvometric measurement is the equivalent of two water sample analyses a month using standard physical and chemical measurements, requires little or no human maintenance or intervention and consumes minimal energy. Other industrial sites have plans to deploy the system.
"The purpose of research is to innovate. Nature is our greatest inventor. So let's try to imitate and improve on it to obtain fast, accurate, usable results," says Laurent Cazes.
1 Suspended matter that makes the water cloudy.