Detection and treatment of pollutants in water: innovative solutions

Many substances can pollute the water that flows through our taps. Scientists and SMEs innovate to detect, quantify and eliminate them.

It is a fact that our domestic water contains micropollutants, mineral, biological, organic or radioactive substances from medicines, cosmetics, metals, pesticides, etc., which are present in water in minute concentrations (micrograms or less). These pollutants pass through waste water treatment plants, discharging into watercourses. Their identification, detection and treatment are therefore a major challenge for sustainable water resource management.

 

 

In its action plan, the Water Framework Directive (WFD) includes a reduction or even deletion of a target list of micropollutants in order to ensure the return of water bodies to good ecological status by 2015. In France, these objectives gave rise to a "national micropollutant action plan", adopted in 2010. A monitoring of micropollutants leaving wastewater treatment plants was launched the following year.

 

In June 2015, the French National Institute for Industrial Environment and Risks (INERIS) published the results of a vast measurement campaign carried out between April 2012 and April 2013 on so-called emerging contaminants in French waters. This study, carried out on behalf of the Ministry in charge of Ecology (MEDDE) and under the project management of Onema (National Office for Water and Aquatic Environments), established an inventory of the presence of little researched or poorly known pollutants. Some 80,000 data were obtained to be used in the prioritisation exercises required by the WFD. Conducted in surface and coastal waters, as well as in sediments, the study selected and searched for more than 180 substances on 158 sampling points in agricultural, urban or industrial areas. In particular, it noted the "omnipresence" of 34 specific compounds, such as plasticizers, including Bisphenol A (BPA), body care products or polycyclic aromatic hydrocarbons (PAHs).

 

The generic term "emerging" contaminants includes chemical or biological pollutants with no clearly defined regulatory status. "These are often molecules, not necessarily of new use, but newly identified, for which data on their presence, their fate in the environment and their potential impacts on health or the environment are patchy. Among these emerging pollutants are medicines (antibiotics, pharmaceuticals, hormones) for human or veterinary use, products for daily use (detergents, disinfectants, antioxidants, etc.) and products of industrial origin (flame retardants, nanoparticles, etc.), which may or may not require a medical prescription. The number of molecules concerned is constantly changing both in terms of parent products and their degradation products (natural or from treatment)", is explained within BRGM (Bureau de Recherches Géologiques et Minières), France's national geological service.

 

However, existing analytical techniques have limitations for low concentrations and mixtures in complex matrices. Moreover, they do not take into account possible interactions between substances and are not fully developed for continuous measurements. Scientists and industrialists are therefore working on new processes and solutions for detecting pollutants.

For example, Marine Bittel, a doctoral student in biology, is working on the detection of chemical micropollutants using bacterial biosensors coupled with Raman spectroscopy. Other types of biosensors are being studied, in particular detectors based on fluorescence variation. Ingrid Bazin, a researcher at the Ecole des Mines d'Alès, is working on biosensors designed to detect glycophosate, a herbicide, in water. "Glyphosate is not the most toxic herbicide found in the environment but it is the most present because it is still used by many people. Manufacturers are obliged to monitor it, particularly in the production of drinking water, which must not exceed a concentration of 0.1 µg/l", says the researcher in an article published on the Mines Alès website.

As the article reminds us, the aim is to optimize the monitoring of the water cycle with bio-detection tools that are sufficiently sensitive, easy to use, fast, robust and low cost. Hence the idea "to use peptides of 6 to 15 amino acids as bioreceptors and to develop a rapid test that can be used in the field, in the form of a test strip emitting light in contact with glyphosate and AMPA, its metabolite, in order to eventually design an "all-in-one" biosensor capable of immediately assessing the concentration of herbicides. »

 

Watchfrog, a biotechnology company based at the Genopole® campus and member of Opticsvalley, has developed an innovative solution for measuring water quality using amphibian or fish larvae that fluoresce in the presence of endocrine disruptors in the water. It has developed a new device for measuring water quality, the FrogBox, which enables real-time reading.

 

Effective treatments have yet to be found. In terms of micropollutants, three main treatment processes are currently used: retention by membrane filtration (to capture drug residues), ozonation (chemical treatment by oxidation that deactivates pesticides and pathogenic organisms) and absorption on activated carbon (to fix certain antibiotics and products used in medical imaging).

 

To replace its old wastewater treatment plant that has become obsolete, the municipality of Saint-Pourçain-sur-Sioule (03), for example, has chosen to anticipate future standards on micropollutants and has invested 4 million euros to equip itself with a new wastewater treatment plant capable of eliminating by ozonation polluting molecules resulting from human activity and which were not previously included in water treatment.

 

The Water Framework Directive (WFD) gives concrete expression to EU water policy. It sets ambitious objectives for the preservation and restoration of the status of surface waters (freshwater and coastal waters) and groundwater, defining a framework, a working method and deadlines.

 

Earlier, more specific directives, such as those on drinking water supplies, bathing water, urban waste water and nitrates of agricultural origin remain in force.

 

The general objective of the WFD is to achieve good status of the various aquatic environments throughout Europe by 2015, which means managing water resources sustainably, preserving aquatic ecosystems and groundwater from pollution, supplying the population with good quality drinking water, limiting polluting discharges and involving the users.

 

In concrete terms, the assessment of good status of surface water bodies depends on good chemical status (defined on the basis of the concentration of 41 hazardous or priority chemical substances) and ecological "good status" of waters, with good ecological status being the result of an intersection between the physico-chemical and biological status of waters. Good groundwater status is, for its part, assessed on the basis of good chemical status (compliance with environmental quality standards for man-made pollutants) and quantitative status (balance between abstraction and renewal capacity).

 

The National Water Committee, an advisory body to the Minister for the Environment, met on Tuesday 7 July 2015. It recalled the main lines of a new water policy for 2016:

- Reinforce the prevention of pollution (nitrates, phytosanitary products, micropollutants) rather than having to carry out costly treatments that weigh on the water bill.

- Fighting against waste and promoting economical management of water resources

- Improving the management of aquatic environments, restoring ecological continuity and combating soil artificialisation

- Making the water sector a lever for economic activity and the creation of jobs that cannot be relocated

- Take into account the impact of climate change and the priorities to be set by COP 21

 

In June 2013, Onema, the water agencies and the ministry in charge of ecology, in partnership with the Ministry of Health, launched a call for projects entitled "Innovation and changes in practices: micropollutants in urban water", a call that was part of the national plan to combat micropollutants. The 13 selected projects were made public by Ségolène Royal, Minister of Ecology, Sustainable Development and Energy, on 23 July. They will mobilize local authorities and their local private partners as well as laboratories over 5 years (2014 - 2018). Among the initiatives rewarded, those relating to changes in the practices of users and professionals figure prominently.

 

Yaël LANDAUOptics Valley - November 24, 2015