How can micropollutants be eliminated from water?

Water is one of life’s essentials. But when human activity is uncontrolled, this vital resource can become polluted. Which is why the availability and quality of water are major issues for our societies. Fortunately, we now have effective solutions for removing micropollutants from treated wastewater before it is discharged into the natural environment. Global overview.

From pesticides to pharmaceuticals, industrial waste and DIY waste, the lives we lead are not without their consequences for water quality. We are the starting point for the entry into the natural world of organic substances (solvents, pharmaceuticals, endocrine disruptors, pesticides, hydrocarbons and more) and pollutants of mineral origin (heavy metals, metalloids and even radioactive elements), which damage the environment and harm our health. The relevant European regulation currently lists more than 100,000 of them.

These micropollutants are now being detected in wastewater, albeit at very low concentrations in the microgram - or even nanogram - per liter range. In comparison, the concentrations of mineral salts found in drinking water are between a thousand and a million times higher. Nevertheless, researchers remain concerned about their medium- and long-term implications for our health.

Water pollution and regulation

France has introduced discharge standards for micropollutants like heavy metals, for example. They are eliminated in wastewater treatment plants during the traditional stage of biological treatment for water pollution, and are present in the residual sludge remaining at the end of this process.

But the same regulations do not set standards for organic micropollutants in general, and drug residues in particular, where endocrine disruptors are a particular concern. For these pollutants, the authorities are relying on a policy of reduction at source. The intention of the policy may be commendable, but its effectiveness is debatable. Hospitals are certainly able to introduce clean treatment processes, but discharges as a result of pharmaceutical product use by the general public are much more problematic to control.

Solutions for eliminating micropollutants from wastewater

Although the microorganisms used in wastewater treatment plants are extremely effective in breaking down certain types of pollution, they are much less effective with organic micropollutants. But for all those who want to build a more sustainable future today, there are solutions that can be implemented right now to protect and conserve water resources. They include the so-called tertiary treatments:

• Chemical oxidation, which generally uses ozone, sometimes with the addition of ultraviolet radiation. The oxidizing capacity of ozone comes from the fact that it is highly unstable. By adding a biological filtration stage, oxidation can remove many of the micropollutants commonly found in wastewater.
• Adsorption, a technique that fixes micropollutants on the surface of activated carbon. Traditionally this has involved the use of granular activated carbon filters. A more innovative and effective solution is the use of fluidized beds of activated carbon micro-granules. This is the principle behind the Saur Group CarboPlus solution.
• Membrane filtration [nanofiltration or reverse osmosis] provides a physical barrier that micropollutants cannot pass through, and is particularly effective in the treatment of drug residues. Unfortunately, it comes with a high price tag and leaves behind it the problem of dealing with the concentrated mass of micropollutants retained by the membranes.

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