What if the solution went through filtration? Recent revelations about significant pesticide levels in the water of certain municipalities, or the presence of nanoplastics in water bottles can push some people to equip themselves with a home filtration system. There are some that are attached to taps, others that are added in the form of a cartridge to the home water network. We take stock.
What is filtered water?
The term filtration is often used to designate processes that have nothing to do with filtration, deplores Christelle Wisniewski, university professor and specialist in wastewater treatment.
Filtered water passes through a membrane containing pores « which retain compounds, such as bacteria, viruses or certain pesticides,” explains the expert. So no more carbon, which absorbs certain micropollutants, but does not filter them.
It exists different types of filtration which “depend on the fineness of the pores of the membrane”, adds Yves Lévi, professor emeritus in Public Health-Environmental Health.
What is microfiltration?
It's the least fine filtration system. Membrane pores are between 0.1 and 1 micron (μm).
What is she stopping?
THE suspended matterthat is to say the sablethe mudl’claybut also the bacteria. However, it allows viruses, pesticides and chemical residues (pharmaceuticals and cosmetics) to pass through.
Is it interesting at home?
“In mainland France, have a device to microfilter tap water has absolutely no health benefit », Say the two experts. “Everything that is retained by microfiltration has already been arrested at a water purification station », describes Christelle Wisniewski. Microfiltration therefore makes no difference compared to tap water for health.
What is ultrafiltration?
The water passes through a membrane whose pores measure between 0.01 and 0.1 μm.
What is she stopping?
She permits to remove everything that is already retained by microfiltration (sand, mud, bacteria) and it also removes micro-organisms. In ultrafiltered water, chemical pollutants and pesticides therefore remain.
Is it interesting at home?
Same observation as for microfiltration. A home device brings nothing more to tap water, which is already ultrafiltered in a drinking water station.
Viruses like bacteria are eliminated before arriving in our homes. Professor Christelle Wisniewski
What is reverse osmosis?
This process uses a coupled membrane to a pressure difference between two liquids.
What is she stopping?
“All salts. It is used for desalinate sea water », explains Christelle Wisniewski.
Is it interesting at home?
Cela n'a no interest according to experts and perhaps even dangerous. The water obtained must be remineralized to be consumed.
Ultrapure water is not good for your health because it no longer contains mineral salts. If you drink it all year round it is dangerous. Yves Lévi, professor emeritus in Public Health-Environmental Health.
What is nanofiltration?
These devices have pores that are approximately one nanometer.
What is she stopping?
“Everything that is already retained by ultrafiltration. Furthermore, it retains certain ionic speciesas the limestone and part of pesticides », explains Christelle Wisniewski. On the other hand, it does not stop all micropollutants or all pesticides.
Is it interesting at home?
If, in certain regions where the water is hard, attaching a nanofiltration system to the water inlet of the washing machine can help it last longer, However, experts do not recommend such an installation, which has no positive impact on health. They also warn of the heaviness and cost (from €600 to €1,500) of these transformations.
The finer the filtration, the more pressure it requires to pass the water, which can cause damage to the pipes. In addition, the conformity of these installations is little checked, because they are not controlled by the health authorities, but by the Fraud Repression, which does not rule on effectiveness. Professor Yves Lévi
What do you give pesticides?
Christelle Wisniewski argues that nanofiltration only removes part of the pesticides and reminds that the drinking stations adapt depending on the origin of the water: “in Montpellier, the water has a high limestone content but it is of good quality. It is therefore very little treated. In Paris, there are more treatments, so it can be nanofiltered.”
Expert opinion: what about nanoplastics?
“Nanoplastics are filtered using ultrafiltration, therefore with nanofiltration and reverse osmosis too,” explains Christelle Wisniewski. However, nanoplastics in raw water intended for drinking water are generally in very low concentration and, to this day, do not appear to be very problematic. Recent studies have also shown that a large part would be retained by the sand filters found in almost all water treatment plants.
