Membrane technology for new wastewater treatment methods
One of Arkema's R & D priorities is to develop efficient and cost-effective water filtration processes to meet the growing demand for drinking water and to help respond to UN's sustainable developement goals (SGD 6) "Ensure availability and sustainable management of water and sanitation for all".
Access to drinking water: a global issue
Given the increase in the world's population (by 2050 it is expected to exceed 9 billion people), the increase of the regions with water stress and the many competing needs for water (domestic uses, agriculture, industry), increasing volumes of water will need to be treated.
And bearing in mind the present and future difficulties with access to drinking water (60% of people may not have access to it), effective management of this resource is as crucial as that of oil. The challenge is to develop efficient and optimized processes to remove pollutants, bacteria and viruses.
In addition to its R&D commitment, Arkema was the main sponsor of the Sail for Water association as part of the latter’s mission to "Take action to support universal access to clean drinking water". In the face of the global issue of water quality, the Group decided to support this fledgling NGO and lent it its support by supplying water filter cartridges.
Following this mission, in 2018 Arkema is supporting a new NGO, No-Thirst Initiative, for a mission in Nepal (from october to december 2018) and will distribute 300 water filtration kits to people living in remote areas of the country, North East of Katmandou.
Membrane filtration: from micro to ultrafiltration
Over the last decade, significant advances have been made for the production of drinking water using the microfiltration membrane technology.
The principle: water is fed under pressure through thousands of tubular modules containing hollow and porous long fibers, usually made of PVDF, a very tough polymer. With pores of around 0.1 to 1 micron diameter, these fibers retain suspended particles and impurities including bacteria.
However, this microfiltration process has drawbacks:
- High energy consumption (the water is conveyed under pressure).
- High cost of treatment and maintenance.
- It does not filter out ultrafine impurities, in particular viruses. Additional chemical treatment is required.
Kynar® PVDF ultrafiltration membranes: how does it work?
Arkema has wide-ranging expertise in the synthesis of block copolymers, or controlled radical polymerization, known as the Blocbuilder® technology.
The new Kynar® grade used for ultrafiltration membranes benefits from this unique technology: it allows a perfectly controlled architecture of the PVDF’s various molecules on a nanometric scale, combining within the same chain:
- A block of "miscible" hydrophobic molecules (light gray area in diagram below)
- A block of molecules that provides the hydrophilic function (dark gray area).
Thus, in each pore, the hydrophilic part of Kynar® "attracts" the water, which has the effect of increasing the flow rate of the membrane. As a result, the filtered water flow improves by 20% for the same energy consumption.
These Kynar® PVDF ultrafiltration membranes also benefit from:
- Greater mechanical strength (the lifetime of the membranes thus increasing from 5 to 10 years).
- Smaller pore size allowing the filtration of ultra-fine particles, in particular bacteria and viruses.