Oh, patents! LifeStraw® (Vestergaard®) filtering system

Copyright © Françoise Herrmann

Vestergaard Frandsen, a company originally founded in 1957 for the production of uniforms in Denmark, partnered with The Carter Center for Peace and Health Programs in 1994, under the leadership of the founder’s grandson, Mikkel Vestergaard Frandsen. The partnership was established to produce water filters for the prevention of Guinea Worm Disease (GWD). The needed water filters had to be both tough enough to cover the opening of water jars for repeated use, and fine enough to filter out the larvae of Dracunculus medinensis nematodes, causing GWD.

GWD, also called Dracunculiasis, is a water-borne disease, affecting people who drink larvae-contaminated water.  In 1986, when the Carter Center for Peace and Health Programs began leading the CDC (Centers for Disease Control) Program for the eradication of GWD, approximately 3.5 million people were infected, each year, in 21 Sub-Saharan countries. In 2019, a total of 53 cases were reported in a spectacular countdown to zero (Carter Center GWD Campaign). When eradication occurs, in other words, zero cases with no further control measures required, GWD will be the second disease eradicated in the world after smallpox, and the first parasitic disease eradicated without the use of vaccines.

In partnership with the Carter Center for Peace and Health Programs, Vestergaard Frandsen not only produced filters for water jars, they also pioneered personal,  long-lasting  (up to 4000 liters of filtration), battery-free, water filtering systems, called pipe filters, which eventually became known, and marketed, as the LifeStraw®, for both humanitarian and athleisure purposes. A filtering system with an uncommon trajectory, since it has, in fact, migrated from R&D (research & development) for humanitarian purposes to mass consumer, home, outdoor and sports markets, embodied in a host of different water-filtering products. Products that are currently garnering many accolades, including a Gold Halo Award for social entrepreneurship in 2017, and a Red DotDesign Award in 2019.

The original Lifestraw® design is not only remarkable in the way it is designed to look and function like a straw,  it is first and foremost, a highly reliable filtering system. The micro membrane filters, with a pore size measuring .2 microns, are designed to remove 99.999999% (log 8) of bacteria (including E. coli), 99.999% (log 5) of parasites (Giardia, Cryptosporidium, etc.), and 99.999% (log 5) of microplastics and turbidity (dirt). The  submicron ultrafilter membranes, with a pore size measuring .02 microns (10 x smaller than the micron membrane filters), are also able to filter 99.999% (log 5) of viruses. However, LifeStraw® filtering systems not only use microfilter and ultrafilter membranes for filtering of microbiological substances, the filtration systems are also synergistically combined with low doses of antimicrobial agents and activated carbon filters, designed to filter out any remaining chemicals, odors and heavy metals. This combination of filters results in both safer and better-tasting water.  

The Lifestraw® filtering invention is recited in several patents, one of which is US20100051527A1, titled Microporous filter with an antimicrobial source. In this patent, the LifeStraw® filtering process is patented, in contrast to patenting of a specific filter product. Thus, the filtering invention recited in this patent has a large scope of embodiments, found in the many various LifeStraw® models, whether they are intended for personal, home or community use, respectively contained within straws and water bottles, pitchers, or larger vessels.

The LifeStraw® filtering invention disclosed in US20100051527A1, recites the synergistic combination of two different sorts of filtering processes, mechanical and chemical filtration, both of which present known disadvantages, when they are used separately. Mechanical filtration subsumes the use of a micro- or submicro- porous membrane, acting as a barrier that separates microbial particles (e.g.; viruses and bacteria), by particle size, from the drinking water.  In contrast, chemical filtration releases an antimicrobial agent (e.g.; chlorine or iodine) into the drinking water, to deactivate microbes on contact.  

Disadvantages of chemical filtration are the inverse ratio of dwell-time to concentration of anti-microbial agent. In other words,  the shorter the dwell-time or contact of the water with an anti-microbial agent, the higher the concentration of antimicrobial agent needed, resulting in taste and odor distortion. A distortion that may even have harmful health effects. Thus, chemical filtration also uses iodine scavengers (i.e.; absorbers), such as Granulated Activated Carbon (GAC) filters, which are in turn sometimes enhanced with silver and copper for additional anti-microbial properties, in view of removing traces of the iodine or chlorine anti-microbial agents, causing taste and/or odor distortion.  

Disadvantages of mechanical filtration are the potential “caking” of the micropores, through which water is filtered, resulting in clogged filters. Clogging that might be partially prevented via flushing of the surface of the filtering membrane, but that does not prevent the formation of a sticky biofilm elsewhere, upstream of the membrane, within the membrane fibers, or on the inner walls of the filter housing. A biofilm generated by separated, but non-deactived microbial particles, and other remaining particles, which together might create a potentially dangerous situation, if the filtering membrane were to rupture for one reason or another, releasing microbial particles in the drinking water.

In response to the problems associated with both sorts of filtering systems (distortion of taste and odor due to the use of high doses of chemical filtration agents, on the one hand, and caking of mechanical means plus the formation of a biofilm, on the other), the LifeStraw® filtering system combines both mechanical and chemical filtering processes. In combining both systems, the LifeStraw® filtering system invention is able to take advantage of their synergy. In other words, LifeStraw® filtering systems are able to use lower doses (lower elution rates) of antimicrobial substances (causing less or non-detectable distortion), because the purification of drinking water relies on mechanical filtration, rather than on chemical filtration alone to purify the water flowing through the filter. Indeed, LifeStraw®  chemical filtration means are used just for preventing the formation of a biofilm. Conversely, incomplete mechanical filtration is supplemented by the use of an anti-microbial agent, able to deactivate the separated microbial particles that breed biofilm, and that cannot be completely flushed out via mechanical means, thereby preventing release of microbes in case of membrane rupture.

The advantages of this synergistic system are, at least, threefold. The filters are longer lasting and less costly to produce. They use less depletable chemicals via chemical-releasing resins or eluting coatings, which is important considering availability for deprived locations, or isolated areas. They are also safer, in case of membrane rupture, since an anti-microbial agent is used to deactivate separated microbes that would otherwise risk contaminating drinking water, while breeding biofilm within and outside of the mechanical filtration means (i.e; the membrane). The use of less anti-microbial agents also means less potentially adverse effects on health.

The abstract of this invention is included below, together with the patent Figure 1 drawing, and an image of a personal LifeStraw® user drinking river water. The Figure 1 drawing, extracted from the patent, illustrates the principle of the LifeStraw® filtering system 1, comprising a fluid inlet 2 and a fluid outlet 3. Downstream from the fluid inlet 2, there is a chamber 4, containing an antimicrobial agent 5, preferably a halogen such as iodine or chlorine, in the form of a halogenic resin, through which the inlet fluid passes, in the direction of the arrow 7. After contacting the halogenic resin, the halogenated fluid passes through a micro- or submicro- porous membrane 8, designed to separate microbial substances 11, such as bacteria, parasites and even viruses, from the inlet fluid. The separated substances 11 accumulate on the surface 12 of the membrane, where they will be eventually deactivated by the anti-microbial agent, and/or partially flushed out (e.g. when the user blows out any water remaining in the straw). Before the halogenated fluid exits through the fluid outlet 3, it might additionally pass through a third chamber 10, containing a halogen absorber 9, designed to remove any distortions of taste and odor caused by the halogenic substance (e.g.; iodine or chlorine).

A fluid filtration device having a fluid inlet and a fluid outlet and a confined fluid path between the inlet and the outlet through a microporous filter with a pore size adapted for filtering microbes, for example bacteria and virus. The device comprises an antimicrobial source, preferably halogen source, adding antimicrobial substance to the fluid in the confined fluid path between the fluid inlet end the microporous filter in order to prevent biofilm formation in the microporous filter. [Abstract US20100051527A1]

References

LifeStraw®

https://www.lifestraw.com/

The Carter Center

https://www.cartercenter.org/

The Carter Center – Guinea Worm Disease Campaign

https://www.cartercenter.org/news/features/h/guinea_worm/guinea-worm-disease-campaign-led-by-carter-center.html

The Carter Center – Guinea Worm Disease Fact Sheet

https://www.cartercenter.org/resources/pdfs/factsheets/guinea-worm-facts.pdf

Gorvett, Z (March 5, 2018) The Miraculous Straw that lets you drink dirty water - BBC

https://www.bbc.com/future/article/20180305-the-miraculous-straw-that-lets-you-drink-dirty-water/?referer=http%3A%2F%2Fblogs.umb.edu%2Fbuildingtheworld%2F2018%2F02%2F20%2Fstraws-that-filter-bacteria-and-parasites%2F

Potter, E. (Jan 17, 2019) LifeStraw: Water for a Changing World – Forbes.com

https://www.forbes.com/sites/everettpotter/2019/01/17/lifestraw-water-for-a-changing-world/#6693d67543f9

Red Dot Award (2019)

https://www.red-dot.org/search?q=%22lifestraw%22

Gold Halo Award (2017

https://engageforgood.com/halo-awards-winners-2017/