I got a request from S., author of A Misplaced Pen blog, to cover this topic (thanks for the suggestion!). I don’t use a water filter at the moment, partly to reduce waste and partly because (like Mulder) I want to believe. In my case, I want to believe that safe water is provided for us – it’s the very least we should expect in return for paying taxes. However, based on the following points I think I’d like to start filtering my water again:

1. There are many many dangerous chemicals that are not at all regulated by the EPA (in any country). Here’s a good article from the NY Times.
2. As we learned from the (still ongoing) Flint water crisis, contamination of water with heavy metals like lead can and does happen, and is not limited to Flint.
3. In the US, I think we have to be extra vigilant while the Cheeto-In-Chief is in control and the EPA is crumbling. (FYI: here’s a handy list of other nicknames for Bratman).
4. Even in Ireland (where I also drink tap water) there have been concerns over carcinogenic trihalomethane levels.

So, considering all of that, I’d like to decide on a sustainable yet effective way to filter water.

Common types of water filter

I’ll briefly mention reverse osmosis here – it’s an effective way to purify water but is also very wasteful – about 3 liters of water are wasted for every 1 liter purified. You can set up system to recycle the waste water (e.g., into your warm water tank) but most people won’t go to those lengths. Most other water filters are based on activated carbon, often coupled with an ion-exchange resin. Here’s what they do:

Activated carbon is basically charcoal (usually made from wood) that has been treated to increase porosity. It’s generally good at removing chlorine, chloramine, trihalomethanes, and a range of carbon-based compounds from pesticides to volatile organic compounds (VOCs).

Most cartridge filters (Brita, Pur, ZeroWater, etc.) also include a layer of ion-exchange resin to complement the charcoal by efficiently removing metals.  

Cartridge recycling 

(The benefits of sharing information via reviews) 

I wrote a review on Brita filters and mentioned that it’s possible to recycle used cartridges in the Preserve Gimme 5 bins at Whole Foods (information that I discovered while writing the review). At least 100,000 people have seen this review (estimated from the number of “helpful” votes) so it changed not just my own behavior but probably also that of several other people. So, writing reviews is an effective way to share info and influence people 🙂

Unfortunately, as of 2017, Brita switched from working with Preserve to relying on Terracycle for cartridge recycling. The cartridges have to be mailed to Terracycle, so not so many people are likely to partake, and on top of that the Terracycle program is full so that’s no longer an option either. So, Brita have pretty much dropped the ball there, and Pur are in the same boat (excuse the mixed metaphors; apparently arch-rivals Brita and Pur are playing football in an unstable boat). But ZeroWater allows you to send used cartridges back to them and they incentivize you to do this by giving you a $10 coupon for every two filters you recycle. The other benefit here is that since ZeroWater accepts them directly, they are in in a position to recycle the ion-exchange resin as well as the polypropylene casing.

Here’s a handy guide to substances removed from water by the ZeroWater filter in comparison to a Brita filter (data was independently produced by the EPA). The ZeroWater filter removes chlorine, chromium, lead and several other heavy metals, and pesticides with 99% efficiency. However, there are more minimal options available.

Ceramic-based water filters

One of the oldest water filter systems that is still in use is the Berkey. Back in 1827 the Doulton pottery company developed ceramic filters for water filtration (actually it’s water purification since they also filter out bacteria and viruses). It’s apparently how the Queen has traditionally filtered her water, although these days I believe she only drinks gin (just kidding!). Berkey still sells ceramic filters to go into their large stainless steel urns (and they also sell cartridges that are more like the ion-exchange filters above).

On the other end of the scale, there’s the tiny GoPure Pod, based on a ceramic that’s made primarily from diatomaceous earth. The ceramic is encased in a plastic (polypropylene) pod but it’s very small (about the size of a wine cork) so there’s a lot less plastic compared to a Brita filter (and you can recycle the pod at places that accept polypropylene, such as the Preserve bins at Whole Foods). Each pod is effective for 1000 liters of water (about 6 months) – pretty impressive, considering its size. (The much larger cartridge filters like Brita are only good for around 150 liters.) GoPure is also a member of 1% for the Planet. This should give you a rough idea of how they’re made:

Low-waste water filtration

A few years ago I was interested in the filter from Soma (a certified B-Corporation), since they have a glass carafe. The housing for the filters is made from plant-based plastic, but disappointingly they don’t take them back for refilling. More recently I came across Miyabi – this is perhaps the most minimal version of water filter, being simply pieces of charcoal (made from bamboo) that you can drop into any container of water. It’s only activated carbon (no ion-exchange resin) so it won’t be quite as effective at removing metals. However, studies do show that activated carbon alone can remove a good percentage of many metals. Kishu is another brand of charcoal filter, also made in Japan, but from oak tree branches. Kishu have published data showing pretty effective removal of most metals (except for arsenic). Correct preparation is essential for production of charcoal with good filtration properties. Here are some images of charcoal being prepared from bamboo in Japan by Miyabi:An upside of this filtration method is that activated carbon works best when left in contact with the water for a long period. So it’s probably more effective than cartridge filters (where the water passed through the carbon briefly) at removing chlorine, chloramines, VOCs, and pesticides.  When you’re finished with a piece (after a month) simply drop it in your garden or compost.

Water filtration using a tree branch

Researchers at MIT developed an even more basic type of water filter using a branch from a pine tree. It requires some tubing and it has only been tested for removing particles and microbes but it could be applied to remove pathogens from water in developing countries (or in the wilderness). Here’s a video showing it in action:

 

The most sustainable water filter?

Any of these options are way better than buying bottled water. Considering that ion-exchange resins are made from polystyrene, I’d rather avoid all of the cartridge-based filters (like Brita), with the possible exception of ZeroWater since they can recycle the resin for you (Update: ZeroWater told me that, sadly, they can’t regenerate and reuse the resin). The GoPure Pod looks like perhaps the best option if you want very effective treatment and are okay with using a piece of plastic about the size of a wine cork every 6 months. I think I’m going to try the Miyabi bamboo charcoal (Kishu also looks fine but I prefer to use bamboo over oak). Straight-up charcoal is not as effective at removing heavy metals as the other two options but it’s the best minimal / low-waste option that I’ve come across. Any others you’d like to share?

PS: I hope none of this looks like advertising (I certainly make nothing from it!). It’s more about understanding the life-cycle of the items we use: how they’re made and what happens to them after use. Kanpai!