WASH 101: Physical Interventions – Boiling and Distillation

August 8, 2019

Posted by Chip, Managing Director

We’re finally to our final category of solutions! Physical Intervention – specifically Boiling & Distillation. The physical intervention category is designed to cover the most basic, simplest forms of interventions. We saved it for the end because that allows us to mention how these basic steps are utilized in other, more complex interventions that we’ve already discussed.

Which leads us to our standard reminder: You’re joining 20 Liters in an ongoing conversation. We’ve already covered each part of the WASH acronym [WaterSanitationHygiene], made sure we have a shared language, and looked into disparities for vulnerable populations.

A reminder of our solution categories:
Physical Intervention: including filtration, adsorption, sedimentation, boiling & distillation
Biological Intervention: including antimicrobial metalsactivated carbon & bio-sand filters
Chemical Alteration: including chlorination & flocculation
Electromagnetic Radiation: including UV Light treatment
Sourcing: including rainfall, groundwater, underground aquifers, springs, and human-intervened (bottled, wells or municipal water).

Boiling

Many of us are familiar with “boil water notices”. You know those notices from local officials when there’s a known risk of biological contamination to our drinking water systems. For example, when there is a cracked water main or a sudden loss of pressure.

But, let’s dig into how boiling works to make dirty water clean.

To quote myself from our post on EM Radiation: “Like all living things, bacteria, viruses and protozoa require certain conditions to survive. In this case, we need an adequate temperature range and a limit on our exposure to radiation. But, if our goal is to kill off germs that make us sick, we just need to mess with those variables.”

In that discussion, we talked about dialing up the radiation to dangerous levels and zapping our water. But, a simpler, and much older approach, is to simply crank up the heat.

But, why does an excess amount of heat kill living things?

If you dare to ask, get ready to hear terrifyingly cool phrases, like “thermal death point”. I do encourage you to go down that rabbit hole, and have given you a few starting links down below. It’s fascinating.

But, in case you don’t have a few hours to burn, I’ll give you the short version. Our cells rely upon intricately shaped proteins to perform their functions. The bonds that hold each protein in its specific shape only function within a certain temperature range. When these bonds fail, the protein unravels (or denatures) into a long, useless strand. The cell loses whatever function that protein performed, and if it was a critical function, the whole house of cards begins to collapse.

Okay, so that is WHY boiling water works. Let’s zoom back out to see HOW to effectively boil water to make dirty water clean. The standard recommendation is to bring water to a full, rolling boil for at least one minute. Microbes actually start dying off at 60 °C (140 °F), so a full, rolling boil temperature of 100 °C (212 °F) for a full minute is a good amount of over-kill (pun intended).

The advantages of boiling water to make it safe to drink are pretty simple.

Boiling is a simple, single-step process… it is easy to do correctly, repeatedly, and doesn’t require any fancy equipment or materials. If you have a pot and a heat source, you can boil water. In addition, boiling is effective despite other particulates or contaminants in the water.

There are some downsides to boiling water.

Most importantly, while boiling will remove biological contaminants, it won’t remove chemicals. It also won’t remove particulates or improve the taste of the water. So, if your water is full of mud, boiling the water will not remove the mud. Next, some heat sources can be costly or produce hazardous by-products like carbon monoxide. In addition, if you’re relying on a wood-burning stove, finding fuel for your stove can contribute to deforestation and other environmental impacts.

Finally, a watched pot doesn’t boil, but an active heat source also needs some tending. And, the amount of time spent waiting for water to heat, boil, and cool before being used is time that could be spent having a refreshing drink or doing other more productive activities.

One additional downside that we haven’t mentioned yet is that we lose some volume of water as vapor when we boil it. But, what if we caught that vapor, cooled it back down, and condensed it back into water?

Great idea, it’s called distillation.

We have been using distillation since at least 3,000 BCE and still rely heavily on this method today to produce exceptionally pure water. Take a minute to think about the water cycle and you have to believe some smart people 5,000 years ago took inspiration from nature itself as they observed evaporation and condensation happening all around them and thought “yeah, we could use that.”

The process of distillation relies on the impurities in your water having a higher boiling point than the water itself. Thus, you can thermally “lift” all the pure, clean water out and re-capture it in a new container, leaving everything you don’t want in the original container.

There are several advantages to distillation:

First, distillation is highly effective at removing all contaminants, including biological, chemical, and particulate contaminants. Second, distillation is a two-step process that involves simple equipment. Finally, it is an easy process that can be done correctly and repeatedly without needing testing equipment to be sure you did it right.

On the downside,

First, because boiling is step one of the distillation process, you’re going to see the same downsides from boiling for distillation, including the cost of fuel and impacts from your fuel source on your environment. Also, there is a pretty significant possibility of re-contaminating your water. If you use a dirty container to catch your water vapor, you end up with dirty water.

Finally, there is a high volume of loss between the amount you boil and the amount of distilled water you collect, unless you have really fancy equipment. You also lose the time required to heat, boil, evaporate, collect, condense, and cool your water before you can use it.

When I look back through previous blog posts at all the complex technologies we’ve considered, from special light bulbs to activated carbon and fancy chemical compounds, the simplicity and reliability of something like a pot of boiling water is a humbling reminder of how long we as a species have been combating dirty water and how sometimes the oldest strategies are still the best. Keep in mind, when our large-scale municipal water systems go on the fritz, this is still what we rely on every time.

Boiling & Distillation reading list (for the curious among you):

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