Environment, Water

Water’s Journey Beyond the Tap

When I was young, I hated the taste of water. My parents had to trick me into drinking water by dressing it up with fruits or fun ice cube shapes, but usually to no avail. I’d take a sip, squish my nose in disgust, and push that glass of water away. As I grew older, I learned the importance of staying hydrated and forced myself to drink water, but I generally never liked it. I always preferred other beverages over water.

Oddly enough, I ended up working as an Aquatic Toxicologist once I finished school. It was all by accident that I ended up with a career in the field of water resources – but the things I learned in my early years in the field completely changed my perspective and made me realize that my sensitivity to water all these years was for good reason! To fully understand what I mean, you need to better understand the journey a drop of water makes to reach our homes. Once you do, I bet it will make you think of water differently as well. Let’s begin at the toilet.

Ah yes, the toilet – one of the first places you spend time when you wake up in the morning. That drop of water in the toilet has been chilling there all night waiting for its next move. Once you’ve done your business and flush that drop from the porcelain throne, it begins its journey through miles and miles of underground pipes along with all the other lovely components of sewage. Sometimes those pipes combine with stormwater pipes where storm drains meet home drains. After what seems like an eternity, that drop finally makes it’s way through a large filter, or more like a wire screen, that intercepts debris like branches, toilet paper, and other…large chunky things found in sewage.

The mostly fluid sludge that makes its way past that initial filter is sent to a huge round water tank called a settling tank. This is the first of three wastewater treatment processes that takes place to clean sewage. The settling tank, a.k.a. primary treatment tank, allows the thick fluid to sit long enough for gravity and natural water properties to separate out its contents into layers within the tank. The layer that settles to the bottom of the tank consists of heavier debris that was not filtered through the wire grid. Things like dirt, finger nails (ew), egg shells…stuff like that. The middle layer is the fluid, and the top layer consists of any floatable substances that naturally separate from water, like oils and grease. A skimmer positioned at the surface of this open tank slowly skims off that top layer of oil and grease.

This image has an empty alt attribute; its file name is watertreatment.jpg
Wastewater settling tanks with surface skimmers.
Photo credit: EPA.gov

The second portion of wastewater treatment occurs when the (mostly) clear fluid layer is siphoned out and transferred to a secondary treatment tank. This is where the magic happens, and the part of wastewater treatment that blew my mind the first time I learned about it. The bacteria and microorganisms present in sewage water actually CLEAN the water! Yup, you read that right. The bacteria in our sewage is what’s cleaning the sewage for us.

There’s a few different ways this can happen, but the most common method is to have large tanks where the water sits long enough for the bacteria in water to basically eat up all the harmful particles and poop out less harmful byproducts. There’s usually some type of aeration going on in these tanks to introduce oxygen into the water and allow the bacteria to thrive. Secondary treatment tanks, a.k.a aeration tanks, are pretty much an all-inclusive resort for bacteria. An endless food and drink buffet in a cozy, warm, and moist environment – every microorganism’s dream.

Secondary treatment aeration tank.
Photo Credit: Colorado.gov

Secondary treatment continues past the aeration tank into a secondary treatment settling tank. This tank, similar to the primary treatment settling tank, allows the water to sit long enough for heavier particles to settle out while the clean treated water remains on top. Sometimes a coagulant is added to help the particles separate and settle to the bottom easier. At this point, the water is basically clean enough to drink!! Crazy huh? Sometimes, an additional tertiary treatment disinfection is used to give the water one last zap. This ensures all harmful substances and bacteria are removed before the water is dumped back into a river/lake/reservoir…whatever. This could include the addition of chlorine, ozone or UV treatment, among others. So now you know how sewage is cleaned, but what about drinking water? Well let’s keep following that drop of water through the outfall pipe exiting the wastewater treatment plant into a nearby river.

Wastewater outfall pipe.

About 20 miles downstream is another pipe that’s sucking water from that same river and that water drop gets swooped right up. This is a drinking water intake pipe. They’re usually positioned underwater so you don’t normally see intake pipes. The water is pumped through underground pipelines to the water treatment plan where that drop will make it through five treatment steps before it’s safe to distribute and use as drinking water. The first step is coagulation where certain chemicals are added to the water to make the suspended particles in water begin sticking together. Step two is flocculation which simply swirls around the water and slowly mixes the coagulated particles until they stick together even more and create even bigger, heavier particles. The third step is sedimentation where the flocculated large particles settle out to the bottom. Finally, the clear water from the sedimentation tank is disinfected with chlorine or a similar form of treatment before it is filtered through coal and sand. That filtered water is disinfected one last time before it’s pumped out to our homes.

Drinking water treatment process.

That same drop of water made it all the way from our toilet, through pipelines and treatment, down the river, through treatment again, and back into our homes. Water is used and re-used, and used again a million times before it makes it to the ocean. Uses for water are not only household uses, they also include industrial uses, agricultural uses, and tons of other uses around the country, and the world.

Generally speaking, the technology used to treat water as discussed above is the same technology used back in the 1800s when water treatment was first discovered! There have been some innovative new ways to treat more complex water sources that have known contaminants, but for the most part, the majority of systems are designed to primarily remove organic and pathogenic compounds from water (ex: dirt, food waste, bacteria), not complex chemical or hormonal compounds. This means that most waters flowing down rivers, into lakes, and out our taps, still have trace levels of certain chemicals in them. Things like drugs, household cleaning agents, pesticides, and other persistent chemical compounds are usually NOT treated and continue to accumulate and flow downstream. In fact, some chemicals and compounds, both natural and manmade, never break down and are impossible to treat, meaning they will remain on this planet long after any of us. More on persistent chemicals in the environment and their effect on us coming soon.

To put this into perspective, check out this topographic map of the US. Considering water flows from high to low elevations, water at higher altitudes are used and re-used less often. Most of the drinking water in those areas come from new precipitation or groundwater. But as you move into the flatter, coastal areas of the country, that water has been used and treated and used and treated WAY more often! Based on this map, the Gulf of Mexico is basically the toilet of the US. Sorry folks – I lived there for a while too, and yes, you can taste the difference!

These arrows show very rough estimates of the direction of river water flows based on US topography.

Other factors impact taste and water odor as well, including the water source (groundwater, river, lake, saltwater), but the water uses upstream are a huge contributing factor in not only the taste and odor of your water, but also it’s safety. So that’s the story of the water drop and it’s journey beyond the tap and through the water treatment cycle. What are your thoughts? Did you know this about your water already? Now that you do, does it change the way you think about your drinking water?

I hope you enjoyed this lesson on water and I didn’t freak you out too much! Just know that even though the water quality of drinking water may not be perfect, it is still highly regulated and safe for us to drink. Nevertheless, it is important to be aware of potential problems with your water and familiarizing yourself with your water source and the treatment facility in your area.

I’m a total nerd about this sort of stuff, so let me know if you have any random water questions I could answer! Until next time.

XoXo

Mina

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