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Water & Sanitation

Sanitation–breaking down more than you think

Meghan Werft

I’ve had several pets growing up, and my favorite were fish. I loved watching the colors shine in each scale as they swam around the tank. And I remember when my first pet fish died. My brother and I had a little ceremony, saying some nice words for our recently deceased friend, then we flushed him down the toilet.

Having a funeral service for a fish is weird. I guess at the time, flushing a fish down the toilet–to return to it’s “natural habitat” made sense. Today, it makes me wonder, did my pet fish make it to the ocean? And what else actually does end up in the ocean or wherever things go post-flush? Looking at sanitation systems can help to better understand this and why it’s important to have access to sanitation and working sewage systems.

So what happens when you flush?

When I flushed my dead fish, or you flush more pleasant things like poop, a magical multi-step process begins to take place. Water combines with whatever you flush to create wastewater which travels to a sewage treatment plant, ideally via the power of gravity.

STEP 1: The Solids

Wastewater is then treated at the plant, first by filtering out solids. This happens in a step known as primary treatment. Here, solids, water, and a layer of “scum” (nutrients and organic materials) separate. Solids (sludge) are sifted or strained out and placed into a landfill or incinerator. Treated sludge can be used as fertilizer too. And this is more common than you think! Over 200 million farmers use human waste as fertilizer.

Yes, I am devastated that a landfill or incinerator is probably where my fish ended up. But it’s also a reminder to be cautious of what you put down the toilet so toxic waste doesn’t end up in landfills and pose a threat to human health.

STEP 2: The Bacteria

The next step is known as secondary treatment. Here, organic material and nutrients are separated thanks to bacteria. That’s right--bacteria consume all the nutrients your body didn’t want! This happens in big aeration tanks filled with wastewater that has already gone through primary treatment. 90 percent of solids and organic matter are removed in this way.

sanitation-breaking down more than you think-b1.jpgImage: Flickr: Asian Development Bank


Almost done!

STEP 3: The Chemicals

There’s a third step known as tertiary treatment (sanitation doesn’t mess around, even with their titles.) This part varies by treatment plant but usually involves treating water with chemicals to kill remaining bacteria and remove elements like nitrogen and phosphorous. These elements need to be removed because they create environments for harmful algal blooms (overgrowth of algae) to grow. Algal blooms decrease quality of water and can be toxic to humans and other animals.

Lastly, after treatment, water levels are measured and tested to check for balanced pH levels, contaminants, bacteria etc. then water is released into nearby rivers, streams and carried eventually out to the ocean. Water from sinks, bathtubs, and other drains can be run through treatment plants too.


For all those visual learners, here is video from ASAPScience that really breaks it down.

(Side note: These folks are going to be 2015 Global Citizen YouTube livestream hosts! Woo!)

Sanitation and sewage systems are extremely important in keeping A LOT of things out of the ocean and freshwater. But, not everyone has equal access to sewage treatment like this.

Over one billion people still practice open defecation. This means a lot of human waste carrying deadly bacteria, parasites, and harmful microorganisms that can make their way into water sources. In fact, 2.4 billion people this year do not have access to improved sanitation. Some of these billions of people even include Olympic athletes as my colleague Hans points out in this great video.

Progress has been made on improving sanitation. In the last twenty years, 1.9 billion people gained access to improved sanitation. And progress can continue until the gap on sanitation and access to clean water is closed.


Go to TAKE ACTION NOW and tell world leaders that water and sanitation MUST be a priority in the new Global Goals.