Hidey Ho! A Tour of Yonkers Wastewater Treatment Plant

Photo by GRACELINKS on flickr

My ex-husband once told me that when he was little he flushed his father’s keys down the toilet. He was fascinated by the swirling action of the water and wondered where everything went.

Apparently a lot of people wonder this. On a recent (early) Saturday morning I met a group of 20 or so curious people at the Yonkers Wastewater Treatment Plant (Yonkers WWTP) who all shared my ex’s childhood curiosity.

Sewage treatment is an essential part of a city’s health and ecology infrastructure. If you question this, just think about the last time you were out in public and had trouble finding a public restroom. Now imagine a million people who suddenly lack water and sanitation as a result of an earthquake and tsunami. How do you provide emergency sanitation for such a huge number of people? Rebuilding this aspect of Japan’s infrastructure will be a lot of work and I feel for everyone impacted by the situation.

Back in Yonkers, the tour was organized by local water advocate Matt Malina, founder of NYC H2O, an organization whose mission is “to educate the NYC public about the amazing systems and natural resources that bring NYC its high quality drinking water.” Matt embodies the concept of one individual making a difference. He is a teacher (as were about half the people on the tour - yay teachers!) who loves water and sets up tours and talks so he can share the love.

The Yonkers WWTP serves a population of over 500,000, and covers a large part of Westchester County. The plant treats, on average, 100 million gallons per day (MGD) using primary and secondary processes (go to “Following the Flow” in the first bullet of that link). It has capacity to treat up to 300 MGD, at which point the plant is overwhelmed and the sewage flows into the Hudson River with only the brief addition of chlorine. This can happen if it rains 1 inch in a single day depending on how hard it’s coming down (the rate of precipitation).

I'm fascinated by what it takes to keep cities going. In this country we're fortunate to have adequate infrastructure for our sanitation needs, although our infrastructure is underfunded and declining. Others around the world aren’t so lucky.

By the time most wastewater gets to the treatment plant it looks like chocolate milk. Essentially it’s water with a lot of dissolved fecal matter and toilet paper. The wastewater is run through a bar screen to remove trash. All we saw was toilet paper but often times you can see feminine hygiene products, plastic bags and other trash. The trash comes from people using their toilets and sinks as trash receptacles and from trash that gets dropped or blown into gutters and storm drains. If you flush trash down the toilet, don’t! The amount of trash screened out of the wastewater was actually fairly minimal, due to street sweeping efforts.

The function of the plant is to separate at least 95 percent of the dissolved solids from the liquid. ‘Primary treatment' uses gravity to settle out 10% of the dissolved solids. ‘Secondary treatment' uses bacteria and other microbes that naturally occur in and mimic your gut to eat the remaining 85% of the dissolved solids. The solids, called ‘sludge cake' in their final form, become a nutrient-rich fertilizer and are used to help reclaim mining sites. The liquid is treated further then discharged to the Hudson River and most of the time is cleaner than the river water itself. You could drink it if you really had to, although typically when wastewater is reused it receives additional treatment such as UV or ozone disinfection.

Thomas Niciu, a Process Control Technician at the plant, led us through the facility. We went into the smelliest parts of the operation (the sludge digesters and the sludge centrifuges) and he showed us some sludge cake. This guy really seems to love his job and he grinned widely when we all plugged our noses in the digester room. He said his wife isn’t too happy when she can smell the plant on him. I guess when you work there you get used to it.

The plant has solar panels on its roof that supply around 3% of the plant’s power, a small but significant percentage because the plant uses a lot of electricity. It also has an anaerobic gas digester which captures the methane gas produced by the bacteria that feed on the sewage and produce methane and carbon dioxide as a byproduct. The captured methane gas is used to fuel a generator.

Some of my friends thought I was nuts for getting up early on a weekend morning to go look at a poop plant (one of my coworkers referred to it as "taking one for the team"), but I love this stuff. I'm fascinated by what it takes to keep cities going. In this country we're fortunate to have adequate infrastructure for our sanitation needs, although our infrastructure is underfunded and declining. Others around the world aren’t so lucky.

According to the World Health Organization, "About 2.6 billion people – half the developing world – lack even a simple ‘improved' latrine." For them, there is no fascinated flushing of keys down the toilet – in fact, there is no flushing, period -- because without managed waste treatment systems, there is nowhere for that waste to go except into waterways. This creates major public health problems, aside from the stink. As many as 1.6 million people die every year from diarrheal diseases (including cholera) attributable to lack of access to safe drinking water and basic sanitation; 90% of these are children under five years old.

Take a moment today to consider your sanitary advantages. Be thankful for your wastewater treatment plant and people like Thomas Niciu, who give us a lot to be thankful for.

View a slideshow from the tour.


The United Nations has designated today, March 22, as World Water Day. This year’s theme is "Water for Cities."