“Water go down the hole.”

-Plucky Duck, Tiny Toon Adventures

A friend’s four-year old boy was fascinated with the toilet — totally amazed that when you flushed it; water went down the hole. It was a real mystery.

In a related way, he was terrified of the toilet plunger. It brought things up from the hole — scary, icky things. When we helped them move away, the kid was excitedly dancing on the lawn as we pulled boxes out of the house and loaded the rental truck. He was nearly speechless with anxiety until his dad made a show of bringing the plunger out of the house, and giving it a special place in the truck. He immediately relaxed, but did stay away from the truck until the door was finally closed.

I understand that a fixation with the toilet is a natural offshoot of potty training. And frankly, what’s liable to come up out of the toilet is pretty scary. As a sanitary engineer and owner of a house that came with the original 1913-era plumbing, I have been up close and personal with what goes into toilets and what can come up.

Most people see their toilet as a disposal mechanism, but it’s really just the first step in a long journey from your house to its ultimate end. We think, “out of sight, out of mind,” but it actually flushes to somewhere.

I once volunteered to teach my son’s ninth grade class about water and sewer systems. Most of these kids (or their parents) had little clue as to where their water came from and where their sewage went. Water came out of the tap and went “down the hole.”

I started by explaining how water in the western U.S. is collected from the streams and rivers or pumped from underground. Then water is usually channeled into a water treatment facility where is treated to remove sediment, certain minerals, some chemicals and bacteria. Most of the kids knew that raw water, water straight from the stream, wasn’t suitable to drink, but few had any idea what kinds of things could be in their water if not treated. I then described the network of tanks and pumps and pipes that send the clean water to their homes — and ultimately out their taps.

Then we followed the water “down the hole” through the sewers and mains until it reached the sewage treatment plant. There was quite a bit of chatter about that side of the system, particularly when I described that the treated water ended up back in the streams and rivers. The term “downstream beer” was discussed as was the fact that the Mississippi River water has been through as many as 18 million people before the people of New Orleans get to drink it. Those of us in the Rocky Mountains are lucky that we get the first shot at the water we drink.

We also discussed the quality of our water. Recent studies have expanded the list of contaminants in water to include chemicals, minerals and various microorganisms. Some of these are natural, such as the metals like uranium in Colorado surface waters or the radium in groundwater. Other contaminants like petroleum and volatile organics are from leaks, spills and other discharges. Some are point source (end of pipe) discharges and others come from storm or agricultural runoff, including pesticides, herbicides and fertilizers.

These contaminants can have dire effects on fish and other aquatic organisms, even if treated before use in municipal water supply. However, one troubling set of contaminants that cannot usually be removed in sewage treatment plants are generated by humans. As a pharmacist friend of mine once explained, “If you take too much of that medicine, it just passes through your system,” and goes down the hole.

Recent studies have reinforced the lists of medicines and drugs that we discharge into our streams and rivers every day. Methamphetamine, antibiotics and hormones are just a few of the contaminants that pass through our bodies into sewage, and go straight through our treatment plants into the environment. Three-headed frogs, diseased trout, and other mutations send a warning to us that it doesn’t merely go “down the hole.” All of that goes into streams and the drinking water of the next place downstream to be ingested by the next community.

We’re also learning about the devastating effects of plastics that become degraded in the environment into tiny particles, ultimately collecting in the oceans and taken up by all manner of marine animals. The particles are ingested by various creatures, not effectively eliminated, and become lodged inside them. This leads to disease and, in some cases, starvation.

I took the class to the local waterworks, starting with the stream diversion, ditch and pipeline. Then we visited the water treatment plant and storage reservoir and tanks. Finally, we visited the metro-area waste water plant that collects the sewage from the entire city. We saw the bar screens, grit chambers, aeration basins, settling tanks, flocculation system, chlorination tanks, sludge digesters and drying beds (those were a hit).

However, the highlight of the tour was standing at the end of the pipe where millions of gallons of raw sewage cascaded out of the huge collector main into the plant. The sheer mass of sewage is overwhelming and actually a little frightening.

The kids stood in silent awe for a few minutes, solemnly grasping the immensity of the issues. Then one of the girls pointed down into the rushing stream and called across to one of the boys, “Hey Kal, there’s one of yours!”

That broke the spell and they became teenagers again.