WTF: What's with the citrusy stink on the Burlington waterfront? 

You’re strolling down the Burlington waterfront recreation path on a dreamy summer afternoon. The sun is glinting off the lake, the Adirondacks seem to shimmer in the distance, and the air smells of ... phewww, cccack, what is that?

The odor that hits you is vaguely sweet but not like the scent of lilacs or the lilies that line the path. No flower would smell so foul.

It’s not that the entire waterfront path reeks. Were that the case, it wouldn’t be nearly as crowded as it is in the three weeks of decent weather we get during a Vermont summer. The malodorousness occurs in just one section of the waterfront — the ribbon of paved path between Perkins Pier and the barge canal.

For as long as I have lived in Burlington and used the rec path, I have wondered WTF was up with that rank odor. It smells like a combination of oranges, drugstore perfume and a Dumpster on a hot day. Which is almost exactly what it is, according to Tim Grover, chief operator of two of the city’s three wastewater-treatment plants.

The tang, Grover tells me, is called VaporScent, a “vapor phase odor neutralizer,” which is designed to do exactly what it sounds like — neutralize odors. It’s like a massive Glade PlugIn for wastewater treatment plants.

The VaporScent product is a citrus-based oil made by a company outside Scranton, Pa. The product’s fact sheet says it’s used to treat “fugitive nuisance odor emissions.” I know a few people who could use some of that.

To mitigate the stink, the city runs hoses that release VaporScent into the air through parts of the facility. The neutralizing mist hangs over the smelly stuff, preventing odors from escaping into the wider world.

To understand exactly why VaporScent is necessary (as if it wasn’t completely obvious at the start), I ask Grover to give me the nickel tour of the facility. He’s used to such requests — he regularly leads gaggles of gagging schoolchildren through the plant. (“Kids, this is where your poop goes. Yes, Johnny, that’s a condom.”)

Before the tour begins, I learn that the main treatment plant on the waterfront processes the city’s raw sewage and storm water, from Burlington High School in the north to the south end of town. In a day, the plant can process up to four million gallons of wastewater.

As we head toward the screening room, Grover offers a disclaimer. “This isn’t the Ben & Jerry’s tour,” he says with a smirk. Inside the screening room — the first step in the wastewater’s journey to become effluent — are giant combs that remove large debris from the water. That debris, Grover says, can be anything from grass clippings and leaves to “unmentionables.”

To contain the stench in the screening room, as well as in some of the other plant buildings, the city uses a coconut-based activated carbon system made by Calgon. It works to soften the odor but does not completely mask it. Not that Grover would notice. He’s worked in wastewater treatment since the early 1980s, so he’s inured to the plant’s unique bouquet.

From the screening room, the water flows into the pump room and then on to the grit-removal process, in which dirt and stones are eliminated. “Basically, we’re mining for grit,” Grover jokes.

This is the point in the tour, he notes, where schoolchildren would be clutching their shirts around their mouths and noses. I am proud I have held out this long, though I’ve been holding my breath for about eight minutes.

The grit-removal room is hot and sticky. When I leave it, I feel like I’m wearing garbage musk. But this is an essential step in the process. It separates what is going to be turned into landfill-destined sludge from what is returning to the ocean.

We move through the primary clarifier room and outside to the aeration tanks — the heart and soul of the process, Grover says. Here, the wastewater is mixed with “bugs” — microscopic organisms such as protozoa — and oxygen to convert organic matter (poo) into a living sludge biomass.

These open tanks are the reason VaporScent is used. As the water churns and swirls and the bugs do their thing, a fine mist is sprayed over the tanks to suppress the fetidness. During the summer, Grover says, the plant crew cranks up the VaporScent so as not to overwhelm the recreating public.

Once the wastewater has been aerated for six to eight hours, it heads through more clarifiers and separators. There are 10 steps in all. At the end, the treated water is sent through a tube a half-mile offshore, where it slowly mixes with lake water. Eventually, lake water becomes drinking water, and thus the process begins anew.