The first thing that struck me on the tour was the overwhelming lack of odor. I had steeled myself to endure the rotten egg stench, but even when I stood atop the huge covered vats where raw sewage is first treated the smell was less offensive than what one might find in many locker rooms. Dempsey said that controlling offensive odor is one of their biggest challenges, and that from the very beginning of the process the hydrogen sulfide gas is sucked away and the sulfur molecules are biologically consumed by gracious microbes.
During the next phase of treatment the solids/sludge and the water are separated and sent on different paths. Dempsey described how the waste water is sprayed over huge vats of rocks that are home to more microbes that consume the nastier stuff found in sewage. The waste sludge is then pumped into other containers where a different species of friendly bacteria feast on the organic matter. And, as animals like us know all too well, the consumption of food produces flatulence in the form of methane gas. Rather than allow this global warming gas to escape into the atmosphere, however, the waste treatment facility captures the methane gas and uses it for operating boilers and electric generators on the site. Most of the sludge is sent on to be dewatered and turned into fertilizer for farm fields. Prior to dewatering, though, some of the sludge and its bacteria is kept like a sourdough “starter,” to be used for kicking off the decontamination process for the next batch of sludge. Promise fulfilled.
I did ask Dempsey about all that stuff pouring into the rivers from those culverts. He said the discharge was primarily surface water run-off from streets and roofs. My uniformed response was to query — “Wouldn’t it be better to run all that water through the wastewater treatment plant and eliminate any pollutants?” Dempsey patiently explained that we Daytonians were lucky that the creators of Dayton’s wastewater system had the foresight not to construct a “one pipe” system like Cincinnati and Columbus. All their waste and surface run-off water is funneled through their treatment facilities.
Dayton has a “two pipe” system that sends waste water from toilets etc. to the treatment plant and sends street run-off directly to the rivers. He added that no one would install a one-pipe system today. First, the water coming off streets and roofs is basically clean, after the first 15 minutes of rain when surface oil and grit is washed off the streets. To pump all that water, run it through the bacteria baths, aerate it, chlorinate it and then de-chlorinate it would be an unnecessary waste of resources.
Secondly, one-pipe systems may actually increase the amount of pollution that ends up in rivers. A big rain event will overload the system. In order to keep toilets in the city from backing up on the bathroom floor, some of the raw sewage must be diverted directly into the river. For cities like Cincinnati, which get their drinking water straight from the Ohio River, that can be a problem. This is another example of the debt we owe to our Dayton forbearers. When designing our waste water treatment system, they had the wisdom not to install the two pipe system.
How clean is the water that goes back in the Miami River from the treatment facility? Dempsey says that in the summer months when the city chlorinates the water the effluent might be clean enough to drink. At the end of his tour, Dempsey typically hands you a bucket of the clear water processed by the plant, but he is now a bit more cautious about handing it around to groups. At the end of one tour, a high school student grabbed the bucket and took a big gulp. Dempsey reminded the student that he had said the water was clean, not that the bucket was clean. He called the school the next day to check on the student. The student was fine, which sort of proved Dempsey’s point about the water. If you would like a tour of the facility, call Dempsey at 937-333-1837. You will not be disappointed.
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