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Construction Corner: It’s time to look at a new breed of sewage plants

0 68 Technology

by Korky Koroluk

So now there are two good-sized chunks of the United States faced with hurricane-induced flooding.
Korky Koroluk
Korky Koroluk

First, it was Houston and much of Southeast Texas that was swamped by Hurricane Harvey. Just two weeks later it was Florida's turn, where Hurricane Irma inundated most of the state and parts of southern Georgia.

Both areas found themselves short of drinking water as purification plants were swamped and in both areas sewage treatment plants suffered a similar fate.

There's a historic irony here. A couple of millennia ago and half a world away, sewers were built in ancient Rome as a means of draining the marsh that surrounded the city.

Others were working on drainage, as well. Archeologists have uncovered sewers in such widely placed locations as the Orkney Islands, just off the north coast of Scotland, and the Indus civilization in what is now Pakistan.

Mesopotamia, which we now know as Iraq, had stormwater drain systems in the streets as early as 4000 BCE. By 3200 BCE, there were drainage systems on the Orkney Islands.

Such systems were mainly for drainage, although some also accommodated sewage.

But it was the Romans who first tackled sanitation for a whole city. Engineers built what would eventually become known as the Cloaca Maxima, or "greatest sewer," parts of which are still in use.

It was originally conceived as an open canal to drain marshlands but was converted gradually into an underground sewer running through the Forum and emptying into the Tiber River. It carried everything from street trash to public bathwater to excrement flowing from the city's "rooms of easement" or public latrines.

Marden Nichols is a professor of classics at Georgetown University in Washington, D.C. She says the main function of the sewer system "was not actually to make Rome cleaner, but to empty the city of the great amounts of water the aqueducts were bringing in."

In spite of the system, she says Rome remained "absolutely, disgustingly dirty."

It wasn't until the mid-1800s that a clear link was established between sewage and waterborne diseases like cholera.

That was when the River Thames in London, which had dealt with human waste for centuries, finally reached its limits. The consequence was three major cholera outbreaks between 1800 and 1850 that took more than 30,000 lives and finally forced the city's leaders to act.

In 1859, the city began a decade-long project to build a network of sewers that ran parallel to the Thames intercepting all manner of dirty surface water and underground waste and diverting it all downstream to be flushed out to sea.

In the 1840s, the older half of Hamburg, Germany, burned. When the area was rebuilt, a totally new sewer system was designed which vented through the roof drains of connected buildings and which had a flushing system that poured tidewater through the mains once a week.

It was a design that found its way, with modifications, to other cities in Europe and the United States.

In the wake of two hurricanes, it's time to look at a new breed of sewage plants emerging in Europe. They don't serve simply as waste management centres but as full-scale, self-powering recycling systems that can extract energy, clean water and valuable commodities from human waste.

In Hamburg, a pilot plant opened in 2015 that incinerates all sewage sludge then treats the resulting ash with phosphoric acid.

The acid acts as a catalyst in recovering phosphorus, which is a key element in agricultural fertilizers.

The process also yields calcium, gypsum, aluminum and iron.

The latest figures from the pilot project tell us that the Hamburg plant generates 17 million kilowatt-hours of electricity per year. That's enough to power nearly 6,500 homes.

It would be nice to think that after cleaning up the mess left by Harvey in Texas and Irma in Florida, something better might emerge.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com.

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