Thermal hydrolysis (when sludge goes pssh – boom!)

Readers of this blog know that an ordinary wastewater treatment plant creates sewage sludge, a concentrate of solids.  That sludge can be “digested” to generate biogas.  But that still leaves behind huge volumes of digested sludge.  What to do with it is usually the main headache of treatment managers.

But imagine putting sludge in a pressure cooker – high heat, high pressure.  Then release the pressure at once.  I’ll let you imagine what that may look like (yes, a sewage explosion) but here are the results: any cellular component (sludge is largely made up of microbial cells) is blasted apart – “lyzed”.

An overview of the sludge treatment process using thermal hydrolysis (Wikipedia)

Then cool, and feed to live biogas bacteria.  These bacteria, notoriously fussy, now have access to more food, released from the cells of the blasted sludge. Result: more gas is produced, more than enough to power the hydrolysis process.

But the key advantage may be downstream: the lyzed sludge is not only easier to pump, but also to dewater.  That means much less sludge to deal with; it becomes a concentrate that can be used as fertilizer.  And that is closing the cycle.

I was reminded of this relatively recent technology because Edinburgh has just announced that it will implement it.  But the Blue Plains WWTP, in Washington DC, has had a system running successfully for a few years now.  They claim to have the “most advanced wastewater treatment plant in the world”.  Not sure I agree, but it’s nice to bragging about sewage.

The Blue Plains, DC treatment plant with the “pressure cookers” in the foreground

How much energy can we get from poo?

The digester in Linkoping, Sweden, produces enough biogas for all the city buses and taxis to run on.

That’s the question that tackled Robin Andrews, writing for the popular site IFLS.  There are two basic approaches: burn it, or digest it anaerobically and burn the resulting biogas.

The first approach yields precious little energy, since feces are mostly water (75%).  But even if it were all dried (say, by the sun), the energy released by burning all human production remains small: enough to power seven million US homes, so enough for the residential needs of about 3% of us humans.

Unfortunately, Andrews’ methodology is questionable; for one thing, he assumes (for no clear reason) that only 30% of the dry matter is combustible; in fact most of it, except for a few salts, is.  So you can triple that number.

In fact, the figure of 30% is not a bad rule of thumb when it comes to anaerobic digestion; indeed, only some of the organic matter produces biogas.  But at least digestion does not require some magic form of drying.  And energy for seven million homes is nothing to sneer at.  But tsk to Andrews for his strange approach.

But what about some vaunted systems, such as the one used at Jenfelder Au, the residential development  in Hamburg?  Doesn’t it produce 40% of its energy need needs just from its residents poop?

Yes, it does.  What that points out, if anything, is that some German homes are way, way more efficient than US ones…

Exercising changes the microbiome

Vancouver Sun Runners may be selecting for healthier bugs

Could working out change the ecology of the bacteria in our intestines?  It may be so.  Gretchen Reynolds, of the New York Times, writes

Past studies have shown that endurance athletes tend to have a somewhat different collection of microbes within their intestines than sedentary people do, especially if the athletes are lean and the sedentary people are not.

[A] new study, which was published in November in Medicine & Science in Sports & Exercise, scientists from the University of Illinois at Urbana-Champaign decided to track the guts of people who undertook an unfamiliar exercise routine.

The scientists took blood and fecal samples [of the volunteers] and tested everyone’s aerobic fitness. Then they had the men and women begin supervised workouts, during which their efforts increased over time from about 30 minutes of easy walking or cycling to about an hour of vigorous jogging or pedaling three times.  The volunteers were asked not to change their normal diets.

After six weeks, the scientists collected more samples and retested everyone, and then asked the volunteers to stop exercising altogether.  Six weeks later, the tests were once again repeated.

[The researchers] noted widespread increases in certain microbes that can help to produce substances called short-chain fatty acids. These fatty acids are believed to aid in reducing inflammation in the gut and the rest of the body. They also work to fight insulin resistance, a precursor to diabetes, and otherwise bolster our metabolisms.  Most of the volunteers had larger concentrations of these short-chain fatty acids in their intestines after exercise, along with the microbes that produce them.

What’s in our intestines is not just poop…it is a non-ending source of wonder.

Dog poo lights the way

In Malvern Hills, England, is a new street lighting device that uses dog poo, the first one in the UK.  Here’s how it works, according to Nic Fleming:

[D]og walkers deposit the product of a hearty walk into a hatch and turn a handle. The contents are then broken down by microorganisms in the anaerobic digester, producing methane to fuel the light, and fertiliser.

The inventor, Brian Harper, calculates that ten bags of poo can power the light for about two hours.  The system is quite simple: the depositor turns a handle, which agitates the contents of the tank, and promotes biogas production, which is stored until the evening when it produces its warm glow.  You can see the whole thing in operation in a video from BBC, here.

This is not the first such system: Park Spark, in Massachusetts, has that honour.  And Waterloo, Ontario, may join the club.

This may not be a lot of energy – just some light.  But it reinforces the idea that poo can be useful; and that is brilliant.

Septic Anmore

In the Greater Vancouver we may have issues with combined sewer overflows, but that is pretty much the only serious problem we have with sewage.  Right?

Anmore in Metro Vancouver

Wrong – as demonstrated by the issues faced by the village of Anmore.  Kids have been warned to stay away from an area near their schools, to avoid risk of contamination by sewage.

The problem appears to be a failing septic field of Anmore Green Estates, a 125 residents strata property.  According to CBC’s Tina Lovgreen,

Robert Boies, the strata president for Anmore Green Estates, says the only fix is to hook up to Port Moody’s sewer system. Boies said the development’s septic system isn’t operating properly, adding the construction of the two schools had a negative impact on it.

Right now, in the Village of Anmore, residents are responsible for their own septic system. Boies said one solution to the faulty septic problem would be for Anmore Green Estates to connect to the Port Moody sewage system. But in order to connect to that sewer line, the village must first join the Greater Vancouver Sewerage and Drainage District.

The problem with that is the cost; not just of the pipe, but the fee that would be owed by Anmore to connect to the Greater Vancouver Sewerage and Drainage District.

Anmore Green Estates

Lovgreen’s article may give the impression that Anmore mandates septic systems, which is not so.  The bylaws state that proper sewage systems must be installed and maintained.  A small on-site wastewater treatment plant, such as a sequencing batch reactor, may well be an appropriate solution here.  But then, who pays?  Did the schools really contribute to the septic failure?

Or is the village at fault, ultimately?  Septic is appropriate for rural properties (with good, deep soils), less so for a denser development like Anmore Green Estates.

Whatever the ultimate responsibility, it’s a mess.  But it’s also a missed opportunity: this would have all been avoided with a system such as Jenfelder Au’s methane cogen.  Poop as a resource saves money; poop as a waste is just a source of pollution – and headaches.

CSO, green infrastructure, and storm storage

I came across a puzzling article the other day. TunnelTalk, the voice of the US tunneling industry (yes, there is such a thing; why I was on their website is a long story), featured an opinion piece entitled “Green surge threatens CSO storage solution”. Well, now.

How a combined sewer outfall works

A bit of background: tunnelers have been busy making sewers bigger and wider, so as to have room to store storm water runoff. In the diagram above, it’s as if the top pipe has been made much bigger below the dam. This way, combined sewers are not overwhelmed, and sewage is less likely to overflow into rivers without treatment.  It’s a system that works well; Portland’s Big Pipe project, for instance, has reduced overflows down to an average of 4 per year, down from 50 previously.

Cincinnati has shelved deep level CSO tunnel in favour of daylighting a natural creek (TunnelTalk)

But the industry is afraid that green infrastructure – rain gardens, green roofs, and other ways to reduce runoff – will preclude the use of tunnel storage.  They point to Cincinnati, where the city opted for daylighting a creek instead of a tunnel storage project.

Point taken.  But in the long term, I believe that these are misplaced fears.  With the climate changing, the frequency of huge storms will only increase.  That means that both green infrastructure and large underground storage will be needed. Indeed, it was a record-breaking storm that led to the huge sewage overflow in Portland in January 18 2012, after the Big Pipe project was completed.  Chill, guys – you’ll be needed.  And so will you, landscapers, tree planters, rain garden makers. There will be, alas, a need for all systems together.

Unless you want more shit down your rivers, as in the good ol’days.

Marcel Duchamp’s Fountain

2017 is the hundredth anniversary of Marcel Duchamp’s celebrated piece, Fountain.  The importance of the piece that launched the whole “but is it art?” conversation is reviewed by the Globe’s Russell Smith.  Writes Smith:

What much of the recent discussion of Duchamp shows is that his symbols were always more subtle and more complicated than they appeared – they were more than just symbols. A paradox of Fountain, for example, is that the original was never actually exhibited in a show (it was refused for its “indecency”) and all we have ever known of the original is a photograph, taken by Alfred Stieglitz. In a sense it is that photograph that is the original. “The original” is of course an inapplicable concept, since it was supposedly a mass-produced object, but the fact that we must talk about it that way shows how magical it became once signed with a (fake) artist’s name. (Duchamp signed it “R. Mutt,” a name that sounds a lot like the German word Armut, poverty.)

Of course, it belongs in this blog; the object in question is a mass-produced urinal, from the JL Mott Iron Works, 118 Fifth Avenue, New York. As befits a pioneering work of art, homages are many. Smith mentions these:

Lipstick Urinals

Sherrie Levine made a shining bronze copy of the urinal in 1998, called Fountain (Buddha), enshrining it as valuable and sacred. Mike Bidlo made a bronze recreation of it in 2015 that looks as if it has been shattered and glued together (possibly a reference to the story that someone deliberately smashed the original just after it was made). Most seductive of all these homages is Rachel Lachowicz’s sculpture Lipstick Urinals (1992) – three urinals in a row on a wall as if ready for use in a men’s washroom, but made out of waxy red lipstick.

Duchamp coyly hinted that the work may not even be his own; art historians contend that it may have been from

the Dadaist Baroness Elsa von Freytag-Loringhoven, whose scatological aesthetic echoed that of Duchamp.

It’s not just that “scatological aesthetics” is of interest to this blog.  Man, this is about the defining point of modern art!  And it’s a urinal!  Let’s celebrate!