[Greenbuilding] Urine-diverting toilets Re: Greenbuilding Digest, Vol 89, Issue 8

[John Salmen]

I like this conversation – have to say that composting toilets were the most challenging things to design. Fortunately the ones I did were custom so didn’t have to be made into a commodity- they only had to work. The biggest challenge was what to do with urine. Essentially it was the biggest potential polluter and creating a leach field for urine defeated the purpose. Employing electricity to dehydrate seemed also an oxymoron for something that was supposed to be both passive and conversing. Diverting captures limited flows and doesn’t really deal with it. What I wanted was a contained unit that dealt with both liquid and solids that didn’t have to be dealt with for at least 2 years.

 

The best design was similar to a pot boiler (a container within a container). The inside container was a large round commercial garbage container with a grid of racks every 4” – the racks were 3/4” perforated pvc pipe and were drilled and connected through the side of the container (to allow air flow). The pipe was cross gridded to create 2” openings. The bottom of the container was also perforated to allow urine to collect in an outside container. The inside container was suspended over an insulated outside container (larger commercial garbage thing) which was connected to a 6” vent chimney.  The bottom of the outside container was plumbed to a hand pump – located next to the toilet paper roll.

 

The idea was the moist feces and paper would collect on the first rack – as it dried (with air flow from perforated and heat) and reduced in mass would tumble to the next. Operating the hand pump would send an aerated spray of urine over the racks which would reduce the urine volume through evaporation and effect some denitrification. The tumbling effect allowed for some active composting eventually settling at the bottom where it would then moulder. I put in twin containers – one would fill up within roughly a year (was used for a rural commercial tai chi studio) and then the second was used leaving the first to moulder for a year at which point it was emptied (lifted out and emptied into an outdoor composting chamber where it would sit for another year before use). After use and emptying the containers were dry and well composted. The urine piping had a valve to switch between the two containers. The maintenance of having to empty a container every 2 years is a bit of a hassle but not bad. The large flue connection to the outer insulated container was extremely effective in ventilation so was one of the least smelly composters I’ve been around.

 

This was the only effective self contained composting toilet I managed to design and is still in use 15 years later. 

 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Carol Steinfeld
Sent: Thursday, January 11, 2018 11:53 AM
To: Green Building
Subject: [Greenbuilding] Urine-diverting toilets Re: Greenbuilding Digest, Vol 89, Issue 8

 

Reuben,

Complaints about odor vary. 

We supplied our own tips with the toilets.

Every time Del Porto or I would visit an odor situation, we'd find drainage (not enough slope) and/or air draw issues. (The best was publicly toured historic house that had the air intake for the HVAC system in the basement next to the big composting toilet composter.)

 

The Bullitt Foundation decided not to install a urine-diverting toilet because they decided to vent the bathroom through the solids/feces pipe to the composter. They knew this would draw odor from the urine line and the other toilet. Of course, there was a workaround for this, but they weren't motivated.)

 

We haven't had many folks complain about odor, so I think you're pulling a draw on the urine line. Or one of the other factors I listed is at play here such as not enough slope in your drainline. 

Did you say where the urine goes?

 

Also, urine sludges up pipes after awhile---this is well known with urinals---so it's worth blasting the hose periodically or replacing it. 

I do this for the high-capacity urine-div composting toilet at my friend's farm every year. Even I'm surprised by how much white sludge comes out of it. Young kidneys.

 

Most folks use the hose that came with the EcoDry, which is the same hose used for bilge tanks. It is not corrugated.

 

I'd guess about a third of owners use the urine-flush mechanism.

 

You can put a P-trap in the urine line. I'm not crazy about doing that with no-flush urine-div toilets. 

 

I also tell folks to pour old coffee, tea, sugary drinks, etc. down the urine drain to give it an acid chaser.

 

The odor filter in the EcoFlush urine-diverting toilet is new. It's something else to maintain. I can pull one out and photograph it. 

 

(Sven was an investor who said things like "when the U.S. market explodes"--even though urine diversion is still little known in Sweden. He took over when the sales manager died of a brain tumor. The current operators understand the nature of the market.)

Carol @ Ecovita

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