Monday 20 March 2017


A lot of people get unduly exercised, indeed a bit hysterical, about urine; which is a) sterile b) mildly antiseptic and c) remarkably good for the garden. It's less true of women than men that urine is sterile because there is a natural flora in the vagina, but those are Good Bacteria.  I've written before about the virtues of peeing in the shower which include getting fewer cases of athlete's foot and verruccas [it's the antisepsis, silly].  Actually, that potentially beneficial effect is probably unlikely because of the dilution factor.

The dilution factor came up front & centre earlier in the month when the Grauniad and the blogosphere [Metafilter] spent a penny's worth on the subject of urination in swimming pools and whether we the swimming public should be concerned. I don't really like swimming - the medium is cold and wet - but I did go with Dau.I and Dau.II when they were a) small and b) grew importunate about having their father in the pool with them. I was a convenient post to hold on to when they got tired. When actually swimming, I always felt I was going to bump into a bobbing band-aid with my nose, which has indeed happened to me once - once too much! But I never worried about the skin flakes, sweat or other bodily fluids which made up the medium because I am a) numerate and b) not OCD [much]. The point is that there is a lot of water in a swimming pool and only a little water in a bladder.  Even if every punter leaked a little, it wouldn't amount to much. And what is it that you're concerned about? given that urine is a dilute solution of urea with vanishingly small quantities of other compounds.  It is increasingly the custom to ensure that all swimmers wear bathing caps to keep the hair on their heads and I guess that is a good idea. I can imagine that an accumulation of hair will eventually clog the filters. Bald ? You often have to wear the hat aNNyway, because the operatives [I won't call them Effectives] in the pool can't be programmed to interpret the rules for sense.  Is it only a matter of time before we are compelled to shave our oxters or wear little under-arm covers?

Another pee-pee link was in the blogosphere a while back. The German space agency DLR Deutsches Zentrum für Luft- und Raumfahr has been investigating the value of urine for providing sustainable food on long-time space voyages - either going round and round in the ISS or making a bee-line for Mars or TRAPPIST-1. One of the key elements in the scheme is using bacteria to process the nitrogen in the urine - primarily urea which is rather inert and mostly harmless but which has a tendency to break down into ammonia which is quite toxic: ammonia will clean your toilet bowl and U-bend rather effectively. When I worked in the aquarium in Rotterdam we filtered the water through a sandwich of filterwatten and activated charcoal. The filterwatten - I just looked this up - was probably made of polyethylene terephthalate = PET; another use for this remarkable polymer.  Between two layers of PET to catch the big bits, the activated charcoal was basically a set of microscopic tubes and hidey-holes effectively infinite in size. Lodged on the sides of these hollows a community of Nitrosomonas and Nitrobacter grows up and does the chemical conversion. Periodically we would clean the filters, but we'd only tip out and replace half the charcoal the remainder served to seed the fresh stuff. Likewise, once a month we'd do a water-verversen: empty half the tank and fill up with unchlorinated fresh water.

Plants prefer nitrates and we prefer to eat plants rather than cakes made of compressed bacteria; although that is surely another option for feeding those astronauts.  If this all reminds you of Dune - book or film - where water is the precious resource and limiting factor - it must be the way I tell it. If you haven't read the book, the relevant spoiler is that when a person died on the desert planet they wrapped the body up in a special cloth and wrung it dry; keeping the water and discarding the husk. I guess the Germans will be too squeamish about the scared temple that is the human body to do anything like that. The metafilter re-churn of the BBC report elicits some wit - if those Longdistancespacejourneygermans [Langstreckenraumfahrt is a word] are going to grow tomatoes from urine surely they will be better growing peas or leeks - ho ho, pee-pee jokes, I too was schoolboy once upon a time.

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