Bruce Napier wrote: > On 25 Jun 2007, at 13:54, Mike Stevens wrote: > >> When we commissioned our present boat, we took advice from Chris >> Coburn of >> Lee Sanitation. He recomended us to fit a Vacu-flush loo with a >> remote holding tank, and said that if we provided enough ventilation >> for the holding tank (two vents), then natural decay by aerobic >> bacteria (which are >> killed by any of the blue or green products) would take care of the >> system >> with no additives. So that's what we've done, and it works. The >> only time >> we get any smell out of the system (through the external vents) in >> when (a) >> the tank's nearly full and (b) the weather's warm,and then the smell >> only >> occurs while the vacuum system is actually pumping. >> >> We did experiment with using blue for a few weeks, but it made >> absolutely no >> difference to the effect, so we stopped using it again. >> > The only thing we found when not using any additive at all was that > the sludge didn't break down completely. In particular, any oily > component made the sludge quite adhesive to the sensors for the > Tankwatch guage. Mind you, we only have one vent on the tank, so may > not have been achieving ideal conditions in the tank for aerobic > fermentation.
One vent might be tricky. Most of the bacteria present will make *some* gas - with only one vent one is likely to have a one-way traffic of gas (out of the tank). That will reduce the oxygen level... (a) Oxygen replaced by gas.... and (b) Oxygen consumed by the bacteria (they are aerobes after all) As the oxygen level drops down so the bacteria will cease. The only other problem one might have in relying on such a system is that there is also likely to be some facile anaerobes as well. These will grow slowly with oxygen present, producing more gas in an effort to eliminate the oxygen completely, then they switch to a full fermenting mode and can grow at full pace and allow other anaerobes to grow. Anaerobes you don't want, they tend to be the more pathogenic bugs. Ron Jones Process Safety & Development Specialist Don't repeat history, unreported chemical lab/plant near misses at http://www.crhf.org.uk Only two things are certain: The universe and human stupidity; and I'm not certain about the universe. ~ Albert Einstein
