To me the real issue with sewage systems/holding tanks
isn't being addressed on boats. They aren't usually properly addressed on land either, for that matter.
I've been involved a fair bit with this (on land) as a friend has a company providing equipment
to sort a lot of problems out.
No 1 issue, is problems created by anaerobic bacteria. Sludging, crusting (floating on top of the sludge), and the slime that anaerobic bacteria surround themselves with as a protective barrier. Plus the smell associated with the process of anaerobic bacteria making methane.
Now a boat doesn't have a septic tank, where treatment using anaerobic bacteria is split into two tanks
(settlement tank and the next runoff tank) prior to dispersion through a soakaway or drain field. This system can work successfully for decades, until the anaerobic bacteria gum up every part of it (with the slime completely blocking even the drain field).
Now the speed with which an aerobic system can clean up a septic drainage system, is quite surprising. I have seen aerobic bacteria fully restore a septic system, including the drain field, in about 10 months. This was a system that had functioned without interference
, for over 50 years, and then blocked up solid.
Perhaps the most pertinent aspect, is what happened to that first tank in the system, which bears a close relationship to a boat holding tank
. It started off with such a heavy crust, floating on a thick treacle of sludge, the owner had even tried breaking it up with steel
I got him to buy a heavy duty air pump (for long term reliability
and the volume of air it could supply), run a hose from it to a piece of tube long enough to get to the bottom of the tank, and fit an air diffuser to it, for lots of fizzy little bubbles to be pumped into the tank. The aerobic bacteria will also attack the anaerobic bacteria, and treat their slime protection as another food
source. It took a few weeks for that first tank to start circulating properly, with more and more oxygen content, but within a month, and plenty of extra flushes to get enough water
in there to help dilute and assist (as an aside, reduced flush water
in 'saving' water, is having a terrible effect on sewage systems everywhere), the inches thick crust (I wasn't going to get too close to look at it, but it seemed to be a bit over a foot thick) was gone, and in another couple of weeks, the contents were transparent, and a dipped sample looked like tap water. Within a year, the complete drain field was restored, as all the blocking slime was consumed by the aerobic bacteria. Associated smells had long disappeared too.
So that is why I would be interested in a small reliable airpump, with a diffuser to go into the bottom of the holding tank
. I don't think there'd be much problem with wear and tear of fittings and hoses, with one (and vegetable oil
as a lube, once it had done its work, they would eat to dispose of it too).
Frankly, if such a system was installed, as long as you could guarantee tank contents not being added to for a week, with the diffuser working constantly, I think you should be able to pump out quite safely, anywhere.
I have seen somebody drink the runoff from an aerobic system, but you wouldn't catch me doing it.
When I get a good look at the system my boat arrives with, I'll have to look a lot closer at this.
PS. The speed with which aerobic bacteria deals with 'stuff' used to be easily observed in practice. Unfortunately, thanks to 'Pooper Scoopers' this process isn't as easy to observe for most people any more.