On-board sewage treatment?

[Rohorn]

Hi....one sees lots of posts about holding tanks or buffer tanks, and the polemic seems mainly to revolve around when / where does one jettison the load, and the ethics, ecological consequences and so on.
Are there no sytems which go all or part of the way towards neutralising the stuff, breaking it down, before it goes?. I'm not thinking of PortaPotti fluid, which I guess, is more aimed at keeping the P.P. liveable with, than favouring the environment.
For example, if one's holding tank was a quarter or half neutralised before it was unloaded that would be better than not at all? If one simply aerated the holding tank with something like a fishtank aerator wouldn't that help? What about some of those septic tank accelerator tablets which get one's septic tank system going at full chat after a long absence?
Such a system should clearly not eat electrical energy or make rude noises, or cost a fortune, but there's a fortune out there for someone who can, as it were, go through the motions, and produce a solution.
What about it Headmistress?
Cheers.....R


<hr width=100% size=1>

 

[boatless]

I remember that there was a Swedish sytem which dried the stuff out. Was then harmless and odourless, apparently.

But I can see why it hasn't caught on.

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[HeadMistress]

There is nothing that can be added to holding tank (portapotty tanks included) that can make it legal to discharge overboard. There are, however, "approved" treatment devices that can replace a holding tank in all waters except those specifically designated "no discharge." Most can be used with any toilet...the most popular worldwide is the Raritan Lectra/San, which treats and discharges a flush at a time.

The only downsides to treatment devices are:

1. Cost...the Lectra/San, oddly enough, is not only the best, but also the least expensive (a VERY rare combination for anything)--about $750 USD at discount in the US--and,

2. It needs power--1.7 AH/flush (others consume even more). However, that sounds a lot scarier than it is to anyone who isn't determined to have nothing aboard that uses power...the total daily consumption for two people is only about 10-12 AH.

3. At present, it cannot be used to dump a holding tank...the maximum flush volume it can accept at a time is only about 1 gallon, the treatment cycle is 2.5 minutes. However, Raritan has in development a system that can be added which will make it possible to use a Lectra/San to empty a holding tank...it should be available some time this year.

The upside is, the discharge is actually cleaner than most coastal waters...and totally unnoticeable to anyone who didn't happen to be diving under your boat next to the thru-hull when the toilet is flushed--completely liquified, no odor, color is about the same as skim milk that's been cut 2-1 with water.

If you're curious to know more, go the "waste treatment" page on the Raritan website at http://www.raritaneng.com

But if you're only hoping to find something to make it legal--or even socially acceptable --to dump a holding tank within miles of shore, it doesn't exist.

<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987

 

[Bergman]

The resultant methane gas could be a bit of a problem. Or perhaps an opportunity if the red diesel is banned.

Bit of pipework and fancy engineering and off you go.

More seriously, I don't know what the festering time is, how long it takes to break down, may be that holding/septic tank would have to be pretty big.

<hr width=100% size=1>

 

[roger]

Scandinavian composting toilets

Many Scandinavians have country huts with no mains drainage so the composting toilet is well developed. For info just visit any large Swedish or Norvegian DIY store.
They would not be convenient on a boat due to the size but might be an answer in the future.
In use its best if one can deposit urine elsewhere. The drill is to perform then cover the deposit with a handful of trated tree bark. With through ventilation sometimes helped by a little electric heating the contents compost quite fast and the resulting dryish product is useful in the garden. Our Norwegian cousin grows excellent potatoes!!
I can just about imagine the system being used on a large traditional boat.

<hr width=100% size=1>Roger

 

[HeadMistress]

You're referring to composting toilets, boatless...the Swedes aren't the only ones to have them. But unfortunately composters don't work without any power either....composters must have blowers to evaporate excess liquids, 'cuz wet soggy waste doesn't compost, it just rots and stinks. One that's catching on in the US is the Airhead...but it's not without its drawbacks either. You can read all about it on their website (http://www.airheadtoilet.com/Index/Page_1x.html). A Canadian company--Sun-Mar--also makes a self-contained composter for marine use called the Ecolet...you can read all about it on their website at http://www.sun-mar.com

IMO, composters are an option worth considering for boats on inland "no discharge" waters, but don't make a lot of sense for boats in coastal waters, especially those who cruise offshore where the toilet can be flushed directly overboard...why store waste aboard in ANY form if you don't have to???

Roborn, "If one simply aerated the holding tank with something like a fishtank aerator wouldn't that help?"

No...aeration would only eliminate odor, nothing else.

"What about some of those septic tank accelerator tablets which get one's septic tank system going at full chat after a long absence?"

Nope...now you're going backwards. For waste to be acceptable in coastal waters, the bacteria count must be below a certain level (<1,000/100 ml in the US, which I believe is also the standard in all countries that have marine sanitation laws)...septic tank "accelerators" do just the opposite--jump start bacteria production in a "dead" septic tank.

And, without a considerable amount of maceration--far more than an overboard macerating pump is able to do in the amount of time it takes for tank contents to pass through it --there's the matter of sludge in the tank...even undissolved or incompletely dissolved solids and/or TP.

While there are some treatment devices that can be used with holding tanks, they're VERY expensive, need even more power than the Lectra/San, and/or require the use of toxic chemicals.

Boat owners and "inventors" have been looking for some way to "neutralize" the contents of a holding tank for just about as long as holding tanks have been around. They've been searching for inexpensive alternatives to holding tanks that don't require power almost as long. Some day someone may succeed, but it hasn't happened yet...the closest anyone has managed to come is composting toilets (which aren't without their own drawbacks).


<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987

 

[anchorhandler]

"No...aeration would only eliminate odor, nothing else."

Errm...Not quite, Aerating a sewage tank is one of the most effective ways of disolving sewage sludge.
By supplying clean pressurised air through a bubbler system, the formation of 'aerobic' bacteria is promoted, this bacteria then thrives by digesting the faecal remains.
This has been the preffered (non-vacuum) system for commercial vessels for some 20 years now.

Granted when pumping out, the discharged waste needs to be chlorinated to kill off the bacteria but otherwise its a very simple reliable system.

Anyway, to clarify what can and what cant be pumped, current MARPOL regulations state the following:

Under 4 nautical miles from land: NO discharges except from IMO approved sewage treatment plants.

Between 4 and 12 nautical miles from land: No discharges except from treatment plant refered to above or an IMO approved comminuting plant (macerator).

More than 12 nautical miles from land: Any discharge permitted (treated or not) as long as vessel is traveling at more than 4knts. (keep in mind that human waste is bio-degradable and that many species of fish actually enjoy the 'free lunch')

At the end of the day, unless your tank is frequently being filled up while in port, try to head 12 miles of the coast and pump the tank out.
Regards
Simon


<hr width=100% size=1>I'v got 2 ears.2 eyes and 1 mouth....if only i could use them in that proportion!

 

[DepSol]

Try Clea it All in Brixham they have a solution that you stick down the bog which sorts that out.

<hr width=100% size=1>Dom

<A target="_blank" HREF=http://www.soltron.co.uk>the website</A>

 

[HeadMistress]

I've been preaching non-chemical aerobic holding tank maintenance to prevent odor for at least 20 years--in fact, I was the first to do so in the US marine sanitation industry--BECAUSE it works with the naturally occuring bacteria in waste, keeping it alive to break it down and emulsify it...something that chemicals prevent in addition to being mostly ineffective for eleiminating odor. And finally, one US mfr--Groco--has put an aeration system on the market...they call it the Sweetank System. You can read all about it on their website at http://www.groco.net.

Although the same principles apply in both large and small systems--in fact, apply to ALL organic matter--not all functions work as well in small systems/holding tanks as they do in large ones...and due to the limited size of holding tanks on most recreational boats, waste rarely remains in the tank long enough for emulsification to be complete....so some sludge is inevitable.

But the real point is, just aerating the tank doesn't "treat" waste to acceptable standards for overboard discharge in territorial coastal waters.

Where'd you find the MARPOL regs for onboard waste disposal? If they're on the web, I'd love to have the link. Fwiw, US law is slightly different. No discharge of raw untreated waste directly from a toilet or by dumping a tank within 3 miles of the nearest point on the US coastline...no limitations beyond the "3 mile limit." In a few places on the west coast of Florida, that limit has been extended to 6 or 12 miles.

<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987

 

[robind]

Hi Peggy SIMSS1987

Try:- http://sedac.ciesin.org/entri/texts/acrc/maniv.txt.html

I seem to remember they had a copy of some?
Regards
Rob

<hr width=100% size=1><A target="_blank" HREF=http://www.rejuvanu.com>RejuVanu</A>

 

[Rohorn]

Hi Headmistress....very many thanks for chapter and verse once again. My original stainless holding tank literally rotted inside five years, unbelievably full of holes, so I put in a 9mm polypropylene Tek Tank which has literally rendered the boat useable again. I made all the structural mods to the boat to make the exchange, so the access environment is pretty good for improvements.
If there was an add-on device to simply improve the situation I'd be interested, but I'm thinking more of a DIY approach, or thoughtful routine or practice, to satisfy myself that I've done all I could with reasonable ingenuity and meagre resources before pushing the eject button.
Frankly very few yachts (in my sailing area..Paros, Cyclades) go three miles or even one mile out to unload... even, that is, if they have a tank. The island authorities have gone a long way to process island waste before sending it down a pipe which reaches about a mile offshore to the north. The local shoreline bacterial count has improved enormously as a result.
Thanks again, Headmistress, Anchorhandler, Roger and the others ...there's a lot here to digest......maybe there will be some more comment, but anyway, I'll print the thread and put it in the "Think about seriously" folder.

Cheers.....R

<hr width=100% size=1>

 

[anchorhandler]

Hi Peggy
Although i use a personal copy of the regulations, Annex IV of MARPOL 73/78 covers pretty much everyhting you would need to know.
It can be read at www.imo.org
Click on 'marine enviroment'...located at the top of the page
Click on 'prevention of pollution'...located on right of page
Click on 'sewage' ...also located on right of page

Best regards
Simon

<hr width=100% size=1>I'v got 2 ears.2 eyes and 1 mouth....if only i could use them in that proportion!

 

[HeadMistress]

Thanks for the links, both of you...I've looked at both and bookmarked both. Very helpful!!

As I suggested in the other thread on this subject, I think you'll find the information on holding tank maintenance and breakdown on the Tek-Tank site very useful understanding how waste--all organic material, in fact--breaks down. They adapted it from an article I wrote called "Marine Sanitation: Fact vs. Folklore," that was on the web for nearly 10 years (till I realized that it needed so much updating and expanding that I decided to write a book instead). I only discovered that Tek-Tank had adapted it on their own site just a few months ago, and was very glad to see that they had, because explains holding tank installation, maintenance and the principles at work in either creating or preventing odor in much greater detail than is practical to post here.

<hr width=100% size=1>Peggie Hall
Specializing in marine sanitation since 1987