DIY Holding Tank aerator.

[HeadMistress]

I was wondering if your heads were FW or SW flush. As I am only familiar with land based septic systems, which are obviously FW flush, I thought perhaps the SW would effect the bacteria I am seeking to produce.Thanks.

There's so much bacteria in waste that tank contents don't even notice whether the toilets are flushed with fresh water--raw or treated municipal- or sea water. However, I'm very curious to know just what kind of bacteria you expect aeration to produce. All it should be doing is introducing oxygen into the tank contents.

Mischief wrote, I plan to add a T fitting between my vacuflush pump output and the tank. I will add air via the extra port on the T with an aquarium pump with two one-way valves inline so that sewage can never back up the air line.

That's a very bad idea 'cuz it will interfere with the vac pump's ability to move the flush to the tank. Any aeration tubing needs to be connected directly to the tank.

--Peggie

 

[ronobrien]

There's so much bacteria in waste that tank contents don't even notice whether the toilets are flushed with fresh water--raw or treated municipal- or sea water. However, I'm very curious to know just what kind of bacteria you expect aeration to produce. All it should be doing is introducing oxygen into the tank contents.

Mischief wrote, I plan to add a T fitting between my vacuflush pump output and the tank. I will add air via the extra port on the T with an aquarium pump with two one-way valves inline so that sewage can never back up the air line.

That's a very bad idea 'cuz it will interfere with the vac pump's ability to move the flush to the tank. Any aeration tubing needs to be connected directly to the tank.

--Peggie

The difference is the type of bacteria present in the tank. The lack of oxygen produces anaerobic bacteria, which is the awful smells that are produced. Adding oxygen produces aerobic bacteria, which consumes the waste and eliminates (nearly) the odor. On land we call them denitrification systems, as they reduce the level of nitrogen in the effluent. These are used primarily in sensitive coastal areas. The nitrogen contributes to the proliferation of algae (red tide), which consumes oxygen in the estuaries, killing off much sea life. These are required by law in many coastal areas. The unintended. but appreciated benefit to these denitrification systems is that they are nearly odorless. The also produce effluent which is, with some filtration, potable. I merely thought that adapting an air injection system to a holding tank would, primarily, reduce odors on board and, secondarily, make the discharge less impactful to the environment. I did not realize that anyone had done this on a boat already. I am grateful for everyone's input on adapting an on board tank.

 

[ronobrien]

There's so much bacteria in waste that tank contents don't even notice whether the toilets are flushed with fresh water--raw or treated municipal- or sea water. However, I'm very curious to know just what kind of bacteria you expect aeration to produce. All it should be doing is introducing oxygen into the tank contents.

Mischief wrote, I plan to add a T fitting between my vacuflush pump output and the tank. I will add air via the extra port on the T with an aquarium pump with two one-way valves inline so that sewage can never back up the air line.

That's a very bad idea 'cuz it will interfere with the vac pump's ability to move the flush to the tank. Any aeration tubing needs to be connected directly to the tank.

--Peggie

I forgot to add that land based denitrification system owners are advised to use chlorine bleach or any other acidic product very sparingly as it can have a detrimental affect on the aerobic bacteria. That was the reason for my question as to whether anyone experienced a difference bewtween FW & SW flush. Salt ( common table salt is sodium chloride, NaCl) is created with the combination of a base with and acid. So I am still wondering about the affect of salt on aerobic bacteria.

 

[HeadMistress]

The difference is the type of bacteria present in the tank. The lack of oxygen produces anaerobic bacteria, which is the awful smells that are produced. Adding oxygen produces aerobic bacteria, which consumes the waste and eliminates (nearly) the odor.

When organic material (tank contents) break down aerobically (oxygenated), they generate CO2, which is odorless. It's only when material breaks down without oxygen that they generate anaerobic gasses--hydrogen sulfide and sulfur dioxide which not only stink but are toxic--and methane, which is odorless but flammable. The amount of salinity in sea water has no impact on this process.

Bleach is another matter. It has NO place on a boat because it's not just salt, it's sodium hypochlorite (NaOCl),a solution made from reacting chlorine with a sodium hydroxide solution to create a product that kills bacteria in both aerobic and anaerobic conditions.


--Peggie

 

[HeadMistress]

I should have added that aeration has a benefit in addition to oxygenating the contents: The CO2 that's generated by aerobic breakdown can lie on the surface in a tank like a blanket, creating the anaerobic conditions that result in stinky gasses. Someone posted the bubbles generated by an aerator have no value...not so! Those bubbles break up the CO2 blanket.


As for whether adapting an air injection system to a holding tank would make the discharge less impactful to the environment, the answer is no. E-coli and other bacteria and viri can grow in both aerobic and anaerobic conditions and is the reason why it's illegal to dump a holding tank within the "3 mile (6 miles in a few places) limit"...which means you must be at at sea at least 3 miles from the nearest point of land on the entire US coastline to do so or to flush a marine toilet directly overboard.



--Peggie

 

[ronobrien]

I should have added that aeration has a benefit in addition to oxygenating the contents: The CO2 that's generated by aerobic breakdown can lie on the surface in a tank like a blanket, creating the anaerobic conditions that result in stinky gasses. Someone posted the bubbles generated by an aerator have no value...not so! Those bubbles break up the CO2 blanket.


As for whether adapting an air injection system to a holding tank would make the discharge less impactful to the environment, the answer is no. E-coli and other bacteria and viri can grow in both aerobic and anaerobic conditions and is the reason why it's illegal to dump a holding tank within the "3 mile (6 miles in a few places) limit"...which means you must be at at sea at least 3 miles from the nearest point of land on the entire US coastline to do so or to flush a marine toilet directly overboard.



--Peggie

Peggy, I think you have basically concurred with me as to what type of bacteria I was expecting. You clearly have a broad knowledge on the subject. I don't know your background, but it was my conversation with a PHD in marine biology that lead me to believe that there may be some positive effect, just not enough to allow discharge within the demarcation line. Thanks for your input.

 

[OldToby]

Seems like this thread is circling the drain, but before it does, I have a question. I am installing a diy bubbler in my holding tank using the Marine Metal 12v pump. Because our boat is never on shore power (solar panels feeding Firefly G31x3), I want to minimize even the small power draw of the pump by running it for, say, ten minutes every hour (controlled by a little Chinese timer). Is this adequate to encourage the aerobic bacteria vs the anaerobic bacteria? Or should I run it more than ten minutes per hour?

 

[Martin J]

I leave mine running, they burn so little. my tank is 1oo gall. I have noticed that it has to run for 2-3 days before it seems to have an effect on the tank when 50% full ? I deduce it's having a effect because when first using there was a odor near the tank vent. After a few days it cleared so one assumes it is/or has removed bad odorous bacteria.

 

[Comodave]

I don’t know if 10 minutes is enough or not, we always ran ours 24x7. I guess you could try less run time and see what happens. Maybe Peggie has more info.

 

[TrawlerAJ]

Worth a try if your holding tank situation could benefit from added air!


I installed a Marine Metal 110v to bubble because the power was convenient. We disconnect from shore power at anchorages for, say, 36 hours at a time, and all is still well.



Who knew bubbling poop would be such a hot topic???

 

[dhays]

Seems like this thread is circling the drain, but before it does, I have a question. I am installing a diy bubbler in my holding tank using the Marine Metal 12v pump. Because our boat is never on shore power (solar panels feeding Firefly G31x3), I want to minimize even the small power draw of the pump by running it for, say, ten minutes every hour (controlled by a little Chinese timer). Is this adequate to encourage the aerobic bacteria vs the anaerobic bacteria? Or should I run it more than ten minutes per hour?

Toby, I have considered doing the same thing. The pump only draws less than a 1/2 amp, but over a 24 hour period that puts it close to 12 Ah of battery capacity. I was going to use a small digital timer as well. Something like this:

http://timers.shop/assets/documentation/LivewellAeratorTimerWiFi.pdf

The advantage of that is that you can easily change the duration. I have another timer that I bought from the same guy a while ago to control a relay that is used to run my fuel transfer pump. It works great, but it a pain to program (much like trying to program a Balmar product). With this you can test different cycle times.

I’d start by running it 100%. After using it it that way for a week, you will know how well the system works. Then I would reduce the ON time by 20% and run it another couple weeks. If you notice no odor, then reduce another 20% and repeat until you find a level that you start to notice some odor after a couple weeks of use. Then bump back up to the prior level.

I think I would use 10 minutes as a base rather than an hour. On for 8 minutes, off for 2. Then on for 6 and off for 4, etc…

Hm… trouble typing. Even if you reduced it to a 40% ON time, you would only be reducing your daily battery draw by 8 Ah if my math is correct.

 

[OldToby]

I like the “start at 100% for a while then back off until it stinks” idea. That’s what I will do. Thanks, Dave!

 

[TrawlerAJ]

The contents of the tank will certainly influence it's ability to fester. You can't add too much fresh air, but, if your venting isn't enough, you can starve the tank of oxygen. Nobody wants you to wait for it to stink...