Holding tank aerator to reduce smell.

[Simi 60]

We have a large 100+ gallon holding tank and it has an aeration pump that I believe is there to promote good bacteria growth and eliminate smells and, it is supposed to be left running continuously???

In the 4 years we have been living aboard we have not used it and rarely get a whiff of nastiness but yesterday after a recent pump out we are getting a pong.

I fired up the aerator and got bad smells for a while but that seems to have dropped off considerably this morning - that, or we are used to the smell.

But I am wondering..........if we have treatment plants onboard that give each flush a shot of chlorine (saniloo) wouldn't that shot of chlorine kill any of the good bacteria we are supposedly trying to grow?

 

[Bacchus]

I am familiar with aeration as I built and run a DIY version. I am not familiar with treatment systems.
I would think the chlorine will kill the good (aerobic) bacteria you are trying to promote. Is there an option to treat when / before discharging vs every flush.
My understanding is treating and hold for later discharge doesn't qualify as treated waste but again I'm not an expert.
I do run my aerator 24/7 during our boating season.bi also use NoFlex and planning on switching hing to bulk sodium percarbonate when current supply runs out.
Is the odor inside or outside? When / what conditions?
Any inline vent filter?
Raw or fresh water flush?

 

[Comodave]

On a previous boat we had an 80 gallon holding tank. The smell was worse than horrible out of the vent when a head was flushed. I talked to Peggie and she suggested a Groco Sweettank. We added one and turned it on, late on Sunday so others on the dock would be gone. It was really bad for 2 hours and then the smell was gone. We owned that boat for another 8 years and never added any chemicals into the tank. No chemicals at all of any kind and had no more smell. Just adding oxygen into the tank promoted the aerobic bacteria and killed the anerobic bacteria, and the anerobic bacteria is what causes the smell. We ran the Sweettank 24X7. Does it need to run continuously? Not sure but my wife demanded it run continuously since the smell was gone and she didn’t want it back. We added a Sweettank to our current boat last winter but with the virus we have not used the boat much this summer so it seems to be working but not much usage this year. I can’t recommend the Sweettank highly enough. You can make your own and save some money but the kit is just easier. It only takes an hour or so to install it if you have power nearby. Drilling a 2” hole in the holding tank takes a bit of gumption but that is the worst part...

 

[Simi 60]

I am familiar with aeration as I built and run a DIY version. I am not familiar with treatment systems.
I would think the chlorine will kill the good (aerobic) bacteria you are trying to promote. Is there an option to treat when / before discharging vs every flush.
My understanding is treating and hold for later discharge doesn't qualify as treated waste but again I'm not an expert.
I do run my aerator 24/7 during our boating season.bi also use NoFlex and planning on switching hing to bulk sodium percarbonate when current supply runs out.

Doesn't really matter as we pump out the same as if it was untreated

Is the odor inside or outside? When / what conditions?

Inside coming up through the toilet after flush
And in the er where tank is
Comes in waves, not continuous

Any inline vent filter?

No

Raw or fresh water flush?

Usually fresh but on this trip we have bucket of salt water and a ladle so as to conserve fresh.
Maybe its the saltwater causing the pong

 

[Simi 60]

I talked to Peggie and she suggested a Groco Sweettank. ...

Same same but different to what we have running now

240v hiblow

https://www.septicsolutions.com/septic-parts/septic-air-pumps/hiblow-air-pumps

 

[Bacchus]

Simi
Can you simply disable the treatment and activate the aerator as an experiment? If so that would be my first move and go from there based on results.
Second move might be to try to inspect tank (even if only from outside w lighting?) to see if there is any residual sludge or solids that a good clean up might help.

 

[HeadMistress]

But I am wondering..........if we have treatment plants onboard that give each flush a shot of chlorine (saniloo) wouldn't that shot of chlorine kill any of the good bacteria we are supposedly trying to grow?

It's not that you're trying to GROW aerobic bacteria, it's that you want to keep them alive...which can't happen if you're injecting chlorine to every flush 'cuz chlorine doesn't discriminate.


Treatment devices are designed to discharge treated waste overboard...that's the whole point of having one--to avoid the need to store toilet waste in a tank. So why have you directed your Saniloo to discharge into the tank? Why not have a y-valve in the toilet discharge line that provides a choice of discharging via the Saniloo or going into the tank?

I fired up the aerator and got bad smells for a while but that seems to have dropped off considerably this morning - that, or we are used to the smell.

You didn't just get used to the smell. Aerators need to run 24/7 to keep the environment in the tank aerobic. When it sits unused, there's no source of oxygen to create that aerobic condition, and without it the anaerobic (stinky) bacteria thrive. When it's turned on again, it pushes the air in the tank out the vent...initially stinky but gradually the influx of oxygen "turns" the tank aerobic again, eliminating the odor. And it works this way regardless of whether the toilet uses sea water or fresh.


--Peggie

 

[Comodave]

+1 on what Peggie said. It took exactly 2 hours for the smell to go away when we turned on the Sweettank. We never turned it off, it was still on when the new owners took possession.

 

[Lepke]

On a dairy, for the house and barn toilets, I had a system that added a small amount of air (aquarium air pump) to the first chamber of the system thru nozzles near the bottom. It encouraged aerobic bacteria that ate the sewage, leaving clear water that could be discharged without chlorine treatment. It was a system commonly used in remote places like mining and lumber camps. For the cows I had a digester using anaerobic bacteria that made hydrogen and dissolved the manure into a liquid. The discharged liquid had double the fertilizer valve of the original manure and had no smell. The hydrogen ran a multi fuel generator that turned my meter backwards.

 

[Simi 60]

Simi
Can you simply disable the treatment and activate the aerator as an experiment? If so that would be my first move and go from there based on results.

Not simply, no

Second move might be to try to inspect tank (even if only from outside w lighting?) to see if there is any residual sludge or solids that a good clean up might help.

It has a screw out port in the top and its pretty shitty in there, but you'd expect that being what it is

 

[Simi 60]

[
It's not that you're trying to GROW aerobic bacteria, it's that you want to keep them alive...which can't happen if you're injecting chlorine to every flush 'cuz chlorine doesn't discriminate.

Thought as much, so probably best off not adding any more chlorine

Treatment devices are designed to discharge treated waste overboard...that's the whole point of having one--to avoid the need to store toilet waste in a tank. So why have you directed your Saniloo to discharge into the tank?

Not me, previous owner/installer

Why not have a y-valve in the toilet discharge line that provides a choice of discharging via the Saniloo or going into the tank?

I would think because the discharge is ABOVE waterline, not the sort of thing you want to see happening though it would scare those to close neighbours away.

You didn't just get used to the smell. Aerators need to run 24/7 to keep the environment in the tank aerobic. When it sits unused, there's no source of oxygen to create that aerobic condition, and without it the anaerobic (stinky) bacteria thrive. When it's turned on again, it pushes the air in the tank out the vent...initially stinky but gradually the influx of oxygen "turns" the tank aerobic again, eliminating the odor. And it works this way regardless of whether the toilet uses sea water or fresh.


--Peggie

So it makes me wonder why it hasn't really been an issue for the previous 4 years we have not been using the air pump?
The only thing that has changed recently is using salt water assist for the flush.

 

[Panacea123]

But I am wondering..........if we have treatment plants onboard that give each flush a shot of chlorine (saniloo) wouldn't that shot of chlorine kill any of the good bacteria we are supposedly trying to grow?

It's not that you're trying to GROW aerobic bacteria, it's that you want to keep them alive...which can't happen if you're injecting chlorine to every flush 'cuz chlorine doesn't discriminate.


Treatment devices are designed to discharge treated waste overboard...that's the whole point of having one--to avoid the need to store toilet waste in a tank. So why have you directed your Saniloo to discharge into the tank? Why not have a y-valve in the toilet discharge line that provides a choice of discharging via the Saniloo or going into the tank?

I fired up the aerator and got bad smells for a while but that seems to have dropped off considerably this morning - that, or we are used to the smell.

You didn't just get used to the smell. Aerators need to run 24/7 to keep the environment in the tank aerobic. When it sits unused, there's no source of oxygen to create that aerobic condition, and without it the anaerobic (stinky) bacteria thrive. When it's turned on again, it pushes the air in the tank out the vent...initially stinky but gradually the influx of oxygen "turns" the tank aerobic again, eliminating the odor. And it works this way regardless of whether the toilet uses sea water or fresh.


--Peggie

Could you use a 12v bait tank aerator? Sweettank seems kinda pricey!

 

[Bacchus]

Could you use a 12v bait tank aerator? Sweettank seems kinda pricey!

You Betcha!
See Holding Tank Aeration project at https://dkloeber.wixsite.com/bacchus/projects-pg-2

Only change I made was to change out the copper tube to PVC. I'm not convinced that it even needs a diverse stream of bubbles - a single stream should work OK in my opinion. That assumption is based on the fact that adequate venting to the surface of a tank works without any bubbling action and even a single stream of bubbles has to help the oxygenation IMO

The fish tank bubbler was <$40 including a $5 2YR extended warranty. My low cost DIY bubbler has been in operation for 6 seasons now without a problem. I would still like to find & try a simple lo cost timer that would allow adjustable on/off times in the neighborhood of 5-10 mins every hour but the continuous operation for 6 seasons hasn't been an issue so annual cost even if replacement was needed is around $5 / yr - cheaper than treatment chemicals! I still use NoFlex (belt & suspenders and for tank "cleanliness") but plan to follow Ted - OC Diver - lead to switch to bulk sodium percarbonate when my supply runs out.

 

[HeadMistress]

So it makes me wonder why it hasn't really been an issue for the previous 4 years we have not been using the air pump?
The only thing that has changed recently is using salt water assist for the flush.

Maybe not the only thing... Odor is a result of anaerobic conditions, regardless of whether the flush water is fresh or sea water and too many people who have sea water toilets have odor-free tanks for sea water to the culprit. If the vent was allowing enough air exchange to prevent odor before, there's a good chance something is preventing it from doing so now....There may be a partial blockage--buildup due to tank overflow, an insect, or just dust, salt air, pollen. All of which is one of the reasons to replace the "vent" thru-hull (designed to keep sea water out of fuel and fresh water tanks) with an open bulkhead or "mushroom" thru-hull that'll let you put a hose nozzle against it to backflush it every time you wash the boat and/or pump out. At the very least, clean out the thru-hull...use a screwdriver blade, ice pick--whatever works. A full tank can just splash enough in heavy seas to create a buildup at the other end of the vent line and/or vent fitting on the tank that restricts the air exchange.



--Peggie

 

[Swfla]

You can buy high output air bubblers for home aquarium use. They are 120v and can have two diaphragms for true dual output. It didn't buzz like the cheap bubblers do. I used it on my fishing skiff bait well with a $50 square wave inverter. As to why it only smelled bad after many years, it could be a combined reaction of several things you ate. Just think about how asparagus still retains certain characteristics after digestion. Cheers.

 

[DDW]

Curious about the bubbler and sodium percarbonate. Isn't that an oxidizer that kills the bacteria? Aren't these two methods defeating each other?

 

[Bacchus]

Curious about the bubbler and sodium percarbonate. Isn't that an oxidizer that kills the bacteria? Aren't these two methods defeating each other?

No problems using both last 6 seasons. Amount of sodium percarbonate is small. Best daily in small doses. But oxygen is what you want for aerobic bacteria so I don't see where an oxidizer would be bad.
If oxygen kills bacteria it must be the anaerobic variety but I'm no expert in the biologic arena other than some casual reading. I do believe one of the applications for bulk sodium percarbonate is sewage treatment but not sure of the specifics.

 

[Simi 60]

.There may be a partial blockage--buildup due to tank overflow, an insect, or just dust, salt air, pollen. All of which is one of the reasons to replace the "vent" thru-hull (designed to keep sea water out of fuel and fresh water tanks) with an open bulkhead or "mushroom" thru-hull that'll let you put a hose nozzle against it to backflush it every time you wash the boat and/or pump out.

That's what we have in the hull side now
I'll stick the deck wash nozzle in and give it a blast

A full tank can just splash enough in heavy seas to create a buildup at the other end of the vent line and/or vent fitting on the tank that restricts the air exchange.



--Peggie.

And we did have full tank and rough water a while back when the macerator pump died so that could be it

Thanks

 

[Bacchus]

Curious about the bubbler and sodium percarbonate. Isn't that an oxidizer that kills the bacteria? Aren't these two methods defeating each other?

After thinking about this more and checking in the technical sense there are many oxidizers including chlorine, bromine, bleach, and acids that may very well kill bacteria. Sodium percarbonate in the presence of water releases oxygen, water and sodium carbonate. So I'm thinking what we are benefiting from, regarding smell, is the release of oxygen that is not necessarily the case with other oxidizers.

 

[Comodave]

After putting the aerator in a previous boat we never added any chemicals to the tank for 8 + years and never had any smells or issues. We put one in our current boat and have not added any chemicals but with the virus have not really been able to use the boat much this summer so not sure how it will turn out.

 

[DDW]

After thinking about this more and checking in the technical sense there are many oxidizers including chlorine, bromine, bleach, and acids that may very well kill bacteria. Sodium percarbonate in the presence of water releases oxygen, water and sodium carbonate. So I'm thinking what we are benefiting from, regarding smell, is the release of oxygen that is not necessarily the case with other oxidizers.

Not a chemist so I'm hoping someone like Peggy will chime in with knowledge on this. I don't know the answer, but thought sodium percarbonate was a disinfectant of sorts. It decomposes into hydrogen peroxide is my understanding.

 

[Bacchus]

Not a chemist so I'm hoping someone like Peggy will chime in with knowledge on this. I don't know the answer, but thought sodium percarbonate was a disinfectant of sorts. It decomposes into hydrogen peroxide is my understanding.

Im no chemist either but that's consistent with my understanding. From Wiki...

"Dissolved in water, sodium percarbonate yields a mixture of hydrogen peroxide (which eventually decomposes to water and oxygen), sodium cations Na+ , and carbonate CO2− "

My thought is that the hydrogen peroxide isn't very stable and breaks down fairly quickly into H2O & O2. All I know for sure is it works for eliminating odors and tank cleaning (likely helped by the NaCO2 which is washing soda - a laundry "enhancer".

 

[catalinajack]

I recently put some sodium percarbonate in my open shower sump that was black with some sort of thin scum. A day later the portion of the sump that was immersed in water became as white as any white I have seem. My sump has no odor. I did have to remove some hair from the base of the pump but it really wasn't much considering it was the first time I have done since purchasing the boat 6.5 years ago. I will soon be disabling the float switch, filling the sump to the brim, and treating all the surfaces to a sodium per bath.

 

[catalinajack]

Follow-up - I filled up my shower sump with water earlier this evening and added about two tablespoons of sodium percarbonate. Went back 20 minuutes later and found the water bubbling away with a residue on the surface. I will report back tomorrow with the results.

 

[Joe Pica]

We had a Groco sweet tank system on our N-37 with a 120+ gal holding tank that was mounted directly under the master. The tank was fiberglass and had 3 chambers in it separated by baffles with mouse holes (two baffles). First, the system (pump and resulting bubbling) was noisy enough to heard when in bed as it was directly under our heads. The air down tube into the tank was only in the chamber at the forward end of the tank. Unless there was circulation between the chambers, only the forward chamber was being aeriated. The down tube was a bronze/copper alloy and the tank contents quickly corroded it. I've since heard Groco has changed to plastic down tubes. Also, the tank did not have adequate venting as it inly had one 1/2" vent hose on one side. So I installed a second vent and enlarged both vent hoses from 1/2" id to 3/4" to better permit cross flow ventilation. The extra venting help immensely as I had discontinued the noisy nonfunctional sweet tank pump. I also began using an agricultural manure pit digestant (Gempler's) as an additive as it was very inexpensive and worked the same as Norflex. I had no further issues with smell and pump outs were quick and uneventful.

 

[Vinny]

We use a Type II MSD unit. It just breaks everything down and puts it overboard, or to the holding tank if in a no discharge zone.

I add “bugs” to it once a month to keep it thriving... works super.

https://www.envmar.com/pdf/TheMSD.pdf

You can put the same bugs in the holding tank along with the air pump/bubbler.

Good bacteria growth doesn’t stink like bad bacteria. The good bacteria grows on the waste surface in the waste tank, and will block the smell some what.

Chlorine and heavy loaded phosphate cleaners will kill the good bacteria.

The MSD (marine sanitation device) runs the treated waste through a clarifier (PVC tube) with chlorine tablets in it on it’s way to the overboard to kill off the active bacteria before going overboard.

 

[HeadMistress]

The tank was fiberglass and had 3 chambers in it separated by baffles with mouse holes (two baffles).

Mouse holes in a half wall might work ok to baffle a water tank, but not to baffle a waste holding tank...even the slightest clog in one of the mouse holes would seriously negatively the ability to pump out the blocked "chamber" and make it impossible aerate the entire tank. Baffles should have been 1-2" off the bottom of the tank in all 3 chambers.

Vinny wrote:
Good bacteria growth doesn’t stink like bad bacteria. The good bacteria grows on the waste surface in the waste tank, and will block the smell some what.

Not quite. When organic material breaks down aerobically (oxygenated) it generates CO2 which is odorless. It only generates toxic smelly gasses--hydrogen sulfide and sulfur dioxide along with methane which is odorless--when it breaks down ANaerobically. However without a means of exchanging either types with fresh ar, whether passive via tank vents or actively via aeration, the CO2--which is heavier than air, so doesn't rise--can sit on the surface of the tank contents and "smother" then, turning the contents anaerobic and stinky.


--Peggie

 

[dhays]

FWIW, I installed a tank bubbler very similar to Bachas. I just bought a 12v bait tank aerator and used some 1/2 pvp pipe and fittings and ran it through the 3’ cap at the top of the tank.

It was easy to and all in cost maybe $50 in materials. Somewhere I wrote it up, but can’t find it now.

I have it wired to the same circuit as the shower sump pump. That is left on all the time when we are on the boat and most of the time when we are off it. The bubbler runs 24/7. I have considered using an intermittent timer to cut down on its run time, but haven’t bothered to do it yet. As cheap as the bubbler is, I’ll just buy another if this one dies.

This is the bubbler I bought.

http://www.marinemetal.com/products/12-vt-air-pumps/power-bubbles/item/power-bubbles

 

[Bacchus]

David
Thats the same tank bubbler I used and original is still working fine.

 

[BDofMSP]

David
Thats the same tank bubbler I used and original is still working fine.

I have two 1" vent lines to my tank. Would there be any reason that I couldn't run the air line tubing down the vent line rather than drilling another hole into the tank? It doesn't seem like it would restrict it much, especially since it's forcing air in there.

BD