Sciencemadness Discussion Board - My daughter is breeding flies - and the smell is awful! Help!

My daughter is breeding flies - and the smell is awful! Help!

Twospoons - 29-2-2020 at 18:19

To feed her pet frogs my daughter has taken to breeding flies, which naturally involves maggots swimming in rotting meat. Yummy.

Despite her project being banished to the far corner of my property, some days the smell permeates the entire back yard.

So I'm going to build a negative pressure box for this enterprise, so that I can filter the stink.

I would welcome suggestions on just how to destroy the nasties - activated carbon is the first thing that comes to mind, but i'm unsure how long I could expect it to last. I expect the air flow rate to be on the order of 1 litre per minute or less.

Any chemical suggestions need to be OTC and low running costs.

Please ... help me!

barbs09 - 29-2-2020 at 19:28

Nice! Why not breed something a little less smelly, like meal worms?

Twospoons - 29-2-2020 at 20:24

Meal worms either have too much chitin or too much fat or both - cant remember which.
Black Soldiers would be good, but we haven't managed to breed them yet.

G-Coupled - 29-2-2020 at 22:13

I've independently discovered that 'pancake batter' - milk, eggs, flour etc. seems to act as a fantastic maggot growth medium.

Probably a *lot* less smelly than rotting meat.

Sulaiman - 29-2-2020 at 23:02

A big fan that blows the smell away ?
... towards your neighbours

or
a large water spray/mist that would 'scrub' the air ?

seriously though ...
I'd be tempted to try an axial fan exhausting at the end of a drain pipe filled with diy lumpwood charcoal.
and
investigate less smelly, fly breeding options

Σldritch - 1-3-2020 at 00:03

Depending on the temperature i think acetic acid is your best option. May work to just put a bowl next to the flies or if that is not enough a magnetic stirrer or fan. It should react with the amines from the rotting meat producing odourless amine salts. Could also cause corrosion i guess if steel is near.

B(a)P - 1-3-2020 at 01:10

You could try breeding soldier flies. They feed on vegetable scrapes. If you start a fairly wet compost bin you will likely attack them. It can be odorous, but not rotting meat odorous.
If you must have meat flies, activated charcoal is just charcoal with a large surface area. Get yourself cheap bbq charcoal and break it down as small as possible. You could fill a long piece of pipe, think PVC down pipe, with it to maximize contact time, could be done dirt cheap.
Please report back with your selected solution and results.

unionised - 1-3-2020 at 01:24

BBQ charcoal really isn't the same as activated charcoal.

However, it's possibly a good substrate for some other sort of sorbent.
The problem is that there are many different components to the pong.
You can trap out the delightfully named putrescine and cadaverine using some acid- I'd suggest phosphoric since it's strong enough, involatile and hygroscopic.

On the other hand, some of the sulphur compounds are likely to be removed by oxidation under alkaline conditions. There's not much point trying to use a stronger base than carbonate because the CO2 in that air will convert it to carbonate anyway.
Washing soda is cheap.

One counterintuitive option would be to pass the polluted air through a compost heap. Those volatile organics are food for other bugs.
And you could try UV/ ozone.

andy1988 - 1-3-2020 at 01:27

Black soldier flies are nice, I tried them but chickens broke the netting to get the flies and I lost them all. Fun experiment.

Consider in your sewage system, how water traps are used to keep the bad odors out of the house. You could pump air from your negative pressure box into your sewage system, behind the water trap. As simple as running a hose through the toilet, or redoing the plumbing under the sink. I'm not sure how well this would work out I have not tried it, but read the website of a man who did (context was getting rid of chemistry odor). He had nice diagrams/photos, but I can't find his website again.

You may enjoy reading on this wet scrubber too, but too expensive to run...

B(a)P - 1-3-2020 at 01:50

Quote: Originally posted by unionised

BBQ charcoal really isn't the same as activated charcoal.

However, it's possibly a good substrate for some other sort of sorbent.
The problem is that there are many different components to the pong.
You can trap out the delightfully named putrescine and cadaverine using some acid- I'd suggest phosphoric since it's strong enough, involatile and hygroscopic.

On the other hand, some of the sulphur compounds are likely to be removed by oxidation under alkaline conditions. There's not much point trying to use a stronger base than carbonate because the CO2 in that air will convert it to carbonate anyway.
Washing soda is cheap.

One counterintuitive option would be to pass the polluted air through a compost heap. Those volatile organics are food for other bugs.
And you could try UV/ ozone.

Thanks for calling me out on that. I thought AC was charcoal treated with steam to increase surface area?

Tsjerk - 1-3-2020 at 03:35

I heard a story about a guy growing marijuana getting caught because the neighbors smelled the air he was blowing into the sewage when the were unclogging something

I think the sewage idea is a good one!

wg48temp9 - 1-3-2020 at 05:19

Quote: Originally posted by Tsjerk

I heard a story about a guy growing marijuana getting caught because the neighbors smelled the air he was blowing into the sewage when the were unclogging something

I think the sewage idea is a good one!

Blowing smelly air into the sewer system is probably illegal and there is a good chance it will exit via your neighbour's roof vents or your own roof vent.
Probably not a good idea.

unionised - 1-3-2020 at 05:19

Quote: Originally posted by B(a)P

Thanks for calling me out on that. I thought AC was charcoal treated with steam to increase surface area?

It is.
And BBQ charcoal is typically treated by being compressed to increase the density- especially for briquettes.
So they are really not the same thing.
The BBQ coal may work a bit, but not for long.

Harristotle - 1-3-2020 at 05:20

So, the off smells are likely to be cadaverine or putrescine, aliphatic amines.

A broad area dish, with maybe 100cm^2 or more surface area of citric acid might help. The amine becomes protonated, and, ahem, no longer "flies". This may reduce or mitigate odour. Could the vents to the box be covered with a cloth dipped in citric acid (I am thinking of something like a Coolgardie safe)?

Just a couple of thoughts.

Cheers,
H.

Tsjerk - 1-3-2020 at 05:37

Quote: Originally posted by wg48temp9

Quote: Originally posted by Tsjerk

I heard a story about a guy growing marijuana getting caught because the neighbors smelled the air he was blowing into the sewage when the were unclogging something

I think the sewage idea is a good one!

Blowing smelly air into the sewer system is probably illegal and there is a good chance it will exit via your neighbour's roof vents or your own roof vent.
Probably not a good idea.

Roof vent? The system I know isn't vented anywhere until it reaches the sewer plant.

wg48temp9 - 1-3-2020 at 06:22

Quote: Originally posted by Tsjerk

Quote: Originally posted by wg48temp9

Quote: Originally posted by Tsjerk

I heard a story about a guy growing marijuana getting caught because the neighbors smelled the air he was blowing into the sewage when the were unclogging something

I think the sewage idea is a good one!

Blowing smelly air into the sewer system is probably illegal and there is a good chance it will exit via your neighbour's roof vents or your own roof vent.
Probably not a good idea.

Roof vent? The system I know isn't vented anywhere until it reaches the sewer plant.

In Florida and in the UK the sewer pipe of houses have vents. They are required to stop the U bends in toilets and sinks from emptying.

I checked a few pics of dutch houses that showed the roof. They all had what looks like sewer roof vents.

[Edited on 3/1/2020 by wg48temp9]

Twospoons - 1-3-2020 at 12:25

Thanks for the suggestions. The sewer option is a no-go. As pointed out, the sewer lines have roof vents to prevent a pressure lock draining the u-bends and allowing the sewer air inside.
I have phosphoric and oxalic acids handy. I'll set up a bubbler with one of those and see if thats sufficient to take out the worst smells.
The "pancake batter" idea is interesting - we'll have to try that one.

Again - very grateful for all the suggestions.

Tsjerk - 1-3-2020 at 13:18

Quote: Originally posted by wg48temp9

I checked a few pics of dutch houses that showed the roof. They all had what looks like sewer roof vents.

[Edited on 3/1/2020 by wg48temp9]

That doesn't look like anything I have ever seen, maybe someone else from North West Europe could comment? What I have here is all drains locked from the sewer with U bends. During heavy rain they can overflow, but that rarely happens. I never saw it at least.

Edit: I'm sure I've never seen a roof vent on any house in the Netherlands and I've lived in a couple.

[Edited on 1-3-2020 by Tsjerk]

mayko - 1-3-2020 at 15:24

I don't know if your fly species will take to it, but for drosophila we use a medium that's basically cornmeal, yeast, and water. Here's a typical recipe:

https://bdsc.indiana.edu/information/recipes/bloomfood.html

Syn the Sizer - 1-3-2020 at 17:33

Quote: Originally posted by Tsjerk

Quote: Originally posted by wg48temp9

I checked a few pics of dutch houses that showed the roof. They all had what looks like sewer roof vents.

[Edited on 3/1/2020 by wg48temp9]

All houses need a vent for their pluming to work properly, usually out the roof. In Canada its part of our building code and I am sure most other places. When a full sink drains, or a toilet flushes the air in the pipes need to go somewhere, or your stuff won't drain properly. Its not an issue when just running water and it going down the drain, same concept as trying to empty a bottle of water by holding it upside down or just tipping it.

woelen - 2-3-2020 at 00:02

Our house has no sewer roof vent. I think that there are vents somewhere in the sewer system itself, not in the houses, but somewhere downstream.

wg48temp9 - 2-3-2020 at 13:04

From wiki https://en.wikipedia.org/wiki/Drain-waste-vent_system

"In modern plumbing, a drain-waste-vent (or DWV) is part of a system that allows air to enter a plumbing system to maintain proper air pressure to enable the removal of sewage and greywater from a dwelling. Waste is produced at fixtures such as toilets, sinks, and showers. As the water runs down, proper venting is required to avoid a vacuum from being created. As the water runs down air must be allowed into the waste pipe either through a roof vent, or the "drain waste vent." (or DWV)"

The vent does not have to be in roof. In some houses its external on an external wall. To work correctly the vent must be upstream of the flow not down stream. It is possible to replace the vent with a one way valve that only allows air into the pipe but not out of the pipe. In the diagram the drain on the left side of the main vertical pipe is fitted with such valve.

In some bodged systems with no vent or the vent in the wrong place when the bath is draining or the toilet is flushed the sink gurgles.

PS: What happens without the vent the water flow down the sewer forms a Sprengel vacuum pump that can suck the water out of other u bends, that generates the gurgling sounds.

[Edited on 3/2/2020 by wg48temp9]

SWIM - 2-3-2020 at 14:00

Thank god this is a project for feeding pets.

When I read the tittle I was afraid it was a hygiene issue.

I second the suggestions that you look into less stinky alternate foods.

Maybe fruit flies would have decent nutrition? I'd much rather have a bucket of rotting plums in my yard than a bucket of week-old carnitas.

And be sure to warn her not to let anybody put lead shot in her frog before a jumping contest.

Twospoons - 2-3-2020 at 17:03

We started with fruit flies, but they're just not big enough now. Wax moths are a possibility, but it been difficult to get a good colony going.
There will be no jumping contests or anything of that nature! These frogs were rescues from a petshop with a tank full of dying tadpoles. Out of the seven survivors, 3 have leg deformities as a result of the fungal infection that was killing all the tadpoles.

My daughter also rescues ducks - raising lost ducklings, fixing the injured ones, providing meds to the sick ones. She gives them names and sees the same mothers come back every year to raise their brood in our back yard.

j_sum1 - 2-3-2020 at 17:44

What a cool daughter you have.
(The monster in me wants to feed the frogs to the ducks but we have our favourite bits of the food chain that we want to promote for... well, arbitrary reasons involving cuteness.)

I will be in the homeland in a couple of weeks.: just passing through for the weekend for a family event. IIRC you are in the South Island so I won't be going near you. But if I have that detail wrong send me a U2U. There is a chance of a drive-by.

clearly_not_atara - 2-3-2020 at 17:56

All of these ideas are fine but they may be overkill. You might be able to just get a bucket of antifreeze -- ethylene or propylene glycol are both fine -- and bubble the outgas through that. Hydrogen bonds and all. Bonus points if you can keep it cold.

If that's not enough, then we can start looking at acids/oxidizers/etc possibly as a second stage so it doesn't get used up as fast.

Tsjerk - 3-3-2020 at 05:17

Quote: Originally posted by wg48temp9

From wiki https://en.wikipedia.org/wiki/Drain-waste-vent_system

"In modern plumbing, a drain-waste-vent (or DWV) is part of a system that allows air to enter a plumbing system to maintain proper air pressure to enable the removal of sewage and greywater from a dwelling. Waste is produced at fixtures such as toilets, sinks, and showers. As the water runs down, proper venting is required to avoid a vacuum from being created. As the water runs down air must be allowed into the waste pipe either through a roof vent, or the "drain waste vent." (or DWV)"

The vent does not have to be in roof. In some houses its external on an external wall. To work correctly the vent must be upstream of the flow not down stream. It is possible to replace the vent with a one way valve that only allows air into the pipe but not out of the pipe. In the diagram the drain on the left side of the main vertical pipe is fitted with such valve.

In some bodged systems with no vent or the vent in the wrong place when the bath is draining or the toilet is flushed the sink gurgles.

PS: What happens without the vent the water flow down the sewer forms a Sprengel vacuum pump that can suck the water out of other u bends, that generates the gurgling sounds.

[Edited on 3/2/2020 by wg48temp9]

In the Netherlands no one has a vent, really. As long as the diameters of the pipes are big enough you won't pull a vacuum anywhere and you won't need an open connection to the sewer every other ten meters.

[Edited on 3-3-2020 by Tsjerk]

phlogiston - 3-3-2020 at 08:15

I'm Dutch too, and my house definitely does have a vent on the roof for the sewer.
I've had to repair it once, so I know exactly how the tubing runs from the space under the house, to the roof. My house was built in the early seventies. Maybe different techniques for venting the sewers were used in different areas/times?

unionised - 3-3-2020 at 13:55

Just a thought:
https://www.argos.co.uk/product/5787366

SWIM - 3-3-2020 at 15:03

Ozone sounds like an answer with lower maintenance and operating costs to me.
ozone.jpg - 7kB

So blow the vented air through a box with one of these in it, or maybe even just an ozone bulb as Unionized suggested.

I'd probably try a large container like a 5 gallon bucket so the air is in there for a while with the uvc/ozone generator/whatever else makes ozone.

Twospoons - 3-3-2020 at 16:35

Ozone seems a likely candidate - I have an HV HF source I can test with. I'd build the O3 generator as a glass tube with inner and outer electrodes and pass the waste air directly through the glow discharge to get the benefits of direct ionization, thorough mixing with O3, and UV light.

Corrosive Joeseph - 3-3-2020 at 17:26

/CJ

Growshop.jpg - 11kB

SWIM - 3-3-2020 at 19:37

Hey, if you push that air/ ozone/ maggot stink mixture through a Dreschel bottle full of water you might get ammonium nitrate.

Make nitric acid from scratch, fertilize your garden, whatever.

I've read that Ozone will oxidize ammonia solution to ammonium nitrate, but I've yet to try it out.

At the very least it might retain the ozone long enough to help scrub the air one more time.
It is somewhat water soluble.

OldNubbins - 4-3-2020 at 12:50

What about venting the box through 16-20 vertical ft. of black ABS pipe? You can tuck it up under a tree, the sun will warm the tube and add some velocity to the gasses so they exit well above the area to disperse throughout the neighborhood.

Twospoons - 13-3-2020 at 17:11

I built a 600mm tall bubble tower using 100mm PVC drain pipe with a circular aquarium bubble stone at the bottom. The internal space is filled with rings cut from 25mm PVC conduit, as a means of increasing the residency time of the bubbles.
For the acid fill I used 100g of oxalic acid in 3.5l of tap water. This fills the bubble tower to about 100mm from the top.
Timing the bubbles (by turning the pump on/off) I get a residence time of about 4 seconds.

Testing with a box of breeder flies that are just beginning to smell like week old rubbish bags ...

It works quite well - I can't smell rotting meat at all. There is a faint sulfurous smell, like extremely weak H2S, if I get my nose right up to it.

I would call this a success.
Thanks again for the suggestions, and the interesting discussion on the global variations on sewer plumbing

[Edited on 14-3-2020 by Twospoons]

Tsjerk - 13-3-2020 at 23:36

Nice! I'm interessed in how long it keeps working!

Are you planning on trying different acids? Cleaning acetic acid could be a cheap option.

[Edited on 14-3-2020 by Tsjerk]

Twospoons - 13-3-2020 at 23:58

Oxalic acid is ten bucks a kilo here (NZD) so its pretty cheap. It also doesn't smell. So long as it keeps working I'll keep using it, and I expect the 100g I used in the scrubber will last quite a while.
Its also a surprisingly strong acid - I measured the pH with a cheap chinese meter (of dubious calibration) at 0.5. An online calculator predicted pH 0.6.

Frankenshtein - 19-9-2020 at 13:01

The traps in plumbing are there to prevent the sewer gases from entering the home. Best to leave those alone. You also dont want bugs to infest your plumbing system. That could get extremely expensive.

I think a fan with activated charcoal is a good idea, sometimes laying baking soda around can also remove odors. Raising bugs is best done outdoors. You could maybe create an air tight seal on their container and change out the air outdoors as well.

Oxalic acid is extremely toxic to pets or anyone else that might ingest it. It's what kills when ethylene glycol (antifreeze) is ingested. Ethylene glycol should also not be inhaled, dont let it get hot. Propylene glycol is much safer but I dont know what to say about that. Read MSDS on everything you work with.

[Edited on 19-9-2020 by Frankenshtein]