Formaldehyde: septic system killer ?


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Old 02-17-15, 03:06 AM
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Formaldehyde: septic system killer ?

Hi -- I'm a greenhorn, just joined. I couldn't find a thread that addressed my issue, so I'm starting this new thread. I apologize for the length of this post, but I want you to fully understand the issue.

My wife and I have an off-grid property. We use a couple of portable toilets. We had a septic field installed with two intake pipes: one (capped underground at present) is for the sewage pipe of a future cabin, and the other is a stand-pipe into which we can dump the tanks from our portable toilets.

For the two years we've been using the portable toilets, we've been adding an odor-control product to the holding tanks. It's called Thetford Aqua-Kem. It works beautifully, completely masks the smell, and has a pleasant fragrance. Whenever I dump a 5-gallon holding tank, I add an extra 15 gallons of clean water to reduce the concentration of waste in the septic tank.

The only problem: Aqua-Kem contains formaldehyde. There are lots of articles that decry the dangers of using this horrible, monstrous, deadly toxin in your black-water tanks, whether in RVs, boats, or portable toilets. On the other hand, Thetford puts out literature that says Aqua-Kem is safe and the formaldehyde is 100% biodegradable, if the product is used properly (by "properly", they mean donít use too much, and donít dump your tank until it's full). At first I was baffled by these two conflicting points of view.

Then I found a site that said formaldehyde was only dangerous if used at strengths greater than recommended by the product manufacturers, or if tanks were dumped when only partly full (i.e., with enough chemical for a full tank, but not enough waste to dilute the chemical in the holding tank). One scientific study showed that the bacteria-balance in the septic tanks at Virginia state parks could be overwhelmed by a heavy surge of users using formaldehyde odor-control products, but that the bacteria in the parks' septic systems had rebounded and normalized after only two or three days.

I'm no expert, but what I THINK I've been reading is a lot of scare-propaganda based on EPA findings done in the '70s, showing that a heavy load of formaldehyde would kill the bacteria in a septic system, and could destroy the entire drain field, and contaminate ground water. All absolutely true, BUTÖif used correctly, these products don't contain enough formaldehyde to significantly harm your septic system, and the bacteria "will rise again".

Our septic tank has two chambers, 500 gallons each. In the two years we've been using the portable toilets, I've dumped full tanks about 40 or 50 times (we're only there part time, spring-summer-fall). With all the extra water, I may have dumped close to 1,000 gallons, so the two chambers are now approaching full...for the first time, liquid effluent is soon going to be flowing down to the drain-field. Thetford suggests using four ounces of Aqua-Kem for a 5-gallon tank. I use about three ounces. I have gone through almost one gallon of Aqua-Kem.

Do any of you know if I have anything to worry about? Barring the digging up of my holding tank and taking a sample of the goop to a testing lab, how do I determine the health of the bacteria in my goop? If the concentration of formaldehyde has been sufficient to harm the bacteria in my system, what would you suggest as an approach to restore it to good health? Should I just bite the bullet and have my septic tank pumped?
 
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Old 02-17-15, 05:52 AM
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Welcome to the forums! Any type chemical introduced into your septic system can kill the good bacteria needed for dissolution of waste. Formaldehyde, bleach, harsh drain openers, and the like should not be placed there. Your product has already done the job of dissolving the waste. Introducing it to an operating septic tank could have adverse effects on it.

All septic tanks will be "full" at optimum usage. It is the only way the water can get into the drain field. It won't overflow if the drain field is operating properly. I would have someone check your tanks visually to see if you have a dead system and possibly pump it. If you continually use it to dump chemical laden waste, then regular inspection and pumping would be advised, as it is now a "holding" tank, and not part of a septic system.
 
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Old 02-17-15, 09:01 AM
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Formaldehyde is used in a camper or portable toilets for the exact reason you don't want it in your septic tank. Your septic and and leach field system functions on biological activity. Formaldehyde is added to portable toilets to stop biological activity to help limit the smell.

You might want to have your tank pumped but it won't help if you continue to use formaldehyde. The tank can accommodate some. More is worse and how much you can get away with depends specifically on your system and what you're putting in it.
 
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Old 02-18-15, 05:43 PM
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Thank you...

My heartfelt thanks to both Chandler and Pilot Dane -- your posts are clear and infomative. You both clearly feel that formaldehyde is a chemical best left out of a septic tank.

I can appreciate your viewpoints, and as I said in my initial post, I've found plenty of references that support you. I may yet come around to agreeing with you. However, after discussion with my wife (read: "the boss"), I am still in quandary-mode. She is very happy with the odor-killing properties of Aqua-Kem blue. We tried the green, and it didn't do the job nearly as well. I am loath to go to another product if I can be convinced that Aqua-Kem blue can be used safely in my system.

I'm doing some in-depth checking, and I'm going to pull a sample from my septic tank to have the bacteria tested.

Here's what I've found so far:
- Formaldehyde does kill bacteria, but it won't kill ALL bacteria in waste unless it is maintained at a high concentration. Additionally, it can be broken down into dangerous byproducts, methanol and carbon monoxide, BUT ONLY AT VERY HIGH TEMPERATURES. At temperatures found in waste water holding tanks (say, from 32-110 degrees F), when formaldehyde biodegrades it breaks down into carbon dioxide and water, both harmless.
- Aqua-Kem blue is 37% formaldehyde, but this percentage goes down on contact with human waste. The natural bio-degradation of formaldehyde is increased by several factors: high waste concentration, temperature, and length of time held in the tank. The concentration of waste in an RV's holding tank is about 10-to-15 times higher than waste flushed from a home toilet, and the waste concentration in the tank of a portable toilet is much higher even than that from an RV. We don't dump until the tank is full, which takes 5-to-6 days. We only use the toilet in warmer months. Thus, the amount of active formaldehyde in our porta-potty's tank will be greatly reduced by the time it is dumped.
- At least some of the tests showing formaldehyde to be bad for septic systems were performed using very high concentrations of formaldehyde (300 ppm or greater). These tests do not reflect conditions resulting from normal use of Aqua-Kem. I'd like to see some tests run with more reasonable dilutions, say 50-to-100 ppm.

While we're at the "ranch", every 5 or 6 days or so I dump 20 gallons -- one full 5-gallon porta-potty tank and an extra 15 gallons of water. Each tank-load starts out with 3-to-4 ounces of Aqua-Kem...say 3.5 oz. At 37% formaldehyde, that's 1.3 oz of formaldehyde. By the time I dump, that should have dropped to about 0.3 oz, but for the sake of argument, let's say it's still 0.6 oz of active formaldehyde. Once dumped into the 1,000-gallon tank, that would equate to less than 5 ppm. From what I've read, a healthy septic system can easily handle concentrations of formaldehyde of 100 ppm or greater. Surely, 5 ppm should be no problem, once I am assured that my system is healthy.

My last point it this: our septic tank is left alone throughout the winter (mid-Nov through mid-Apr). The ranch is so cold, the holding tanks would freeze. I'm guessing that this gives the system a good long time to recover. So I think I'm OK to continue to use Aqua-Kem blue, carefully. But I'll leave another post when I've finished doing my homework, and testing.
 
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Old 02-18-15, 05:54 PM
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As long as you are using your septic tank as a holding tank until it is pumped, it should be OK. You absolutely do not want solid waste matter to enter the drain field. We used "blue" water in aircraft, and once it is extricated, solid waste has been broken down to liquid. It is not aerobic, however as all the bacteria has been broken down. It may be a much higher concentration of chemicals than what you are using. Keep us informed.
 
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Old 02-19-15, 01:58 PM
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It sounds to me like you don't really understand how septic systems work. You seem to think that it works like a bigger holding tank than what is in an RV. Like folks are trying to tell you, they are the complete opposite.

The only way a septic system can "recover" is by using it properly. That means flushing plenty of untreated poop down the toilet and not much else. Inactivity doesn't help it, in fact it hurts it.

Dumping in 15 gallons of water will hurt it more than it helps it. In fact, lots of people prefer to drain their washing machine elsewhere rather than dilute the biology working in the septic tank with a rush of water.

It would be cheaper for you to switch to compost toilets or the incinilator or something like that because to are not using the septic system properly now and until you install flush toilets, you won't be. Or you can do what most people do, drive into town and dump the tanks into a gas station toilet on city sewer.

Drain fields are expensive to replace.
 

Last edited by Vey; 02-19-15 at 02:24 PM.
 

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