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Holding Tank Treatment Systems

by Peter Gnemmi

We dry camp often with our 5 kids (ages 2 months to 10 years) in our Rockwood 1280XL Pop-Up. Having held my nose at emptying our Porta-Potti(R) and gray water tank upon returning home, with chemistry and biology degrees in my past, I was interested about how commercial deodorizers worked.

I called the Thetford folks and their chemist, Mary Burrows was so helpful and detailed in answering my questions, that I figured this information would be nice to share with the rest of you. This information was in a file I uploaded February 16, 1994. Things sort of snowballed then, and I faxed every one of the companies in a national directory of RV suppliers, plus some that weren't listed, and this paper is the result of our communications.

Some chemical compounds smell bad (an old sneaker) and some smell good (roses). Most bad waste materials' odors come from compounds containing nitrogen and sulfur. Following, are the main ways deodorizers work:

1. Change the odorous compounds to less volatile and odorous compounds. Chemicals that react with the waste like formaldehyde are used up depending on how much waste you have. Enzymes are catalysts and thus facilitate, but aren't used up by the chemical reactions.

2. Chemicals like quaternary ammonium chlorides kill the bacteria that change waste compounds into more odorous ones. These same chemicals also work by mechanism #1 if their concentrations are high enough.

3. Bacterial systems are made up of good bacteria (as opposed to those mentioned in #2) that break down the waste material into less smelly and harmful chemicals. This is a mechanism similar to that employed in sewage treatment plants.

4. Perfumes cover odor up with a stronger, more pleasant smell.

5. Surfactants are soaps that can increase the degree of penetration of the active ingredient.

6. Some products have other ingredients such as lubricants, seal conditioners, etc. that help the mechanical operation of your waste system.

Glutaraldehyde, Formaldehyde, and Paraformaldehyde can be grouped as ALDEHYDES. These are strong chemical reducers and actually "pickle" waste. Formaldehyde is used to preserve animals and biopsy specimens.

With the whole family of QUATERNARY AMMONIUM __s , the "__" can be salts, chlorides, compounds, or complexes. A quaternary ammonium chloride you may be familiar with is the usually blue liquid your barber keeps his combs in, benzalkonium chloride.

ENZYMES are what make your body work. There isn't a chemical reaction that keeps you or for that matter, any living thing alive, that isn't mediated by one kind of enzyme or another. Enzymes are usually substrate-specific. In other words a certain kind of enzyme breaks down a certain kind of chemical and none other. For instance, the enzymatic products that are intended to break down toilet tissue only contain a single enzyme that breaks down cellulose (a cellulase). There are enzymes that break down fats and oils (lipases), proteins (proteases), etc, each specific to its particular substrate. The general application enzyme products are usually blends of different enzymes, each doing its own job to break down different parts of the waste.

AEROBIC AND ANAEROBIC BACTERIAL SYSTEMS are how nature breaks down waste products. Bacteria can be good (non-disease and/or non-odor causing) or bad (cause disease and/or odors), aerobic (breathe oxygen) or anaerobic (don't need oxygen). Aerobic bacteria would work well as you're driving down the road, mixing air into the tank as the contents slosh around. If you are stationary and the contents remain undisturbed for a while, the anaerobic bacteria work better down below the surface. Good bacteria keeps the bad bacteria under control by competing with it.

Product Active Ingredient Chemical Mechanism

RV-Trine natural enzymes digests waste and tissue
Instant Deodorizer phenolics breaks down wastes and antibacterial
Travel-Jon quaternary am- kills bacteria and reacts with waste
monium chloride products to reduce odor
Bio-Green enzymes,aerobic & break down & digest waste & tissue
anaerobic bacteria
Potty-Chem quaternary am- kills bacteria and reacts with waste
monium compounds products to reduce odor
Sure & Easy quaternary am- kills bacteria and reacts with waste
monium chloride products to reduce odor
(in development) enzyme based breaks down waste and odorous chemicals
NFB Products quaternary am- wets and penetrates waste, allowing the
monium compounds quaternary ammonium to kill bacteria
Kilodor natural aerobic bacteria devour & enzymes break down waste
bacteria & enzymes materials & odorous chemicals
Monochem T-5 paraformaldehyde reacts with nitrogenous and sulfur compounds
forming less volatile and odorous compounds
Monochem T-5NF quaternary am- kills bacteria and reacts with waste
monium complex products to reduce odor
Liquid Gold quaternary am- neutralizes odor molecules, inhibits the
monium compounds growth of fecal coliform bacteria

Tank Deodorant
Liquid formaldehyde reacts with nitrogenous and sulfur compounds
Solid paraformaldehyde forming less volatile and odorous compounds
Instant Fresh
Toilet Treat- quaternary am- kills bacteria and reacts with organic mate-
ment monium Compounds ials to reduce gassing and associated odors
Aqua-Kem formaldehyde reacts with nitrogenous and sulfur compounds
forming less volatile and odorous compounds
CampaChem formaldehyde not as concentrated or effective as Aqua-Kem
Aqua-Kem bronopol reacts with nitrogenous and sulfur compounds
Green forming less volatile and odorous compounds

Aqua-Zyme natural enzymes enzymes break down waste compounds, minimal
deodorization non-toxic

Gray Water glutaraldehyde reacts with nitrogenous and sulfur compounds
Odor Control forming less volatile and odorous compounds

RM 41 Liquid aerobic & anaerobic biological system in which bacteria consume
RM 41 Solid bacteria and break down odor causing chemicals
Potty Toddy quaternary am- kills bacteria and reacts with waste
monium salt products to reduce odor

I tried to make the information in this chart as complete and accurate as possible. It mostly reflects the information given to me by the manufacturers. If I wasn't sent adequate information, I referred to ingredient lists on labels and MSDS data sheets, and drew my own conclusions. Also, products with ingredients that weren't listed either on the product's container or on its MSDS data sheets, because it was a proprietary secret, aren't listed. Chemicals that the government doesn't consider hazardous, don't have to be listed on labels. Some obscure chemicals that are hazardous, aren't on the government list because they are too new or not used by enough companies to attract attention. For this reason, I never buy anything unless I have some idea of what's in it (and what it will do to my health) and neither should you. Imagine yourself at the emergency room after your kid downs a bottle of this mystery stuff, the doctor having to guess what it was. Don't get me started...

As you noticed, aldehydes, bronopol, enzymes, quaternary ammonium compounds, and bacterial systems are present in more than one manufacturer's products. Amounts of active ingredients, other ingredients, shelf life, and different fragrances will provide different levels of deodorization with different waste compositions. Also, other additives such as detergents or lubricants can make one product more effective in your particular system.

Aldehydes and quaternary ammonium compounds will deactivate both biological and enzymatic products. Bacterial systems are particularly sensitive to even trace amounts of aldehydes and quaternary salts and require very thorough multiple rinses and neutralization of those chemicals in the holding tanks before using products that employ good bacteria.

There are automatic systems, by Thetford, Land & Sea, Fantastic Vent, and others that dispense a measured amount of the active chemical with each flush. This keeps handling of chemicals to a minimum. They also make an appropriate concentration easier to attain than manual systems.

ALL HOLDING TANK WASTES should be dumped into an appropriate station, even if you use an environmentally safe treatment system.

BIOLOGICAL & BACTERIAL SYSTEMS are environmentally harmless, non-toxic, biodegradable, and safe. The bacterial systems can actually help septic tanks because they can repopulate them with good bacteria.

ENZYME SYSTEMS, because they break down chemicals, can cause skin and eye irritation, but are otherwise readily biodegradable and safe.

QUATERNARY AMMONIUM COMPOUNDS, due to their antibacterial properties, can affect a septic tank. These can also irritate skin and eyes and aren't as biodegradable as the two above.

FORMALDEHYDE, GLUTARALDEHYDE,and PARAFORMALDEHYDE, are very strong reducing agents thus contact with skin and eyes is to be avoided. Formaldehyde and paraformaldehyde must be listed as probable carcinogens on MSDS sheets. They will affect septic tanks at concentrations above 100 parts per million (0.01%) and are toxic in their concentrated state. In a full holding tank, at the recommended concentration, aldehydes are somewhat less hazardous. They're still nasty chemicals though.

LYSOL is based on phenolic compounds (carbolic acids). These weak acids are strong antibacterials and pretty corrosive, although at their diluted states in a holding tank, the corrosiveness may not be a problem.

PINE-SOL is 19.9% active ingredient, pine oil. It has good antiseptic properties and a strong, pleasant smell as it comes in the bottle. As an organic solvent related to turpentine, it would dissolve and suspend fats and oils. It probably would have the same corrosive effects on rubber and plastic that turpentine has. There are reports that rubber seals are affected by pine oil in the matter of a day and make valves, etc. difficult to operate.

CLOROX (sodium hypochlorite) is one of the worst chemicals to use. It chews up rubber seals. Mixing a strong oxidizer and reducer together like chlorine and formaldehyde can even cause explosions! Better to have a nice awning or good food to attract attention at your campground!

There are some companies that, despite multiple faxes and phone calls, refused to give me any information of any kind. Some were nice about it and some were not. This, in my opinion, bodes ill for any of their customers who have problems with their products and need help. I was VERY tempted to list these companies in a sort of rogue's gallery, but won't. I figure any unhelpful nationally advertised brands will be conspicuous by their absence. If it seems some company isn't listed that should be, you catch any mistakes, or if you have any further questions, please leave a message on the forum or e-mail.

Any more questions, just leave me e-mail. Peter Gnemmi (This email address is being protected from spambots. You need JavaScript enabled to view it.).