Picture credit: https://twitter.com/odorfree
It really IS possible to have a completely odor-free system!
You’ve probably read or heard, over and over again, that the key to odor control is the “right” hose, that the “wrong” hose permeates with sewage and causes the system to stink. That’s folklore…a little truth coupled with a lot of misunderstanding. The real key to odor control is in knowing how to incorporate proven sewage management principles—the same ones used in composting and sewage treatment—into the installation of the entire system. What very few people in the marine industry have learned, and why there is so much folklore about odor, is the very nature of sewage itself and how it breaks down, what creates odor and what prevents odor from forming. Once we understood these principles and learned how to apply them to onboard systems, we were able to install systems that are completely odor-free and correct the ones that weren’t. Once you understand it—and it’s so simple!—you can do the same thing.
Marine Holding Tank Odor Solutions
There are two ways to deal with marine holding tank odor: try to reduce it, mask it and contain it after it’s formed, by using chemicals and filters—which has never proven very successful…or prevent odor from forming in the first place.
Sewage contains both aerobic (needs oxygen) and anaerobic bacteria (functions in an airless environment); neither can function in the other’s environment. Why is that important? Because only the anaerobic bacteria in sewage produce foul-smelling gasses! Aerobic bacteria break sewage down, as does anaerobic bacteria—but aerobic bacteria do not generate odor. So as long as there is a sufficient supply of air to the tank and an aerobic bacteria treatment is added to aid that which naturally occurs in sewage, the aerobic bacteria thrive and overpower the anaerobic bacteria and the system remains odor free.
A bio-active (Iive aerobic bacteria) holding tank treatment, such as our own “K.O.”, works with the aerobic bacteria in sewage, eliminating odor, completely emulsifying solids and paper and preventing sludge from forming. Enzymes do little if anything—a brief respite from odor immediately after adding them, then odor begins to build again. Chemical products mask odor with another odor and they kill not only odor-causing anaerobic bacteria, but beneficial aerobic bacteria as well—not good, because the aerobic bacteria are needed in the system to break down and emulsify solids and paper. Otherwise, they only break UP and dissolve them into little tiny particles that settle to the bottom of the tank, along with chemical residue, to become sludge that turns to concrete. Chemicals, unlike bio-active products, are also unwelcome in landside sewage treatment facilities and are especially unappreciated by those living and working near them!
The bacteria in sewage produce a variety of sulfur monoxides and dioxides (which are the malodorous gasses), methane—which has no odor but is flammable—and carbon dioxide, which also has no odor but creates the environment in which the aerobic bacteria cannot function but allows the anaerobic bacteria to thrive. Carbon dioxide does not rise or fall, it is ambient—like the atmosphere, but heavier than air. Without a sufficient flow of fresh air through the tank to allow it to dissipate, it simply lies like a blanket on top of any pool of sewage (whether inside hose or a holding tank) and builds, suffocating the aerobic bacteria and creating the perfect environment for the anaerobic bacteria to take over. The system literally “turns septic” and the result: a stinking boat…or at least foul gasses out the vent line every time the head is flushed.
Importance of Discharge Hoses in Marine Holding Tanks
To prevent this, let’s start with the head: the discharge hose, no matter whether it goes overboard, to a Type I or II MSD, or to a holding tank, should be installed, if at all possible, with no sags or low places where sewage can stand. When a marine head is not flushed sufficiently to clear the hose of sewage and rinse the hose behind the sewage, that sewage sits in low spots in the hose or bits of it cling to the walls of the hose—getting no air, allowing the anaerobic bacteria to thrive and produce their stinking gasses. If sewage stands in a low spot which gets no air in hose which is susceptible to a high rate of water absorption, it will permeate the hose. This is what has given rise to the myth that the “wrong” hose causes odor. Therefore, it’s important to flush your head thoroughly enough to clear the entire hose of sewage and rinse behind it. And when you leave your boat to go home, flush the head thoroughly one last time, this time with fresh water. Until marine holding tanks came along, the hose was the source of most odor, but incomplete flushing was the real cause.