Feeding Wastewater Bacteria
When you think of “nutrients,” what comes to mind? Components of healthy eating like fruits, veggies, and whole grains, right? Well, if you’re bacteria living in a septic tank, the idea of “nutrients” takes on a whole other meaning.
It turns out microscopic organisms like Nitrosomonas, Azospirillum, and Pseudomonas love to nosh nutrients found in tanks and treatment plants. In the right environment, they thrive as they biologically process waste in the effluent.
“Because this is biological treatment to treat nitrogen and wastewater in general, we have to have a certain level of nutrients to support the microorganisms within the system,” says Bill Hensley, senior systems engineer for Orenco Systems®.
The hungry little bacteria don’t necessarily need to be treated like a pet, but they do benefit from a little attention. Here’s how to feed and care for the microbes as they go to work in a septic system.
Phosphorus, sulfur, potassium, magnesium, calcium, iron, sodium, and chloride are some of the nutrients found in wastewater, Hensley says, but nitrogen is the No. 1 nutrient of interest for both the microbes and humans.
Nitrogen is a colorless, odorless, nonmetallic element that makes up about 78% of the Earth’s atmosphere as a stable gas. In its gaseous state, it’s unusable by plants and animals – but it is usable when it’s in one of its other forms, like ammonia, ammonium, nitrite, and nitrate.
“The goal is to get that nitrogen back up into the atmosphere, back into its gaseous form as much as possible,” Hensley says.
To do that, it has to go through the nitrogen cycle, a process that describes how nitrogen is converted from an inert, atmospheric gas into usable forms and back to atmospheric gas.
First, a set of specific, free-living, symbiotic bacteria, including soil microbes like Rhizobia, Frankia, Azotobacter, and Azospirillum, go to work as fixers. They take inert nitrogen gas from the atmosphere and convert it to ammonia and ammonium via a process called nitrogen fixation.
The resulting ammonium is then consumed and turned into nitrite by bacteria called Nitrosomonas. Lastly, bacteria called Nitrobacter transform the nitrite into nitrate, which is readily absorbed by plants. They then use it as their own nutrient source. This whole process is called the nitrification cycle.
As far as caring for them, that job is relatively easy – except when those bacteria get too much food. It’s kind of like Audrey II, who went from a docile houseplant to a bloodthirsty monster in “Little Shop of Horrors:” if the bacteria overeat, they’ll overfeed the plants, which will grow into big problems, like algae blooms, aquatic plant proliferation, and, in some cases, hypoxic zones.
“Discharging excess concentrations of nitrogen at or near waterways can result in algae blooms and excessive plant development,” he says. “What ends up happening is during the night, the algae and plants actually take up oxygen that’s in that water, and they can create hypoxic zones where the fish and the other organisms can actually suffocate.”
This is why it’s crucial that wastewater is biologically and mechanically cleaned and treated before being returned to the soil via drainfield or other form of dispersal.
“… It’s not like we’re getting rid of nitrogen,” Hensley explains of the treatment process. “We’re transforming it into a state that’s no longer an environmental threat. When we think about wastewater treatment, using that word ‘wastewater’ is a misnomer. It’s really a resource.”
Listen to the “Make It Clear” podcast for Bill Hensley’s complete interview entitled, “A Primer on Nutrients in Wastewater” on your favorite platform. For more information about Orenco Systems and its complete line of wastewater treatment and dispersal solutions, visit Orenco.com or call 800-348-9843.