When confronted with new effluent limits, many municipalities feel their only option is to scrap their otherwise adequate lagoon system and replace it with a mechanical treatment process, like an activated sludge, SBR, or MBBR plant. There’s a better option: A lagoon can be upgraded to remove ammonia and phosphorus, treat BOD and solids, and produce an effluent quality as good as a mechanical plant—at a fraction of the cost.Continue reading →
Whether your facility has a lagoon nitrogen (TN, TKN, or TIN) or ammonia (NH3) effluent limit depends on your local environmental regulatory body, your discharge parameters, and if the watershed you discharge to is impaired. So far, most lagoon permits with an ammonia or nitrogen limit restrict only unionized ammonia (NH3), although some (and going forward, potentially more) restrict Total Nitrogen (TN), largely due to the danger of nitrates in groundwater.
This article will present a simplified overview of the difference between lagoon ammonia and lagoon nitrogen and the biological processes of nitrification and denitrification.
Sources of Lagoon Nitrogen
Urine is a primary source of lagoon ammonia.
There are many sources of nitrogen in wastewater lagoons:
Human urea (urine) and fecal matter
Food processing waste
Household cleaning products
Benthal feedback from anaerobically digesting sludge
Nitrogen is present in several different forms in wastewater lagoons:
Organic nitrogen is primarily from urea (urine) but is also present from fecal matter, plant and animal proteins, dead and decaying bacteria and algae. A percentage of organic nitrogen cannot be removed through any biological treatment process.
Ammonia Nitrogen occurs in two forms, NH3 and NH4+. NH3 is a toxic gas and is sometimes referred to as free ammonia. NH4+ is the ionized form of ammonia, or ammonium.
Total Nitrogen, or TN, is the sum of all these forms of nitrogen:
According to Michael Gerardi in his book The Biology and Troubleshooting of Facultative Lagoons, approximately 75 percent of organic nitrogen breaks down to ammonia-nitrogen in the water. Whether it tends more heavily towards the gaseous (NH3) or ionized (NH4+) form depends on the lagoon’s pH. A more acidic solution, towards the lower numbers, favors NH4+. A more alkaline solution, towards the higher numbers, favors NH3. Since most municipal wastewater lagoons typically have a pH in the 6.8–7.6 range, most of the ammonia will be in the form of NH4+. Even if most of the ammonia is in the ionized NH4+ form, there’s still NH3 lurking around that needs to be removed to prevent damage to the receiving waterway.
The Nitrification Process
Once all the organic nitrogen—urine, cleaning products, industrial chemicals, food processing waste, fertilizer runoff—has entered the lagoon, most of it immediately converts to ammonia-nitrogen, or NH3 and NH4+. Now the nitrifying bacteria start their work, converting NH3 and NH4+ into nitrites (NO2) and then nitrates (NO3).
Here’s the recipe, simplified:
(NH3 + NH4+) + O2 + Nitrosomonas bacteria = NO2
NO2 + O2 + Nitrobacter = NO3
In other words, given the proper conditions, including a healthy amount of dissolved oxygen, Nitrosomonas bacteria will consume ammonia-nitrogen and excrete nitrites, or NO2. Then another type of nitrifiers called Nitrobacter convert the nitrites (NO2) to nitrates (NO3).
Nitrifiers convert ammonia to nitrates.
Sounds simple enough, but nitrifying bacteria are picky. They require more DO than BOD consuming bacteria do—up to 5 mg/L. BOD-consuming bacteria also outcompete nitrifying bacteria, so BOD levels have to be reduced to 20–30 mg/L to give the nitrifiers a fighting chance.
Nitrifying bacteria are attached-growth organisms, so they need surfaces to grow on. The more surface area is available in the lagoon, the more nitrifiers the system can cultivate. Plus, nitrifiers are temperature sensitive. The colder it gets, the less they work. A lagoon system may be able to achieve sufficient nitrification during the summer but struggle during the winter.
If your lagoon permit only restricts NH3, you’re done. There is still nitrogen in the lagoon, but it has been converted from toxic ammonia to nitrates.
The Problem with Nitrates
According to a recent article on wateronline.com, drinking water in 49 states is contaminated with nitrates, which can cause health problems, especially in babies. Facilities whose effluent, through discharge or land application, contributes high levels of nitrates into groundwater may have a more restrictive nitrogen permit. Permits that include limits for TN, TKN, or TIN will require an additional step to convert the nitrates (NO3) to nitrogen gas (N2), which is then stripped to the atmosphere.
The biological process of converting nitrates to nitrogen gas is called denitrification. Denitrifying bacteria are as picky as nitrifying bacteria, but prefer different conditions.
The recipe for denitrification is
NO3+ BOD + denitrifiers = N2
Denitrifying bacteria require a low oxygen environment and need soluble BOD. Since there is little BOD remaining after the nitrification process, an external carbon source (such as glycerin or methanol) is added to the reactor to ensure the denitrifying bacteria have enough food. To consume the BOD, denitrifiers require an oxygen source. In the absence of DO, they get it by stripping the oxygen from the nitrate molecules, converting them to nitrogen gas.
Lagoon Ammonia and Nitrogen Removal
Because NitrOx reactors thermally regulate influent, they work in all weather.
Lagoon systems can be upgraded to meet low ammonia and nitrogen effluent limits. Triplepoint’s NitrOx™ Process is a two-stage reactor that optimizes conditions for biological nitrification. Through mixing and aeration, controlling temperature, and maximizing surface area for nitrifiers to grow on, NitrOx ensures rapid ammonia removal in any weather.
To help lagoons meet Total Nitrogen limits, Triplepoint has developed NitrOx+D™, a reactor that optimizes conditions for biological denitrification. NitrOx+D is an anoxic tank added after the NitrOx reactor that supplies surface area, mixing, and carbon to promote rapid nitrate digestion.
Both NitrOx and NitrOx+D were designed to cost effectively retrofit a lagoon to meet ammonia or nitrogen limits while preserving the low maintenance and ease of operation of a lagoon system. By thermally regulating influent, both NitrOx and NitrOx+D work in all climates year round.
For more information on how Triplepoint can help your lagoon meet lagoon nitrogen or ammonia limits, download the NitrOx and NitrOx+D brochures or contact us.
The National Oceanic and Atmospheric Administration (NOAA) has released its annual winter forecast and predicts the likelihood of another year of La Niña conditions. The northernmost portion of the U.S. is expected to have a winter that’s colder and wetter than average, while the south is likely to be warmer and drier. The nation’s mid-section is predicted to experience average winter temperatures and precipitation. With the winter season upon us, it’s a good time to examine what happens to a wastewater lagoon when temperatures drop and highlight ways to optimize winter lagoon operations.
In this brief article, we’ll look at the effect of temperature on a wastewater lagoon, what happens in your lagoon when the weather gets cold, and how you can ensure the best possible treatment levels despite the weather.
Water temperature affects virtually every aspect of wastewater lagoon performance. As Steve Harris states in his operators’ guide, Wastewater Lagoon Troubleshooting, “Water temperature is a reliable predictor of water quality and can aid the operator in preparing for changes in pond performance.”
Falling temperatures have predictable effects on a winter lagoon operations. A freezing water temperature:
May damage structures and equipment: Icing over of liners, baffles, air and power lines, aerators and the like can cause significant damage. In addition, aeration equipment, especially surface aerators, can freeze and malfunction, leaving the lagoon without aeration and more prone to ice over.
Causes destratification: As temperatures drop in winter, the surface layer of the lagoon cools and becomes denser. The heavier water sinks, displacing the warmer water at the bottom of the lagoon. This process, known as densimetric mixing, causes the lagoon to destratify and distributes cold water throughout the entire lagoon.
Encourages short-circuiting: Warmer influent, if not properly mixed or if subject to wind, may short-circuit, or ride warmer thermoclines out with the effluent without being fully treated, especially if the lagoon surface is iced over.
Builds up BOD: Every 10 degree reduction in temperature reduces microbial activity by 50%. Bacteria and algae slow down their digestive processes in colder temperatures, allowing BOD to accumulate.
Reduces DO: Ice covering the lagoon surface prevents surface adsorption of oxygen from the atmosphere.
Causes sludge buildup: Without sufficient DO, anaerobic conditions prevail and solids settle at the bottom of lagoon. Also, the bacteria slow down in colder temperatures leading to lower sludge digestion.
Promotes conditions for spring lagoon turnover: The ice cover seals in the gaseous byproducts of anaerobic digestion. In spring, warming water instigates a burst of biological activity as dissolved oxygen levels improve and the microbes feast on the backlog of BOD. Gases entrained in the sludge cause it to rise to the surface. As the ice cover melts, the built-up gases and sludge are released all at once—along with terrible sulfurous odors that can linger for over a week—making your neighbors very unhappy. For more information see our article on Lagoon Turnover.
Optimizing winter lagoon operations
The best defense against cold weather lagoon challenges is to be prepared:
Protect equipment: Be sure surfaces around the lagoon are clear of road gravel, which can penetrate the lagoon liner with the freeze-thaw cycle. Cover or store unnecessary equipment.
Check and maintain outdoor equipment: If you have any motors sitting outside all winter long, including blowers or surface aerators, change the oil and check any belts for wear and tear. By properly maintaining these motors now you can reduce the risk that they will fail during the cold winter months when it will be harder to access them.
Prevent short-circuiting and spring lagoon turnover: Thorough mixing of the entire water column will ward off thermal stratification. Without thermoclines, warmer influent will incorporate into the overall mix and not flow out untreated. In addition, with a homogeneous water temperature and environment, no spring lagoon turnover can occur.
Increase DO to reduce BOD and sludge buildup: Microbial populations require dissolved oxygen to digest BOD and keep it from building up as sludge. Provide sufficient oxygenation by adding aeration.
MARS Aeration is reliable year round
With no moving parts in the water, MARS will not freeze and malfunction like this surface aerator.
The MARS Lagoon Aeration System optimizes lagoon performance year round, combining the mixing advantages of lagoon coarse bubble diffusers to keep solids in suspension with the efficiency of fine bubble diffusers for superior oxygenation in a high flexibility, low maintenance, portable unit. Each self-weighted unit is connected to an on-shore air supply via flexible weighted tubing. Because there are no mechanical parts submerged in the water, the MARS will not malfunction due to freezing, ensuring reliable performance no matter the weather.
We know good data leads to good decisions, so we’re always looking for ways to improve our data. Recently, we commissioned a CFD (Computational Fluid Dynamics) study of our MARS lagoon diffuser to refine our data about its performance.
A previous article, CFD Modeling Lagoon Aeration: A Peek Inside the Black Box, talked about how these sophisticated flow simulations can be an important tool in cracking the black box that is wastewater lagoon treatment. In this followup, we’ll take a close look at the results of the CFD study of our MARS lagoon diffuser—complete with cool animations—and highlight what it reveals about its performance. Continue reading →
Lagoon treatment has been referred to as a “black box” because the specific mechanisms of treatment are hidden below the surface. Computational fluid dynamics (CFD) modeling provides a peek inside this black box, demonstrating how various elements of a facility (such as depth, baffles, influent and effluent structures, aeration and mixing) work together to either help or hinder wastewater treatment.
In this article, we’ll discuss CFD as a tool to optimize lagoon systems, why we commissioned CFD studies of our MARS Aerator, and what the results say about the MARS’ mixing capability. Continue reading →
We’ll be exhibiting at both Process Expo (Booth #3714) and WEFTEC (Booth #1961) in the next few weeks, and we’re happy to have the opportunity to show off our hometown of Chicago!
Rather than talk about our usual blog topics like sludge and algae, we thought we’d share some of Team Triplepoint’s Chicago favorites: our recommendations of places to go while you’re in town. Continue reading →
Due to the success of the pilot, the Iowa DNR has approved a full installation of Triplepoint’s NitrOx® Process for lagoon nitrification in De Soto.
Like many Iowa municipalities, the City of De Soto required an upgrade to their lagoon system to meet more stringent ammonia effluent requirements. In this article, we’ll review the conditions that led De Soto to choose to pilot Triplepoint’s NitrOx® Process for lagoon ammonia removal, outline why NitrOx was the most attractive option, describe the pilot setup, and reveal the results of the pilot that led to the Iowa DNR’s approval. Continue reading →
To paraphrase an old saying, some companies that sell hammers try to turn every problem into a nail. We’re not that kind of company.
We manufacture lagoon aeration, among other things, and while we know that sufficient aeration and mixing in a lagoon can improve treatment and prevent problems like odor and sludge buildup, we also know that adding aeration is not always feasible. Continue reading →
Pretty much everything that happens in town eventually makes its way into the wastewater system. So what happens to your lagoon if there’s a methamphetamine lab?
An operator asked us whether meth lab discharge would upset his lagoon. Since meth labs are sadly not rare in rural areas, it seemed like a good topic to tackle. In this article, we’ll provide an overview of what having a meth lab in town is likely to do to your wastewater lagoon, and provide links to more detailed information. Continue reading →
We love hearing from operators–their questions give us insight into what may be going on in other lagoon systems. An operator asked if we could identify some red bugs he saw floating on the edge of his lagoon. At first we thought midge fly larvae, which are little red worms that hatch into swarming clouds of nuisance insects (more on midge flies in our previous article, What are these red worms in the lagoon?). From the photo he sent us, however, the red streaks are a telltale sign of lagoon Daphnia. This gives us the perfect opportunity to discuss what they are, why they can cause red streaks in a lagoon, and what they indicate about treatment conditions. Continue reading →
It’s our belief, our motto, and our mission. Lagoons provide reliable, cost-effective, low maintenance wastewater treatment, and should be reinvented, not replaced. We’ve dedicated our 30+ years of lagoon engineering expertise to innovating technologies that leverage existing infrastructure while minimizing capital expense. Our cutting-edge lagoon process solutions include efficient lagoon aeration and mixing, cold weather ammonia-nitrogen removal, advanced lagoon treatment, and tertiary phosphorus removal.