How does anammox work in wastewater treatment?
The application of the ANAMMOX process in wastewater systems has resulted in lower energy requirements and high rates of nitrogen removal than those for conventional nitrogen removal (Laureni et al. 2016 ). This treatment system needs the supply of oxygen for the production of nitrite.
What is an anammox reactor?
The full-scale Anammox reactor is a 70m 3 reactor designed by Paques BV (www.paques.nl). The reactor combines a high loading rate with efficient biomass retention, characteristics the Anammox process has in common with anaerobic wastewater treatment.
Can granular anammox biomass be used as an alternative to biofilms?
Granular anammox biomass can be used as a successful alternative to anammox biofilms when high DO concentrations are required to facilitate partial nitrification.
What are the advantages of anammox?
Factsheet Block Body The Anammox process requires much less oxygen than conventional nitrification/denitrification processes resulting in important energy savings. Because autotrophic bacteria carry out Anammox, there is no need for organic carbon sources, which saves on chemical dosage costs.
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What is anammox in wastewater treatment?
Anammox (Anaerobic Ammonium Oxidation) Bacteria combine ammonia and nitrite directly into dinitrogen gas. This allows a new and very efficient treatment possibility of wastewater. Large-scale treatment with the Anammox process is very complex in design, operation and maintenance.
What is anammox process?
Anammox (anaerobic ammonium oxidation), which is a reaction that oxidizes ammonium to dinitrogen gas using nitrite as the electron acceptor under anoxic conditions, was an important discovery in the nitrogen cycle.
Where does anammox occur?
The anammox process was originally found to occur only from 20 °C to 43 °C but more recently, anammox has been observed at temperatures from 36 °C to 52 °C in hot springs and 60 °C to 85 °C at hydrothermal vents located along the Mid-Atlantic Ridge.
How can you reduce ammoniacal nitrogen in effluent?
The most widely used methods for removing ammonia from wastewater are air stripping [6,7], ion exchange [8,9], breakpoint chlorination [10], and biological nitrification-denitrification [11,12]. The traditional method of removing ammonia from municipal and industrial wastewaters is based on biological treatments.
What is the purpose of Anammoxosome?
The anammoxosome organelle is crucial for the energy metabolism of anaerobic ammonium oxidizing bacteria.
What are the electron donor and acceptor in the anammox process?
Anammox bacteria convert ammonium (NH4+) to dinitrogen gas (N2) using intracellular electron acceptors such as nitrite (NO2−) or nitric oxide (NO).
Which two nitrogen species are required substrates in anammox?
Anammox involves the anaerobic oxidation of ammonium to N2 using nitrite as electron acceptor (Figure 9).
Who discovered anammox?
In collaboration with the Fuerst group10, Jos Schalk11 discovered that this compartment contained large quantities (more than 10–15% of total cell protein levels) of a hydroxylamine oxidoreductase (HAO)-like enzyme, which we postulated was responsible for the oxidation of hydrazine to N2 gas.
Does nitrate reduction require oxygen?
16.3. Most microbes utilize ammonium preferentially, when it is present, to avoid having to reduce nitrate to ammonium, a process requiring energy. So, if ammonium is present in the environment, assimilatory nitrate reduction is suppressed. Oxygen does not inhibit this activity.
How do you reduce ammonia levels in wastewater?
Nitrification is the most common way to biologically remove ammonia in wastewater lagoons. In this process, ammonia treatment occurs via bacteria already present in the water. These bacteria break down the ammonia and eventually promote the release of nitrogen gas into the atmosphere.
Does aeration remove ammonia?
Aeration also reduces ammonia levels through physical means. Ammonia levels in wastewater can decrease through the process of desorption (Patoczka and Wilson, 1984). Desorption of ammonia is often referred to as stripping.
What causes high ammonia nitrogen in wastewater?
Remember, ammonia in wastewater could originate from a variety of sources, including proteins (meat and blood), urea, amino acid products, casein, corrosion inhibitors, process chemicals and raw materials, or cleaning chemicals containing quaternary ammonium compounds.
Why is anammox important?
Anammox bacteria are playing a critically important role in global nitrogen cycling. This review focuses on discussing the metabolism, inhibition conditions, and utilization of anammox bacteria in treating ammonia rich wastewater. Even though, the anammox process is employed as a successful venture in treating ammonia in wastewater, addressing the concerns regarding the limiting factors of the anammox process is of prime importance. Similarly, unraveling the anammox diversity in specified environmental and eco-physiological conditions will expand opportunities in further effective utilization of the anammox process over diverse conditions.
How does anammox bacteria fulfill carbon requirements?
Anammox bacteria being chemoautotrophic, fulfill carbon requirements by fixing atmospheric CO 2 ( Gao et al., 2018 ). Hence, organic carbon is assumed to interfere with the growth of anammox bacteria. Out-competition is a form of inhibition that could occur when non-toxic organic carbon is in abundance where heterotrophic bacteria would go on to outcompete anammox bacteria. This form of inhibition is expected, primarily due to the fast growth rate exhibited by heterotrophic bacteria and the slow growth rate exhibited by anammox bacteria ( Jin et al., 2012, Mattei et al., 2015 ). The co-existence of anammox bacteria with other heterotrophic bacteria is also clearly reported in the literature ( Jin et al., 2012, Zhou et al., 2018 ). In fact, this co-existence is also known to play a crucial role in the complete removal of nitrogen from wastewater.
What enzymes are involved in the catabolic anammox reaction?
They include nitrite reductase, hydrazine synthase, hydrazine dehydrogenase, hydroxylamine oxidase, and nitrite oxidoreductase. These enzymes catalyze a sequence of reactions in the anammox process ( Almeida et al., 2015, Gao et al., 2018 ). Anammox bacteria are also metabolically versatile and the metabolic pathways used for the anammox process also differ. However, comparative genomic analysis has revealed that genes encoding HZS and HDH are conserved among all anammox genera ( Oshiki et al., 2016 ). Of all reactions, hydrazine synthesis seems to play a critical role in anammox catabolism ( Kartal et al., 2012 ).
What is the complete anammox reaction?
As in Equation 2 ammonium and nitrite are converted into nitrogen gas and the free energy related to this reaction is high ( Δ G ° = - 375 K J / m o l), which could be utilized in the growth processes anammox bacteria derive energy for growth using inorganic compounds. For biomass production, anammox bacteria use hydrogen carbonate as the sole carbon source, making anammox autotrophic. The reducing equivalents required for biomass synthesis are generated via oxidation of nitrite to nitrate (Equation 3).
How does anammox interact with other bacteria?
Limited knowledge of anammox metabolism is a significant drawback to capitalize on many different anammox species that have been discovered from the natural environment. Specifically, how the anammox bacteria interact with other bacteria in the nitrogen cycle is not clearly understood. Developing this understanding has been a challenge because it has not been possible to produce a pure culture of anammox bacteria. This lack has prevented detailed studies of its metabolic pathways, physiological properties, biochemical characteristics, and genetics. Similarly, the understanding of the interactions and the ecology between the main organisms dominating the PN-A system is crucial for the successful mainstream PN-A performance. The functional dynamics and the microbial composition of the major microbial groups including anammox in a PN-A system directly affect the rate of nitrogen removal from wastewater treatment systems. Therefore further studies concerning the microbial community composition in anammox reactor systems will extend the feasibility of generating novel treatment options. Metagenomic and metatranscriptomic analyses are reported as successful ventures in understanding gene expression and metabolic capabilities of uncultured anammox species under different conditions. Consequently, novel high throughput molecular technologies such as meta -omics contribute to the understanding of genetic variations associated with anammox and PN-A systems. These methods will assist in unraveling the metabolic versatility and interactive mechanisms incorporated in anammox bacteria that will broaden its applications. Similarly, further studies focusing on the performance of anammox systems under varying seasonal conditions are critically important in utilizing this method as a wastewater treatment system in temperate regions of the world.
How to remove ammonia from wastewater?
Stringent discharge limits and environmental regulations are increasingly forcing industries to explore sustainable and economical methods to eliminate ammonia from wastewater. A range of physical, chemical, and biological approaches are available to remove ammonia from wastewater. Physiochemical approaches include membrane filtration (such as reverse osmosis, microfiltration, ultrafiltration, and nanofiltration) ( Hasanoĝlu et al., 2010 ), ion exchange using natural minerals ( Seruga et al., 2019 ), ozone oxidation ( Luo et al., 2015 ), chemical precipitation and iron stripping ( Limoli et al., 2016 ). These methods have their own advantages and disadvantages, and the major drawback is the high operational cost and skilled labor requirement ( Karri et al., 2018, Tang et al., 2017 ). The significant operational cost mainly manifests the importance of using biological approaches to remove ammonia from wastewater primarily because it is economical and eco-friendly ( Karri et al., 2018 ). Anaerobic ammonium oxidation (Anammox) is a biological approach to nitrogen removal that uses anammox bacteria in the direct oxidation of ammonium to form dinitrogen gas (N 2 ). This method has received recent attention as an effective and environmentally friendly technique to treat ammonia-rich wastewater ( Fan et al., 2020, Jo et al., 2020, Tang et al., 2017 ).
What is the anammoxosome?
Anammox bacteria possess a membrane-bound organelle (anammoxosome) where the anammox reactions take place. Using antibody studies, Almeida et al. (2015) confirmed that the main enzymes associated with the anammox process are localized inside the anammoxosome. This further supports the notion that the anammoxosome is unique to anammox bacteria ( Fig. 2 ). The anammoxosome membrane, in this instance, is responsible for generating and maintaining the proton motive force required in ATP synthesis ( Ren et al., 2020 ). Anammox metabolism involves a series of reactions catalyzed by different enzymes. The overall anammox reaction or the energy-generating process in an anammox cell is given in Equation 1 ( Du et al., 2019 ).
What are the characteristics of anammox bacteria that are of particular interest for wastewater treatment?
The characteristic of anammox bacteria that is of particular interest for wastewater treatment is their ability to convert ammonium ion and nitrite ion into nitrogen gas in an anaerobic environment.
What is anammox bacteria?
The discovery of the type of bacteria now commonly called anammox bacteria is quite recent. In the mid-1990s anaerobic oxidation of ammonium ion was observed in a wastewater denitrifying pilot plant1. Subsequently the bacteria commonly called anammox bacteria were isolated and identified2. At about that time, it was also discovered that anammox bacteria are responsible for the conversion of a great deal of ammonia and nitrite nitrogen to nitrogen gas in our oceans and seas. The characteristic of anammox bacteria that is of particular interest for wastewater treatment is their ability to convert ammonium ion and nitrite ion into nitrogen gas in an anaerobic environment.
What happens if ammonia is oxidized?
If only half of the ammonia nitrogen in a wastewater flow were oxidized just to nitrite, then the remaining ammonia nitrogen and the nitrite nitrogen that has been formed could be converted to nitrogen gas by anammox bacteria in an anaerobic (absence of oxygen) environment. It turns out that this can be accomplished in a practical manner resulting ...
What is the next normal step in the nitrogen cycle?
The next normal step in the nitrogen cycle is oxidation of the ammonia nitrogen to nitrite ion (NO2-) by the appropriate aerobic bacteria and then oxidation of the nitrite ion to nitrate ion (NO3-) by another variety of aerobic bacteria. These oxidation processes taken together are called nitrification and require oxygen in order to take place.
What is the nitrogen cycle in wastewater?
For more details see “ Easy to Understand Nitrogen Cycle Diagram .” When waste organic matter is decomposed in nature or in a wastewater treatment plant, the nitrogen in proteins is released as ammonia nitrogen (either dissolved ammonia gas, NH3, or ammonium ion, NH4+, depending upon the pH). This release of ammonia nitrogen from protein is one step in the nitrogen cycle. The next normal step in the nitrogen cycle is oxidation of the ammonia nitrogen to nitrite ion (NO2-) by the appropriate aerobic bacteria and then oxidation of the nitrite ion to nitrate ion (NO3-) by another variety of aerobic bacteria. These oxidation processes taken together are called nitrification and require oxygen in order to take place. If wastewater effluent containing ammonia nitrogen is discharged to a river, lake, or stream, nitrification will take place there, exerting a biochemical oxygen demand (BOD), and using up dissolved oxygen from the water, thus affecting aquatic life. This is the reason that nitrification is required of most wastewater treatment plants.
Why is nitrification required in wastewater treatment plants?
If wastewater effluent containing ammonia nitrogen is discharged to a river, lake, or stream, nitrification will take place there, exerting a biochemical oxygen demand (BOD), and using up dissolved oxygen from the water, thus affecting aquatic life. This is the reason that nitrification is required of most wastewater treatment plants.
How does nitrification work?
The nitrification that is required of most secondary wastewater treatment plants can be accomplished in a typical activated sludge wastewater treatment process by ensuring that there is adequate aeration to provide the necessary oxygen and by maintaining a long enough sludge retention time so that the slower growing nitrifying bacteria aren’t washed out of the system. With these steps the bacterial oxidation of ammonia nitrogen to nitrate (nitrification) will take place along with the bacterial oxidation of hydrocarbon BOD, as shown in the process flow diagram at the left. Nitrification, however, doesn’t remove the nitrogen from wastewater. It simply removes the oxygen demand, by converting ammonia nitrogen to nitrate nitrogen. If discharge of wastewater treatment effluent containing nitrate is a problem for the receiving body of water, then another process, denitrification, is also required.
