Anaerobic Ammonium Oxidation in Waste Water -An Isotope Hydrological Perspective

Abstract

Excess nitrogen components must be removed from wastewater to protect the quality of the water bodies that it will be eventually discharged to. A conventional wastewater treatment system for nitrogen removal is often involved with two processes, nitrification and denitrification. Nitrification is mostly achieved by complete oxidation of ammonium (NH 4 +) to nitrite (NO 2-) by the appropriate aerobic bacteria and then oxidation of the nitrite to nitrate ion (NO 3-) by another variety of aerobic bacteria. Subsequently, the formed nitrate will be reduced to dinitrogen gas under anoxic conditions at the expense of organic carbon and released into the atmosphere as a harmless product (van Dongen et al., 2001). The introduction of oxygen into wastewater for nitrification requires a large amount of energy. Furthermore, the carbon source is often limited in wastewater, so purchasing of carbon source (typically methanol) is necessary too. A newly discovered anaerobic ammonium oxidation (anammox) may circumvent the limitations and open up a new possibility for nitrogen removal from wastewater. The alternative approach is a microbiological involved activity which requires less energy and enables more efficiency on N removal. 2. The history and physiology of anammox The discovery of anammox activity and anammox bacteria is quite recent. Even though Richards (1965) has noticed NH 4 + deficits in anoxic marine basins, and proposed that the missing NH 4 + was anaerobically oxidized to N 2 by some unknown microbe using nitrate as an oxidant, which was coined one of two "lithotrophs missing in nature" by Broda (1977). Because there was no known biological pathway for this transformation, biological anaerobic ammonium oxidation received littler further attention (Arrigo, 2005). It was not until mid-1990s, work with bioreactors designed to remove NH 4 + from wastewater provided direct evidence for anaerobic ammonium oxidation, and the process was termed "anammox" by Mulder and his colleagues (1995). A series of 15 N-labellling experiment were carried out to study the metabolic mechanism and intermediates of anammox reaction (van de Graaf et al., 1995; 1997). It is a chemolithotrophic process in which 1 mol of NH 4 + is oxidized by 1 mol of NO 2-to produce N 2 gas in the absence of oxygen (Strous et al., 1999). NH 4 + + NO 2-→ N 2 +2H 2 O (1) www.intechopen.com Waste Water-Treatment and Reutilization 90 The pathway of N 2 formation clearly distinguishes anammox from denitrification which combines N from two NO 3-molecules to form N 2 and presents as an elegant shortcut in the natural nitrogen cycles (Fig 1.) Physical purification of the anammox microbes from the multispecies biofilms yielded a 99.6% pure culture that was capable of carrying out PCR amplification of the DNA. The microbes responsible for anammox process were identified as members of the bacterial order Planctomycetales (Strous et al., 1999). The first genome sequence of a representative anammox bacterium was published in 2006 (Strous et al., 2006). To date, five anamm...

Evaluation of anaerobic and anoxic reactors installed in serial to treat fish tank effluent

“…Therefore, ammonia and nitrite removal should occur in a single reactor. In fact, Xiao et al (2009) confirmed the coexistence of nitrifiers, denitrifiers, and anammox bacteria in a single batch sequencing reactor by using PCR-DGGE, and justified that ammonia removal occurred due to the growth of aerobic bacteria in the surface and anaerobic bacteria inside the biofilm. According to the authors, aerobic bacteria supply nitrite to anammox bacteria.…”

“…These reactions are widely known and have been successfully applied in most wastewater treatment systems (Egli et al, 2001). However, this process has some limitations when the objective is to treat effluents containing high concentrations of nitrogen and low concentration of carbon (low C / N ratio) since there are difficulties in the transfer of large amounts of oxygen necessary for nitrification and the need for a large amount of biodegradable organic matter in the denitrification phase (Xing and Clark, 2012). Fish farming effluents are characterized by the high concentration of biochemical oxygen demand (BOD) and the presence of organic and inorganic matter; in this way the efficiency of the process can be impaired and other processes must be explored.…”

“…Microbial community analysis was carried out by molecular biology tools in treatment systems (Xiao et al, 2009). Genetic fingerprinting of microbial communities provides banding patterns or profiles that reflect the genetic diversity of the community in a given environment.…”