Overlooked nitrogen-cycling microorganisms in biological wastewater treatment

Abstract

Nitrogen-cycling microorganisms play key roles at the intersection of microbiology and wastewater engineering. In addition to the well-studied ammonia oxidizing bacteria, nitrite oxidizing bacteria, heterotrophic denitrifiers, and anammox bacteria, there are some other N-cycling microorganisms that are less abundant but functionally important in wastewater nitrogen removal. These microbes include, but not limited to ammonia oxidizing archaea (AOA), complete ammonia oxidation (comammox) bacteria, dissimilatory nitrate reduction to ammonia (DNRA) bacteria, and nitrate/nitrite-dependent anaerobic methane oxidizing (NOx-DAMO) microorganisms. In the past decade, the development of high-throughput molecular technologies has enabled the detection, quantification, and characterization of these minor populations. The aim of this review is therefore to synthesize the current knowledge on the distribution, ecological niche, and kinetic properties of these “overlooked” N-cycling microbes at wastewater treatment plants. Their potential applications in novel wastewater nitrogen removal processes are also discussed. A comprehensive understanding of these overlooked N-cycling microbes from microbiology, ecology, and engineering perspectives will facilitate the design and operation of more efficient and sustainable biological nitrogen removal processes.

Treatment of organic matter and ammonia nitrogen in wastewater by electrocatalytic oxidation: a review of anode material preparation

“…In the presence of organics, physisorbed "reactive oxygen species" play a major role in "electrochemical combustion" (eqn (2-5)), whereas chemisorbed "reactive oxygen species" primarily participate in "electrochemical conversion," which is the selective oxidation of organics (such as aromatics, but not fatty acids), as shown in eqn (2)(3)(4)(5)(6).…”

“…Considering that chloride ions can be electrooxidized to active chlorine, the presence of chloride ions can improve the degradation and removal efficiency of organic pollutants. For the chloride-containing system, chloride ions in solution were electrolyzed to generate chlorine gas first and then to produce hypochlorous acid and hypochlorite ions (eqn (2-7), (2)(3)(4)(5)(6)(7)(8), and (2-9)).…”

“…H 2 O 2 reacts with Fe 2+ to produce ˙OH when Fe 2+ is present in the solution, which oxidizes poorly degradable macromolecular organics to CO 2 , H 2 O, or smallmolecule organics. 31 The reaction equations are as follows: eqn (2-10), (2)(3)(4)(5)(6)(7)(8)(9)(10)(11), and (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12).…”

“…In many countries, severe pollution and eutrophication of oceans, lakes, and reservoirs result from incomplete treatment of industrial and domestic wastewater with high levels of organic matter and ammonia nitrogen. 1 Many physical, chemical, and biological technologies have been applied to the treatment of organic matter and ammonia nitrogen in wastewater, 2 such as biological methods, 3,4 electrocatalytic oxidation, stripping, 5,6 chemical precipitation, 7 membrane separation, 8 ion exchange, 9 and breakpoint chlorination. 10 Electrocatalytic oxidation is often used as an auxiliary technology of biochemical methods for water pretreatment or advanced treatment because of its high efficiency and small footprint, and this technology also has no secondary pollution.…”

The main anammox-based processes, the involved microbes and the novel process concept from the application perspective

“…Over the past several decades, many researchers have engaged in the pursuit of the ultimate goal of the smooth and reliable application of anammox process over a broader scope (Guo et al, 2020a;Fang et al, 2021;Fu et al, 2021). The theoretical knowledge obtained from the research work on this process is extensive, from the chemical perspective, microbial perspective, engineering perspective and process application perspective (Bi et al, 2020;Ding et al, 2021;Li et al, 2021;Qiu et al, 2021;Xu et al, 2021). In practice, many installations adopting…”