Search Results (17)

Anaerobic ammonium oxidation (anammox) technologies have attracted substantial interest due to their advantages over traditional biological nitrogen removal processes, including high efficiency and low energy demand. Currently, multiple side-stream applications of the anammox coupling process have been developed, including one-stage, two-stage, and three-stage systems such as completely autotrophic nitrogen removal over nitrite, denitrifying ammonium oxidation, simultaneous nitrogen and phosphorus removal, partial denitrification-anammox, and partial nitrification and integrated fermentation denitritation. The one-stage system includes completely autotrophic nitrogen removal over nitrite, oxygen-limited autotrophic nitrification/denitrification, aerobic de-ammonification, single-stage nitrogen removal using anammox, and partial nitritation. Two-stage systems, such as the single reactor system for high-activity ammonium removal over nitrite, integrated fixed-film activated sludge, and simultaneous nitrogen and phosphorus removal, have also been developed. Three-stage systems comprise partial nitrification anammox, partial denitrification anammox, simultaneous ammonium oxidation denitrification, and partial nitrification and integrated fermentation denitritation. The performance of these systems is highly dependent on interactions between functional microbial communities, physiochemical parameters, and environmental factors. Mainstream applications are not well developed and require further research and development. Mainstream applications demand a high carbon/nitrogen ratio to maintain levels of nitrite-oxidizing bacteria, high concentrations of ammonium and nitrite in wastewater, and retention of anammox bacteria biomass. To summarize various aspects of the anammox processes, this review provides information regarding the microbial diversity of different genera of anammox bacteria and the engineering aspects of various side streams and mainstream anammox processes for wastewater treatment. Additionally, this review offers detailed insights into the challenges related to anammox technology and delivers solutions for future sustainable research. Full article

Nitrogen removal in the sewage treatment process is a significant challenge. The increase in nitrogen content in sewage leads to the eutrophication of water bodies and the deterioration of water quality in polluted environments. Therefore, converting nitrogen into non-polluting gases is a crucial and essential part of the sewage treatment process. Compared to physical, chemical, and physicochemical methods, biological denitrification is not only simple to operate and economically effective but also has less secondary pollution and saves energy. This paper summarizes the latest research progress on mainstream biological denitrification technology in WWTPS (wastewater treatment plants) and discusses its research background, methodology, and challenges. It is noted that the traditional biological nitrogen removal method is stable and widely used, but it has drawbacks such as high costs and long reaction times, especially in high-nitrogen-load wastewater treatment where its effectiveness is limited. The short-cut nitrification–denitrification process suits high-nitrogen-loading and a low C/N ratio wastewater as it reduces carbon source consumption. However, the problems of water quality fluctuation and unstable dissolved oxygen still need to be solved. The anaerobic ammonia oxidation process efficiently converts ammonia and nitrite to nitrogen using anaerobic ammonia-oxidizing bacteria, consuming less energy but facing limitations due to slow bacterial growth rates and stringent environmental conditions. The heterotrophic nitrification–aerobic denitrification process merges the traits of heterotrophic nitrifying bacteria and aerobic denitrifying bacteria, effectively reducing the ecological footprint and enhancing treatment efficiency. This approach is a pivotal focus for future research endeavors. Full article

Poyang Lake is the largest freshwater lake in China, which boasts unique hydrological conditions and rich biodiversity. In this study, metagenomics technology was used to sequence the microbial genome of soil samples S1 (sedimentary), S2 (semi-submerged), and S3 (arid) with different water content from the Poyang Lake wetland; the results indicate that the three samples have different physicochemical characteristics and their microbial community structure and functional gene distribution are also different, resulting in separate ecological functions. The abundance of typical ANME archaea Candidatus Menthanoperedens and the high abundance of mcrA in S1 mutually demonstrate prominent roles in the methane anaerobic oxidation pathway during the methane cycle. In S2, the advantageous bacterial genus Nitrospira with ammonia oxidation function is validated by a large number of nitrification functional genes (amoA, hao, nxrA), manifesting in that it plays a monumental role in nitrification in the nitrogen cycle. In S3, the dominant bacterial genus Nocardioides confirms a multitude of antibiotic resistance genes, indicating their crucial role in resistance and their emphatic research value for microbial resistance issues. The results above have preliminarily proved the role of soil microbial communities as indicators predicting wetland ecological functions, which will help to better develop plans for restoring ecological balance and addressing climate change. Full article

Anaerobic ammonia oxidation (anammox) is considered an efficient and low-energy biological nitrogen removal process. However, there are limited studies addressing the changes in antibiotic resistance genes (ARGs) during the startup of an anammox reactor inoculated with activated sludge. In this study, an up-flow anaerobic sludge bed (UASB) reactor was initiated with synthetic wastewater at room temperature (20–28 °C). Metagenomic sequencing was employed to analyze the shifts in the bacterial community, nitrogen removal functional genes, and ARGs in both the seeding sludge and anammox sludge. The results show that the reactor achieved anammox activity after 122 days of cultivation, with NH₄⁺-N and NO₂⁻-N removal rates reaching 99.8% and 99.6%, respectively. Compared to those in inoculated sludge, the relative abundance of the anammox bacterium Candidatus kuenenia increased from 0.01% to 50.86%, while the relative abundance of denitrifying Acidovorax bacteria decreased from 8.02% to 1.77%. Meanwhile, the relative abundance of Nitrosomonas declined from 2.91% to 1.87%. The functional genes hzs, hdh, nirK, and nirS increased in relative abundance in the anammox sludge, while the ARGs decreased in relative abundance from 294.77 RPKM to 155.62 RPKM in the sludge. These findings offer valuable insights into the initiation of the anammox process using ordinary activated sludge as an inoculum and provide a scientific basis for the mitigation of ARGs through anammox technology. Full article

Nutrient removal in conventional wastewater treatment systems is expensive due to the high aeration costs. An alternative method for effective and sustainable nitrogen removal in wastewater treatment is anaerobic ammonium oxidation (Anammox) implemented with other innovative technologies, such as membrane-aerated biofilm reactors (MABRs). A major challenge associated with the Anammox process is effective control of nitrite-oxidizing bacteria (NOB). High temperature operation in wastewater treatment systems can promote Anammox bacterial growth and inhibit NOB activity. This research aims to investigate the feasibility of integrating Anammox processes with a lab-scale MABR and to examine the effects of high temperature aeration supplied to MABR systems on Anammox bacterial growth and NOB suppression. Experimental results indicate that the membrane’s air permeability was a critical parameter for the successful operation of Anammox-integrated MABR systems due to its influence on the system’s dissolved oxygen concentration (0.41 ± 0.39 mg O₂/L). The ammonia removal by AOB and Anammox bacteria was determined to be 7.53 mg N/L·d (76.5%) and 2.12 mg N/L·d (23.5%), respectively. High temperature aeration in MABRs with the Anammox process shows a promising potential for improving energy consumption and sustainable nitrogen removal in wastewater treatment systems. Full article

The Anammox anaerobic fluidized bed microbial fuel cell (Anammox AFB-MFC) exhibits exceptional performance in both nitrogen removal and electricity generation, effectively eliminating ammonia nitrogen (NH₄⁺-N) and nitrite nitrogen (NO₂⁻-N) pollutants. This technology offers the advantages of high efficiency in nitrogen removal and low electricity consumption. By coupling an AFB with an MFC, the Anammox AFB-MFC was developed through the introduction of anaerobic ammonia-oxidizing bacteria (AnAOB) into MFC. Anammox AFB-MFC’s nitrogen removal ability was found to be superior at an influent COD concentration of 200 mg/L, as determined by a study conducted under unchanged conditions. Subsequently, an open and closed-circuit experiment was performed on the Anammox AFB-MFC system while maintaining a COD concentration of 200 mg/L in the influent. Remarkably, the reactor exhibited significantly enhanced nitrogen removal performance when electricity generation occurred. Throughout the entire experimental process, the reactor consistently maintained high nitrogen removal efficiency and electricity production performance. Under optimal experimental conditions, the reactor achieved a remarkable nitrogen removal rate of 91.8% and an impressive output voltage of 439.1 mV. Additionally, the generation of Anammox bioparticles in MFC significantly contributed to efficient pollutant removal. This study elucidates the impact of organic matter on both the nitrogen removal and electricity generation capabilities of Anammox AFB-MFC, as well as highlights the synergistic effect between MFC electricity generation and nitrogen removal in the reactor. Full article

Anaerobic digestion of animal manure results in the production of renewable energy (biogas) and nutrient-rich biofertilizer. A further benefit of the technology is decreased greenhouse gas emissions that otherwise occur during manure storage. Since animal manure makes anaerobic digestion cost-efficient and further advance the technology for higher methane yields, it is of utmost importance to find strategies to improve bottlenecks such as the degradation of lignocellulose, e.g., in cattle manure, or to circumvent microbial inhibition by ammonia caused by the degradation of nitrogen compounds in, e.g., chicken, duck, or swine manure. This review summarizes the characteristics of different animal manures and provides insight into the underlying microbial mechanisms causing challenging problems with the anaerobic digestion process. A particular focus is put upon the retention time and organic loading rate in high-ammonia processes, which should be designed and optimized to support the microorganisms that tolerate high ammonia conditions, such as the syntrophic acetate oxidizing bacteria and the hydrogenotrophic methanogens. Furthermore, operating managements used to stabilize and increase the methane yield of animal manure, including supporting materials, the addition of trace elements, or the incorporation of ammonia removal technologies, are summarized. The review is finalized with a discussion of the research needed to outline conceivable operational methods for the anaerobic digestion process of animal manure to circumvent process instability and improve the process performance. Full article

Composting is a promising technology for treating organic solid waste. However, greenhouse gases (methane and nitrous oxide) and odor emissions (ammonia, hydrogen sulfide, etc.) during composting are practically unavoidable, leading to severe environmental problems and poor final compost products. The optimization of composting conditions and the application of additives have been considered to mitigate these problems, but a comprehensive analysis of the influence of these methods on gaseous emissions during composting is lacking. Thus, this review summarizes the influence of composting conditions and different additives on gaseous emissions, and the cost of each measure is approximately evaluated. Aerobic conditions can be achieved by appropriate process conditions, so the contents of CH₄ and N₂O can subsequently be effectively reduced. Physical additives are effective regulators to control anaerobic gaseous emissions, having a large specific surface area and great adsorption performance. Chemical additives significantly reduce gaseous emissions, but their side effects on compost application must be eliminated. The auxiliary effect of microbial agents is not absolute, but is closely related to the dosage and environmental conditions of compost. Compound additives can reduce gaseous emissions more efficiently than single additives. However, further study is required to assess the economic viability of additives to promote their large-scale utilization during composting. Full article

Anaerobic ammonia oxidation (ANAMMOX) technology is a novel biological nitrogen removal technology with potential applications for the treatment of nitrogenous wastewater treatment prospects. Most of the literature explores the growth environment of anaerobic ammonia-oxidizing bacteria and total nitrogen removal efficiency but the influence of reactor operating conditions (such as up-flow rate) on the treatment efficiency and sludge growth property of anaerobic ammonia-oxidizing bacteria is rarely discussed. Therefore, the purpose of this study is to discuss the effect of up-flow rate on the treatment efficiency and sludge property of the anaerobic ammonia oxidation treatment procedure adopting up-flow anaerobic sludge bed (UASB) as a reactor. The results show that up-flow rate has a significant effect on sludge concentration and sludge growth rate. The highest sludge concentration and maximum sludge growth rate could be obtained at the up-flow rate of 3.21 m/h. According to the analysis results of the sludge concentration, we speculate that when the flow rate was lower than 3.21 m/h, the sludge particles did not easily collide with each other to produce a larger sludge floc. On the contrary, when the up-flow rate was higher than 3.21 m/h, the larger sludge floc could be decomposed by the shear force. The sludge concentration was reduced by these two reasons. On the other hand, the average total nitrogen volume removal rates in test runs 1 through to 4 were 0.18 g-N/m³/d, 0.19 g-N/m³/d, 0.20 g-N/m³/d and 0.20 g-N/m³/d at up-flow rates from 1.95 m/h to 3.70 m/h, respectively. Therefore, the treatment efficiency was not affected by the up-flow rate in these operating conditions. Full article

Anaerobic digestion (AD) and sewage sludge digestion (SD) plants generate significant quantities of ammoniacal nitrogen in their digestate liquor. This article assesses the economic viability and CO₂ abatement opportunity from the utilisation of this ammonia under three scenarios and proposes their potential for uptake in the United Kingdom. Each state-of-the-art process route recovers ammonia and uses it alongside AD-produced biomethane for three different end goals: (1) the production of H₂ as a bus transport fuel, (2) production of H₂ for injection to the gas grid and (3) generation of heat and power via solid oxide fuel cell technology. A rigorous assessment of UK anaerobic and sewage digestion facilities revealed the production of H₂ as a bus fleet transport fuel scenario as the most attractive option, with 19 SD and 42 AD existing plants of suitable scale for process implementation. This is compared to 3 SD/1 AD and 13 SD/23 AD existing plants applicable with the aim of grid injection and SOFC processing, respectively. GHG emission analysis found that new plants using the NWaste2H2 technology could enable GHG reductions of up to 4.3 and 3.6 kg CO₂e for each kg bio-CH₄ supplied as feedstock for UK SD and AD plants, respectively. Full article

With the development of economy and the improvement of people’s living standard, landfill leachate has been increasing year by year with the increase in municipal solid waste output. How to treat landfill leachate with high efficiency and low consumption has become a major problem, because of its high ammonia nitrogen and organic matter content, low carbon to nitrogen ratio and difficult degradation. In order to provide reference for future engineering application of landfill leachate treatment, this paper mainly reviews the biological treatment methods of landfill leachate, which focuses on the comparison of nitrogen removal processes combined with microorganisms, the biological nitrogen removal methods combined with ecology and the technology of direct application of microorganisms. In addition, the mechanism of biological nitrogen removal of landfill leachate and the factors affecting the microbial activity during the nitrogen removal process are also described. It is concluded that the treatment processes combined with microorganisms have higher nitrogen removal efficiency compared with the direct application of microorganisms. For example, the nitrogen removal efficiency of the combined process based on anaerobic ammonium oxidation (ANAMMOX) technology can reach more than 99%. Therefore, the treatment processes combined with microorganisms in the future engineering application of nitrogen removal in landfill leachate should be paid more attention to, and the efficiency of nitrogen removal should be improved from the aspects of microorganisms by considering factors affecting its activity. Full article

Novel technologies such as partial nitritation (PN) and partial denitritation (PDN) could be combined with the anammox-based process in order to alleviate energy input. The former combination, also noted as deammonification, has been intensively studied in a frame of lab and full-scale wastewater treatment in order to optimize operational costs and process efficiency. For the deammonification process, key functional microbes include ammonia-oxidizing bacteria (AOB) and anaerobic ammonia oxidation bacteria (AnAOB), which coexisting and interact with heterotrophs and nitrite oxidizing bacteria (NOB). The aim of the presented review was to summarize current knowledge about deammonification process principles, related to microbial interactions responsible for the process maintenance under varying operational conditions. Particular attention was paid to the factors influencing the targeted selection of AOB/AnAOB over the NOB and application of the mathematical modeling as a powerful tool enabling accelerated process optimization and characterization. Another reviewed aspect was the potential energetic and resources savings connected with deammonification application in relation to the technologies based on the conventional nitrification/denitrification processes. Full article

Suspended sludge deammonification technologies are frequently applied for sidestream ammonia removal from dewatering liquors resulting from a thermal hydrolysis anaerobic digestion (THP/AD) process. This study aimed at optimizing the operation, evaluate the performance and stability of a full-scale suspended sludge continuous stirred tank reactor (S-CSTR) with a hydrocyclone for anaerobic ammonia oxidizing bacteria (AMX) biomass separation. The S-CSTR operated at a range of nitrogen loading rates of 0.08–0.39 kg N m⁻³ d⁻¹ displaying nitrogen removal efficiencies of 75–89%. The hydrocyclone was responsible for retaining 56–83% of the AMX biomass and the washout of ammonia oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was two times greater than AMX. The solid retention time (SRT) impacted on NOB washout, that ranged from 0.02–0.07 d⁻¹. Additionally, it was demonstrated that an SRT of 11–13 d was adequate to wash-out NOB. Microbiome analysis revealed a higher AMX abundance (Candidatus scalindua) in the reactor through the action of the hydrocyclone. Overall, this study established the optimal operational envelope for deammonification from THP/AD dewatering liquors and the role of the hydrocyclone towards maintaining AMX in the S-CSTR and hence obtain process stability. Full article

Nitrogenous compounds attract great attention because of their environmental impact and harmfulness to the health of human beings. Various biological technologies have been developed to reduce the environmental risks of nitrogenous pollutants. Bioelectrochemical systems (BESs) are considered to be a novel biological technology for removing nitrogenous contaminants by virtue of their advantages, such as low energy requirement and capacity for treating wastewaters with a low C/N ratio. Therefore, increasing attention has been given to carry out biological processes related to nitrogen removal with the aid of cathodic biofilms in BESs. Prior studies have evaluated the feasibility of conventional biological processes including nitrification, denitrification, and anaerobic ammonia oxidation (anammox), separately or combined together, to remove nitrogenous compounds with the help of BESs. The present review summarizes the progress of developments in BESs in terms of the biological process, cathodic biofilm, and affecting factors for efficient nitrogen removal. Full article

Anaerobic ammonia oxidation (anammox) has been one of the most innovative discoveries for the treatment of wastewater with high ammonia nitrogen concentrations. The process has significant advantages for energy saving and sludge reduction, also capital costs and greenhouse gases emissions are reduced. Recently, the use of anammox has rapidly become mainstream in China. This study reviews the engineering applications of the anammox process in China, including various anammox-based technologies, selection of anammox reactors and attempts to apply them to different wastewater treatment plants. This review discusses the control and implementation of stable reactor operation and analyzes challenges facing mainstream anammox applications. Finally, a unique and novel perspective on the development and application of anammox in China is presented. Full article