Response of Anammox bacteria to elevated nitrogen and organic matter in pre-digested chicken waste at a long-term operated UASB reactor initially seeded by methanogenic granules

Physiological and transcriptomic response of enriched anammox culture upon elevated hydrazine exposure

Anammox has emerged as a cost-effective and eco-friendly biological treatment technology for high-strength wastewater, and hydrazine (N2H4) is a unique intermediate in the anammox metabolism. This study presents the first investigation into the genetic responses of anammox bacteria to elevated N2H4 concentrations, offering critical insights into their potential for sustainable environmental applications. In this scope, anammox cultures were exposed to high levels of N2H4 (up to 3 g/L) over a short-term period to evaluate their nitrogen treatment capacity and transcriptional responses. The results indicated that anammox activity continued at N2H4 concentrations of 1.88 g/L or less. However, acute N2H4 exposure significantly downregulated key genes, such as acetyl-CoA synthase beta and delta subunits, hydrazine synthase, hydrazine dehydrogenase, and hydroxylamine oxidoreductase, except for AAA family ATPase. Overall, high exogenous N2H4 concentrations severely constrained the metabolism and survival of anammox bacteria at a molecular level. Understanding the genetic responses of anammox bacteria to elevated N2H4 concentrations is crucial for optimizing their application in further anammox-based technologies. Future studies should focus on improving the resilience of anammox bacteria to high N2H4 concentrations, thereby broadening their applicability in engineered wastewater treatment and biotechnological processes while maintaining system stability and efficiency.

Advancement in Anaerobic Ammonia Oxidation Technologies for Industrial Wastewater Treatment and Resource Recovery: A Comprehensive Review and Perspectives

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.

Nitrogen removal in improved subsurface wastewater infiltration system: Mechanism, microbial indicators and the limitation of phosphorus

To enhance the nitrogen removal capacity, scrap iron filings and Si-Al porous clay mineral material (PCMW) was used to improve a subsurface wastewater infiltration system (SWIS). The results showed TN and NH₄⁺-N removal efficiencies of improved SWIS were 20.72% and 5.49% higher than those of the control SWIS, respectively. Based on the response of the removal performance, microbial community and function analysis of 16s rRNA amplicon sequencing results, the amending soil matrix substantially enriched the nitrogen removal bacteria (Rhizobiales_Incertae_Sedis and Gemmatimonadaceae), and significantly improved the activities of key enzymes (Hao, NasAB, NarGHI, NirK, NorBC, NirA and NirBD), particularly at co-occurrence zone of nitrification and denitrification (70-130 cm depth). The amending soil matrix not only extended the growth space of microbes, but also provided additional electrons and carbon sources for denitrifying bacteria by regulating the structure and function of the microbial community. In addition, amending soil matrix could enhance phosphate metabolism genes and phosphate solubilizing microbes in the denitrification zone by increasing the phosphorus source, thus strengthening nitrogen metabolism. Nitrospiraceae, Rhizobiales_Incertae_Sedis and Gemmatimonadaceae related to nitrogen removal and Bacillaceae with phosphate-solubilizing ability could be used as microbial indicators of nitrogen removal in SWISs. The reciprocal action of environmental on microbial characteristics exhibited microbial functional were related to DO, Fe²⁺, TOC, TP, TN, NH₄⁺-N and NO₃^--N. Those could be used as physicochemical and biological indicators for application and monitoring of SWIS. In conclusion, this study provided a low-cost and efficient enhancement approach for the application of SWIS in decentralized domestic sewage treatment, and furnished theoretical support for subsequent applications.

A novel vertical dual-loop reactor for rapid start-up of simultaneous partial nitrification and anammox process in treating landfill leachate: Performances and mechanisms

A novel vertical dual-loop reactor (VDLR) was developed to start and conduct a single-stage partial nitritation (PN) and anammox (PN/A) process for treating landfill leachate. Results showed that the total nitrogen (TN) removal reached 1.54 kg N/m3·d in the VDLR. It exhibited excellent mixing uniformity and buffer performance, which can increase the nitrogen removal performance up to 42.1 % via the improvement of anammox granular sludge activity (a particle size of 0.5-1 mm). Mass balance and microbial analysis indicated that the VDLR achieved efficient TN removal via anammox (99.24 %) and AOB (Nitrosomonas and Ellin6067) and anAOB (Candidatus kuenenia) played a vital role in this process.

Unravelling the importance of Ca2+ and Mg2+ as essential in anammox culture medium

The mechanism and nitrogen removal performance of anammox process under different concentrations of Ca²⁺ and Mg²⁺ were explored from the perspective of molecular biology analysis based on the metabolic changes of the second messenger cyclic diguanylate (c-di-GMP). After 100-day operation, reactor with 98 mg/L Ca²⁺ and 30 mg/L Mg²⁺ achieved a higher anammox performance with an average total nitrogen (TN) removal efficiency of 85.8%. Under the Mg²⁺concentration of 30 mg/L, a higher Ca²⁺ could accelerate anammox process by promoting the amplification of Candidatus Brocadia (0.62%) and production of Diguanylate cyclase (DGC-s: 6.54 × 10⁸ copies/μL DNA) which function was to synthesize c-di-GMP. While under the Ca²⁺concentration of 49 mg/L, Mg²⁺ concentration at appropriate rang could promote the degradation process of c-di-GMP. Since Ca²⁺ had positive linear relationship with TN removal (R² = 0.96), a higher Ca²⁺ concentration is recommended in the culture medium. This study provided a potential method for optimization of anammox process.

Process performance and anammox community diversity in a deammonification reactor under progressive nitrogen loading rates for swine wastewater treatment

The performance of a deammonification reactor fed with increasing nitrogen loading rates (NLR) was evaluated. The digestate from a continuous stirred tank reactor (CSTR) treating sludge from a swine production unit was diluted to provide different ammonia concentrations. The biomass samples from the end of each experimental phase were analyzed for microorganism community evaluation. The results proved that deammonification system supported a NLR up to 3.27 ± 0.13 g N L^-1 d^-1 with nitrogen removal efficiency of 83%. The specific ammonia consumption rate (µ_NH3-N) did not decrease up to this NLR proving the stability of reactor performance. Anammox bacteria genus shifted along the experiment and at the end the predominant anammox bacteria found in the reactor was candidatus Brocadia. Finally, it was proved that a deammonification reactor for nitrogen removal from CSTR digestate could be easily controlled only by monitoring pH and dissolved oxygen.

Comparative assessment of modeling and experimental data of ammonia removal from pre-digested chicken manure

The aim of this study was to interpret the development of Anammox activity by a mathematical model in an UASB reactor -originally inoculated with methanogenic granules- at which Anammox progress has been also experimentally observed while treating chicken manure digestate. Since ammonium is derived from anaerobic degradation of nitrogenous compounds in chicken manure similar to any other nitrogen-rich organic wastes; the reactor was operated intentionally at favorable conditions [i.e.; with external nitrite source for NH₄ ⁺:NO₂ ^-≅1.0] in order to make Anammox process to prevail as operation continued. Results indicated significant ammonia removals (60% on average) although influent concentration was gradually increased up to 200 mg L-¹. A modeling exercise has been undertaken to investigate the performance of the laboratory scale UASB reactor. In this scope, the experimental results were modeled by using Mantis2 model within GPS-X 6.5 simulation software that included several built in libraries. Accordingly, effluent chemical oxygen demand (COD) and total ammonia nitrogen (TAN) concentrations could be predicted with reasonably good accuracy demonstrating successful calibration. The regression coefficient (R² ) and mean relative absolute error (MRAE) parameters were found as 0.66 and 16% and 0.70 and 19%, respectively.

Sustainable energy from waste organic matters via efficient microbial processes

This review emphasizes utilization of waste organic matters from water bodies and soil sources for sustainable energy development. These organic waste matters (including microplastics) from a variety of environmental sources have created a big challenge to utilize them for energy development for human needs, maintaining a cleaner environment and thereby, producing useful bioproducts (sustainable bioenergy or other primary metabolites). Anaerobic digestions as well as other effective wastewater treatment approaches are discussed. From the water bodies, waste organic matter reduction can be achieved by a reduction of chemical oxygen demand and biological oxygen demand after the waste treatment. Other forms of organic waste matter are available in the form of agro wastes or residues (stalk of wheat or rice, maize, corn etc.) due to crop cultivation, which are generally burnt into ashes. Such wastes can be utilized for bioenergy energy production, which would help for the reduction of climate changes or other toxic gases. Hydrogen, bioelectricity, ethanol, butanol, methane and algal diesel or other types of fuel sources would help to provide sustainable source of bioenergy that can be produced from these wastes via degradation by the biological processes. This review will discuss in depths about the sustainable nature of organic matters to produce clean energy via application of efficient biological methods to maintain a clean environment, thereby providing alternative options to fossil energy fuels.

Up-Flow Anaerobic Sludge Blanket (UASB) Technology for Energy Recovery: A Review on State-of-the-Art and Recent Technological Advances

Up-flow anaerobic sludge blanket (UASB) reactor belongs to high-rate systems, able to perform anaerobic reaction at reduced hydraulic retention time, if compared to traditional digesters. In this review, the most recent advances in UASB reactor applications are critically summarized and discussed, with outline on the most critical aspects for further possible future developments. Beside traditional anaerobic treatment of soluble and biodegradable substrates, research is actually focusing on the treatment of refractory and slowly degradable matrices, thanks to an improved understanding of microbial community composition and reactor hydrodynamics, together with utilization of powerful modeling tools. Innovative approaches include the use of UASB reactor for nitrogen removal, as well as for hydrogen and volatile fatty acid production. Co-digestion of complementary substrates available in the same territory is being extensively studied to increase biogas yield and provide smooth continuous operations in a circular economy perspective. Particular importance is being given to decentralized treatment, able to provide electricity and heat to local users with possible integration with other renewable energies. Proper pre-treatment application increases biogas yield, while a successive post-treatment is needed to meet required effluent standards, also from a toxicological perspective. An increased full-scale application of UASB technology is desirable to achieve circular economy and sustainability scopes, with efficient biogas exploitation, fulfilling renewable energy targets and green-house gases emission reduction, in particular in tropical countries, where limited reactor heating is required.

Biological nutrient removal and recovery from solid and liquid livestock manure: Recent advance and perspective

Rapid development of livestock industry produces large amount of livestock manure rich in nutrients, organic matters, antibiotics, and heavy metals, thus imposes great harms to human and environment, if the manure is not suitably treated. Biological removal and recovery of nutrients from manure as agriculture fertilizer is attractive due to low cost and simple operation. This review offers an overview of recent development in biological nutrient removal and recovery from livestock manure. Livestock manure is divided into solid manure and liquid manure. Composting and anaerobic digestion of solid manure are fully discussed and important parameters are investigated. Then various processes of nutrient removal and recovery from liquid manure are summarized. Brief economic sustainability and eco-environmental effects are carried out. Finally, current challenges and future prospects in this field are analyzed.