Wastewater Treatment Technologies Research Articles

Technical and financial feasibility of a chemicals recovery and energy and water production from a dairy wastewater treatment plant

Due to the high volume of wastewater produced from dairy factories, it is necessary to integrate a water recovery process with the treatment plant. Today, bipolar membrane electrodialysis units (BMEUs) are increasingly developed for wastewater treatment and reutilizing. This article aims to develop and evaluate (technical and cost analyses) a combined BMEU/batch reverse osmosis unit (BROU) process for the recovery of chemicals and water from the dairy wastewater plant. The combined BROU/BMEU process is able to simultaneously produce water and strong base-acid, and reduce power consumption due to the injection of concentrated feed flow into the BMEU. A comprehensive comparative analysis on the performances of two combined and stand-alone BMEU configurations are developed. The proposed combined technology for dairy factory wastewater treatment is designed on a new structure and configuration that can address superior cost analysis compared to similar technologies. Further, the optimal values of permeate flux and current density as two vital and influencing parameters on the performance of the studied dairy wastewater treatment process were calculated and discussed. From the outcomes, the total cost of production in the combined configuration has been reduced by approximately 26% compared to the stand-alone configuration. Increasing the feed concentration rate using the batch reverse osmosis process for the dairy wastewater treatment process can be an ideal solution from an economic point of view. Moreover, point (current density, feed concentration rate, total unit cost) = 328.9,7,14.37\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left(328.9, 7, 14.37\\right)$$\\end{document} can be considered as an optimal point for the economic performance of the studied wastewater treatment process.

Influence of Different Proportions of the Addition of Electrocoagulated Metal Sludge (EMS) Obtained from Oily Wastewater Treatment on the Properties of Laboratory Bricks

Electrochemical wastewater treatment technologies are increasingly being used in practice, and the combination of electrocoagulation with advanced oxidation processes has been shown to increase treatment efficiency. The treatment of oily wastewater produces electrocoagulated metal sludge (EMS). In this work, the possibility of using different ratios of EMS produced during oily wastewater treatment was investigated. EMS was dried conventionally in an oven at 105 °C and used as a partial substitute for clay in the manufacture of laboratory bricks. The main research objectives of this study were to examine the possibility and justification of introducing EMS in brick production. The results show that an increase in the proportion of EMS in the manufacturing of bricks leads to a deterioration in the quality of the bricks. Bricks with an addition of 1 wt% and 5 wt% EMS showed the best properties. The loss on ignition (LOI), compressive strength, boiling water absorption and initial water absorption were determined at 5.7%; 49 N/mm2, 16%, 14 g/min/200 cm2, 15% for modified bricks with 1 wt% EMS and 6.3%, 48 N/mm2, 20%, 15 g/min/200 cm2 for modified brick with 5 wt%.

Performance evaluation of a microbial fuel cell for resource recovery as struvite and bioelectricity generation from slaughterhouse wastewater

AbstractBACKGROUNDThe microbial fuel cell (MFC) is a potential cost‐effective technology for the energy‐neutral treatment of wastewater. However, the successful implementation of this technology in resource recovery is still limited. In this study, a microbial electrochemical cell was designed and operated for 30 days. Critical factors for removal and recovery of nitrogen and phosphorus as struvite from wastewater were assessed.RESULTSOptimization studies on critical factors such as the chemical oxygen demand (COD) of wastewater (500–2000 mg L−1) and cathode aeration rate (45–135 mL min−1) were conducted using a pure culture of Escherichia coli. The system yielded an average power density of 465 mW m−2, average current density of 915 mA m−2 and phosphorus recovery at an extent of 40% as struvite. Additionally, a maximum reduction in the COD of 90% with an average coulombic efficiency of about 82% was obtained at a short interval of 30 days. Solubility studies of the recovered struvite for 12 h at different pH values from 4.5 to 9 showed a maximum solubility of 80% at pH 4.5 and a minimum of 3.5% at pH 9.CONCLUSIONThis study moves one step closer to applying MFC technology for nitrogen‐ and phosphorus‐rich wastewater treatment with concurrent struvite precipitation and electricity production. In this way, Sustainable Development Goals 2, 6 and 7 can be achieved through resource recovery, clean water and bioenergy. © 2024 Society of Chemical Industry (SCI).

Bibliometric Analysis of Nanostructured Anodes for Electro-Oxidative Wastewater Treatment

Last decade, a growing emphasis on developing sustainable and environmentally friendly technologies for electro-oxidative wastewater treatment has catalyzed innovation and spurred research efforts worldwide. Researchers may explore the use of renewable energy sources to drive electrochemical processes, as well as the development of eco-friendly electrode materials for wastewater treatments. The integration of nanostructured anodes into the electrolytic system for wastewater treatment has led to significant advancements in the removal of pollutants via electro-oxidation. Despite the great number of research articles related to the development and use of nanostructured anodes for electro-oxidative wastewater treatment, to our knowledge, no bibliometric analysis has been published in this domain. Therefore, this work presents a bibliometric study of publications on the designated theme, retrieved from the Web of Science Core Collection database, which were published over the last decade. The visual and network analysis of co-authorship among authors, organizations, countries, co-citation of authors, citation of documents and sources, as well as the co-occurrence of author keywords was performed using two compatible pieces of scientometric software, namely VOSviewer (version 1.6.18) and CiteSpace (version 6.2.R4). From 2013 to 2023, there has been a gradual increase in the number of publications regarding the development and use of nanostructured anodes for electro-oxidative wastewater treatment. It suggests a steady advancement in this field. The People’s Republic of China emerges as the most productive country, and it is a leader in international collaborations. Also, the United States of America, South Korea, and European Union countries have significant impacts on the research in this domain. The development and application of nanostructured materials for urea electro-oxidation is a main and prospective research theme. This bibliometric analysis allowed for the visualization of the present landscape and upcoming trends in this research field, thereby facilitating future collaborative research endeavors and knowledge exchange.

Impact of Nitrate on the Removal of Pollutants from Water in Reducing Gas-Based Membrane Biofilm Reactors: A Review

The membrane biofilm reactor (MBfR) is a novel wastewater treatment technology, garnering attention due to its high gas utilization rate and effective pollutant removal capability. This paper outlines the working mechanism, advantages, and disadvantages of MBfR, and the denitrification pathways, assessing the efficacy of MBfR in removing oxidized pollutants (sulfate (SO4−), perchlorate (ClO4−)), heavy metal ions (chromates (Cr(VI)), selenates (Se(VI))), and organic pollutants (tetracycline (TC), p-chloronitrobenzene (p-CNB)), and delves into the role of related microorganisms. Specifically, through the addition of nitrates (NO3−), this paper analyzes its impact on the removal efficiency of other pollutants and explores the changes in microbial communities. The results of the study show that NO3− inhibits the removal of other pollutants (oxidizing pollutants, heavy metal ions and organic pollutants), etc., in the simultaneous removal of multiple pollutants by MBfR.

High-performance internal circulation anaerobic granular sludge reactor for cattle slaughterhouse wastewater treatment and simultaneous biogas production

This research investigates the efficacy of a high-performance pilot-scale Internal Circulation Anaerobic Reactor inoculated with Granular Sludge (ICAGSR) for treating cattle slaughterhouse wastewater while concurrently generating biogas. The primary objective is to assess the efficiency and performance of ICAGSR in terms of organic pollutant removal and biogas production using granular anaerobic sludge. The research methodology entails operating the ICAGSR system under ambient conditions and systematically varying key parameters, including different Hydraulic Retention Times (HRTs) (24, 12, and 8 h) and Organic Loading Rates (OLRs) (3.3, 6.14, and 12.83 kg COD/m³. d). The study focuses on evaluating pollutants’ removal and biogas production rates. Results reveal that the ICAGSR system achieves exceptional removal efficiency for organic pollutants, with Chemical Oxygen Demand (COD) removal exceeding 74%, 67%, and 68% at HRTs of 24, 12, and 8 h, respectively. Furthermore, the system demonstrates stable and sustainable biogas production, maintaining average methane contents of 80%, 76%, and 72% throughout the experimental period. The successful operation of the ICAGSR system underscores its potential as a viable technology for treating cattle slaughterhouse wastewater and generating renewable biogas. In conclusion, this study contributes to wastewater treatment and renewable energy production by providing a comprehensive analysis of the ICAGSR system’s hydrodynamic properties. The research enhances our understanding of the system’s performance optimization under varying conditions, emphasizing the benefits of utilizing ICAGSR reactors with granular sludge as an effective and sustainable approach. Identifying current gaps, future research directions aim to further refine and broaden the application of ICAGSR technology in wastewater treatment and renewable energy initiatives.

Salt stimulates sulfide−driven autotrophic denitrification: Microbial network and metagenomics analyses

Sulfur autotrophic denitrification (SADN) is a promising biological wastewater treatment technology for nitrogen removal, and its performance highly relies on the collective activities of the microbial community. However, the effect of salt (a prevailing characteristic of some nitrogen−containing industrial wastewaters) on the microbial community of SADN is still unclear. In this study, the response of the sulfide−SADN process to different salinities (i.e., 1.5 % salinity, 0.5 % salinity, and without salinity) as well as the involved microbial mechanisms were investigated by molecular ecological network and metagenomics analyses. Results showed that the satisfactory nitrogen removal efficiency (>97 %) was achieved in the sulfide−SADN process (S/N molar ratio of 0.88) with 1.5 % salinity. In salinity scenarios, the genus Thiobacillus significantly proliferated and was detected as the dominant sulfur−oxidizing bacteria in the sulfide−SADN system, occupying a relative abundance of 29.4 %. Network analysis further elucidated that 1.5 % salinity had enabled the microbial community to form a more densely clustered network, which intensified the interactions between microorganisms and effectively improved the nitrogen removal performance of the sulfide−SADN. Metagenomics sequencing revealed that the abundance of functional genes encoding for key enzymes involved in SADN, dissimilatory nitrate reduction to ammonium, and nitrification was up−regulated in the 1.5 % salinity scenario compared to that without salinity, stimulating the occurrence of multiple nitrogen transformation pathways. These multi−paths contributed to a robust SADN process (i.e., nitrogen removal efficiency >97 %, effluent nitrogen <2.5 mg N/L). This study deepens our understanding of the effect of salt on the SADN system at the community and functional level, and favors to advance the application of this sustainable bioprocess in saline wastewater treatment.

EVALUATION OF THE CARBON FOOTPRINT IN THE TREATMENT OF URBAN WASTEWATER IN THE CANARY ISLANDS (SPAIN)

ABSTRACT: Wastewater treatment plants play an important role within the urban water cycle to prevent the natural water environment and human health from being negatively affected by human activities. However, wastewater treatment processes, such as effluent discharge and indirect emissions resulting from energy or chemical production, also negatively affect the environment. Footprints have been used to track human influence on the environment in different areas of interest and have been applied to assess the sustainability of wastewater treatment plants. In this article, a comprehensive review of footprint assessment was investigated to evaluate the wastewater treatment process in wastewater treatment plants. The review showed that carbon footprinting was used to assess the sustainability of WWTPs, and that other footprint assessment applications (such as nitrogen and phosphorus footprinting) were also introduced to assess eutrophication of water bodies. To promote the application of footprint assessment, this article regulates the study objectives, frameworks, system boundaries, data processing methods, and the resulting interpretation process. The pros and cons of the footprint assessments were discussed and investigated in detail, examining the CO2 production on each island of the Canary archipelago, and several suggestions were proposed to improve the footprint assessments. Analysis of footprint assessments at different wastewater treatment plants revealed that wastewater treatment technologies and scales had a significant impact on footprints. Furthermore, research hotspots identified using a keyword network diagram showed that the water-carbon-energy nexus was a promising direction for future studies. The purpose of the study is to improve the reduction of the carbon footprint both at the level of direct and indirect emissions factors using new tools and methodologies. Key Words: Footprint; Waste water; Canary Islands

Natural mineral raw materials as granular filtering materials in industrial and waste water treatment

Analysis of currently existing methods of natural and waste water treatment from heavy metals has shown that one of the most promising is the sorption method using natural inorganic materials as sorbents: zeolite, diatomite, and vermiculite. The relevance of the topic is dictated by the need to develop an original technology of wastewater treatment and water treatment, which allows constant monitoring of the level of pollution of natural waters by industrial wastewater from metallurgical enterprises. The proposed methods of sorbent modification create a basis for studying the structure, porosity, and sorption capabilities of the mentioned natural materials. All three minerals: zeolite, diatomite, and vermiculite belong to highly porous, structured materials, promising for use as stable sorption systems in water treatment and water purification. The influence of physical and chemical characteristics of natural sorbents and the application of new promising environmentally safe materials and reagents for water treatment are considered. The sorption of copper ions on natural zeolite material before and after its modification by hydrothermal method was investigated. The activity of sorbents was estimated by the value of sorption capacity, i.e. the amount of heavy metal ions absorbed by a unit mass of sorbent based on zeolite and its modified form.

N-coordinated single cobalt atoms catalyst triggering concerted radical-nonradical process in catalytic ozonation for efficient water decontamination

Heterogeneous catalytic ozonation (HCO) has been developed as a promising technology for wastewater treatment, while traditional radical-based HCO process still suffers from insufficient mineralization of organic pollutants. Herein, we constructed a N-coordinated single cobalt atoms catalyst (CoSAC-N-C) triggering concerted radical-nonradical process in catalytic ozonation for efficient decontamination of pollutants. Experiments and theoretical calculations proved that mediate O in O3 obtained electrons from electron-rich N sites for hydroxyl radical (·OH) production, and the terminal O in O3 was attracted on electron-deficient Co sites for nonradical *O generation by O-O cleavage. The synergistic oxidation of ·OH and *O enabled excellent pollutants mineralization, surpassing most of conventional HCO catalysts. CoSAC-N-C exhibited excellent treatment performance for the coking wastewater in a continuous-flow reactor with COD reducing from 86 mg/L to less than 50 mg/L. This work provided a viable strategy of developing dual-site HCO catalysts to promote concerted radical-nonradical oxidations for wastewater treatment.

Approaches for Enhancing Wastewater Treatment of Photocatalytic Fuel Cells: A Review.

Environmental pollution and energy crises have garnered global attention. The substantial discharge of organic waste into water bodies has led to profound environmental contamination. Photocatalytic fuel cells (PFCs) enabling the simultaneous removal of refractory contaminants and recovery of the chemical energy contained in organic pollutants provides a potential strategy to solve environmental issues and the energy crisis. This review will discuss the fundamentals, working principle, and configuration development of PFCs and photocatalytic microbial fuel cells (PMFCs). We particularly focus on the strategies for improving the wastewater treatment performance of PFCs/PMFCs in terms of coupled advanced oxidation processes, the rational design of high-efficiency electrodes, and the strengthening of the mass transfer process. The significant potential of PFCs/PMFCs in various fields is further discussed in detail. This review is intended to provide some guidance for the better implementation and widespread adoption of PFC wastewater treatment technologies.

Phytic acid metal complex as precursor for fabrication of superhydrophilic membrane with photo-Fenton self-cleaning property for microalgae dewatering and oil/water emulsion separation

Membrane technology is regarded as one of the most effective approaches for microalgae dewatering in the biofuel production industrial and oil/water emulsion separation. However, it inherently suffers from the issue of membrane fouling, particularly irreversible membrane fouling, which is hard to remove by physical methods. Herein, a robust superhydrophilic membrane combined with photo-Fenton self-cleaning property was developed for microalgae dewatering and oil/water emulsion separation. Phytic acid (PA) and FeIII formed a hydrophilic PA-FeIII complex on the polyethersulfone (PES) membrane as the precursor for the in situ growth of β-FeOOH nanorods. When used for microalgae filtration, the irreversible fouling that blocked membrane pores could be degraded by the photo-Fenton reaction. Hence, the obtained PES/PA@β-FeOOH membrane possessed a flux recovery rate (FRR) of 90.2 % (within 30 min), which was significantly higher than that of the PES membrane (32.9 %). The proteins and polysaccharides (extracellular organic matter) attached on the PES/PA@β-FeOOH membrane with photo-Fenton cleaning were 11.2 and 9.1 mg/m2, which was considerably lower than that of PES after hydraulic cleaning (184.1 and 334.9 mg/m2). Moreover, due to the superhydrophilic, the prepared PES/PA@β-FeOOH membrane also exhibited excellent oil/water emulsion separation ability. This work presents a facile and mild strategy to design an anti-fouling coating with superhydrophilic and photo-Fenton activity, which can be used in membrane technology for microorganism filtration and wastewater treatment.

Analysis and standardization of coal chemical wastewater treatment and reuse systems

To meet the practical needs of classified collection, graded treatment, and quality recycling of coal chemical wastewater, and in accordance with the standardization requirements of wastewater resource utilization, the Standardization Administration of China released the national standard GB/T 42,866-2023 ″Guidelines for Coal Chemical Wastewater Treatment and Recycling Technology” on August 6, 2023, for the first time. Based on the standard, this paper comprehensively and systematically sorts out and analyzes the characteristics, processes, water circulation systems, and standardization paths of units such as coal chemical wastewater collection and treatment, recycling, and the treatment of concentrated brine water, through extensive industry research. Furthermore, by integrating typical engineering case practices, this paper explains the feasibility of the paths, which provides technical guidance and experience for relevant cases of coal chemical wastewater treatment and recycling. It is also of great importance for promoting the standardized management and development of coal chemical wastewater treatment and recycling worldwide.

The water energy food nexus: A multi-objective optimization tool

Many methods and tools are used to model and optimize various aspects of the water energy food nexus (WEFN). This work presents a novel software tool for the multi-objective optimization of the WEFN (MOO-WEFN). The model underlying the tool captures all three nexus sectors and the interlinkages between them. In addition, the model imposes constraints that mimic forces affecting the nexus, such as economics, environment, health, and nutrition. The software tool couples Excel with Python, which facilitates the tool's accessibility and ease of use due to its widespread usage and availability. A case study application demonstrates the tool's execution and provides examples of how changes can be made to the data to simulate different nexus developments. Five scenarios are applied to reflect such changes with results demonstrating the overall impact on resource production and consumption. Removing one of the less water-intensive food items results in a 20% increase in water consumption. Limiting the availability of surface water results in a reallocation of water resources such that 80% of water needs are satisfied from surface water and groundwater and 20% from wastewater, compared to the baseline of 100% surface water. Moreover, upon introduction of the conventional activated sludge treatment technology for wastewater (compared to the incumbent membrane bioreactor technology), energy consumption decreased by 10%. These results show changes beyond the immediate sector of change and reflect the necessity for integrated modeling that captures the impact of one change on the nexus as a whole, in terms of resource consumption and allocation. Thus, the tool supports the capability of testing how new resources, technologies, and limitations will impact nexus interactions. Furthermore, the tool facilitates carrying out sensitivity and Pareto analyses for data generation and result evaluation.

Investigating a batch-flow photocatalytic LED system for diclofenac removal in wastewater treatment plants: Assessing the influence of reaction conditions on photocatalytic efficiency

This work introduces an innovative batch-flow photocatalytic LED system aimed at efficiently removing diclofenac from wastewater. The study highlights the novelty of fabricating TiO2-loaded carbon fiber photocatalysts through a hydrothermal process, exhibiting a blue shift in their absorption spectrum and enhancing their photon absorption capability. A crucial design feature is the spectral matching between the LED light source and the photocatalyst, which is critical for achieving high photodegradation efficiency. A significant innovation of our study is the testing of the system under real conditions at an operational sewage treatment plant. Here, the designed system demonstrated high efficacy in degrading diclofenac across various treatment stages, highlighting its robustness and adaptability to changing environmental conditions. The highest degradation efficiency was achieved with sewage from the secondary settling tank, where nearly 90 % efficiency was observed after 6 h of irradiation. Moreover, the use of renewable energy sources emphasizes the system's sustainability, presenting a greener alternative to traditional wastewater treatment methods. The investigation not only showcases the system's effectiveness in diclofenac degradation but also its adaptability and stability under real-world conditions, marking a significant advancement in sustainable wastewater treatment technologies.

Synthetic greywater treatment using a scalable granular activated carbon bioelectrochemical reactor

Greywater reuse has emerged as a promising solution for addressing water shortages. However, greywater needs treatment before reuse to meet the required water quality standards. Conventional wastewater treatment technologies are unsuitable for recreating highly decentralized domestic greywater. This study evaluated bioelectrochemical reactors (BERs) with granular activated carbon (GAC) as a sustainable alternative for developing decentralized and low-cost biological treatment systems. BERs using GAC as the anode material and conventional GAC biofilters (BFs) for synthetic greywater treatment were operated in batch mode for 110days in two stages: (i) with polarized anodes at −150 mV vs. Ag/AgCl and (ii) as a microbial fuel cell with an external resistance of 1 kΩ. Anode polarization produced an electrosorption effect, increasing the ion removal of the BERs. Power production during the operation and cyclic voltammetry tests of the extracted granules revealed electrochemically active biofilm development on the BERs. Although low power density (0.193 ± 0.052 µW m−3) was observed in BERs, they showed a similar performance in sCOD removal (BER = 91.6–89.6 %; BF = 96.2–93.2 %) and turbidity removal (BER = 81–82 %; BF = 30–62 %) to BFs that used 50% aeration. Additionally, scanning electron microscopy of sampled granules showed higher biomass formation in BER granules than in BF granules, suggesting a higher contribution of sessile (vs. planktonic) cells to the treatment. Thus, the results highlight the synergistic removal effect of the GAC-based BER. The scalable design presented in this study represents a proof-of-concept for developing BERs to use in decentralized greywater treatment systems.

Application and effect evaluation of membrane bioreactor technology in municipal wastewater treatment

Due to the increasing amount of urban sewage and improved standards in sewage discharge, simple traditional biological sewage treatment fails to meet the needs of municipal sewage treatment. Therefore, to treat wastewater more efficiently, the process of combining biofilm technology with traditional biological wastewater treatment appeared. This paper analyzes the advantages and problems of the combined processes of membrane separation technology and traditional biological sewage treatment technology from and perspective of complementary processes, and puts forward relevant measures to alleviate membrane fouling. The study found that Membrane Bioreactor (MBR) technology occupies a small area, and has a better sewage effluent quality and strong stability, also the sludge output is low. Anaerobic Membrane Bioreactor (AnMBR) technology can increase the effectiveness of removing organic matter and enable resource reuse, which satisfies the demand for low energy consumption. Membrane Aeration Bioreactor (MABR) technology involves bubble-free aeration that greatly improves the quality of sewage effluent, and the production of sludge in MABR technology decreases. Anaerobic ammonium nitrogen membrane bioreactor technology can enhance the efficiency of Anammox bacteria, and the energy consumption and economic cost of this technology are low. Although these membrane combination processes can effectively treat sewage, they can easily be limited by factors such as temperature, microbial communities, and membrane fouling. This paper provides guiding opinions for decision makers in the field of urban sewage treatment so that they can apply appropriate sewage treatment technology to local municipal sewage treatment, promoting the sustainable development of sewage treatment.

Intensive Microalgal Cultivation and Tertiary Phosphorus Recovery from Wastewaters via the EcoRecover Process.

Mixed community microalgal wastewater treatment technologies have the potential to advance the limits of technology for biological nutrient recovery while producing a renewable carbon feedstock, but a deeper understanding of their performance is required for system optimization and control. In this study, we characterized the performance of a 568 m3·day-1 Clearas EcoRecover system for tertiary phosphorus removal (and recovery as biomass) at an operating water resource recovery facility (WRRF). The process consists of a (dark) mix tank, photobioreactors (PBRs), and a membrane tank with ultrafiltration membranes for the separation of hydraulic and solids residence times. Through continuous online monitoring, long-term on-site monitoring, and on-site batch experiments, we demonstrate (i) the importance of carbohydrate storage in PBRs to support phosphorus uptake under dark conditions in the mix tank and (ii) the potential for polyphosphate accumulation in the mixed algal communities. Over a 3-month winter period with limited outside influences (e.g., no major upstream process changes), the effluent total phosphorus (TP) concentration was 0.03 ± 0.03 mg-P·L-1 (0.01 ± 0.02 mg-P·L-1 orthophosphate). Core microbial community taxa included Chlorella spp., Scenedesmus spp., and Monoraphidium spp., and key indicators of stable performance included near-neutral pH, sufficient alkalinity, and a diel rhythm in dissolved oxygen.

Comammox Nitrospira cooperate with anammox bacteria in a partial nitritation–anammox membrane bioreactor treating low-strength ammonium wastewater at high loadings

Research has revealed that comammox Nitrospira and anammox bacteria engage in dynamic interactions in partial nitritation–anammox reactors, where they compete for ammonium and nitrite or comammox Nitrospria supply nitrite to anammox bacteria. However, two gaps in the literature are present: the know-how to manipulate the interactions to foster a stable and symbiotic relationship and the assessment of how effective this partnership is for treating low-strength ammonium wastewater at high hydraulic loads. In this study, we employed a membrane bioreactor designed to treat synthetic ammonium wastewater at a concentration of 60 mg N/L, reaching a peak loading of 0.36 g N/L/day by gradually reducing the hydraulic retention time to 4 hr. Throughout the experiment, the reactor achieved an approximately 80 % nitrogen removal rate through strategically adjusting intermittent aeration at every stage. Notably, the genera Ca. Kuenena, Nitrosomonas, and Nitrospira collectively constituted approximately 40 % of the microbial community. Under superior intermittent aeration conditions, the expression of comammox amoA was consistently higher than that of Nitrospira nxrB and AOB amoA in the biofilm, despite the higher abundance of Nitrosomonas than comammox Nitrospira, implying that the biofilm environment is favorable for fostering cooperation between comammox and anammox bacteria. We then assessed the in situ activity of comammox Nitrospira in the reactor by selectively suppressing Nitrosomonas using 1-octyne, thereby confirming that comammox Nitrospira played the primary role in facilitating the nitritation (33.1 % of input ammonium) rather than complete nitrification (7.3 % of input ammonium). Kinetic analysis revealed a specific ammonia-oxidizing rate 5.3 times higher than the nitrite-oxidizing rate in the genus Nitrospira, underscoring their critical role in supplying nitrite. These findings provide novel insights into the cooperative interplay between comammox Nitrospira and anammox bacteria, potentially reshaping the management of nitrogen cycling in engineered environments, and aiding the development of microbial ecology-driven wastewater treatment technologies.

Nutrient Removal and Recovery from Municipal Wastewater

With the ongoing amendment of the EU legislation on the treatment of urban wastewater, stricter requirements for the removal of pollutants are expected, which calls for the need for innovative wastewater treatment technologies. Biological systems are still the first choice. A survey of typical bioreactors applied in wastewater treatment is presented. The wastewater treatment objective, biochemical environment, and microbial growth are selected as the main criteria for the classification of these bioreactors. Hydraulic and kinetic aspects are considered, along with the advantages and drawbacks of these bioreactors regarding the selection of the appropriate type of reactor; as well, details regarding the operation of reactors are mentioned. The aim of this paper is to provide operators and designers with a brief overview of the selected traditional and advanced processes, reactors, and technologies for nutrient removal from municipal wastewater. The possibilities and limitations in complying with more strict effluent standards are also discussed. Methods of nutrient recovery are added value. From the evaluation of the published papers, we determine that the currently applied traditional methods for nutrient removal have the potential to also convey the expected stricter limits.