Response of Anammox biofilm to antibiotics in trace concentration: Microbial activity, diversity and antibiotic resistance genes

Norfloxacin affects inorganic nitrogen compound transformation in tailwater containing Corbicula fluminea

The Asian clam, Corbicula fluminea, commonly used in engineered wetlands receiving tailwater, affects nitrogen compound transformation in water. This study investigates how a commonly observed antibiotic in tailwater, norfloxacin, impact nitrogen compound transformation in tailwater containing C. fluminea. The clam was exposed to artificial tailwater with norfloxacin (0, 0.2, 20, and 2000 μg/L) for 15 days. Water properties, C. fluminea ecotoxicity responses, microorganism composition and nitrification- or denitrification-related enzyme activities were measured. Results revealed norfloxacin-induced increases and reductions in tailwater NH4+ and NO2- concentrations, respectively, along with antioxidant system inhibition, organ histopathological damage and disruption of water filtering and digestion system. Microorganism composition, especially biodiversity indices, varied with medium (clam organs and exposure water) and norfloxacin concentrations. Norfloxacin reduced NO2- content by lowering the ratio between microbial nitrifying enzyme (decreased hydroxylamine oxidoreductase and nitrite oxidoreductase activity) and denitrifying enzyme (increased nitrate reductase and nitrite reductase activity) in tailwater. Elevated NH4+ content resulted from upregulated ammonification and inhibited nitrification of microorganisms in tailwater, as well as increased ammonia emission from C. fluminea due to organ damage and metabolic disruption of the digestion system. Overall, this study offers insights into using benthic organisms to treat tailwater with antibiotic residues, especially regarding nitrogen treatment.

Potential electron acceptors for ammonium oxidation in wastewater treatment system under anoxic condition: A review

Anaerobic ammonium oxidation has been considered as an environmental-friendly and energy-efficient biological nitrogen removal (BNR) technology. Recently, new reaction pathway for ammonium oxidation under anaerobic condition had been discovered. In addition to nitrite, iron trivalent, sulfate, manganese and electrons from electrode might be potential electron acceptors for ammonium oxidation, which can be coupled to traditional BNR process for wastewater treatment. In this paper, the pathway and mechanism for ammonium oxidation with various electron acceptors under anaerobic condition is studied comprehensively, and the research progress of potentially functional microbes is summarized. The potential application of various electron acceptors for ammonium oxidation in wastewater is addressed, and the N2O emission during nitrogen removal is also discussed, which was important greenhouse gas for global climate change. The problems remained unclear for ammonium oxidation by multi-electron acceptors and potential interactions are also discussed in this review.

Response mechanism of a highly efficient partial nitritation-anammox (PN/A) process under antibiotic stress: Extracellular polymers, microbial community, and functional genes

The Partial nitritation-Anammox (PN/A) process can be restricted when treating high ammonia nitrogen wastewater containing antibiotics. This study aims to explore the response mechanism of the PN/A process under antibiotic stress. Results showed the PN/A process achieved a nitrogen removal rate higher than 1.01 ± 0.03 kg N/m3/d under long-term sulfamethazine stress. The increase of extracellular polymers from 22.52 to 43.96 mg/g VSS was conducive to resisting antibiotic inhibitory. The increase of Denitratisoma and SM1A02 abundance as well as functional genes nirS and nirK indicated denitrifiers should play an important role in the stability of the PN/A system under sulfamethazine stress. In addition, antibiotic-resistant genes (ARGs) sul1 and intI1 significantly increased by 8.78 and 5.12 times of the initial values to maintain the resistance of PN/A process to sulfamethazine stress. This study uncovers the response mechanism of the PN/A process under antibiotic stress, offering a scientific basis and guidance for further application in the future.

Effects of antibiotics on microbial nitrogen cycling and N2O emissions: A review

Sulfonamides, quinolones, tetracyclines, and macrolides are the most prevalent classes of antibiotics used in both medical treatment and agriculture. The misuse of antibiotics leads to their extensive dissemination in the environment. These antibiotics can modify the structure and functionality of microbial communities, consequently impacting microbial-mediated nitrogen cycling processes including nitrification, denitrification, and anammox. They can change the relative abundance of nirK/norB contributing to the emission of nitrous oxide, a potent greenhouse gas. This review provides a comprehensive examination of the presence of these four antibiotic classes across different environmental matrices and synthesizes current knowledge of their effects on the nitrogen cycle, including the underlying mechanisms. Such an overview is crucial for understanding the ecological impacts of antibiotics and for guiding future research directions. The presence of antibiotics in the environment varies widely, with significant differences in concentration and type across various settings. We conducted a comprehensive review of over 70 research articles that compare various aspects including processes, antibiotics, concentration ranges, microbial sources, experimental methods, and mechanisms of influence. Antibiotics can either inhibit, have no effect, or even stimulate nitrification, denitrification, and anammox, depending on the experimental conditions. The influence of antibiotics on the nitrogen cycle is characterized by dose-dependent responses, primarily inhibiting nitrification, denitrification, and anammox. This is achieved through alterations in microbial community composition and diversity, carbon source utilization, enzyme activities, electron transfer chain function, and the abundance of specific functional enzymes and antibiotic resistance genes. These alterations can lead to diminished removal of reactive nitrogen and heightened nitrous oxide emissions, potentially exacerbating the greenhouse effect and related environmental issues. Future research should consider diverse reaction mechanisms and expand the scope to investigate the combined effects of multiple antibiotics, as well as their interactions with heavy metals and other chemicals or organisms.

Microbial response and recovery strategy of the anammox process under ciprofloxacin stress from pure strain and consortia perspectives

Ciprofloxacin (CIP) poses a high risk of resistance development in water environments. Therefore, comprehensive effects and recovery strategies of CIP in anaerobic ammonia oxidation (anammox) process were systematically elucidated from consortia and pure strains perspectives. The anammox consortia was not significantly affected by the stress of 10 mg L-1 CIP, while the higher concentration (20 mg L-1) of CIP caused a dramatic reduction in the nitrogen removal performance of anammox system. Simultaneously, the abundances of dominant functional bacteria and corresponding genes also significantly decreased. Such inhibition could not be mitigated by the recovery strategy of adding hydrazine and hydroxylamine. Reducing nitrogen load rate from 5.1 to 1.4 kg N m-3 d-1 promoted the restoration of three reactors. In addition, the robustness and recovery of anammox systems was evaluated using starvation and shock strategies. Simultaneously, antibiotic resistance genes and key metabolic pathways of anammox consortia were upregulated, such as carbohydrate and energy metabolisms. In addition, 11 pure stains were isolated from the anammox system and identified through phylogenetic analysis, 40 % of which showed multidrug resistance, especially Pseudomonas. These findings provide deep insights into the responding mechanism of anammox consortia to CIP stress and promote the application of anammox process for treating wastewater containing antibiotics.

An integrated meta-omics approach reveals the different response mechanisms of two anammox bacteria towards fluoroquinolone antibiotics

The emerging fluoroquinolone antibiotics (FQs) are highly influential in nitrogen removal from livestock wastewater. However, beyond the capability of nitrogen removal, little is known about the molecular mechanisms (e.g., shift of core metabolism and energy allocation) of different anaerobic ammonium-oxidizing bacteria (AnAOB) under continuous FQ stress. This study investigated the effects of ciprofloxacin, ofloxacin and their mixture at concentrations detected in livestock wastewater on two key anammox species in membrane bioreactors. It was found 20 μg/L FQs promoted nitrogen removal efficiency and community stability, and42-51 % of FQs were removed simultaneously. Integrated meta-omics analysis revealed varied gene expression patterns between the two dominant AnAOB, Candidatus Brocadia sapporoensis (B AnAOB) and Candidatus Kuenenia stuttgartiensis (K AnAOB). The nitrogen metabolic processes were bolstered in B AnAOB, while those involved in anammox pathway of K AnAOB were inhibited. This difference was tentatively attributed to the up-regulation of reactive oxygen species scavenger genes (ccp and dxf) and FQ resistance gene (qnrB72) in B AnAOB. Importantly, most enhanced core biosynthesis/metabolism of AnAOB and close cross-feeding with accompanying bacteria were also likely to contribute to their higher levels of biomass yield and metabolism activity under FQ stress. This finding suggests that B AnAOB has the advantage of higher nitrogen metabolism capacity over K AnAOB in livestock wastewater containing FQs, which is helpful for efficient and stable nitrogen removal by the functional anammox species.

Green manure incorporation enhanced soil labile phosphorus and fruit tree growth

Introduction

The incorporation of green manures substantially enhances the conversion of external phosphorus (P) fertilizers and soil-reserved P into forms readily available to plants. The study aims to evaluate the influence of green manure additions on soil phosphorus dynamics and citrus growth, considering different green manure species and initial soil phosphorus levels. Additionally, the research seeks to elucidate the microbiological mechanisms underlying the observed effects.

Methods

A citrus pot experiment was conducted under both P-surplus (1.50 g·P·kg-1) and P-deficient (0.17 g·P·kg-1) soils with incorporating legume (Leg), non-legume (Non-Leg) or no green manure residues (CK), and 18O-P labeled KH2PO4 (0.5 g, containing 80‰ δ18Op) was additionally introduced to trace the turnover characteristics of chemical P fertilizer mediated by soil microorganisms.

Results and discussion

In P-surplus soil, compared with the CK treatment, the Leg treatment significantly increased soil H2O-Pi (13.6%), NaHCO3-Po (8.9%), NaOH-Pi (9.5%) and NaOH-Po (30.0%) content. It also promoted rapid turnover of P sources into H2O-Pi and NaHCO3-Pi pools by enhancing the phoC (576.6%) gene abundance. In contrast, the Non-Leg treatment significantly augmented soil H2O-Pi (9.2%) and NaHCO3-Po (8.5%) content, facilitating the turnover of P sources into NaHCO3-Pi pools. Under P-deficient soil conditions, compared with the CK treatment, the Leg treatment notably raised soil H2O-Pi (150.0%), NaHCO3-Pi (66.3%), NaHCO3-Po (34.8%) and NaOH-Pi (59.0%) content, contributing to the transfer of P sources into NaHCO3-Pi and NaOH-Pi pools. This effect was achieved through elevated ALP (33.8%) and ACP (12.9%) activities and increased pqqC (48.1%), phoC (42.9%), phoD (21.7%), and bpp (27.4%) gene abundances. The Non-Leg treatment, on the other hand, led to significant increases in soil NaHCO3-Pi (299.0%) and NaHCO3-Po (132.6%) content, thereby facilitating the turnover of P sources into NaHCO3-Pi and NaOH-Pi pools, except for the phoC gene abundance. Both Leg and Non-Leg treatments significantly improved citrus growth (7.3-20.0%) and P uptake (15.4-42.1%) in P-deficient soil but yielded no substantial effects in P-surplus soil. In summary, introducing green manure crops, particularly legume green manure, emerges as a valuable approach to enhance soil P availability and foster fruit tree growth in orchard production.

Effect and microbial mechanism of pharmaceutical and personal care product exposure on partial nitrification process and nitrous oxide emission

This study focused on the short- and long-term exposure of pharmaceutical and personal care products (PPCPs) to the partial nitrification process and nitrous oxide emission. The corresponding microbial mechanisms were also explored. The results revealed a concentration-dose effect on the partial nitrification process. Moreover, the PPCP concentration of ≥2 μg/L featured inhibitory effects on the process. The solo effect of PPCP on the partial nitrification process was analyzed through microcosmic experiments, and the results revealed significant variations in PN. A dose-effect relationship existed between the PPCP concentration and N2O emission intensity. After exposure to PPCPs, the N2O emission released during the partial nitrification process was significantly reduced. Different PPCPs featured various effects in mitigating N2O emissions. Low PPCP concentrations led to a reduction in the richness and diversity of microbes, but their community structure remained significantly unchanged. High PPCP concentrations (≥5 μg/L) resulted in increased species richness and diversity, but their microbial community composition was significantly affected. The function prediction and nitrogen metabolic pathway analysis indicated that PPCP exposure led to the inhibition of the ammonia oxidation process. However, all genes encoding denitrification enzymes were upregulated. The microorganisms in the microbial community featured modular structural properties and wide synergistic relationships between genera. This study provides valuable insights into the effect of PPCP exposure on the particle nitrification process and corresponding changes in the microbial community.

Purification of aquaculture wastewater by macrophytes and biofilm systems: Efficient removal of trace antibiotics and enrichment of antibiotic resistance genes

The purification performance of aquaculture wastewater and the risk of antibiotic resistance genes (ARGs) dissemination in wetlands dominated by macrophytes remain unclear. Here, the purification effects of different macrophytes and biofilm systems on real aquaculture wastewater were investigated, as well as the distribution and abundance of ARGs. Compared to the submerged macrophytes, artificial macrophytes exhibited higher removal rates of TOC (58.80 ± 5.04 %), TN (74.50 ± 2.50 %), and TP (77.33 ± 11.66 %), and achieved approximately 79.92 % removal of accumulated trace antibiotics in the surrounding water. Additionally, the biofilm microbial communities on the surface of artificial macrophytes exhibited higher microbial diversity with fewer antibiotic-resistant bacteria (ARB) enrichment from the surrounding water. The absolute abundance of ARGs (sul1, sul2, and intI1) in the mature biofilm to be one to two orders of magnitude higher than that in the water. Although biofilms could decrease ARGs in the surrounding water by enriching ARB, the intricate network structure of biofilms further facilitated the proliferation of ARB and the dissemination of ARGs in water. Network analysis suggested that Proteobacteria and Firmicutes phyla were dominant and potential carriers of ARGs, contributing 69.00 % and 16.70 %, respectively. Our findings highlight that macrophytes and biofilm systems have great performance on aquaculture wastewater purification, but with high risk of ARGs.

Role of Biofilms in Waste Water Treatment

Biofilm cells have a different physiology than planktonic cells, which has been the focus of most research. Biofilms are complex biostructures that form on any surface that comes into contact with water on a regular basis. They are dynamic, structurally complex systems having characteristics of multicellular animals and multiple ecosystems. The three themes covered in this review are biofilm ecology, biofilm reactor technology and design, and biofilm modeling. Membrane-supported biofilm reactors, moving bed biofilm reactors, granular sludge, and integrated fixed-film activated sludge processes are all examples of biofilm reactors used for water treatment. Biofilm control and/or beneficial application in membrane processes are improving. Biofilm models have become critical tools for biofilm foundational research as well as biofilm reactor architecture and design. At the same time, the differences between biofilm modeling and biofilm reactor modeling methods are acknowledged.

Sub-inhibitory concentrations of ampicillin affect microbial Fe(III) oxide reduction

Antibiotics are ubiquitous in the iron-rich environments but their roles in microbial reduction of Fe(III) oxides are still unclear. Using ampicillin and Geobacter soli, this study investigated the underlying mechanism by which antibiotic regulated microbial reduction of Fe(III) oxides. Results showed that sub-minimal inhibitory concentrations (sub-MIC) of ampicillin significantly affected ferrihydrite reduction by G. soli, with a stimulatory effect at 1/64 and 1/32 MIC and an inhibitory effect at 1/8 MIC. Increasing ampicillin concentration resulted in increasing cell length and decreasing bacterial zeta potential that were beneficial for ferrihydrite reduction, and decreasing outer membrane permeability that was unfavorable for ferrihydrite reduction. The respiratory metabolism ability was enhanced by 1/64 and 1/32 MIC ampicillin and reduced by 1/8 MIC ampicillin, which was also responsible for regulation of ferrihydrite reduction by ampicillin. The ferrihydrite reduction showed a positive correlation with the redox activity of extracellular polymeric substances (EPS) which was tied to the cytochrome/polysaccharide ratio and the content of α-helices and β-sheet in EPS. These results suggested that ampicillin regulated microbial Fe(III) oxide reduction through modulating the bacterial morphology, metabolism activity and extracellular electron transfer ability. Our findings provide new insights into the environmental factors regulating biogeochemical cycling of iron.

High-risk antibiotics positively correlated with antibiotic resistance genes in five typical urban wastewater

Antibiotic resistance genes (ARGs) and antibiotic amount increased within close proximity to human dominated ecosystems. However, few studies assessed the distribution of antibiotics and ARGs in multiple ecosystems especially the different urban wastewater. In this study, the spatial distribution of ARGs and antibiotics across the urban wastewater included domestic, livestock, hospital, pharmaceutical wastewater, influent of the wastewater treatment plant (WWTP) in Northeast China. The q-PCR results showed that ARGs were most abundant in community wastewater and followed by WWTP influent, livestock wastewater, pharmaceutical wastewater and hospital wastewater. The ARG composition differed among the five ecotypes with qnrS was the dominant ARG subtypes in WWTP influent and community wastewater, while sul2 dominant in livestock, hospital, pharmaceutical wastewater. The concentration of antibiotics was closely related to the antibiotic usage and consumption data. In addition to the high concentration of azithromycin at all sampling points, more than half of the antibiotics in livestock wastewater were veterinary antibiotics. However, antibiotics that closely related to humankind such as roxithromycin and sulfamethoxazole accounted for a higher proportion in hospital wastewater (13.6%) and domestic sewage (33.6%), respectively. The ambiguous correlation between ARGs and their corresponding antibiotics was detected. However, antibiotics that exhibited high ecotoxic effects were closely and positively correlated with ARGs and the class 1 integrons (intI1), which indicated that high ecotoxic compounds might affect antimicrobial resistance of bacteria by mediating horizontal gene transfer of ARGs. The coupling mechanism between the ecological risk of antibiotics and bacterial resistance needed to be further studied, and thereby provided a new insight to study the impact of environmental pollutants on ARGs in various ecotypes.

Mainstream deammonification at ambient temperature treating real sewage by a plug-flow fixed-bed reactor based on zeolite/tourmaline-modified polyurethane carriers

A plug-flow fixed-bed reactor (PFBR) with zeolite/tourmaline-modified polyurethane (ZTP) carriers (PFBR_ZTP) was constructed to realize mainstream deammonification for real domestic sewage treatment. The PFBR_ZTP and PFBR were operated for 111 days treating aerobically pretreated sewage in parallel. A higher nitrogen removal rate of 0.12 kg N·(m³·d)^-1 was achieved in PFBR_ZTP despite lowering the temperature (16.8-19.7 ℃) and fluctuating water quality. Meanwhile, it was indicated that anaerobic ammonium oxidation dominated (64.0 ±13.2%) in PFBR_ZTP, by nitrogen removal pathway analysis and high anaerobic ammonium-oxidizing bacteria (AnAOB) activity (2.89 mg N·(g VSS·h)^-1). And, the lower protein/polysaccharides (PS) ratio further indicated a better biofilm structure in PFBR_ZTP owing to a higher abundance of microorganisms relevant to PS and cryoprotective EPS secretion. Furthermore, partial denitrification was an important nitrite supply process in PFBR_ZTP based on low AOB activity/AnAOB activity ratio, higher Thauera abundance and a remarkably positive correlation between Thauera abundance and AnAOB activity.

Deciphering endogenous and exogenous regulations of anammox consortia in responding to lincomycin by multiomics: quorum sensing and CRISPR system

The widespread use of antibiotics has created an antibiotic resistance genes (ARGs)-enriched environment, which causes high risks on human and animal health. Although antibiotics can be partially adsorbed and degraded in wastewater treatment processes, striving for a complete understanding of the microbial adaptive mechanism to antibiotic stress remains urgent. Combined with metagenomics and metabolomics, this study revealed that anammox consortia could adapt to lincomycin by spontaneously changing the preference for metabolite utilization and establishing interactions with eukaryotes, such as Ascomycota and Basidiomycota. Specifically, quorum sensing (QS) based microbial regulation and the ARGs transfer mediated by clustered regularly interspaced short palindromic repeats (CRISPR) system and global regulatory genes were the principal adaptive strategies. Western blotting results validated that Cas9 and TrfA were mainly responsible for the alteration of ARGs transfer pathway. These findings highlight the potential adaptative mechanism of microbes to antibiotic stress and fill gaps in horizontal gene transfer pathways in the anammox process, further facilitating the ARGs control through molecular and synthetic biology techniques.

A review of anammox metabolic response to environmental factors: Characteristics and mechanisms

Anaerobic ammonium oxidation (anammox) is a promising low carbon and economic biological nitrogen removal technology. Considering the anammox technology has been easily restricted by environmental factors in practical engineering applications, therefore, it is necessary to understand the metabolic response characteristics of anammox bacteria to different environmental factors, and then guide the application of the anammox process. This review presented the latest advances of the research progress of the effects of different environmental factors on the metabolic pathway of anammox bacteria. The effects as well as mechanisms of conventional environmental factors and emerging pollutants on the anammox metabolic processes were summarized. Also, the role of quorum sensing (QS) mediating the bacteria growth, gene expression and other metabolic process in the anammox system were also reviewed. Finally, interaction and cross-feeding mechanisms of microbial communities in the anammox system were discussed. This review systematically summarized the variations of metabolic mechanism response to the external environment and cross-feeding interactions in the anammox process, which would provide an in-depth understanding for the anammox metabolic process and a comprehensive guidance for future anammox-related metabolic studies and engineering applications.

Starting-up performances and microbial community shifts in the coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) and anammox treating nitrate and ammonium contained wastewater

A novel coupling process (SAPD-A) with sulfide autotrophic partial denitrification (SAPD) (NO₃^--N→NO₂^--N) and anaerobic ammonium oxidation (Anammox) was developed using anaerobic sequencing batch reactor (ASBR) in this work. The integrated process comprised two stages. Firstly, the starting-up of SAPD process succeeded by gradually increasing the influent nitrate and sulfide in 95 days. The average nitrate removal efficiency (NRE) and NO₂^--N accumulation rates were 71.24% ± 0.21% and 46.44% ± 0.53% at SAPD process (days 75-95). Then, successful coupling process (SAPD-A) was implemented in two stages (stage I and stage II of SAPD-A). In stage I, it is feasible to promote the successful construction of SAPD-A process by elevating influent ammonium only based on SAPD system, making the NRE increased from 44.45% ± 0.46% (day 95) to 64.62% ± 0.12% at the end of stage I in SAPD-A system (day 126). Meanwhile, the ammonium nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TN-RE) also rose up to 42.46% ± 2.02% and 63.28% ± 0.54% respectively. Furthermore, the average ARE, NRE and TN-RE during the stage II in the bioreactor could reach 65.17% ± 1.45%, 74.50% ± 0.81% and 77.81% ± 0.37% by loading some biofilters (with of approximate 10% of the volume of the bioreactor) attached anaerobic ammonium oxidation bacteria (AnAOB). High-throughput sequencing results showed that the dominant genera concerning nitrogen removal were norank_f_norank_o_Fimbriimonadates (with the abundance of 2.88-8.54%), norank_ o_ norank _ c_ OM190 (2.48-4.41%), norank_f_norank_o_norank_c_WWE3 (11.01-17.69%), subgroup_10 (1.97-3.81%), Limnobacter（2.17-3.49%）, norank_f_n orank_ o_norank_ c_OLB14 (2.03-5.23%), norank-f-PHOS-HE36 (2.18-5.5%), Ellin6067 (1.34-2.24%) and Candidatus_ Brocadia (1.95-2.42%) during the whole starting-up period of coupling SAPD-A process. Batch experiments revealed that the sulfide was fully oxidized within 2 h, with the maximum reaction rate of 38.30 ± 1.53 mg (L h)^-1 in the first 1 h. Simultaneously, the concentration of nitrate sharply decreased from 53.08 ± 0.23 mg L^-1 to 24.16 ± 0.42 mg L^-1 with the reaction rate of 66.41 ± 2.12 mg (L h)^-1 in 0.5 h. Also, the ammonium concentration significantly declined from 47.88 ± 0.34 mg L^-1 to 10.98 ± 0.39 mg L^-1 in 8 h. Anammox process was responsible for the dominant nitrogen removal in the coupling SAPD-A system.

Molecular insights into enhanced nitrogen removal induced by trace fluoroquinolone antibiotics in an anammox system

It has been widely reported that fluoroquinolones (FQs) can affect the anaerobic ammonium oxidization (anammox) microorganisms, which interferes with the performance of nitrogen removal from wastewater. However, the metabolic mechanism of anammox microorganisms responding to FQs has rarely been explored. In this study, it was found that 20 μg/L FQs promoted the nitrogen removal performance of anammox microorganisms in batch exposure assays, and 36-51% of FQs were removed simultaneously. Combined metabolomics and genome-resolved metagenomic analysis revealed up-regulated carbon fixation in anammox bacteria (AnAOB), while purine and pyrimidine metabolism, protein generation and transmembrane transport were enhanced in AnAOB and symbiotic bacteria by 20 μg/L FQs. Consequently, hydrazine dehydrogenation, nitrite reduction, and ammonium assimilation were bolstered, improving the nitrogen removal efficiency of the anammox system. These results revealed the potential roles of specific microorganisms in response to emerging FQs and provided further information for practical application of anammox technology in wastewater treatment.

Occurrence, spatial distribution and ecological risks of antibiotics in soil in urban agglomeration

Antibiotics in soil environment are regarded as emerging pollutants and have introduced increasing risks to soil ecosystem and human health in rapid urbanization areas. Identifying the occurrence and spatial variability of antibiotics in soils is an urgent issue in sustaining soil security. In this study, antibiotics in soils were investigated and analyzed in Beijing-Tianjin-Hebei urban agglomeration. The occurrence, spatial distribution, and related affecting factors of antibiotics in soils were identified and ecological risks of antibiotics in soil environment were assessed. Results showed that (1) The mean concentration of soil antibiotics in Beijing-Tianjin-Hebei urban agglomeration was 21.79 µg/kg. Land use substantially affected the occurrence and concentration of antibiotics in soils. Concentrations of antibiotics in cropland and orchard soils were 2-3 times higher than the other land use types. (2) The concentrations of antibiotics in soils in Beijing-Tianjin-Hebei urban agglomeration presented a spatial pattern of high values in southeast, and low values in northwest. Spatial variability of antibiotics in soils was closely related to the application of organic fertilizer and wastewater irrigation as well as topographical features. Furthermore, soil properties and land management policy had substantial influences on soil antibiotics, and soil heavy metals may aggravate the accumulation of antibiotics in soils. (3) Ecological risks assessment of antibiotics in soils demonstrated that erythromycin (ERY), sulfamethoxazole (SMX), and doxycycline (DOX) may introduce high risks to soil ecosystem health, and more attention should be paid to the areas with intensive human activities that had potential high risk to soil ecosystem health. This study suggests that scientific land and soil management should be considered to prevent soil antibiotic pollution and sustain soil security in urban agglomeration.

Effects of antimicrobials in anammox mediated systems: critical review

Anammox-mediated systems are thought to be cost-effective and efficient technologies for removing nitrogen from wastewater by converting nitrite and ammonium into dinitrogen gas. However, there are inhibitory substances that reduce the effectiveness and efficiency of these processes, preventing their widespread application. Antimicrobial agents are among these substances that have been observed to inhibit anammox-mediated processes. Therefore, this review provides a comprehensive overview of the effects of various antimicrobials on the anammox-based systems with emphasis on the effects in different reactor configurations, sludge types and microbial population of anammox-based systems. In addition, this review also discusses the mechanisms by which nitrifying bacteria are inhibited by the antimicrobials. Gaps in knowledge based on this review as well as future research needs have also been suggested. This review gives a better knowledge of antimicrobial effects on anammox-based systems and provides some guidance on the type of system to use to treat antimicrobial-containing wastewater using anammox-based processes.

Enhanced metronidazole removal by binary-species photoelectrogenic biofilm of microaglae and anoxygenic phototrophic bacteria

High efficient removal of antibiotics during nutriments recovery for biomass production poses a major technical challenge for photosynthetic microbial biofilm-based wastewater treatment since antibiotics are always co-exist with nutriments in wastewater and resist biodegradation due to their strong biotoxicity and recalcitrance. In this study, we make a first attempt to enhance metronidazole (MNZ) removal from wastewater using electrochemistry-activated binary-species photosynthetic biofilm of Rhodopseudomonas Palustris (R. Palustris) and Chlorella vulgaris (C. vulgaris) by cultivating them under different applied potentials. The results showed that application of external potentials of -0.3, 0 and 0.2 V led to 11, 33 and 26-fold acceleration in MNZ removal, respectively, as compared to that of potential free. The extent of enhancement in MNZ removal was positively correlated to the intensities of photosynthetic current produced under different externally applied potentials. The binary-species photoelectrogenic biofilm exhibited 18 and 6-fold higher MNZ removal rate than that of single-species of C. vulgaris and R. Palustris, respectively, due to the enhanced metabolic interaction between them. Application of an external potential of 0V significantly promoted the accumulation of tryptophan and tyrosine-like compounds as well as humic acid in extracellular polymeric substance, whose concentrations were 7.4, 7.1 and 2.0-fold higher than those produced at potential free, contributing to accelerated adsorption and reductive and photosensitive degradation of MNZ.

Recent Advances in Autotrophic Biological Nitrogen Removal for Low Carbon Wastewater: A Review

Due to carbon source dependence, conventional biological nitrogen removal (BNR) processes based on heterotrophic denitrification are suffering from great bottlenecks. The autotrophic BNR process represented by sulfur-driven autotrophic denitrification (SDAD) and anaerobic ammonium oxidation (anammox) provides a viable alternative for addressing low carbon wastewater. Whether for low carbon municipal wastewater or industrial wastewater with high nitrogen, the SDAD and anammox process can be suitably positioned accordingly. Herein, the recent advances and challenges to autotrophic BNR process guided by SDAD and anammox are systematically reviewed. Specifically, the present applications and crucial operation factors were discussed in detail. Besides, the microscopic interpretation of the process was deepened in the viewpoint of functional microbial species and their physiological characteristics. Furthermore, the current limitations and some future research priorities over the applications were identified and discussed from multiple perspectives. The obtained knowledge would provide insights into the application and optimization of the autotrophic BNR process, which will contribute to the establishment of a new generation of efficient and energy-saving wastewater nitrogen removal systems.

Veterinary antibiotics can reduce crop yields by modifying soil bacterial community and earthworm population in agro-ecosystems

Veterinary antibiotics are intensively and widely used in animal farming to treat or prevent diseases, as well as improve growth rate and feed efficiency. Animal manure is an important reservoir of veterinary antibiotics due to their high excretion rates, and thus manure application has been a critical source of veterinary antibiotics in agro-ecosystems. However, how veterinary antibiotics affect agroecosystem functions is still unclearly understood. In this study, we evaluated the effects of veterinary antibiotics on soil bacteria and earthworms in agricultural land with long-term manure application. The potential mechanisms of antibiotic-induced changes in crop yields were also revealed. The results showed that the increasing prevalence of veterinary antibiotics in agro-ecosystems inhibited earthworm abundance and bacterial diversity, and then decreased the bioavailability of soil nutrients. Furthermore, high-dose exposure to veterinary antibiotics improved the abundance of plant pathogenic bacteria. Analysis indicated that veterinary antibiotics played an important underlying role in driving the negative effects on peanut grain yields via disturbing microbe- and earthworm-mediated soil available nutrient contents. The direct toxicity effects of antibiotics on peanut relative yields were stronger than their indirect mediating effects. Additionally, the tradeoffs between antibiotics and agroecosystem functions increased at low exposure levels and then decreased at high exposure levels, which indicated the effects of antibiotics on agroecosystem functions were dose-dependent, except for earthworm biomass. Antibiotic contamination which will impose threats to agricultural sustainability was highlighted and should be paid more attention.

Performance and bacterial community of bio-electrochemical system treating simulated domestic wastewater containing low concentration of cephalosporin antibiotics

This study investigated the effects of five cephalosporin antibiotics (ceftazidime, ceftriaxone, cefdinir, cefixime and cefepime) on performance and bacterial community structure in bio-electrochemical systems (BES) and sequencing batch biofilm reactor (SBBR). The results showed that the external electric field had no significant effect on the removal of COD and ammonia nitrogen in water. The removal rates of five antibiotics in BES increased by 28.5%, 20.0%, 9.1%, 21.0%, and 11.5%, respectively. High-through sequencing showed that microbial membrane-growing process increased species diversity, and antibiotics had a significant inhibitory effect on the initial biofilm of the reactor. As time progressed, the inhibitory effect was weakened, and the microorganism were tolerated and re-enriched. The increase in the type and concentration of antibiotics and the applied electric field had a significant effect on the microorganisms in the reactor. The dominant microorganisms for antibiotic removal in the SBBR were Luteococcus, Cloacibacterium, Dysgonomonas, and Ottowia. The dominant bacteria in the BES were Ottowia and Tahibacte. The abundance of these strains increased significantly during antibiotic acclimation. The abundance of Ottowia, Tahibacter, and Nakamurella were significantly higher than SBBR. Thus the BES system had a good antibiotic degradation effect. The BES can effectively treat simulated domestic sewage containing multiple antibiotics, laying a theoretical foundation for the actual wastewater treatment.

The influence of antibiotics on the anammox process - a review

Anaerobic ammonium oxidation (anammox) is one of the most promising processes for the treatment of ammonium-rich wastewater. It is more effective, cheaper, and more environmentally friendly than the conventional process currently in use for nitrogen removal. Unfortunately, anammox bacteria are sensitive to various substances, including heavy metals and organic matter commonly found in the wastewater treatment plants (WWTPs). Of these deleterious substances, antibiotics are recognized to be important. For decades, the increasing consumption of antibiotics has led to the increased occurrence of antibiotics in the aquatic environment, including wastewater. One of the most important issues related to antibiotic pollution is the generation and transfer of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs). Here, we will discuss the effect of short- and long-term exposure of the anammox process to antibiotic pollutants; with a special focus on the activity of the anammox bacteria, biomass properties, community structures, the presence of antibiotic resistance genes and combined effect of antibiotics with other substances commonly found in wastewater. Further, the defense mechanisms according to which bacteria adapt against antibiotic stress are speculated upon. This review aims to facilitate a better understanding of the influence of antibiotics and other co-pollutants on the anammox process and to highlight future avenues of research to target gaps in the knowledge.

Effects of pharmaceuticals on the nitrogen cycle in water and soil: a review

The effects of pharmaceuticals on the nitrogen cycle in water and soil have recently become an increasingly important issue for environmental research. However, a few studies have investigated the direct effects of pharmaceuticals on the nitrogen cycle in water and soil. Pharmaceuticals can contribute to inhibition and stimulation of nitrogen cycle processes in the environment. Some pharmaceuticals have no observable effect on the nitrogen cycle in water and soil while others appeared to inhibit or stimulate for it. This review reports on the most recent evidence of effects of pharmaceuticals on the nitrogen cycle processes by examination of the potential impact of pharmaceuticals on nitrogen fixation, nitrification, ammonification, denitrification, and anammox. Research studies have identified pharmaceuticals that can either inhibit or stimulate nitrification, ammonification, denitrification, and anammox. Among these, amoxicillin, chlortetracycline, ciprofloxacin, clarithromycin, enrofloxacin, erythromycin, narasin, norfloxacin, and sulfamethazine had the most significant effects on nitrogen cycle processes. This review also clearly demonstrates that some nitrogen transformation processes such as nitrification show much higher sensitivity to the presence of pharmaceuticals than other nitrogen transformations or flows such as mineralization or ammonia volatilization. We conclude by suggesting that future studies take a more comprehensive approach to report on pharmaceuticals' impact on the nitrogen cycle process.

Combining electrochemical nitrate reduction and anammox for treatment of nitrate-rich wastewater: A short review

Treatment of nitrate-rich wastewater is important but challenging for the conventional biological denitrification process. Here, we propose combining the electrochemical reduction and anaerobic ammonium oxidation (anammox) processes together for treatment of nitrate-rich wastewater. This article reviews the mechanism and current research status of electrochemical reduction of nitrate to ammonium as well as the mechanism and applicability of the anammox process. This article discusses the principles, superiorities and challenges of this combined process. The feasibility of the combined process depends on the efficiency of electrochemical nitrate reduction to ammonium and the conditions in the anammox process to use the reduced ammonium as the substrate to achieve deep nitrogen removal. The article provides a feasible strategy for using the electrochemical reduction and anammox combined process to treat nitrate-rich wastewater.

Inhibition of anammox activity by municipal and industrial wastewater pollutants: A review

The use of the anammox process for nitrogen removal has gained popularity across the world due to its low energy consumption and waste generation. Anammox reactors have been used to treat ammonium-rich effluents such as chemical, pharmaceutical, semiconductor, livestock, and coke oven wastewater. Recently, full-scale installations have been implemented for municipal wastewater treatment. The efficiency of biological processes is susceptible to inhibitory effects of pollutants present in wastewater. Considering the increasing number of emerging contaminants detected in wastewater, the impacts of the different types of pollutants on anammox bacteria must be understood. This review presents a compilation of the studies assessing the inhibitory effects of different wastewater pollutants towards anammox activity. The pollutants were classified as antibiotics, aromatics, azoles, surfactants, microplastics, organic solvents, humic substances, biodegradable organic matter, or metals and metallic nanoparticles. The interactions between the pollutants and anammox bacteria have been described, as well as the interactions between different pollutants leading to synergistic effects. We also reviewed the effects of pollutants on distinct species of anammox bacteria, and the main toxicity mechanisms leading to irreversible loss of anammox activity have been identified. Finally, we provided an analysis of strategies to overcome the inhibitory effects of wastewater pollutants on the nitrogen removal performance. We believe this review will contribute with essential information to assist the operation and design of anammox reactors treating different types of wastewaters.

How anammox responds to the emerging contaminants: Status and mechanisms

Numerous researches have been carried out to study the effects of emerging contaminants in wastewater, such as antibiotics, nanomaterials, heavy metals, and microplastics, on the anammox process. However, they are fragmented and difficult to provide a comprehensive understanding of their effects on reactor performance and the metabolic mechanisms in anammox bacteria. Therefore, this paper overviews the effects on anammox processes by the introduced emerging contaminants in the past years to fulfill such knowledge gaps that affect our perception of the inhibitory mechanisms and limit the optimization of the anammox process. In detail, their effects on anammox processes from the aspects of reactor performance, microbial community, antibiotic resistance genes (ARGs), and functional genes related to anammox and nitrogen transformation in anammox consortia are summarized. Furthermore, the metabolic mechanisms causing the cell death of anammox bacteria, such as induction of reactive oxygen species, limitation of substrates diffusion, and membrane binding are proposed. By offering this review, the remaining research gaps are identified, and the potential metabolic mechanisms in anammox consortia are highlighted.

Response of anammox granules to the simultaneous exposure to macrolide and aminoglycoside antibiotics: Linking performance to mechanism

Antibiotic pollution is becoming increasingly severe due to its extensive use. The potential application of the anaerobic ammonium oxidation (anammox) process in the treatment of wastewater containing antibiotics has attracted much attention. As common antibiotics, spiramycin (SPM) and streptomycin (STM) are widely used to treat human and animal diseases. However, their combined effects on the anammox process remain unknown. Therefore, this study systematically evaluated the response of the anammox process to both antibiotics. The half maximal inhibitory concentrations of SPM and STM were determined. The continuous-flow anammox system could adapt to SPM and STM at low concentrations, while antibiotics at high concentrations exhibited inhibitory effects. When the concentrations reached 5 mg L^-1 SPM and 50 mg L^-1 STM, the nitrogen removal efficiency dramatically decreased and then rapidly recovered within 8 days. Correspondingly, the abundances of dominant bacteria and genes also changed with antibiotic concentrations. In general, the anammox process showed a stable performance and a high resistance to SPM and STM, suggesting that acclimatization by elevating the concentrations was beneficial for the anammox process to obtain resistance to different antibiotics with high concentrations. This study provides guidance for the stable operation of anammox-based biological treatment of antibiotics containing wastewater.

Antibiotics in wastewater: From its occurrence to the biological removal by environmentally conscious technologies

In this critical review, we explored the most recent advances about the fate of antibiotics on biological wastewater treatment plants (WWTP). Although the occurrence of these pollutants in wastewater and natural streams has been investigated previously, some recent publications still expose the need to improve the detection strategies and the lack of information about their transformation products. The role of the antibiotic properties and the process operating conditions were also analyzed. The pieces of evidence in the literature associate several molecular properties to the antibiotic removal pathway, like hydrophobicity, chemical structure, and electrostatic interactions. Nonetheless, the influence of operating conditions is still unclear, and solid retention time stands out as a key factor. Additionally, the efficiencies and pathways of antibiotic removals on conventional (activated sludge, membrane bioreactor, anaerobic digestion, and nitrogen removal) and emerging bioprocesses (bioelectrochemical systems, fungi, and enzymes) were assessed, and our concern about potential research gaps was raised. The combination of different bioprocess can efficiently mitigate the impacts generated by these pollutants. Thus, to plan and design a process to remove and mineralize antibiotics from wastewater, all aspects must be addressed, the pollutant and process characteristics and how it is the best way to operate it to reduce the impact of antibiotics in the environment.

Evolution of microbial community and antibiotic resistance genes in anammox process stressed by oxytetracycline and copper

The individual and combined impacts of copper ion (Cu²⁺) and oxytetracycline (OTC) on anaerobic ammonium oxidation (anammox) performance and its self-recovery process were examined. Experimental results showed that the anammox performance and activity of anammox bacteria were inhibited by 1.0 mg L^-1 OTC, Cu²⁺ and OTC + Cu²⁺, and both single and combined inhibitions were reversible. The abundance of functional genes and parts of antibiotic resistance genes (ARGs) were positively related to the dominant bacterium Ca. Kuenenia, implying that the recovery of the performance was associated with the progressive induction of potentially resistant species after inhibition. The above outcomes illustrated that anammox bacteria were stressed by metals and antibiotics, but they still could remove nitrogen at a rate higher than 20.6 ± 0.8 kg N m^-3 d^-1, providing guidance for engineering applications of anammox processes.

A critical review on the effects of antibiotics on anammox process in wastewater

Anaerobic ammonium oxidation (anammox) has recently become of significant interest due to its capability for cost-effective nitrogen elimination from wastewater. However, anaerobic ammonia-oxidizing bacteria (AnAOB) are sensitive to environmental changes and toxic substances. In particular, the presence of antibiotics in wastewater, which is considered unfavorable to the anammox process, has become a growing concern. Therefore, it is necessary to evaluate the effects of these inhibitors to acquire information on the applicability of the anammox process. Hence, this review summarizes our knowledge of the effects of commonly detected antibiotics in water matrices, including fluoroquinolone, macrolide, β-lactam, chloramphenicol, tetracycline, sulfonamide, glycopeptide, and aminoglycoside, on the anammox process. According to the literature, the presence of antibiotics in wastewater could partially or completely inhibit anammox reactions, in which antibiotics targeting protein synthesis or DNA replication (excluding aminoglycoside) were the most effective against the AnAOB strains.

Secondary Effects of Antibiotics on Microbial Biofilms

Biofilms are assemblages of microorganisms attached to each other, or to a surface, and encased in a protective, self-produced matrix. Such associations are now recognized as the predominant microbial growth mode. The physiology of cells in biofilms differs from that of the planktonic cells on which most research has been conducted. Consequently, there are significant gaps in our knowledge of the biofilm lifestyle. Filling this gap is particularly important, given that biofilm cells may respond differently to antibiotics than do planktonic cells of the same species. Understanding the effects of antibiotics on biofilms is of paramount importance for clinical practice due to the increased levels of antibiotic resistance and resistance dissemination in biofilms. From a wider environmental perspective antibiotic exposure can alter the ecology of biofilms in nature, and hence disrupt ecosystems. Biofilm cells display increased resilience toward antibiotics. This resilience is often explained by mechanisms and traits such as decreased antibiotic penetration, metabolically inactive persister cells, and intrinsic resistance by members of the biofilm community. Together, these factors suggest that cells in biofilms are often exposed to subinhibitory concentrations of antimicrobial agents. Here we discuss how cells in biofilms are affected by the presence of antibiotics at subinhibitory concentrations, and the possible ramifications of such secondary effects for healthcare and the environment.

Anammox biofilm system under the stress of Hg(II): Nitrogen removal performance, microbial community dynamic and resistance genes expression

The existence of heavy metals in wastewater has obtained more attention due to its high toxicity and non-degradability. In this study, we investigated the changes of anaerobic ammonium oxidation (Anammox) system under long-term invasion of Hg(Ⅱ). The results indicated that the total nitrogen removal efficiency (TNRE) dropped to around 55 % as Hg(Ⅱ) concentration went up to 20 mg L^-1. But the functional bacteria rapidly developed some resistant abilities and maintained a stable TNRE of 65 % till the end of test. The maximum relative expression fold change of merA, merB, merD and merR were 468.8476, 23.7383, 5.0321 and 15.2514 times, respectively. The high positive correlation between the expression abundance of metal resistance genes and the concentrations of Hg(Ⅱ) revealed the resistant mechanisms of microorganisms to heavy metals. Moreover, the protective strategy based on extracellular polymeric substances also contributed to the stability of Anammox system.

Response of partial nitrification sludge to the single and combined stress of CuO nanoparticles and sulfamethoxazole antibiotic on microbial activity, community and resistance genes

Considering the inevitable release of antibiotics and nanoparticles (NPs) into the nitrogen containing wastewater, the combined impact of CuO NPs and sulfamethoxazole (SMX) antibiotic on partial nitrification (PN) process was investigated in four identical reactors. Results showed that the bioactivity of the aerobic ammonia-oxidizing bacteria (AOB) decreased by half after they were exposed to the combination of CuO NPs and SMX for short-term; however, there was no obvious variation in the bioactivity of AOB when they were exposed to either CuO NPs or SMX. During long-term exposure, the ammonia removal efficiency (ARE) of CuO NPs improved whereas that of SMX decreased, while the combination of CuO NPs and SMX significantly decreased ARE from 62.9% (in control) to 38.2% and had an unsatisfactory self-recovery performance. The combination of CuO NPs and SMX significantly changed the composition of microbial community, decreased the abundance of AOB, and significantly suppressed PN process. Reegarding the resistance genes, the CuO NPs-SMX combination did not improve the expression of copA, cusA, sul1 and sul2; however, it significantly induced the expression of sul3 and sulA.

Impact of substrate material and chlorine/chloramine on the composition and function of a young biofilm microbial community as revealed by high-throughput 16S rRNA sequencing

The bacterial composition of biofilms in drinking water distribution systems is significantly impacted by the disinfection regime and substrate material. However, studies that have addressed the changes in the biofilm community during the early stage of formation (less than 10 weeks) were not yet adequate. Here, we explore the effects of the substrate materials (cast iron, stainless steel, copper, polyvinyl chloride, and high density polyethylene) and different disinfectants (chlorine and chloramine) on the community composition and function of young biofilm by using 16S rDNA sequencing. The results showed that Alphaproteobacteria (39.14%-80.87%) and Actinobacteria (5.90%-40.03%) were the dominant classes in chlorine-disinfection samples, while Alphaproteobacteria (17.46%-74.18%) and Betaproteobacteria (3.79%-68.50%) became dominant in a chloraminated group. The infrequently discussed genus Phreatobacter became predominant in the chlorinated samples, but it was inhibited by chloramine and copper ions. The key driver of the community composition was indicated as different disinfectants according to principle coordination analysis (PCoA) and Permutational multivariate analysis of variance (Adonis test), and the bacterial community changed significantly over time. Communities of biofilms grown on cast iron showed a great distance from the other materials according to Bray-Curtis dissimilarity, and they had a unique dominant genus, Dechloromonas. A metagenomics prediction based on 16S rDNA was used to detect the functional pathways of antibiotic biosynthesis and beta-lactam resistance, and it revealed that several pathways were significantly different in terms of their chlorinated and chloraminated groups.

Degradation pathways, microbial community and electricity properties analysis of antibiotic sulfamethoxazole by bio-electro-Fenton system

Sulfamethoxazole (SMX) is a general antibiotic that is frequently identified in wastewater and surface water. In this study, the degradation and metabolic pathway of SMX by bio-electro-Fenton systems equipped with a CNT/r-FeOOH cathode were investigated. When initial SMX = 25 mg/L, the removal efficiency of SMX reached 94.66% by the bio-electro-Fenton system. The concentrations of sul1, sul2, sul3, sulA, intI1 and 16S rRNA genes were examined in effluents. Four out of the six ARGs analysed were detected. Among all quantified sul genes, sul1 and sulA were the most abundant. High-throughput sequencing revealed that the microbial communities and relative abundance at the phylum and genus levels were affected by different SMX concentrations. In addition, the intermediates were detected and the possible SMX degradation pathway by the bio-electro-Fenton process in the present system was proposed. Furthermore, the highest power density obtained was 283.32 ± 16.35 mW/m² (SMX = 25 mg/L). This study provides an efficient and cost effective method for degrading antibiotics.

An innovative modeling approach of linking land use patterns with soil antibiotic contamination in peri-urban areas

Due to the intensive use and continuous release, high and persistent concentrations of antibiotics are found in soils worldwide. This severe contamination elevates the risks associated with antibiotic exposure and resistance for soil ecosystems and human health. Estimating antibiotic concentrations in soils is a complex and important challenge because the limited information is available on antibiotic use and emission and the high exposure risk to human health occurred in peri-urban areas. In this study, soil antibiotic contamination was linked with land use patterns in a data-scarce peri-urban area in four different seasons, and we established a modeling framework based on land use to estimate spatially explicit distribution of antibiotics in soils. The soil antibiotic concentration was found to be substantially affected by surrounding land use patterns in buffer zones with a radius of 350 m. Agricultural land was the main source of antibiotics entering the soil. Notably, road networks also had considerable impacts on antibiotic residues in soils. Then, a statistical model was developed in describing the linkage between land use patterns and soil antibiotic concentration. Model evaluation suggested that the proposed model successfully simulated the variation of antibiotics in soil with good statistical performance (R² > 0.7). Finally, the model was extrapolated to investigate detailed distribution of antibiotics in soils. Clear spatial and seasonal dynamics can be found in soil antibiotic concentration. To our knowledge, this was the first attempt to adopt a model focusing on land use pattern to estimate the spatially explicit distribution of antibiotics in soils. Despite of some uncertainties, the research provides a land-use-based modeling approach as a reference for preventing and controlling soil antibiotic contamination in the future.

Anammox and partial denitrification coupling: a review

As a new wastewater biological nitrogen removal process, anammox and partial denitrification coupling not only plays a significant role in the nitrogen cycle, but also holds high engineering application value. Because anammox and some denitrifying bacteria are coupled under harsh living conditions, certain operating conditions and mechanisms of the coupling process are not clear; thus, it is more difficult to control the process, which is why the process has not been widely applied. This paper analyzes the research focusing on the coupling process in recent years, including anammox and partial denitrification coupling process inhibitors such as nitrogen (NH₄⁺, NO₂⁻), organics (toxic and non-toxic organics), and salts. The mechanism of substrate removal in anammox and partial denitrification coupling nitrogen removal is described in detail. Due to the differences in process methods, experimental conditions, and sludge choices between the rapid start-up and stable operation stages of the reactor, there are significant differences in substrate inhibition. Multiple process parameters (such as pH, temperature, dissolved oxygen, redox potential, carbon-to-nitrogen ratio, and sludge) can be adjusted to improve the coupling of anammox and partial denitrification to modify nitrogen removal performance.

As a new wastewater biological nitrogen removal process, anammox and partial denitrification coupling not only plays a significant role in the nitrogen cycle, but also holds high engineering application value.

Inhibition of anaerobic ammonium oxidation (anammox) bacteria by addition of high and low concentrations of chloramphenicol and comparison of attached- and suspended-growth

Inhibition of anammox activities was tested with two ranges of chloramphenicol (CAP) concentration (5, 10, 20, 50, and 100 mg L^-1) and (100, 500, and 1000 μg L^-1). In a short-term study, strong inhibition of activity was dependent of CAP concentration in both attached-growth (SBR-A) and suspended-growth (SBR-S) systems. The activities of attached-growth cultures at all CAP concentrations were reversible after 1 day, while activities for suspended-growth cultures were only gradually reversible dependent on the CAP concentrations. In long-term studies with daily additions of 6 mg L^-1 CAP, the anammox activity on day 41 in SBR-A had decreased to 18% baseline (SAA reduced from 0.528 to 0.096 mg N mg^-1 VSS d^-1). More rapid reduction of anammox activity was observed in SBR-S, down to 17% baseline after only 27 days (SAA decreased from 0.576 to 0.096 mg N mg^-1 VSS d^-1). Inhibition was irreversible in both SBR-S and SBR-A after the long-term study. With lower CAP additions (100-1000 μg L^-1), the activities in both reactors were stable during daily CAP addition for two weeks. Attached-growth cultures tended to be more tolerant of CAP addition than suspended-growth cultures. Both un-competitive and non-competitive models could be used to compare anammox activities with the higher CAP concentrations. The SAA_max [fx] (the maximum specific anammox activity) and _hK_i (the inhibition constant) of SBR-A were 0.48 mg N mg^-1 VSS d^-1 and 98.3 mg L^-1, respectively. The SAA_max[fx] and K_i of SBR-S were 1.25 mg N mg^-1 VSS d^-1and 71.1 mg L^-1, respectively.

An innovative strategy for inducing Anammox from partial nitrification process in a membrane bioreactor

Anaerobic ammonium oxidation (Anammox) was an innovative process for nitrogen removal. In this study, CuO nanoparticles (NPs) was step-wise increasingly added to an MBR-based partial nitrification system, to investigate its feasibility for inducing Anammox and establishing autotrophic nitrogen removal system. Results showed that when CuO NPs was elevated to 5 mg L^-1, Anammox was successfully induced. The relative abundance of Nitrosomonas reached 13.73% while Candidatus Kuenenia increased to 4.79% from 0.46%, these two bacteria cooperatively contributed to the autotrophic nitrogen removal and improved the nitrogen removal rate (NRR) to 0.56 kg m^-3 d^-1 in 20 mg L^-1 NPs. However, 50 mg L^-1 NPs deeply suppressed the functional bacteria and decreased NRR to 0.14 kg m^-3 d^-1. Finally, the NPs removal, transformation and adsorption in the system were evaluated. It was concluded that CuO NPs in low concentration (5 mg L^-1) was effective for inducing Anammox and contributed to the survival of Anammox bacteria. The mechanism for inducing Anammox was attributed to the aggregation of CuO NPs which enabled the attached growth of AAOB as well as the suitable survival condition supplied by MBR.

Long-term impact of sulfate on an autotrophic nitrogen removal system integrated partial nitrification, anammox and endogenous denitrification (PAED)

A nitrogen removal system integrating partial nitrification, anaerobic ammonium oxidation (Anammox) and endogenous denitrification (PAED) was established in a sequencing batch reactor (SBR) for treating low nitrogen sewage (approximately 40 mg L^-1 ammonia-nitrogen). The impact of sulfate on PAED sludge was investigated in five identical SBRs, fed with different levels of sulfate (0, 50, 100, 200 and 400 mg L^-1). Ammonia oxidation was improved by the addition of Results showed that the sulfate addition in low concentration of sulfate (≤50 mg L^-1), but was profoundly suppressed by higher levels of sulfate. Sulfate feeding enhanced both total nitrogen removal by Anammox and endogenous denitrification, with the abundance of Candidatus Kuenenia increasing to 4.39% in 400 mg L^-1 sulfate from 0.83% in the control reactor, and Denitratisoma increasing to 6.35% from 2.77%. The results proved the feasibility of the PAED system in treating low nitrogen sewage with sulfate, which also enhanced the nitrogen-sulfate interaction.