Antibiotic resistance genes in manure-amended paddy soils across eastern China: Occurrence and influencing factors

• Manure fertilization resulted in antibiotic residues and increased metal contents. • The tet and sul genes were significantly enhanced with manure fertilization. • Soil physicochemical properties contributed to 12% of the variations in ARGs. • Soil metals and antibiotics co-select for ARGs. Pig manure, rich in antibiotics and metals, is widely applied in paddy fields as a soil conditioner, triggering the proliferation of antibiotic resistance genes (ARGs) in soil. However, comprehensive studies on the effects of manure fertilization on the abundance of ARGs and their influencing factors are still insufficient. Here, pig manure and manure-amended and inorganic-amended soils were collected from 11 rice-cropping regions in eastern China, and the accumulation of antibiotics, metals, and ARGs was assessed simultaneously. The results showed that manure fertilization led to antibiotic residues and increased the metal content (i.e., Zn, Cu, Ni, and Cr). Tetracycline and sulfonamide resistance genes (tetM, tetO, sul1, and sul2) were also significantly enhanced with manure fertilization. According to variance partitioning analysis, the most important factors that individually influenced ARGs were soil physicochemical properties, accounting for 12% of the variation. Significant correlations between soil nutrients and ARGs indicated that manure application enhanced the growth of resistant microorganisms by supplying more nutrients. Metals and antibiotics contributed 9% and 5% to the variations in ARGs, respectively. Their co-occurrence also increased the enrichment of ARGs, as their interactions accounted for 2% of the variation in ARGs. Interestingly, Cu was significantly related to most ARGs in the soil (r = 0.26–0.52, p<0.05). Sulfapyridine was significantly related to sul2, and tetracycline resistance genes were positively related to doxycycline. This study highlighted the risks of antibiotic and ARG accumulation with manure fertilization and shed light on the essential influencing factors of ARGs in paddy soils.     

Distribution of antibiotic resistance genes and their association with bacteria and viruses in decentralized sewage treatment facilities

• Distribution of ARGs in decentralized sewage facilities were investigated. • Bacitracin-ARGs were most predominant ARGs in rural wastewater. • ARGs were identified in bacterial and viral community. • ARGs of rpoB, drfE, gyrA and parC were both correlated with bacteria and phages. • More attention should be paid to the risk of spreading ARG by phages. The distribution of antibiotic resistance genes (ARGs) has been intensively studied in large-scale wastewater treatment plants and livestock sources. However, small-scale decentralized sewage treatment facilities must also be explored due to their possible direct exposure to residents. In this study, six wastewater treatment facilities in developed rural areas in eastern China were investigated to understand their risks of spreading ARGs. Using metagenomics and network analysis tools, ARGs and bacterial and viral communities were identified in the influent (INF) and effluent (EFF) samples. The dominant ARGs belonged to the bacitracin class, which are different from most of municipal wastewater treatment plants (WWTPs). The dominant hosts of ARGs are Acidovorax in bacterial communities and Prymnesiovirus in viral communities. Furthermore, a positive relationship was found between ARGs and phages. The ARGs significantly correlated with phages were all hosted by specific genera of bacteria, indicating that phages had contributed to the ARG’s proliferation in sewage treatment facilities. Paying significant concern on the possible enhanced risks caused by bacteria, viruses and their related ARGs in decentralized sewage treatment facilities is necessary.     

Metagenomic analysis on resistance genes in water and microplastics from a mariculture system

• Total 174 subtypes of ARGs were detected by metagenomic analysis. • Chloramphenicol resistance genes were the dominant ARGs in water and microplastics. • The abundances of MRGs were much higher than those of ARGs. • Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phylum. • Microplastics in mariculture system could enrich most of MRGs and some ARGs. Microplastics existing widely in different matrices have been regarded as a reservoir for emerging contaminants. Mariculture systems have been observed to host microplastics and antibiotic resistance genes (ARGs). However, more information on proliferation of ARGs and metal resistance genes (MRGs) in mariculture system at the presence of microplastics is needed. This study used metagenomic analysis to investigate the distribution of ARGs and MRGs in water and microplastics of a typical mariculture pond. Total 18 types including 174 subtypes of ARGs were detected with the total relative abundances of 1.22/1.25 copies per 16S rRNA copy for microplastics/water. Chloramphenicol resistance genes were the dominant ARGs with the abundance of 0.35/0.42 copies per 16S rRNA copy for microplastics/water. Intergron intI1 was dominant gene among 6 detected mobile genetic elements (MGEs) with the abundance of 75.46/68.70 copies per 16S rRNA copy for water/microplastics. Total 9 types including 46 subtypes of MRGs were detected with total abundance of 5.02 × 10²/6.39 × 10² copies per 16S rRNA copy for water/ microplastics while genes resistant to copper and iron served as the dominant MRGs. Proteobacteria, Bacteroidetes, and Actinobacteria accounted for 84.2%/89.5% of total microbial community. ARGs with relatively high abundance were significantly positively related to major genera, MGEs, and MRGs. Microplastics in mariculture system could enrich most of MRGs and some ARGs to serve as potential reservoir for these pollutants. The findings of this study will provide important information on resistance gene pollution at presence of microplastics in the mariculture system for further proposing suitable strategy of environmental management.     

Determination of 27 pharmaceuticals and personal care products (PPCPs) in water: The benefit of isotope dilution

• Isotope dilution method was developed for the determination of 27 PPCPs in water. • The established method was successfully applied to different types of water samples. • The correction effect of corresponding 27 ILSs over 70 d was investigated. • Benefit of isotopic dilution method was illustrated for three examples. Pharmaceuticals and personal care products (PPCPs) are a unique group of emerging and non-persistent contaminants. In this study, 27 PPCPs in various water samples were extracted by solid phase extraction (SPE), and determined by isotope dilution method using liquid chromatography coupled to tandem triple quadruple mass spectrometer (LC-MS/MS). A total of 27 isotopically labeled standards (ILSs) were applied to correct the concentration of PPCPs in spiked ultrapure water, drinking water, river, effluent and influent sewage. The corrected recoveries were 73%–122% with the relative standard deviation (RSD)<16%, except for acetaminophen. The matrix effect for all kinds of water samples was<22% and the method quantitation limits (MQLs) were 0.45–8.6 ng/L. The developed method was successfully applied on environmental water samples. The SPE extracts of spiked ultrapure water, drinking water, river and wastewater effluent were stored for 70 days, and the ILSs-corrected recoveries of 27 PPCPs were obtained to evaluate the correction ability of ILSs in the presence of variety interferences. The recoveries of 27 PPCPs over 70 days were within the scope of 72%–140% with the recovery variation<37% in all cases. The isotope dilution method seems to be of benefit when the extract has to be stored for long time before the instrument analysis.     

Mesophilic and thermophilic anaerobic digestion of swine manure with sulfamethoxazole and norfloxacin: Dynamics of microbial communities and evolution of resistance genes

• SMX addition had negative effect on acetoclastic methanogens in mesophilic AD. • Thermophilic AD was more effective in eliminating resistance genes than mesophilic. • ARGs variations in AD were mainly affected by succession of microbial community. • Methane production was significant associated to ARGs reduction. The role of norfloxacin (NOR) and sulfamethoxazole (SMX) in mesophilic and thermophilic anaerobic digestion (AD) of pig manure, with respect to methane production and variations in the microbial community and resistance genes, including antibiotic resistance genes (ARGs), class I integrase (intI1), and heavy metal resistance genes (MRGs), was investigated. The results indicated that NOR exerted little influence on the microbial community, whereas SMX negatively affected the acetoclastic methanogens. The abundance of two sulfonamide resistance genes (sul1 and sul2), three quinolone resistance genes (qnrS, parC, and aac(6’)-Ib-cr), and intI1 decreased by 2‒3 orders of magnitude at the end of thermophilic AD. In contrast, mesophilic AD was generally ineffective in reducing the abundance of resistance genes. According to the results of redundancy analysis, the abundance of ARGs was affected primarily by microbial community dynamics (68.5%), rather than the selective pressure due to antibiotic addition (13.3%). Horizontal gene transfer (HGT) through intI1 contributed to 26.4% of the ARG variation. The archaeal community also influenced the changes in the resistance genes, and ARG reduction was significantly correlated with enhanced methane production. Thermophilic AD presented a higher methane production potential and greater reduction in resistance gene abundance.     

Assessment of antibiotic resistance genes in dialysis water treatment processes

• Quantitative global ARGs profile in dialysis water was investigated. • Totally 35 ARGs were found in the dialysis treatment train. • 29 ARGs (highest) were found in carbon filtration effluent. • erm and mtrD-02 occurred in the final effluent. • The effluent was associated with health risks even after RO treatment. Dialysis water is directly related to the safety of hemodialysis patients, thus its quality is generally ensured by a stepwise water purification cascade. To study the effect of water treatment on the presence of antibiotic resistance genes (ARGs) in dialysis water, this study used propidium monoazide (PMA) in conjunction with high throughput quantitative PCR to analyze the diversity and abundance of ARGs found in viable bacteria from water having undergone various water treatment processes. The results indicated the presence of 35 ARGs in the effluents from the different water treatment steps. Twenty-nine ARGs were found in viable bacteria from the effluent following carbon filtration, the highest among all of the treatment processes, and at 6.96 Log (copies/L) the absolute abundance of the cphA gene was the highest. Two resistance genes, erm (36) and mtrD-02, which belong to the resistance categories macrolides-lincosamides-streptogramin B (MLSB) and other/efflux pump, respectively, were detected in the effluent following reverse osmosis treatment. Both of these genes have demonstrated the potential for horizontal gene transfer. These results indicated that the treated effluent from reverse osmosis, the final treatment step in dialysis-water production, was associated with potential health risks.     

Effect of the ultraviolet/chlorine process on microbial community structure,typical pathogens,and antibiotic resistance genes in reclaimed water

• UV/chlorine can effectively remove VBNC pathogens, ARGs and MGEs in reclaimed water. • Microbial community was changed with reduced diversity during UV/chlorine process. • CRBs-carried MGEswere the predominant groups during UV/chlorine process. • No direct co-selection strategy was shared between UV/chlorine and resistome. Urban wastewater contains a wide range of pathogens and antibiotic resistance genes (ARGs), which are a serious concern if reusing treated wastewater. However, few studies have explored the microbial communities in reclaimed water using ultraviolet (UV)/chlorine treatment and assessed the changes of the resistome. This study investigated the occurrence of typical pathogens, ARGs, and bacterial communities in UV/chlorine-treated reclaimed water samples. The numbers of culturable and viable but non-culturable pathogens were effectively reduced to 0 CFU/mL within 1–10 and 10–30 min after UV/chlorine treatment, respectively. Meanwhile, the physicochemical indices of water quality were not affected. UV/chlorine treatment could significantly change the bacterial community structure of reclaimed water, showing a decrease in bacterial abundance and diversity. Chlorine-resistant Acinetobacter and Mycobacterium were the dominant bacterial genera (>50%) after UV/chlorine treatment. Moreover, the number of ARGs and mobile genetic elements (MGEs) decreased with an increase in UV/chlorine exposure. However, eight ARGs and three MGEs were consistently detected in more than three seasons, making these major concerns because of their potential role in the persistence and dissemination of antibiotic resistance. Overall, the results of this study suggest that UV/chlorine treatment can potentially improve the microbiological safety of reclaimed water. And more attention should be paid to the pathogens that are both chlorine-resistant and carry MGEs because of their potential for resistance transmission.     

A review on anammox process for the treatment of antibiotic-containing wastewater: Linking effects with corresponding mechanisms

• Anammox is promising for nitrogen removal from antibiotic-containing wastewater. • Most antibiotics could inhibit the anammox performance and activity. • Antibiotic pressure promoted the increase in antibiotic resistance genes (ARGs). • Antibiotic-resistance mechanisms of anammox bacteria are speculated. Antibiotic is widely present in the effluent from livestock husbandry and the pharmaceutical industry. Antibiotics in wastewater usually have high biological toxicity and even promote the occurrence and transmission of antibiotic resistant bacteria and antibiotic resistance genes. Moreover, most antibiotic-containing wastewater contains high concentration of ammonia nitrogen. Improper treatment will lead to high risk to the surrounding environment and even human health. The anaerobic ammonium oxidation (anammox) with great economic benefit and good treatment effect is a promising process to remove nitrogen from antibiotic-containing wastewater. However, antibiotic inhibition has been observed in anammox applications. Therefore, a comprehensive overview of the single and combined effects of various antibiotics on the anammox system is conducted in this review with a focus on nitrogen removal performance, sludge properties, microbial community, antibiotic resistance genes and anammox-involved functional genes. Additionally, the influencing mechanism of antibiotics on anammox consortia is summarized. Remaining problems and future research needs are also proposed based on the presented summary. This review provides a better understanding of the influences of antibiotics on anammox and offers a direction to remove nitrogen from antibiotic-containing wastewater by the anammox process.     

Development of combined coagulation-hydrolysis acidification-dynamic membrane bioreactor system for treatment of oilfield polymer-flooding wastewater

• We created a combined system for treating oilfield polymer-flooding wastewater. • The system was composed of coagulation, hydrolysis acidification and DMBR. • Coagulant integrated with demulsifier dominated the removal of crude oil. • The DMBR proceed efficiently without serious membrane fouling. A combined system composed of coagulation, hydrolysis acidification and dynamic membrane bioreactor (DMBR) was developed for treating the wastewater produced from polymer flooding. Performance and mechanism of the combined system as well as its respective units were also evaluated. The combined system has shown high-capacity to remove all contaminants in the influent. In this work, the coagulant, polyacrylamide-dimethyldiallyammonium chloride-butylacrylate terpolymer (P(DMDAAC-AM-BA)), integrated with demulsifier (SD-46) could remove 91.8% of crude oil and 70.8% of COD. Hydrolysis acidification unit improved the biodegradability of the influent and the experimental results showed that the highest acidification efficiency in hydrolysis acidification reactor was 20.36% under hydraulic retention time of 7 h. The DMBR proceeded efficiently without serious blockage process of membrane fouling, and the concentration of ammonia nitrogen (NH₃-N), oil, chemical oxygen demand and biological oxygen demand in effluent were determined to be 3.4±2.1, 0.3±0.6, 89.7±21.3 and 13±4.7 mg/L.     

Mechanistic insight into the biofilm formation and process performance of a passive aeration ditch (PAD) for decentralized wastewater treatment

• A Passive Aeration Ditch was developed to treat decentralized wastewater. • A model was developed to describe the process performance. • A high C/N ratio facilitates microbial growth but nitrification deteriorates. • A high salinity decreases both organic and nitrogen contaminants removal. Decentralized wastewater containing elevated salinity is an emerging threat to the local environment and sanitation in remote coastal communities. Regarding the cost and treatment efficiencies, we propose a passive aeration ditch (PAD) using non-woven polyester fabric as a feasible bubbleless aerator and biofilm carrier for wastewater treatment. Consideration has been first given to PAD’s efficacy in treating saline decentralized wastewater, and then to the impact of chemical oxygen demand-to-nitrogen (C/N) ratio and salinity on biofilm formation. A multispecies model incorporating the salinity effect has been developed to depict the system performance and predict the microbial community. Results showed that the PAD system had great capacity for pollutants removal. The biofilm thickness increased at a higher C/N ratio because of the boost of aerobic heterotrophs and denitrifying bacteria, which consequently improved the COD and total nitrogen removal. However, this led to the deterioration of ammonia removal. Moreover, while a higher salinity benefited the biofilm growth, the contaminant removal efficiencies decreased because the salinity inhibited the activity of aerobic heterotrophs and reduced the abundance of nitrifying bacteria inside the biofilm. Based on the model simulation, feed water with salinity below 2% and C/N ratio in a range of 1 to 3 forms a biofilm that can reach relatively high organic matter and ammonia removal. These findings not only show the feasibility of PAD in treatment of saline decentralized wastewater, but also offer a systematic strategy to predict and optimize the process performance.     

Removal of arsenic by pilot-scale vertical flow constructed wetland

• VFCWs are effective for the treatment of arsenic-containing wastewater. • Arsenic removal did not affect the removal of nutrients, except for TP in CW500. • Arsenic removal was highest when the temperature peaked and the reed was in bloom. • Substrate accumulation contributed more to arsenic removal than plant absorption. Four pilot-scale Vertical Flow Constructed Wetlands (VFCWs) filled with gravel and planted with Phragmites australis were operated for seven months in the field to study the efficiency of arsenic removal in contaminated wastewater. The average arsenic removal efficiency by the VFCWs was 52.0%±20.2%, 52.9%±21.3%, and 40.3%±19.4% at the theoretical concentrations of 50 μg/L (CW50), 100 μg/L (CW100), and 500 μg/L (CW500) arsenic in the wastewater, respectively. The results also showed no significant differences in the removal efficiency for conventional contaminants (nitrogen, phosphorus, or chemical oxygen demand) between wastewater treatments that did or did not contain arsenic (P>0.05), except for phosphorus in CW500. The highest average monthly removal rate of arsenic occurred in August (55.9%–74.5%) and the lowest in November (7.8%–15.5%). The arsenic removal efficiency of each VFCW was positively correlated with temperature (P<0.05). Arsenic accumulated in both substrates and plants, with greater accumulation associated with increased arsenic concentrations in the influent. The maximum accumulated arsenic concentrations in the substrates and plants at the end of the experiment were 4.47 mg/kg and 281.9 mg/kg, respectively, both present in CW500. The translocation factor (TF) of arsenic in the reeds was less than 1, with most of the arsenic accumulating in the roots. The arsenic mass balance indicated that substrate accumulation contributed most to arsenic removal (19.9%–30.4%), with lower levels in plants (3.8%–9.5%). In summary, VFCWs are effective for the treatment of arsenic-containing wastewater.     

Sorption of aromatic organophosphate flame retardants on thermally and hydrothermally produced biochars

• TPhP showed faster and higher sorption on biochars than TPPO. • Pyrochars had higher sorption capacity for TPPO than hydrochar. • Hydrophobic interactions dominated TPhP sorption by biochars. • The π-π EDA and electrostatic interactions are involved in sorption. Aromatic organophosphate flame retardant (OPFR) pollutants and biochars are commonly present and continually released into soils due to their increasingly wide applications. In this study, for the first time, the sorption of OPFRs on biochars was investigated. Although triphenyl phosphate (TPhP) and triphenylphosphine oxide (TPPO) have similar molecular structures and sizes, TPhP exhibited much faster and higher sorption than TPPO due to its stronger hydrophobicity, suggesting the dominant role of hydrophobic interactions in TPhP sorption. The π-π electron donor–acceptor (EDA) interactions also contributed to the sorption process, as suggested by the negative correlation between the sorption capacity of the aromatic OPFRs and the aromatic index (H/C atomic ratios) of biochar. Density functional theory calculations further showed that one benzene ring of aromatic OPFRs has no electrons, which may interact with biochar via π-π EDA interactions. The electrostatic attraction between the protonated P = O in OPFRs and the negatively charged biochar was found to occur at pH below 7. This work provides insights into the sorption behaviors and mechanisms of aromatic OPFRs by biochars.     

PPCPs in a drinking water treatment plant in the Yangtze River Delta of China: Occurrence,removal and risk assessment

• 39 PPCPs were investigated at a DWTP using the Yangtze River as its water source. • Grab and continuous sampling were conducted for the comparison of data consistency. • Ketoprofen & carbamazepine can be risk management indicators because of the high RQ. The occurrence and removal of 39 targeted pharmaceuticals and personal care products (PPCPs) from source water, through a drinking water treatment plant (DWTP) to the water supply station, were investigated around the central part of Yangtze River Delta in China using both grab sampling and continuous sampling. Totally 24 of the 39 targeted PPCPs were detected in raw water, and 12 PPCPs were detected in the finished water. The highest observed concentration was enrofloxacin (85.623 ng/L) in raw water. Removal efficiencies were remarkably negative correlated with log K_ow (r = -0.777, p<0.01) after calibration control of concentration, indicating that more soluble PPCPs are easier to remove by the combined process (prechlorination and flocculation/precipitation), the concentration level also had a great impact on the removal efficiency. The normal process in the pilot DWTP seems to be ineffective for PPCPs control, with the limited removal efficiency of less than 30% for each step: pre-chlorination, flocculation and precipitation, post-chlorination and filter. There were notable differences between the data from continuous sampling and grab sampling, which should be considered for different monitoring purposes. The chlorination and the hydrolytic decomposition of PPCPs in the water supply pipe may attenuate PPCPs concentration in the pipeline network. The PPCPs examined in the effluent of DWTP do not impose a potential health risk to the local consumers due to their RQ value lower than 0.00067.     

An efficient resin for solid-phase extraction and determination by UPLCMS/MS of 44 pharmaceutical personal care products in environmental waters

• A hydrophilic resin (GCHM) was facile synthesis and characterized. • Average absolute recovery of GCHM (75.6%) performs better than Oasis^® HLB. • Detection limits of method (SPE-UPLC-MS/MS) ranged between 0.03 and 0.6 ng/L. • 22 PPCPs were determined in environmental waters ranging from 0.5 to 1590 ng/L. In this study, a hydrophilic resin named GCHM was fabricated based on poly(N-vinyl pyrrolidone-co-divinylbenzene), characterized, and applied as a solid-phase extraction (SPE) material. Up to 44 pharmaceuticals and personal care products (PPCPs) belonging to 10 classes were recovered in environmental water samples. Different variables affecting extraction, such as adsorbent amount, sample pH, and loading speed, were optimized. Under optimal conditions, the average absolute recovery of 44 PPCPs was 75.6% using GCHM, indicating a better performance than the commercial Oasis^® HLB. SPE with home-made hydrophilic polymeric sorbent followed by ultra-performance liquid chromatography and tandem mass spectrometry was validated, and the method achieved good linearity (r²>0.991, for all analytes). In addition, the method detection limits of target compounds ranged from 0.03 to 0.6 ng/L. The developed method was applied to determine PPCPs in 10 environmental water samples taken from the Yangtze River, Huaihe River, and Taihu Lake, 1 groundwater sample from Changzhou in Jiangsu Province, 1 wastewater sample from Xiamen and 2 seawater samples from the Jiulong River in Fujian Province, China. In these samples, 22 compounds were determined at levels ranging from 0.5 to 1590 ng/L.     

Sludge fermentation liquid addition attained advanced nitrogen removal in low C/N ratio municipal wastewater through short-cut nitrification-denitrification and partial anammox

• Sludge fermentation liquid addition resulted in a high NAR of 97.4%. • Extra NH₄⁺-N from SFL was removed by anammox in anoxic phase. • Nitrogen removal efficiency of 92.51% was achieved in municipal wastewater. • The novel system could efficiently treat low COD/N municipal wastewater. Biological nitrogen removal of wastewater with low COD/N ratio could be enhanced by the addition of wasted sludge fermentation liquid (SFL), but the performance is usually limited by the introducing ammonium. In this study, the process of using SFL was successfully improved by involving anammox process. Real municipal wastewater with a low C/N ratio of 2.8–3.4 was treated in a sequencing batch reactor (SBR). The SBR was operated under anaerobic-aerobic-anoxic (AOA) mode and excess SFL was added into the anoxic phase. Stable short-cut nitrification was achieved after 46d and then anammox sludge was inoculated. In the stable period, effluent total inorganic nitrogen (TIN) was less than 4.3 mg/L with removal efficiency of 92.3%. Further analysis suggests that anammox bacteria, mainly affiliated with Candidatus_Kuenenia, successfully reduced the external ammonia from the SFL and contributed approximately 28%–43% to TIN removal. Overall, this study suggests anammox could be combined with SFL addition, resulting in a stable enhanced nitrogen biological removal.     

Partial anammox achieved in full scale biofilm process for typical domestic wastewater treatment

• A full scale biofilm process was developed for typical domestic wastewater treatment. • The HRT was 8 h and secondary sedimentation tank was omitted. • Candidatus Brocadia were enriched in the HBR with an abundance of 2.89%. • Anammox enabled a stable ammonium removal of ~15% in the anoxic zone. The slow initiation of anammox for treating typical domestic wastewater and the relatively high footprint of wastewater treatment infrastructures are major concerns for practical wastewater treatment systems. Herein, a 300 m³/d hybrid biofilm reactor (HBR) process was developed and operated with a short hydraulic retention time (HRT) of 8 h. The analysis of the bacterial community demonstrated that anammox were enriched in the anoxic zone of the HBR process. The percentage abundance of Candidatus Brocadia in the total bacterial community of the anoxic zone increased from 0 at Day 1 to 0.33% at Day 130 and then to 2.89% at Day 213. Based upon the activity of anammox bacteria, the removal of ammonia nitrogen (NH₄⁺-N) in the anoxic zone was approximately 15%. This showed that the nitrogen transformation pathway was enhanced in the HBR system through partial anammox process in the anoxic zone. The final effluent contained 12 mg/L chemical oxygen demand (COD), 0.662 mg/L NH₄⁺-N, 7.2 mg/L total nitrogen (TN), and 6 mg/L SS, indicating the effectiveness of the HBR process for treating real domestic wastewater.     

Wastewater treatment meets artificial photosynthesis: Solar to green fuel production,water remediation and carbon emission reduction

• Mitigating energy utilization and carbon emission is urgent for wastewater treatment. • MPEC integrates both solar energy storage and wastewater organics removal. • Energy self-sustaining MPEC allows to mitigate the fossil carbon emission. • MPEC is able to convert CO₂ into storable carbon fuel using renewable energy. • MPEC would inspire photoelectrochemistry by employing a novel oxidation reaction. Current wastewater treatment (WWT) is energy-intensive and leads to vast CO₂ emissions. Chinese pledge of “double carbon” target encourages a paradigm shift from fossil fuels use to renewable energy harvesting during WWT. In this context, hybrid microbial photoelectrochemical (MPEC) system integrating microbial electrochemical WWT with artificial photosynthesis (APS) emerges as a promising approach to tackle water-energy-carbon challenges simultaneously. Herein, we emphasized the significance to implement energy recovery during WWT for achieving the carbon neutrality goal. Then, we elucidated the working principle of MPEC and its advantages compared with conventional APS, and discussed its potential in fulfilling energy self-sustaining WWT, carbon capture and solar fuel production. Finally, we provided a strategy to judge the carbon profit by analysis of energy and carbon fluxes in a MPEC using several common organics in wastewater. Overall, MPEC provides an alternative of WWT approach to assist carbon-neutral goal, and simultaneously achieves solar harvesting, conversion and storage.     

Treating wastewater under zero waste principle using wetland mesocosms

• Smart wetland was designed to treat wastewater according to zero waste principle. • The system included a dynamic roughing filter, Cyperus papyrus (L.) and zeolite. • It removed 98.8 and 99.8% of chemical and bacterial pollutants in 3 days. • The effluent reused to irrigate a landscape and the sludge recycled as fertilizer. • The plant biomass is a profitable resource for antibacterial and antioxidants. The present investigation demonstrates the synergistic action of using a sedimentation unit together with Cyperus papyrus (L.) wetland enriched with zeolite mineral in one-year round experiment for treating wastewater. The system was designed to support a horizontal surface flow pattern and showed satisfactory removal efficiencies for both physicochemical and bacteriological contaminants within 3 days of residence time. The removal efficiencies ranged between 76.3% and 98.8% for total suspended solids, turbidity, iron, biological oxygen demand, and ammonia. The bacterial indicators (total and fecal coliforms, as well as fecal streptococci) and the potential pathogens (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) showed removal efficiencies ranged between 96.9% and 99.8%. We expect the system to offer a smart management for every component according to zero waste principle. The treated effluent was reused to irrigate the landscape of pilot area, and the excess sludge was recycled as fertilizer and soil conditioner. The zeolite mineral did not require regeneration for almost 36 weeks of operation, and enhanced the density of shoots (14.11%) and the height of shoots (15.88%). The harvested plant biomass could be a profitable resource for potent antibacterial and antioxidant bioactive compounds. This could certainly offset part of the operation and maintenance costs and optimize the system implementation feasibility. Although the experiment was designed under local conditions, its results could provide insights to upgrade and optimize the performance of other analogous large-scale constructed wetlands.     

Research progress and prospects of complete ammonia oxidizing bacteria in wastewater treatment

• Comammox bacteria have unique physiological characteristics. • Comammox bacteria are widely distributed in natural and artificial systems. • Comammox bacteria have the potential to reduce N₂O emissions. • Coupling comammox bacteria with DEAMOX can be promoted in wastewater treatment. • Comammox bacteria have significant potential for enhancing total nitrogen removal. Complete ammonia oxidizing bacteria, or comammox bacteria (CAOB), can oxidize ammonium to nitrate on its own. Its discovery revolutionized our understanding of biological nitrification, and its distribution in both natural and artificial systems has enabled a reevaluation of the relative contribution of microorganisms to the nitrogen cycle. Its wide distribution, adaptation to oligotrophic medium, and diverse metabolic pathways, means extensive research on CAOB and its application in water treatment can be promoted. Furthermore, the energy-saving characteristics of high oxygen affinity and low sludge production may also become frontier directions for wastewater treatment. This paper provides an overview of the discovery and environmental distribution of CAOB, as well as the physiological characteristics of the microorganisms, such as nutrient medium, environmental factors, enzymes, and metabolism, focusing on future research and the application of CAOB in wastewater treatment. Further research should be carried out on the physiological characteristics of CAOB, to analyze its ecological niche and impact factors, and explore its application potential in wastewater treatment nitrogen cycle improvement.     

Insights into simultaneous anammox and denitrification system with short-term pyridine exposure: Process capability,inhibition kinetics and metabolic pathways

• Short-term effect of the pyridine exposure on the SAD process was investigated. • The SAA at 150 mg/L pyridine reduced by 56.7% of the maximum value. • Inhibition kinetics models and inhibitory parameters were indicated. • Collaboration of AnAOB, HDB and PDB promoted the SAD. • Possible metabolic pathways of nitrogen and pyridine were proposed. In-depth knowledge on the role of pyridine as a bottleneck restricting the successful application of anammox-based process treating refractory coking wastewater remains unknown. In this study, the effect of short-term pyridine addition on a simultaneous anammox and denitrification (SAD) system fed with 25–150 mg/L pyridine was explored. The short-term operation showed that the highest total nitrogen (TN) removal efficiency was achieved at 25–50 mg/L of pyridine. As the pyridine addition increased, the contribution of the anammox pathway in nitrogen removal decreased from 99.3% to 79.1%, while the denitrification capability gradually improved. The specific anammox activity (SAA) at 150 mg/L pyridine decreased by 56.7% of the maximum SAA. The modified non-competitive inhibition model indicated that the 50% inhibitory concentration (IC₅₀) of pyridine on anammox was 84.18 mg/L and the substrate inhibition constant (K_i) of pyridine for self-degradation was 135.19 mg/L according to the Haldane model. Moreover, high-throughput sequencing confirmed the abundance of Candidatus Kuenenia as the amount of anammox species decreased, while the amounts of denitrifiers and pyridine degraders significantly increased as the pyridine stress increased. Finally, the possible pathways of nitrogen bioconversion and pyridine biodegradation in the SAD system were elucidated through metagenomic analysis and gas chromatography/mass spectrometry results. The findings of this study enlarge the understanding of the removal mechanisms of complex nitrogenous pyridine-containing wastewater treated by the SAD process.