Sewage Treatment Plant Effluent Research Articles

Interactions between SDBS and Hydrilla verticillata − epiphytic biofilm in wetland receiving STPs effluents: Nutrients removal and epiphytic microbial assembly

The fate and effects of sodium dodecyl benzene sulfonate (SDBS) in sewage treatment plants (STPs) effluents on nutrients and submerged macrophytes are far from clear in wetlands. This study conducted a 24-day experiment to investigate changes in nutrients and epiphytic biofilm of Hydrilla verticillata in wetlands receiving effluents with 0.5, 2 and 5 mg L−1 SDBS. The decrease of SDBS in overlying water followed pseudo-first-order kinetic equation, with over 80 % of SDBS removal achieved. 2 and 5 mg L−1 SDBS decreased nutrient removal efficiency, induced oxidative stress response and damaged cells of H. verticillata. SDBS altered bacterial and eukaryotic community diversity. 0.5 mg L−1 SDBS can promote carbon fixation and methane oxidation of microorganisms. Network analysis revealed that 0.5 mg L−1 SDBS decreased the stability of epiphytic ecosystems. Mantel tests indicated significant influences of SDBS, temperature, and total nitrogen on epiphytic microbial communities.

Ternary photocatalyst Bi5O7I/Bi2O2CO3/Ag2CO3 with double Z-scheme heterojunction for the degradation of levofloxacin under visible light: Practical application and DFT calculation

A novel double Z-scheme heterojunction Bi5O7I/Bi2O2CO3/Ag2CO3 was constructed by a simple hydrothermal calcination and one-step in-situ growth technique, demonstrating efficient levofloxacin degradation (86.9 % in 60 min). The degradation rates of the system are 1.5, 4.1, 1.3 and 1.4 times faster than those of pure Bi5O7I, Bi2O2CO3, Ag2CO3 and binary Bi5O7I/Bi2O2CO3, respectively. The method enhances the photocatalyst performance through improving the separation efficiency of electron-hole pairs (e-/h+) and the production of various free radicals in the double Z-scheme system. The generation of hydroxyl radicals (•OH), superoxide radicals (•O2–) and holes (h+) species were directly confirmed by Electron Spin Resonance test, and their contributions on the degradation of Levofloxacin follow the order of h+ > •OH > •O2–. The band structure, density of states, work function and potential sites of contaminant vulnerability in the material were determined by Density Functional Theory (DFT), which provides additional evidence for the formation of double Z-scheme heterojunction. Besides, the degradation experiment was conducted with four real surface water bodies, including lake water, river water, tap water and effluent of sewage treatment plant. The results show that the degradation rate for Levofloxacin reaches 60∼80 %. Moreover, Levofloxacin and its intermediate products were identified and their toxicity was predicted with Quantitative Structure-Activity Relationship (QSAR) modelling, which can be useful in the future for the actual design of a double Z-scheme heterojunction photocatalyst to efficiently remove pollutants under visible light irradiation.

Simultaneous photocatalytic degradation of remdesivir, favipiravir, and diclofenac from aqueous solutions using a quaternary plasmonic Ag/Ag-SG-TiO2-rGO photocatalyst: Synthesis, characterization, optimization, and toxicity assessment

This study presents a novel quaternary plasmonic photocatalyst, Ag/Ag-Sol-Gel(SG)-TiO2-rGO, designed for efficient removal of remdesivir (RDV), favipiravir (FAV), and diclofenac (DCF) as COVID-19 antiviral drugs from water samples. Various characterization techniques were employed to analyze the Ag/Ag-SG-TiO2-rGO nanocomposites, which were synthesized with different Ag to SG-TiO2-molar ratios. The photocatalyst, containing 30 % Ag plasmonic within its framework, exhibited the highest pollutant removal under visible light. This efficiency is attributed to the surface plasmon resonance (SPR) generated by metallic Ag nanoparticles and the optimal energy alignment between the TiO2 conduction band and the rGO work function. Trapping experiments were used to identify the most active species. It was confirmed that O2− and OH were the main active species in the photocatalytic process. The degradation kinetics, following a pseudo-first-order model, was assessed using an optimized LC-MS/MS. An optimization of the photodegradation process was done using a central composite design, as well as a study of the effects of prolonged irradiation. This resulted in the total elimination of the target compounds at a dosage of 0.087 g, irradiation time of 80 min, and pH value of 8. The photodegradation efficiency of sewage treatment plant effluent and tap water was reduced by matrix components, particularly in highly contaminated samples. An additional confirmatory MTT assay revealed a very low viability difference for mouse fibroblast cells, L929, in untreated, treated (97 %) and control samples. This study sheds light on the photodegradation of anti-COVID-19 drugs and offers insights into their remediation in aquatic environments.

Comparative assessment of microbiome and resistome of influent and effluent of sewage treatment plant and common effluent treatment plant located in Delhi, India using shotgun approach

Antimicrobial resistance (AMR) is a significant threat that demands surveillance to identify and analyze trends of the emerging antibiotic resistance genes (ARGs) and potential microbial carriers. The influent of the wastewater treatment plants (WWTPs) reflects the microbes derived from the population and effluent being the source of dissemination of potential pathogenic microbes and AMR. The present study aimed to monitor microbial communities and antibiotic resistance genes in WWTPs employing a whole metagenome shotgun sequencing approach. The samples were collected from a sewage treatment plant (STP) and a common effluent treatment plant (CETP) in Delhi, India. The results showed the influent of STP to be rich in Bifidobacterium, Bacteroides, Escherichia, Arcobacter, and Pseudomonas residents of gut microbiota and known to cause diseases in humans and animals; whereas the CETP sample was abundant in Aeromonas, Escherichia, and Shewanella known to be involved in the degradation of different compounds. Interestingly, the effluent samples from both STPs and CETP were rich in microbial diversity, comprising organic and xenobiotic compound degrading and disease-causing bacteria, indicating the effluent being the source of dissemination of concerning bacteria to the environment. The functional profile at both sites displayed similarity with an abundance of housekeeping function genes as analyzed by Clusters of Orthologous Genes (COG), KEGG Orthology (KO), and subsystem databases. Resistome profiling by MEGARes showed the dominance of ARGs corresponding to beta-lactams having relative abundance ranging from 16% to 34% in all the metagenome datasets, followed by tetracycline (8%–16%), aminoglycosides (7%–9%), multi-drug (5%–9%), and rifampin (3%–9%). Also, AMR genes oxa, ant3-DPRIME, and rpoB, which are of clinical importance were predominantly and most prevalently present in all the samples. The presence of AMR in effluents from both types of treatment plants indicates that wastewater from both sources contributes to the spread of pathogenic bacteria and resistance genes, increasing the environmental AMR burden and therefore requires tertiary treatment before discharge. This work will facilitate further research towards the identification of suitable biomarkers for monitoring antibiotic resistance.

Tracing phosphorus sources in the river-lake system using the oxygen isotope of phosphate

The biogeochemical cycling of phosphorus (P) in river-lake systems presents significant challenges in tracing P sources, highlighting the importance of effective traceability approaches for formulating targeted management measures to mitigate lake eutrophication. In this study, we used the oxygen isotope of phosphate (δ18Op) as a tracer in the river-lake systems, establishing a tracing pathway from potential end-members, through inflow rivers, and eventually to the lake. Taking Dianshan Lake and its main inflow rivers as the study area, we measured δ18Op values of potential end-members, including domestic sewage treatment plant effluents, industrial effluents from phosphorus-related enterprises (printing and dyeing, electroplating, plastics, etc.), and farmland soils. Notably, the industrial effluent signatures ranged from 13.1 ‰ to 21.0 ‰ with an average of 16.8 ‰ ± 3.2 ‰, enriching the δ18Op threshold database. Using the MixSIAR model, it was found that phosphorus in the Jishuigang River primarily originated from agricultural non-point sources and domestic sewage in the dry season, while the Qiandengpu River, with a higher proportion of urban area, had a greater influence from domestic sewage and industrial effluents. Moreover, significant differences were observed between δ18Op values at the lake entrances of the inflow rivers (13.7 ‰ ± 1.0 ‰) and in acid-soluble phosphate of the lake sediments (9.9 ‰ ± 1.0 ‰). Isotopic tracing revealed that phosphorus in the lake originated from both external inputs (80.6 %) and internal release (19.4 %) in the dry season. Alongside pollutant flux calculations based on the hydrological conditions and water quality of the inflow rivers, our findings indicated that phosphorus in Dianshan Lake was mainly attributed to agricultural non-point sources, domestic sewage and sediment release in the dry season. This study provided novel insights into the identification of pollution sources in the river-lake systems, with broad implications for pollution control and environmental protection.

Reproductive toxicity and molecular responses induced by telmisartan in Daphnia magna at environmentally relevant concentrations

With aging population increasing globally, the use of pharmaceutically active compounds is rising. The cardiovascular drug telmisartan has been widely detected in various environmental compartments, including biota, surface waters, and sewage treatment plant effluents at concentrations ranging from ng/L to μg/L levels. This study evaluated the effects of telmisartan on the microcrustacean Daphnia magna at a wide range of concentrations (0.35, 0.70, 1.40, 500, and 1000 μg/L) and revealed significant ecotoxicological implications of this drug, even at environmentally relevant concentration. Acute exposure to telmisartan (1.40, 500, and 1000 μg/L) resulted in a notable decrease in heart rate, while chronic exposure accelerated the time to the first brood by 3 days and reduced neonate body size. Molecular investigations revealed marked downregulation of vitellogenin genes (Vtg1 and Vtg2). Non-monotonic dose responses were observed for gene expression, early-stage body length, and the total number of offspring produced, while the heart rate and time to the first brood showed clear concentration-dependent responses. These findings highlight the potential risks, notably to reproductive capacity, associated with exposure to telmisartan in environmentally relevant concentration, suggesting the need for further studies on the potential long-term ecological consequences.

Typical emerging contaminants in sewage treatment plant effluent, and related watersheds in the Pearl River Basin: Ecological risks and source identification

Emerging contaminants pose a potential risk to aquatic ecosystems in the Pearl River Basin, China, owing to the high population density and active industry. This study investigated samples from eight sewage treatment plants, and five surface water bodies of related watersheds. To screen the risk of emerging contaminants (ECs), and clarify their sources, this study calculated the risk quotient of detected chemical and performed source identification/apportionment using the positive matrix factorization method. In total, 149 organic pollutants were identified. Pharmaceuticals showed significant concentrations in sewage treatment plant samples (120.87 ng/L), compared with surface water samples (1.13 ng/L). The ecological risk assessment identified three chemicals with a heightened risk to aquatic organisms: fipronil sulfide, caffeine, and roxithromycin. Four principal sources of contaminants were identified: pharmaceutical wastewater, domestic sewage, medical effluent, and agricultural runoff. Pharmaceutical wastewater was the primary contributor (60.4 %), to the cumulative EC concentration and to ECs in sewage treatment plant effluent. Agricultural drainage was the main source of ECs in surface water. This study provides a strategy to obtain comprehensive information on the aquatic risks and potential sources of EC species in areas affected by artificial activities, which is of substantial importance to pollutant management and control.

Effective elimination of Hg(II) from water bodies with acid-modified magnetic biomass spent coffee grounds: conditional optimization and application.

To maximize the efficiency of biomass waste utilization and waste management, a novel acid-modified magnetic biomass spent coffee grounds (NiFe2O4/SCG) was obtained by pyrolysis at 473K and co-precipitation methods and employed to eliminate bivalent mercury (Hg(II)) in water bodies. The prepared NiFe2O4/SCG adsorbent exhibits remarkable magnetism with a strength of 45.78emu/g and can easily be separated from water via a magnetic force. The adsorption of Hg(II) over the NiFe2O4/SCG has an optimal conditions of pH = 8, T = 39 ℃, and dosage of 0.055 g/L, and the maximal adsorption capacity for Hg(II) is 167.44 mg/g via Response Surface Methodology optimization. The removal of Hg(II) over NiFe2O4/SCG primarily involves ion exchange, electrostatic attraction, and chelation; conforms to the pseudo-second-order kinetic and Langmuir models; and is an endothermic reaction. Additionally, the magnetic biomass NiFe2O4/SCG has good regeneration capability and stability. The application research reveal that inorganic salt ions, nitrogen fertilizer urea, humus, and other contaminants in different actual water bodies (river water, lake water, and the effluent of sewage treatment plant) have little effect on the adsorption of Hg(II) over the NiFe2O4/SCG. The prepared adsorbent NiFe2O4/SCG has practical application value for removing Hg(II) from water bodies.

Re-assessment of monoclonal antibodies against diclofenac for their application in the analysis of environmental waters.

The non-steroidal anti-inflammatory drug (NSAID) diclofenac (DCF) is an important environmental contaminant occurring in surface waters all over the world, because, after excretion, it is not adequately removed from wastewater in sewage treatment plants. To be able to monitor this pollutant, highly efficient analytical methods are needed, including immunoassays. In a medical research project, monoclonal antibodies against diclofenac and its metabolites had been produced. Based on this monoclonal anti-DCF antibody, a new indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed and applied for environmental samples. The introduction of a spacer between diclofenac and the carrier protein in the coating conjugate led to higher sensitivity. With a test midpoint of 3 μg L-1 and a measurement range of 1-30 μg L-1, the system is not sensitive enough for direct analysis of surface water. However, this assay is quite robust against matrix influences and can be used for wastewater. Without adjustment of the calibration, organic solvents up to 5%, natural organic matter (NOM) up to 10 mg L-1, humic acids up to 2.5 mg L-1, and salt concentrations up to 6 g L-1 NaCl and 75 mg L-1 CaCl2 are tolerated. The antibody is also stable in a pH range from 3 to 12. Cross-reactivity (CR) of 1% or less was determined for the metabolites 4'-hydroxydiclofenac (4'-OH-DCF), 5-hydroxydiclofenac (5-OH-DCF), DCF lactam, and other NSAIDs. Relevant cross-reactivity occurred only with an amide derivative of DCF, 6-aminohexanoic acid (DCF-Ahx), aceclofenac (ACF) and DCF methyl ester (DCF-Me) with 150%, 61% and 44%, respectively. These substances, however, have not been found in samples. Only DCF-acyl glucuronide with a cross-reactivity of 57% is of some relevance. For the first time, photodegradation products were tested for cross-reactivity. With the ELISA based on this antibody, water samples were analysed. In sewage treatment plant effluents, concentrations in the range of 1.9-5.2 μg L-1 were determined directly, with recoveries compared to HPLC-MS/MS averaging 136%. Concentrations in lakes ranged from 3 to 4.4 ng L-1 and were, after pre-concentration, determined with an average recovery of 100%.

Photocatalytic application towards the degradation of ciprofloxacin and algae by Z-scheme 2D/3D heterojunction of Bi12O17Cl2/UiO-66-NH2

With the continuous emergence of antibiotics in natural water bodies, the crisis of water environment is becoming increasingly serious. To efficiently remove antibiotics, a novel 2D/3D Z-scheme heterojunction of Bi12O17Cl2/UiO-66-NH2 was constructed by in situ growth technology. The formation of Z-scheme heterojunction between Bi12O17Cl2 and UiO-66-NH2 not only significantly improves the transfer rate and separation efficiency of charge carriers, but also greatly prolongs the lifetime of electrons and improves their light absorption ability. Free radical capture experiments and ESR spectra display that ⋅O2− and ⋅OH radicals dominate the degradation process of ciprofloxacin. The synthesized Z-scheme heterojunction shows a high degradation rate of 83.5 % for antibiotic ciprofloxacin within 60 min, much higher than those of Bi12O17Cl2, UiO-66-NH2 monomers and many other reported photocatalysts. The heterojunction Bi12O17Cl2/UiO-66-NH2 also exhibits excellent degrading performance towards antibiotics in three actual water bodies (tap water, lake water and the effluent of domestic sewage treatment plant). Meanwhile, the as-prepared photocatalyst can effectively degrade Microcystis aeruginosa and algal toxin Microcystin-LR in surface water bodies contaminated by algae and antibiotics. The QSAR analysis indicates that the toxicities of both ciprofloxacin and its intermediates are greatly reduced. The degradation pathways of ciprofloxacin were analyzed via Density Functional Theory calculations and QSAR analysis. This study provides an excellent synthesis method of Z-scheme heterojunction for the purification of surface water bodies contaminated by algae and antibiotics via photocatalytic technology.

Synergic Usage of Pistia stratiotes sp., Eichhornia crassipes sp., Typha angustifolia sp., and Lepironia Articulata sp. Plants for Sewage Treatment via Phytoremediation Technology

Introduction Domestic wastewater management is challenging on a worldwide level. The discharge of a large amount of nitrogen and phosphate from sewage accelerates pollution can lead to reduced oxygen levels, excessive algal blooms, the expansion of aquatic weed plants, and the destruction of the aquatic environment. As a result, the right wastewater treatment is required prior to discharge into natural water bodies in order to prevent contamination and fulfill the wastewater acceptable limits established by the government and environmental protection agencies. For Previous studies, most of the research is carried out in a controlled environment within a small time frame. Phytoremediation offers a viable alternative by harnessing the natural capabilities of plants to enhance the degradation and removal of pollutants in sewage. Aims The objective of this study is to evaluate the phytoremediation performance using Pistia stratiotes sp., Eichhornia Crassipes sp., Typha angustifolia sp., and Lepironia Articulata sp. in treating real domestic wastewater. Methods The phytoremediation system conducted continuous treatment at the Sewage Treatment Plant (STP) effluent at Selangor, Malaysia. To the best of our knowledge there are no studies conducted on the phytoremediation plant in real STP using 4 types of aquatic plants in a row to achieve a high percentage removal of pollutants. This research observation was conducted by collecting data every 2 weeks for 4 consecutive months including the maintenance terms. In terms of pollutant removal, the phytoremediation system showed the highest removal efficiency in all tested parameters. Results The highest removal efficiency recorded for biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS) and ammoniacal nitrogen (AN) were 68.38%, 70.95%, 59.21% and 25.00%, respectively. Conclusion Following the guidelines of the Environmental Quality (Sewage Effluent) Regulation 2009 Malaysia, synergic usage of the aquatic plant had successfully achieved Standard A for sewage discharge after applying the phytoremediation technology while it has been proven that the environmentally friendly technologies can reduce the risk of water pollution by using the selected plant and may solve the water shortage with a cost-effective and efficient solution to wastewater treatment.

Mechanism and application of enhanced degradation of phenol through peroxymonosulfate activation by sulfur-doped biochar prepared with sodium thiosulfate as activator and sulfur dopant

Na2S2O3 was used as activator and sulfur dopant for preparation of sulfur-doped biochar (SBC) with high specific surface area and sulfur content, and its performance to activate peroxymonosulfate (PMS) for phenol degradation was studied. In the presence of 0.3 g/L S4BC-800 and 1 g/L PMS, 20 mg/L phenol could be removed completely in 30 min. S doping improved the electron transfer performance of the composite and enhanced the activation property of PMS for phenol degradation. Free radical quenching experiment and electron paramagnetic resonance analysis indicated that SO4•−, •OH, and 1O2 were involved in phenol degradation. In addition, the current oxidation process confirmed that there was also direct oxidation based on electron transfer between PMS and phenol with S4BC-800 as mediator. The S4BC-800/PMS system could effectively decompose the recalcitrant organic pollutants in the effluent of sewage treatment plant, achieving the total organic carbon removal rate of 83.26 %.

Enhancing Contaminant Removal in Sewage Treatment Plant Effluent with PES/Ag Membrane

In this study, a silver-infused membrane was fabricated using an ex-situ method that involved blending silver nanoparticles (AgNPs) with Polyethersulfone (PES) as the base polymer in treating sewage treatment plant (STP) effluent. Three distinct membranes denoted as S1(Ag0), S2(Ag0.5) and S3(Ag2.0) were manufactured with varying weight percentages of polymer and silver (Ag) contents. The objective was to investigate the effect of the dosage of AgNPs on membrane characterization and performance, encompassing pure water flux filtration tests, organic rejection tests, and antibacterial properties. The results showed that all PES/Ag membranes demonstrated robust performance in removing total suspended solids (TSS), chemical oxygen demand (COD), apparent colour (Hazen unit), total dissolved solids (TDS), turbidity, conductivity, total Kjeldahl nitrogen (TKN), and Escherichia coli (E. coli), complying to Class IIB (Recreational use with body contact) of the Interim National River Water Quality Standards (INWQS) for Malaysia ruled by the Department of Environment Malaysia (DOE). The results also highlighted that upon the addition of AgNPs, the E. coli removal of the membrane S3(Ag2.0) was further improved to 99.87%. The results have evidenced that the PES/Ag membranes could reject E. coli effectively, proving their value in treating bacteria-contaminated surface water. In conclusion, this study highlights the effectiveness of PES/Ag membranes as a viable solution for domestic sewage treatment, aligning with stringent water quality requirements.

Multivariate Statistical Analysis of Dyeing Wastewater Organic Matter Indicators

Objectives:Since 2016, TOC (Total Organic Carbon) has replaced COD (Chemical Oxygen Demand) as an organic indicator for effluent wastewater quality standards. However, the distribution of organic substances by process in wastewater treatment facilities is not properly identified, making it difficult to secure stable treated wastewater quality. Therefore, in this study, we identified the correlation between TOC and existing organic matter indicators in raw wastewater, primary treated, secondary treated, and effluent wastewater for dyeing wastewater.Methods:Samples for each process were collected twice a week, a total of 24 times, from a dyeing wastewater treatment plant located in Y-city, Gyeonggi-do, and organic pollutant indicators (TOC, COD<sub>Cr</sub>, COD<sub>Mn</sub>, BOD<sub>5</sub>) were analyzed. TOC was analyzed by the NPOC (non-purgeable organic carbon) method using TOC-VCHP (Shimadzu, Japan). Using the analysis results, the characteristics of organic pollutants in dyeing wastewater were analyzed. In addition, multivariate statistical analysis was performed using SPSS to analyze correlations between organic pollutant indicators and principal component analysis.Results and Discussion:As a result of multivariate statistical analysis, TOC was inflowed at an average of 574.9 mg/L and treated at 58.2mg/L. In the case of COD<sub>Cr</sub>, COD<sub>Mn</sub>, and BOD<sub>5</sub>, the inflow was 1,644, 448.9, and 440.7 mg/L and was treated at 98.2, 39.7, and 10.8mg/L. When evaluated based on effluent water quality standards, all of them satisfied the Region III standards, but were discharged at a relatively high level compared to the TOC concentration of sewage treatment plants effluent. As a result of comparing correlations between organic matter indicators through Pearson correlation analysis, the inflow raw water shows a high positive correlation with TOC:TCOD<sub>Cr</sub> (r=0.720), TOC:TCOD<sub>Mn</sub> (r=0.636), and TOC:TBOD<sub>5</sub> (r=0.302) showed low correlation. This is reason to be due to the fact that most organic substances in dyeing wastewater are non-degradable substances and have low biodegradability. As a result of principal component analysis of influent, primary treated, and final treated, three main components each (two for final treated) were extracted, with cumulative contribution rates of 80.1%, 83.2%, and 95.6%.Conclusion:Because the properties of wastewater differ greatly depending on the type of leather and chemicals handled at the dyeing factory, the correlation between influent water was low, but the correlation between treated water and treated water was relatively high. The correlation between processes in wastewater treatment facilities also tended to increase toward later processes. It is believed that the above statistical analysis can be used as basic data for effective organic matter management.

Cetyl trimethyl ammonium bromide-modified magnetic biochar-integrated sand filter for microplastics removal from secondary-treated sewage effluents: Performance evaluation and mechanistic insights

Microplastics (MPs) discharge from effluent of sewage treatment plants (STPs) has prompted the need for effective treatment techniques. In this context, the present study provides insights on the preparation and use of cetyl trimethyl ammonium bromide (CTAB)-modified magnetic biochar (MBC-CTAB) as an adsorbent and integrated it in a sand filter for improved MPs removal from aqueous matrices. Rice husk biochars were synthesized, surface modified with FeCl3 and CTAB, and assessed for their MPs removal efficiency. Effects of various factors were analyzed from synthetic water spiked with 1 μm sized polystyrene MPs during batch and fixed-bed column studies. Optimal conditions yielded a maximum MPs removal of >97 % with MBC-CTAB at 7 mg/50 mL, pH 4, mixing speed of 180 rpm for 3 min during batch studies. Adsorption kinetics followed the pseudo-second-order model (R2 = 0.91), and the Langmuir model (R2 = 0.94) described the adsorption isotherm with a maximum capacity of 247 mg/g. Column studies removed ∼98 % MPs in real-time secondary sewage effluents using MBC-CTAB-integrated sand filter at flow rate: 5 mL/min, bed height: 4 cm, and MPs concentration: 7 mg/L. Electrostatic and hydrophobic interactions, hydrogen bonding, and pore-filling were the key MPs removal mechanisms. The application of the developed technique in efficient MPs removal highlights its practical relevance as sustainable approach for removing MPs from sewage effluents, which is a shared global concern.

Investigating the antibiotic resistance genes and their potential risks in the megacity water environment: A case study of Shenzhen Bay Basin, China

Antibiotic resistance genes (ARGs) constitute emerging pollutants and pose serious risks to public health. Anthropogenic activities are recognized as the main driver of ARG dissemination in coastal regions. However, the distribution and dissemination of ARGs in Shenzhen Bay Basin, a typical megacity water environment, have been poorly investigated. Here, we comprehensively profiled ARGs in Shenzhen Bay Basin using metagenomic approaches, and estimated their associated health risks. ARG profiles varied greatly among different sampling locations with total abundance ranging from 2.79 × 10−2 (Shenzhen Bay sediment) to 1.04 (hospital sewage) copies per 16S rRNA gene copy, and 45.4% of them were located on plasmid-like sequences. Sewage treatment plants effluent and the corresponding tributary rivers were identified as the main sources of ARG contamination in Shenzhen Bay. Mobilizable plasmids and complete integrons carrying various ARGs probably participated in the dissemination of ARGs in Shenzhen Bay Basin. Additionally, 19 subtypes were assigned as high-risk ARGs (Rank I), and numerous ARGs were identified in potential human-associated pathogens, such as Burkholderiaceae, Rhodocyclaceae, Vibrionaceae, Pseudomonadaceae, and Aeromonadaceae. Overall, Shenzhen Bay represented a higher level of ARG risk than the ocean environment based on quantitative risk assessment. This study deepened our understanding of the ARGs and the associated risks in the megacity water environment.

Assessing resilience of natural treatment system to variable contaminant loads in an urbanizing catchment

Constructed wetlands (CWs) offer solution to increasing wastewater concerns. Long term monitoring data (six years) provides information on robustness and life time of such systems. The CW system examined in this study was deployed to serve as a polishing stage for the sewage treatment plant (STP) effluent, however, it also receives raw sewage through stormwater drains. The hydraulic loading rate (HLR) of system increased from 215.5 ± 6.7 mm/day to 466.9 ± 21.6 mm/day in 6 years thereby reducing the hydraulic retention time (HRT) of the system. The effluent quality complied with the discharge standards except for ortho-P and fecal coliforms. Corresponding to HLR, the organic and nutrient loading rate also displayed significant variation during the period 2015 to 2020. Despite this, the organic load removal efficiency was comparable with only small variation. The nitrogen removal efficiency displayed significant fluctuation with occasional decline followed by improvement in the year 2020. The system released ortho-P into the water column increasing its load at the outlet, the ortho-P removal efficiency reduced from 19 to −44 % during the study period. Desilting, regular macrophyte harvesting, aeration and pre-treatment of raw sewage from open storm water drain can further enhance the system performance and robustness.

Prevalence of diverse antimicrobial resistance genes and bacteria in sewage treatment plant-derived sludge environment.

Antimicrobial resistance (AMR) contamination in the environment is one of the most significant worldwide threats of the 21st century. Since sludge is heavily exposed to diverse contaminants, including pharmaceuticals, the inhabitant bacterial population is expected to exhibit resistance to antimicrobial agents. In this study, sewage treatment plant (STP) sludge samples were analyzed to assess the antibiotic-resistant bacterial population, abundance of AMR genes (ermF, qnrS, Sul1, blaGES, blaCTX-M, and blaNDM), and mobile genetic elements (intl1 and IS26). Out of 16, six bacterial isolates exhibited resistance to 13 antibiotics with a high multiple antibiotic resistance index (MARI) (0.93) and high metal tolerance. Quantitative polymerase chain reaction showed the abundance of target genes ranging from 6.6×103 to 6.5×108 copies g-1 sludge. The overall outcome reveals that STP sludge comprised varied multidrug-resistant bacterial populations. It will give insights into the functions of heavy metals and biofilm development in the selection and spread of AMR genes and the associated bacteria. Therefore, the application of sludge needs proper screening for AMR and metal contamination prior to its countless applications. This study will contribute immensely to the risk analysis of STP effluents on environmental health, including control of AMR transmission.

Influence of watershed characteristics and human activities on the occurrence of organophosphate esters related to dissolved organic matter in estuarine surface water

Organophosphate esters (OPEs) are widespread in aquatic environments and pose potential threats to ecosystem and human health. Here, we profiled OPEs in surface water samples of heavily urbanized estuaries in eastern China and investigated the influence of watershed characteristics and human activities on the spatial distribution of OPEs related to dissolved organic matter (DOM). The total OPE concentration ranged from 22.3 to 1201 ng/L, with a mean of 162.6 ± 179.8 ng/L. Chlorinated OPEs were the predominant contaminant group, accounting for 27.4–99.6 % of the total OPE concentration. Tris(2-chloroisopropyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, and tributyl phosphate were the dominant compounds, with mean concentrations of 111.2 ± 176.0 ng/L, 22.6 ± 21.5 ng/L, and 14.8 ± 14.9 ng/L, respectively. Variable OPE levels were observed in various functional areas, with significantly higher concentrations in industrial areas than in other areas. Potential source analysis revealed that sewage treatment plant effluents and industrial activities were the primary OPE sources. The total OPE concentrations were negatively correlated to the mean slope, plan curvature, and elevation, indicating that watershed characteristics play a role in the occurrence of OPEs. Individual OPEs (triisobutyl phosphate, tris(2-butoxyethyl) phosphate, tris(2-chloroethyl) phosphate, and tricresyl phosphate) and Σalkyl-OPEs were positively correlated to the night light index or population density, suggesting a significant contribution of human activity to OPE pollution. The co-occurrence of OPEs and DOM was also observed, and the fluorescence indices of DOM were found to be possible indicators for tracing OPEs. These findings can elucidate the potential OPE dynamics in response to DOM in urbanized estuarine water environments with intensive human activities.

Reductive sequestration of Cr (VI) by phosphorylated nanoscale zerovalent iron

The cracked phosphorylated nanoscale zerovalent iron (p-nZVI) has a strong electron selectivity towards the reductive removal of many heavy metal ions in waters. However, the unintended environmental risk after interactions with impurities or wastewater are not involved. Therefore, in this study, the phosphate group was successfully adsorbed into p-nZVI, and the cracked p-nZVI was successfully prepared with an optimal P/Fe ratio of 0.5%. The dosages of p-nZVI and temperatures were positively correlated with the removal rates. The removal process of Cr(VI) was more suitable by the Langmuir isothermal model（R2 > 0.99). The process of Cr (VI) (10, 20 and 40 mg/L) removal more fitted the pseudo first-order reaction model, while the process of Cr (VI) (60, 80 mg/L) removal more fitted the pseudo second-order reaction model. The Cr (VI) removal rates gradually decreased when the pH was increased. Dissolved oxygen slowed nanoiron reaction rates. The order of inhibition on the reactivity towards Cr(VI) was SiO32− > SO42− > PO43− > NO3− > HCO3−.The facilitation followed the order of Cd2+>Cu2+>Mg2+>Mn2+>Ca2+. Ca2+ showed an inhibitory effect, but all other cations showed different degrees of facilitation. The promotion effect is relatively similar in presence of Mn2+ or Mg2+. HA had a significant inhibitory effect. Environmental friendly p-nZVI had a good effect in simulated groundwater, seawater, river water and secondary effluent of the urban sewage treatment plant. The main pathway to remove Cr (VI) was in situ reduction by p-nZVI. The improved adsorption and reduction effect of p-nZVI on heavy metal ions in water was due to the structural change and the phosphate group.