Full-scale Municipal Wastewater Treatment Plant Research Articles

Building a simple multivariable filtration model to predict irreversible fouling when directly filtering municipal wastewater

This paper describes a simple generic model designed to predict membrane fouling in municipal wastewater (MWW) treatment. The work was conducted using data from a direct membrane filtration demo-system (middle/long-term filtration periods of about 35 – 124 days) to calibrate the model. Two influents were treated by the demo-system: raw pre-treated MWW and primary settler supernatant from a full-scale MWW treatment plant. A resistance-in-series mathematical model structure was proposed considering fouling due to two different mechanisms: persistent cake layer formation (from suspended material) and pore blocking (from soluble and colloidal compounds). The proposed model represented transmembrane pressure dynamics at different operating solids concentrations (around 1, 2.6, 6 and 11 gL−1) using 7 model parameters, achieving 7–28 mbar differences between the experimental data and model predictions in all cases (calculated as the root mean square error). The model was also able to match the results from two different influents (raw MWW and primary settler supernatant) by modifying 3 of the 7 parameters while low uncertainties were obtained in long-term filtrations, demonstrating its robustness. This model thus provides a good potential to generate reasonable membrane fouling predictions while its simple and open structure makes it easy to implement with complementary materials. Further research will be carried out to enhance the model’s precision and validate its potential for optimizing filtration and fouling control processes.

A comprehensive investigation to the fate of phosphorus in full-scale wastewater treatment plants using aluminum salts for enhanced phosphorus removal

This study investigated the fate of phosphorus (P) in 8 full-scale municipal wastewater treatment plants (WWTPs) in Shanghai, China, in which both biological nutrient removal and aluminum-based chemical phosphorus removal were used. The results showed that 83.8–98.9 % P was transferred to the sludge in the 8 WWTPs by both chemical and biological reactions. P speciation analysis indicated that chemical P precipitates accounted for 84.3 % in the activated sludge, of which crystalline AlPO4 and amorphous iron‑phosphorus compounds (FePs) were the main components. Sludge with more water-soluble and weakly adsorbed P was generated in the anaerobic-anoxic-oxic (A/A/O) process than in other processes. Among the 8 WWTPs, the one with the largest flow rate and relatively short sludge retention time (SRT) had the best potential to release P from all types of sludge. The recovery potential of P from thickened sludge can be improved by separately thickening the sludge produced in the high-efficiency sedimentation tank or feeding it into the dewatering process directly. Different P removal chemicals and dosing points changed the amount of chemical precipitate formed but had little effect on the composition of P accumulating organisms (PAOs) at the genus level. Although aluminum-based coagulants were applied in the investigated WWTPs, Fe in wastewater had the most positive effect on the proliferation of PAOs. The synthesis of polyphosphate was also related to the metabolism of PAOs as it affected transmembrane inorganic phosphate (Pi) transport and polyhydroxybutyrate (PHB) synthesis. The in-depth understanding of the fate of P is beneficial to improve P recovery efficiency in WWTPs.

Primary settling changes the microbial community of influent wastewater to wastewater treatment plants

The continuous immigration of bacteria in influent wastewater strongly impacts the microbial community of activated sludge (AS) in wastewater treatment plants (WWTP), both in terms of species composition and their abundance. Therefore, it is of interest to elucidate the route of immigrating bacteria into the biological tanks, including the effect of primary settlers. These are commonly used pretreatment units that can possibly selectively increase or reduce the relative abundance of certain bacteria. Species-level identification of the microbial composition of influent wastewater before and after primary settling was carried out in four full-scale municipal WWTPs biweekly over one year by 16S rRNA gene amplicon sequencing. Overall, 37–49% of incoming COD was removed in the primary settlers. Most genera and species were present in the wastewater to all four plants and the trend of these were investigated across the primary settlers. Approximately 50% of the genera had the same trend across at least three WWTPs. Few genera significantly increased in relative read abundance (3.7%) after settling, while 22.3% showed a significant reduction in relative abundance. We investigated process-critical species in AS, such as known nitrifiers, polyphosphate-accumulating organisms, and filamentous bacteria. Most taxa were affected similarly in all WWTPs including multiple genera involved in bulking in AS. However, some genera, e.g., important polyphosphate-accumulating bacteria, had inconsistent trends across WWTPs, suggesting that the characteristics of the wastewater are important for the trend of some bacteria through primary settling. In all cases, primary settling changed the microbial community of the influent wastewater, posing an obvious candidate for upstream control to optimize the assembly of the microbial communities in activated sludge.

Carbon accounting of A2O process based on carbon footprint in a full-scale municipal wastewater treatment plant

The traditional carbon accounting model for wastewater treatment plants (WWTPs) only calculates the total amount of each greenhouse gas (GHG), which has no guiding significance for the net zero carbon transformation of WWTPs under the goal of carbon neutrality, and the system boundary is only within the WWTPs. In this paper, the accounting boundary is extended to the outside of the plant, and the CO2 produced by the pumping pump outside the plant and the sludge transport is included in the accounting, which improves the accuracy of the results. In addition, the WWTP is divided into three stages, which are the pretreatment stage, biological treatment stage, and sludge treatment stage. The emission sources in each stage are calculated in detail to determine the key emission reduction targets in each stage. The research shows that the main carbon emission source in the pretreatment stage is indirect CO2 produced by chemicals, the main carbon emission source in the biological treatment stage is N2O emission, and the main carbon emission source in the sludge treatment stage is indirect CO2 produced by electricity consumption. We also found that the carbon intensity of the biological treatment stage was 1.8 times that of the other two stages. Therefore, carbon emission reduction in the biological stage is the focus of plant emission reduction.

Seasonal prevalence of bacteria in the outflow of two full-scale municipal wastewater treatment plants

Despite many modern wastewater treatment solutions, the most common is still the use of activated sludge (AS). Studies indicate that the microbial composition of AS is most often influenced by the raw sewage composition (especially influent ammonia), biological oxygen demand, the level of dissolved oxygen, technological solutions, as well as the temperature of wastewater related to seasonality. The available literature mainly refers to the relationship between AS parameters or the technology used and the composition of microorganisms in AS. However, there is a lack of data on the groups of microorganisms leaching into water bodies whose presence is a signal for possible changes in treatment technology. Moreover, sludge flocs in the outflow contain less extracellular substance (EPS) which interferes microbial identification. The novelty of this article concerns the identification and quantification of microorganisms in the AS and in the outflow by fluorescence in situ hybridization (FISH) method from two full-scale wastewater treatment plants (WWTPs) in terms of 4 key groups of microorganisms involved in the wastewater treatment process in the context of their potential technological usefulness. The results of the study showed that Nitrospirae, Chloroflexi and Ca. Accumulibacter phosphatis in treated wastewater reflect the trend in abundance of these bacteria in activated sludge. Increased abundance of betaproteobacterial ammonia-oxidizing bacteria and Nitrospirae in the outflow were observed in winter. Principal component analysis (PCA) showed that loadings obtained from abundance of bacteria in the outflow made larger contributions to the variance in the PC1 factorial axis, than loadings obtained from abundance of bacteria from activated sludge. PCA confirmed the reasonableness of conducting studies not only in the activated sludge, but also in the outflow to find correlations between technological problems and qualitative and quantitative changes in the outflow microorganisms.

Emerging contaminants in conventional and advanced biological nutrient removal based wastewater treatment plants in India- insights into the removal processes

Emerging contaminants (ECs) in the environment are a cause of concern due to their potential toxic effects. The study investigates the fate of 20 ECs covering a wide range of physical-chemical properties in ten full-scale municipal wastewater treatment plants (WWTPs). The plants were based on conventional technologies such as waste stabilization pond, upflow sludge blanket reactor, activated sludge process, and biological nutrient removal-based technologies such as anoxic-aerobic process, anaerobic-anoxic-aerobic process, biodenipho process, sequencing batch reactor, and densadeg-biofor process. Covering all the wastewater and sludge treatment lines, the mass balance approach was followed to investigate the fate of ECs at each treatment stage. The amount of ECs entering and leaving the WWTPs ranged from 0.82 to 11.94 kg/day and 0.027 to 0.70 kg/day, respectively. Antibiotics showed limited removal and were detected in the 0.006 to 0.18 kg/day range. The ECs were mainly detected in the aqueous phase in all the treatment steps. However, the contribution from the particulate and sludge phase cannot be neglected. The sorption of ECs on sludge depended on the sludge's characteristics. It was found to be the highest in the primary sludge. The measured sorption coefficient indicated that both hydrophobic and electrostatic interactions of ECs with the sludge are insufficient in explaining the sorption behaviour of a contaminant. The mass balance studies show biodegradation as the major removal pathway in all the WWTPs. The study provides the environmental mass load of ECs from Indian WWTPs. It will help understand the removal mechanisms of ECs in different types of wastewater treatment techniques.

Ammonia-Oxidizing Bacteria Maintain Abundance but Lower amoA-Gene Expression during Cold Temperature Nitrification Failure in a Full-Scale Municipal Wastewater Treatment Plant.

In this study, we explore the relationship between community structure and transcriptional activity of ammonia-oxidizing bacteria during cold temperature nitrification failure in three parallel full-scale sequencing batch reactors (SBRs) treating municipal wastewater. In the three reactors, ammonia concentrations increased with declines in wastewater temperature below 15°C. We quantified and sequenced 16S rRNA and ammonia monooxygenase (amoA) gene fragments in DNA and RNA extracts from activated sludge samples collected from the SBRs during the warmer seasons (summer and fall) and when water temperatures were below 15°C (winter and spring). Taxonomic community composition of amoA genes and transcripts did not vary much between the warmer and colder seasons. However, we observed significant differences in amoA transcript copy numbers between fall (highest) and spring (lowest). Ammonia-oxidizing bacteria of the genus Nitrosomonas sp. could maintain their population abundance despite lowering their amoA gene expression during winter and spring. In spite of relatively low population abundance, an amoA amplicon sequence variant (ASV) cluster identified as most similar to the amoA gene of Nitrosospira briensis showed the highest amoA transcript-to-gene ratio throughout all four seasons, indicating that some nitrifiers remain active at wastewater temperatures below 15°C. Our results show that 16S rRNA and amoA gene copy numbers are limited predictors of cell activity. To optimize function and performance of mixed community bioprocesses, we need to collect high-resolution quantitative transcriptomic and potentially proteomic data to resolve the response of individual species to changes in environmental parameters in engineered systems. IMPORTANCE The diverse microbial community of activated sludge used in biological treatment systems exhibits dynamic seasonal shifts in community composition and activity. Many wastewater treatment plants in temperate/continental climates experience seasonal cold temperature nitrification failure. "Seasonal nitrification failure" is the discharge of elevated concentrations of ammonia (greater than 4 mg/liter) with treated wastewater during the winter (influent wastewater temperatures below 13°C). This study aims at expanding our understanding of how ammonia-oxidizing bacteria in activated sludge change in activity and growth across seasons. We quantified the ammonia monooxygenase (amoA) gene and transcript copy numbers using real-time PCR and sequenced the amoA amplicons to reveal community structure and activity changes of nitrifying microbial populations during seasonal nitrification failure in three full-scale sequencing batch reactors (SRBs) treating municipal wastewater. Relevant findings presented in this study contribute to explain seasonal nitrification performance variability in SRBs.

Microbial Transformation of Dissolved Organic Sulfur during the Oxic Process in 47 Full-Scale Municipal Wastewater Treatment Plants.

Dissolved organic sulfur (DOS) is a significant part of effluent organic matter of wastewater treatment plants (WWTPs) and poses a potential ecological risk for receiving waters. However, the oxic process is a critical unit of biological wastewater treatment for microorganisms performing organic matter removal, wherein DOS transformation and its mechanism are poorly understood. This study investigated the transformation of DOS during the oxic process in 47 full-scale municipal WWTPs across China from molecular and microbial aspects. Surprisingly, evident differences in DOS variations (ΔDOS) separated sampled WWTPs into two groups: 28 WWTPs with decreased DOS concentrations in effluents (ΔDOS < 0) and 19 WWTPs with increased DOS (ΔDOS > 0). These two groups also presented differences in DOS molecular characteristics: higher nitrogen/carbon (N/C) ratios (0.030) and more peptide-like DOS (8.2%) occurred in WWTPs with ΔDOS > 0, implying that peptide-like DOS generated from microbes contributed to increased DOS in effluents. Specific microbe-DOS correlations (Spearman correlation, p < 0.05) indicated that increased effluent DOS might be explained by peptide-like DOS preferentially being produced during copiotrophic bacterial growth and accumulating due to less active cofactor metabolisms. Considering the potential environmental issues accompanying DOS discharge from WWTPs with ΔDOS > 0, our study highlights the importance of focusing on the transformation and control of DOS in the oxic process.

Comparison of Nitrogen and Phosphorus Removal between Two Typical Processes under Low Temperature in a Full-Scale Municipal Wastewater Treatment Plant

Given its strict discharge standards for wastewater treatment plants (WWTPs), China focuses on improving the removal effect of nitrogen and phosphorus in biological treatment processes under low temperatures. The variations in nitrogen and phosphorus during the anaerobic–anoxic-oxic (AAO) and AAO-sequencing batch reactor (SBR) processes in a full-scale WWTP were compared by sampling. Results showed that the removal efficiencies of total nitrogen (TN) and total phosphorus (TP) in both processes exceeded 85% and 91%, respectively, when the water temperature was lower than 15 °C. The wastewater treatment potential capacity of the AAO process was larger than that of AAO-SBR, indicating that the AAO process could realize the subjective demand of nitrogen or phosphorus removal by adjusting its operation mode. The anaerobic phosphorus release of the AAO process was affected when part of the internal reflux entered the anaerobic tank. Thus, the biological phosphorus removal of the AAO process was worse than that of the AAO-SBR process. Since the nitrification and denitrification rates of the AAO process were all higher than that of the AAO-SBR process, the TN removal efficiency of AAO was higher than that of AAO-SBR. These results could provide some advice for the upgrade, operation optimization, and process selection of both processes in the future.

A novel two-stage anoxic/oxic-moving bed biofilm reactor process for biological nitrogen removal in a full-scale municipal WWTP: Performance and bacterial community analysis

The application of a novel two-stage anoxic/oxic-moving bed biofilm reactor (TS-A/O-MBBR) was validated in a full-scale municipal wastewater treatment plant (WWTP), and its working mechanism was analysed for biological nitrogen removal in this study. Over one year, at a hydraulic residence time of only 9.8 h, the effluent chemical oxygen demand, ammonia nitrogen and total nitrogen (TN) concentrations remained below 40, 2 and 15 mg/L, which met strict emission standards. The seven compartments in this unit performed different functions, and together accomplished organics and nitrogen removal. TN removal could be controlled by the external carbon sources dosage added to the postanoxic compartments to cost effectively meet the standard with the lowest cost. The maximum TN removal efficiency and minimum effluent TN concentration reached 91.76 % and 4.12 mg/L, respectively. The bacterial communities differed in the suspended solids and preoxic, postanoxic and oxic biofilms (r = 0.87 and P = 0.001). The top 30 most abundant identified bacterial genera in biofilms included 24 denitrifying genera and 2 nitrifying genera. The most abundant biofilm genus was Methylotenera, which played important roles in denitrification in the anoxic compartments. 1 and 24 denitrifying genera were only abundant in the postanoxic and preanoxic compartments, respectively. Nitrosomonas and Nitrospira were abundant in the oxic compartments, and played roles in nitrification. This study verified the feasibility of the TS-A/O-MBBR process in a full-scale WWTP, and investigated its working mechanism.

Redox environment inducing strategy for enhancing biological phosphorus removal in a full-scale municipal wastewater treatment plant

Phosphorus removal from wastewater is crucial for limiting water eutrophication. However, due to improper operating conditions, tremendous phosphorus removal chemicals addition or low C/N ratio in the influent, biological phosphorus removal (BPR) has been regarded as a difficult issue in real full-scale municipal wastewater treatment plants (WWTPs), especially in the membrane bioreactor (MBR) plants with long sludge retention time. Therefore, application of effective enhanced biological phosphorus removal (EBPR) technologies in WWTPs is of great significance to improve the BPR efficiency, reduce chemicals consumption and operating cost. Favorable redox environment, characterized by ORP is important for the growth and enrichment of phosphate-accumulating organisms (PAO), which is mainly responsible for BPR. In this study, a redox environment inducing strategy for EBPR was taken in a real full-scale MBR-WWTP (treatment capacity of 2 × 106 m3/d). The results indicated that the phosphorus release and uptake rate were rather low in the biochemical tank, which reflected the low phosphate-accumulating organisms (PAO) activity and poor BPR efficiency. This problem may be due to inappropriate redox environment, inhibition by phosphorus removal chemicals or low C/N in the influent. After EBPR, the contribution percentage of BPR increased by up to 18% and chemicals dosage reduced by up to 60%. Furthermore, the relative abundance of PAO (Dechloromonas, Thauera and OLB12) was significantly increased in anaerobic tank (4.62, 1.33 and 1.18%), in anoxic tank (4.85, 1.93 and 0.88%) and in oxic tank (5.17, 1.71 and 0.84%) for appropriate redox environment and relieved inhibition by less dosage of phosphorus removal chemicals. In addition, bacteria related to COD degradation and nitrogen removal were also enriched. The simultaneous enhancement of biological phosphorus removal, carbon removal and nitrogen removal was successfully realized in this research, which indicated that the strategy was effective in real large-scale WWTPs.

Valorization of full-scale waste aerobic granular sludge for biogas production and the characteristics of the digestate.

Despite the dynamic development of aerobic granular sludge (AGS) technology in wastewater treatment, there is limited data on how the different properties of AGS and activated sludge (AS) translate into differences in waste sludge management. Waste sludge generated in both AGS and AS technology is the biggest waste stream generated in wastewater treatment plants (WWTPs). This study aimed to assess biogas production from waste AGS from a full-scale system. Additionally, the properties of the digestate were investigated in terms of its management in line with the assumptions of a circular economy. Both aspects are important because the characteristics of AGS differ from those of AS. Its dense, extracellular-polymer-rich granule structure makes the susceptibility of AGS to anaerobic stabilization lower than that of AS. Given the advantages of AGS for sustainable wastewater treatment and its increasing popularity, waste AGS management will pose a serious challenge for WWTP operators. Therefore, AGS from a full-scale municipal WWTP was valorized for biogas production by increasing the accessibility of the organics in the sludge by homogenization or ultrasound pretreatment. Ultrasound pretreatment released about an order of magnitude more organics from the biomass than homogenization and significantly improved the production of methane-rich biogas (455L/kg VS, about 66% of CH4). The digestion time of pretreated AGS was reduced by 25% in comparison with that of untreated AGS making anaerobic digestion of AGS a feasible solution for sludge management. The AGS digestate was rich in Ca (77.0g/kg TS), Mg (10.9g/kg TS), N (35.1g/kg TS) and P (32.4g/kg TS), whereas its heavy metal levels and biochemical methane potential were low. AGS digestate is not only environmentally safe, but it can serve as a rich source of organics and elements essential for soil fertility and stability.

Developing an evolving multi-layer perceptron network by genetic algorithm to predict full-scale ‎municipal ‎wastewater treatment plant effluent

Developing an efficient model for Wastewater Treatment Plant (WWTP) non-linear process simulation is a vital tool for managing wastewater reuse and recycling. A novel evolving Multilayer perceptron (MLP) by the Genetic Algorithm (GA) was applied to a full-scale municipal ‎WWTP providing high-precision models to predict effluent concentration under various conditions and highlight possible bottlenecks’ potential improvements. Besides the MLP architecture optimization by GA, three different scenarios were considered to study the effect of input variable space pre-processing. In the first scenario twenty-one, original input variables were fed into GA-MLP, while in the second scenario, the basic GA-MLP was extended to assign a weight to each input variable simultaneously by architecture optimization, and in the third scenario, input variables were first pre-processed by principle component analysis. Each scenario was repeated 30 times, and a multi-criteria ranking system based on four performance indices was designed to select the best scenario and MLP. Results show that the second scenario and its best MLPs provided the highest level of precision and generalization. The best MLP of the second scenarios’ Nash-Sutcliffe efficiency and root mean square errors for train and test data were (‎1.000‎, 0.004) and (‎0.914, ‎2.741) ‎ for chemical oxygen demand, (‎0.975,‎ 0.329)‎ and (‎0.915, ‎0.689)‎ for biochemical oxygen demand and (‎0.911, ‎1.186) and ‎(0.875, ‎1.415) for total suspended solids. The proposed hybrid intelligent model was able to efficiently develop near-optimal MLPs to simulate the non-linear WWTP processes and provide an accurate monitoring tool for managers to increase the resilience of WWTPs.

Multipoint characterization of the emission of odour, volatile organic compounds and greenhouse gases from a full-scale membrane-based municipal WWTP

Different environmental and social concerns can arise due to the generation of gaseous emissions during the treatment of urban wastewater. However, there is not an extensive knowledge about which are the main potential odour and greenhouse gas (GHG) emission sources in a wastewater treatment plant (WWTP) and their variability. In this study, a multipoint characterization of the gaseous emissions generated in a full-scale municipal WWTP located in Barcelona was conducted, aiming at identifying the main odour and GHG emission sources. The WWTP under study treats an average inlet flow of 33,000 m3 d−1 using a Ludzack-Ettinger system with Membrane BioReactor (MBR) technology, and it has installed a gas caption and treatment system consisting of a biotrickling filter followed by a conventional biofilter to treat part of the off-gases produced during the wastewater treatment. For this work, gaseous emissions characterization campaigns were conducted to assess the proper performance of the gas treatment unit and to estimate the emission factors referred to odorants and GHGs for the different emission sources and to assess the proper performance of the gas treatment system. Besides, a chemical characterization of the different volatile organic compounds (VOC) present in the gaseous emissions was performed through TD-GC/MS. The main potential odour sources were the reception tank, the barscreens building and the primary settler, where odour concentrations were in the range of 1300 and 2600 ou·m−3. Moreover, GHG emissions were found during the primary treatment and in the MBR units, ranging from 2.21 to 68,217.13 mg CO2eq·m−3. Different VOCs such as aromatic hydrocarbons, alkanes and ketones were found in the gaseous emissions with a high variability among all the emission sources. The results obtained are valuable indicators that can be used to develop odour and GHG mitigation strategies in WWTPs and to estimate the environmental impact of these facilities.

Unravelling gradient layers of microbial communities, proteins, and chemical structure in aerobic granules

Most bacteria live in microbial assemblages like biofilms and granules, and each layer of these assemblages provides a niche for certain bacteria with specific metabolic functions. In this study, a gentle (non-destructive) extraction approach based on a cation exchange resin and defined shear was employed to gradually disintegrate biomass and collect single layers of aerobic granules from a full-scale municipal wastewater treatment plant. The microbial community composition of granule layers was characterized using next-generation sequencing (NGS) targeting the 16S rRNA gene, and protein composition was investigated using metaproteomics. The chemical composition of eroded layers was explored using Fourier Transformed Infrared Spectroscopy. On the surface of the granules, the microbial structure (flocculation-supporting Nannocystis sp.) as well as composition of extracellular polymers (extracellular DNA) and proteome (chaperonins and binding proteins) favored microbial aggregation. Extracellular polymeric substances in the granules were composed of mostly proteins and EPS-producers, such as Tetrasphaera sp. and Zoogloea sp., were evenly distributed throughout the granule structure. The interior of the granules harbored several denitrifiers (e.g., Thauera sp.), phosphate-accumulating denitrifiers (Candidatus Accumulibacter, Dechloromonas sp.) and nitrifiers (Candidatus Nitrotoga). Proteins associated with glycolytic activity were identified in the outer and middle granule layers, and proteins associated with phosphorus conversions, in the deeper layers. In conclusion, the use of an existing cation-exchange resin for gradual biomass disintegration, combined with NGS and metaproteomic analysis was demonstrated as a promising approach for simultaneously investigating the identity and functions of microbes in multilayered biofilm structures.

The prevalence and removal of antibiotic resistance genes in full-scale wastewater treatment plants: Bacterial host, influencing factors and correlation with nitrogen metabolic pathway

This study investigated the prevalence of antibiotic resistance genes (ARGs) in the influent, effluent, and waste activated sludge (WAS) of eight full-scale municipal wastewater treatment plants (WWTPs) in Shanghai, China. A comprehensive understanding of the correlation between various influencing factors (characteristics of wastewater and WAS, antibiotics, metals, mobile genetic elements) and ARGs was explored. Among the eight full-scale WWTPs, the Unitank process was inefficient in removing typical ARGs compared with continuous-flow anaerobic-anoxic-aerobic and oxidation ditch processes. Antibiotic was identified as the most influential factor affecting the occurrence of ARGs in wastewater, followed by flow rate and nutrients. Positive correlations were observed between antibiotics and their corresponding ARGs in the influent, while this correlation disappeared in the WAS. Class I integron, wastewater characteristics (nitrogen and flow rate), antibiotics (ofloxacin, sulfamethazine, and erythromycin), metals (Mg, Al, Fe, and Mn) were identified as crucial factors comprehensively affecting the distribution of ARGs in WAS. Dissimilatory nitrate reduction profoundly influenced the fate of ARGs during wastewater treatment processes, and K04561 (norB), K02567 (napA), K00262 (gdhA), K00284 (gltS) were identified as the most significant genes in the nitrogen metabolism pathway (ko00910). This study provides a new perspective for comprehensively understanding the occurrence and dissemination of ARGs in WWTPs.

Green phytoextracts as natural photosensitizers in LED-based photodynamic disinfection of multidrug-resistant bacteria in wastewater effluent

The photodynamic treatment (PDT) process is a promising technology to control emerging pollutants and antimicrobial resistance problems in the water environment. The reactive oxygen species (ROS) produced when natural and nontoxic photosensitizers (PS) are exposed to light are the key functional components of the PDT process that can effectively achieve microbial inactivation with minimal negative impact. This study examined the application of green phytoextracts from two plants, Chamaecyparis obtusa and Moringa oleifera, as natural photosensitizers for the white light-emitting diode (LED) based photodynamic disinfection of multidrug-resistant (MDR) and total coliforms (TC) from secondary effluent in full-scale municipal wastewater treatment plants. Gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy showed that the phytoextracts contained 57 compounds, particularly aromatic and phenolic hydroxyl compounds. The phytoextracts showed an excellent activity as a PS compared to the intrinsic antibacterial effect. Under a light intensity of 17 mW/cm2, the complete inactivation (6.55 Log CFU/mL) was observed at an irradiation time of 100 min for Escherichia coli ART-2 and 80 min for Staphylococcus aureus, meaning that E. coli was resistant. The light intensity was an important factor influencing photodynamic disinfection. For the complete disinfection of TC satisfying the water reclamation regulation, the irradiation time requirement was 20 min under a light intensity of 80 mW/cm2. During the photodynamic reaction, a significant amount of ROS was generated from the phytoextracts as the light irradiation time was increased. The major ROS was singlet oxygen (1O2, Type II) during the initial 40 min of reaction time and hydroxyl radical (•OH, Type I) after 40 min until complete inactivation.

Comprehensive assessment of chemical residues in surface and wastewater using passive sampling, chemical, biological, and fish behavioral assays

Effluents from ten full-scale municipal wastewater treatment plants (WWTPs) that discharge into the Hudson River, surface waters, and wild-caught fish samples were analyzed using liquid chromatography with tandem mass spectrometry (LC/MS/MS) to examine the influence of wastewater discharge on the concentrations of contaminants of emerging concern (CECs) and their ecological impacts on fish. Analysis was based on targeted detection of 41 pharmaceuticals, and non-targeted analysis (suspect screening) of CECs. Biological effects of treated WWTP effluents were assessed using a larval zebrafish (Danio rerio) swimming behavior assay. Concentrations of residues in surface waters were determined in grab samples and polar organic chemical integrative samplers (POCIS). In addition, vitellogenin peptides, used as biomarkers of endocrine disruption, were quantified using LC/MS/MS in the wild-caught fish plasma samples. Overall, 94 chemical residues were identified, including 63 pharmaceuticals, 10 industrial chemicals, and 21 pesticides. Eight targeted pharmaceuticals were detected in 100% of effluent samples with median detections of: bupropion (194 ng/L), carbamazepine (91 ng/L), ciprofloxacin (190 ng/L), citalopram (172 ng/L), desvenlafaxine (667 ng/L), iopamidol (3790 ng/L), primidone (86 ng/L), and venlafaxine (231 ng/L). Over 30 chemical residues were detected in wild-caught fish tissues. Notably, zebrafish larvae exposed to chemical extracts of effluents from 9 of 10 WWTPs, in at least one season, were significantly hyperactive. Vitellogenin expression in male or immature fish occurred 2.8 times more frequently in fish collected from the Hudson River as compared to a reference site receiving no direct effluent input. Due to the low concentrations of pharmaceuticals detected in effluents, it is likely that chemicals other than pharmaceuticals measured are responsible for the behavioral changes observed. The combined use of POCIS and non-target analysis demonstrated significant increase in the chemical coverage for CEC detection, providing a better insight on the impacts of WWTP effluents and agricultural practices on surface water quality.

Identification of visible colored dissolved organic matter in biological and tertiary municipal effluents using multiple approaches including PARAFAC analysis

This study provided insights into the persistent yellowish color in biological and tertiary effluents of municipal wastewater through a multi-characterization approach and fluorescence excitation-emission matrix-parallel factor (EEM-PARAFAC) analysis. The characterization was performed on three to five full-scale municipal wastewater treatment plants (WWTPs), including differential log-transformed absorbance (DLnA) spectroscopy, resin fractionation, size-exclusion chromatography for apparent molecular weight analysis (SEC-AMW), and X-ray photoelectron spectroscopy (XPS) analysis. Hydrophobic acids (HPOA) were abundant in visible colored dissolved organic matter (DOM). The SEC-AMW result showed that the molecular weight of the colored substances in the secondary effluents is mainly distributed in the range of 2–3 kDa. Through XPS analysis, C-O/C-N and pyrrolic/pyridonic (N-5) were found to be positively correlated with chroma. PARAFAC component models were built on biological (two components) and tertiary effluent (three components) and the correlation analysis revealed that PARAFAC component 2 in biological effluent (BE-C2) and component 1 in tertiary effluent (TE-C1), which were ascribed to Hydrophobic acids and Humic acid-like, were the responsible visible colored DOM components cause yellowish color. In addition, component similarity testing found that the identified visible colored DOM PARAFAC BE-C2, and PARAFAC TE-C1 were identical (0.96) in physicochemical properties, with 4% removal efficacy on average, compared with 11% for invisible colored DOM. This implied that tertiary effluents containing colorants (TE-C1) were resistant to degradation/removal using different disinfection and filtration processes in advanced treatments. This sheds light on many physicochemical aspects of PARAFAC-identified visible colored DOM components and provides spectral data to build an online monitoring system.

Evaluating the impacts of leachate co-treatment on a full-scale municipal wastewater treatment plant in Canada.

The objective of this study was to evaluate the impacts of leachate co-treatment on a full-scale municipal WWTPby comparing plant performance at varying levels of leachate contributions and hydraulic loadings.Leachate BOD:COD ratio was 0.08±0.07 and indicated a stabilized, old matrix and concentrations of zinc, iron, aluminum, chloride and sulfate were 0.174, 38, 1.47, 1803 and 119.1mg/L, respectively. The average volumetric leachate ratio (VLR%) was approximately 0.01% corresponding to a daily volume of 30m3 but reaching a maximum of 270m3(VLR% = 0.1%) and fluctuating on a daily-basis. A cluster analysis revealed 5 VLR% groupings that were used for subsequent analyses:no leachate, 0<Low≤0.001, 0.001<Medium≤0.02, 0.02<High≤0.05, 0.05<Very high≤0.2. Treated effluent concentrations of TKN, ammonia, fecal coliforms (FC),E. coli(EC), TSS and TP experienced atrend where effluent quality was improved at low and medium VLR%compared to no leachate addition, but deteriorated in high and very high VLR%.Treated effluent UVT% and EC were not statistically significantly different at varying VLR%, but FC was.Plant hydraulic had a significant impact on removal rates.Ammonia removals and nitrite concentrations improved inhigh flow conditions, whileTP, BOD and cBODremovals deteriorated. Finally,VLR%, leachate COD, TKN ammonia, chloride and arsenic had significant relationships with plant performance. Thus,for leachate with comparable age and strength, VLR% should not exceedlow to medium contributions(0 and 0.02%)during co-treatment at this WWTP.