Impact of biological activated carbon filtration and backwashing on the behaviour of PFASs in drinking water treatment plants.

PFASs are present in surface water, tap water and even commercial drinking water and pose a risk to human health. In this study, the treatment efficiency of 14 PFASs was studied in a large drinking water treatment plant (DWTP) using Taihu Lake as the source, and it was found that the ozone/biological activated carbon (O3-BAC) process was the most effective process for the removal of PFASs in DWTPs. For the O3-BAC process, there were differences in the removal of PFASs by BACs (1,4,7,13 years) of different ages. The sterilization experiments revealed that for GAC, its physical adsorption capacity reached saturation after one year, while for BAC with mature biofilms, biosorption was the main mechanism for the removal of PFASs. The abundance of Alphaproteobacteria and Gammaproteobacteria in biofilms was positively correlated with the age of the BAC. The microbial community with higher abundance is beneficial to the biodegradation of organic matter and thus provides more active sites for the adsorption of PFASs. PFASs can leak in the early stage of filtration after backwashing, so it is necessary to pay close attention to the influent and effluent concentrations of PFASs during biofilm maturation after backwashing.

Fate, mobility, and pathogenicity of drinking water treatment plant resistomes deciphered by metagenomic assembly and network analyses.

Antibiotic resistance genes (ARGs) have been regarded as emerging environmental contaminants. The profile of resistome (collection of all ARGs) in drinking water and its fate during drinking water treatment remain unclear. This study applied metagenomic assembly combined with network analysis to decipher the profile, mobility, host, and pathogenicity of resistomes in two full-scale drinking water treatment plants (DWTPs), each applying conventional treatment and advanced treatment of ozonation followed by biological activated carbon filtration. In source waters and effluents of each treatment process collected from both DWTPs, 215 ARGs belonging to 20 types were detected with total concentration ranging from 6.30 ± 1.83 to 5.20 ± 0.26 × 104 copies/mL. Both the conventional and advanced DWTPs were revealed to effectively reduce the concentration of total ARGs, with the average removal efficiency of 3.61-log10 and 2.21-log10, respectively. Multiple statistical analyses (including network analysis) indicated drinking water resistome correlated tightly with mobile gene elements (MGEs) and bacterial community, with the latter acting as the premier driver of resistome alteration in DWTPs. Further analysis of ARG-carrying contigs (ACCs) assembled from drinking water metagenomes (i) tracked down potential bacterial hosts of ARGs (e.g., Proteobacteria phylum as the major pool of resistome), (ii) provided co-localization information of ARGs and MGEs (e.g., MacB-E7196 plasmid1), and (iii) identified ARG-carrying human pathogens (e.g., Enterococcus faecium and Ralstonia pickettii). This work firstly determined the concentration, mobility incidence, and pathogenicity incidence of DWTP resistomes, based on which the actual health risk regarding antibiotic resistance could be quantitatively assessed in further study, providing a useful direction for decision-making concerning the risk control of ARGs in DWTPs.

Identification of microplastics in conventional drinking water treatment plants in Tehran, Iran.

The presence of microplastics (MPs), as an emerging pollutant is a growing concern in drinking water, yet most of the studies have been carried out in surface waters and wastewater treatment plants and there are few studies on MPs in drinking water treatment plants (DWTPs). This study investigates these particles in three different conventional DWTPs in the city of Tehran, Iran, and aims to analyze these particles down to the size of 1 µm. A scanning electron microscope was utilized in this study to quantitatively analyze MPs. Accordingly, the average abundance of MPs in raw and treated water samples varied from 1996 ± 268 to 2808 ± 80 MPs L-1 and 971 ± 103 to 1401 ± 86 MPs L-1, respectively. While particles smaller than 10 µm comprised 65-87% of MPs. Moreover, µ-Raman spectroscopy was used to characterize MPs. As the results, polypropylene, polyethylene terephthalate, and polyethylene were the most abundant identified polymers among MPs, comprising more than 53% of particles. Additionally, MPs were categorized as fibers, fragments, and spheres. This study fills the knowledge gap of MPs presence in Tehran conventional DWTPs which is of high importance since they supply drinking water for more than 8 million people and investigates the performance of conventional DWTPs in removing MPs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40201-021-00737-3.

Temperature Influenced the Comammox Community Composition in Drinking Water and Wastewater Treatment Plants.

Nitrification is a pivotal step applied in water engineered systems for nitrogen removal. Temperature variation due to seasonal changes is a great challenge for maintaining nitrogen removal efficiency in water engineered ecosystems by affecting nitrifier activities. Research on the abundance, activity, and metabolic characteristics of nitrifiers can provide information for selecting suitable design parameters to ensure efficient nitrogen removal in different seasons. To date, the temperature-related niche separation of comammox, a newly discovered nitrifier with potential high-growth yield, has been rarely investigated. This study addressed the distribution of comammox and canonical nitrifying guilds in drinking water treatment plants (DWTPs) and wastewater treatment plants (WWTPs) in different seasons. qPCR-based surveys showed that comammox ubiquitously distributed and greatly outnumbered other ammonia-oxidizing prokaryotes in both DWTPs and WWTPs, except in Aug samples from DWTPs, suggesting the potential competitive advantage of AOA in summer. The nitrificans-like comammox and nitrosa-like comammox comprised the majority of the comammox community in DWTPs and WWTPs, respectively, and COD and NH4+ concentrations significantly contributed to the distinct comammox phylotype distribution between DWTPs and WWTPs. The temperature-related distribution pattern of the comammox community was observed at each site. Moreover, the network complex of comammox communities was highest in Dec at all the sites, possibly contributing to the survival of comammox community in low temperature conditions.

Impacts alum DWTPs sludge discharge and changes in flow regime of the Nile River on the quality of surface water and cultivated soils in Fayoum watershed, Egypt.

Discharge of Drinking Water Treatment Plants sludge directly on surface waters without any treatment is becoming an important issue in most countries around the world, behavior is not only affecting on the water quality, but also on soil and crops. This study investigated the effect of discharge of alum sludge and the variation in the level of the Nile water (flow regime) on water and soil qualities. The water samples were analyzed for physical, chemical and microbiological parameters. In winter (closure season), the mean values of EC, TDS, major ions, pH, DO and total algae count were higher than in summer. In summer (flooding season), it was noticed that the mean values of SiO2, metals, COD, BOD, TOC, nutrients and bacteriological parameters exceed winter season values. Moreover, the concentrations of Al, Fe, Mn were above WHO permissible limits and the concentrations of aggregate organic parameters exceed the FAO permissible limits in sites near the areas of sludge discharge. Most of water samples exceed the national guidelines. For soil, our findings showed that the concentrations of metals in soil samples collected from areas irrigated from canals receiving alum sludge are more (two-three times) than their concentrations from the pure sites. However, Pb concentration in the contaminated soil reaches ten times more than in the pure one. The management of sludge disposal becomes an urgent priority to save waterways, soil and crops from pollution. Finally, the variation in water flow during the winter closure period with reduction by ≈15 BCM is similar to the same reduction in the Nile flow when the Grand Ethiopian Renaissance Dam starts operation. This indicates that the long-term reduction in water flow due to the construction of this dam may cause serious environmental changes in the Nile River in Egypt.

Antibiotics removal from aquatic environments: adsorption of enrofloxacin, trimethoprim, sulfadiazine, and amoxicillin on vegetal powdered activated carbon.

This study addresses the growing concern about the high levels of antibiotics in water, outlining an alternative for their removal. The adsorption of four representative antibiotics from commonly used families (fluoroquinolones, ß-lactams, trimethoprim, and sulfonamides) was performed over vegetal powdered activated carbon. The evolution of the adsorption was studied during 60 min for different initial antibiotic concentrations, not only individually but also simultaneously to determine competitive adsorption. Moreover, this research studied the adsorption isotherms and kinetics of the process, as well as the pH influence; FTIR of the activated carbon before and after adsorption was carried out. Trimethoprim and sulfadiazine showed more affinity for the adsorbent than amoxicillin and enrofloxacin. This trend might be attributed to their structure, capable of stablishing stronger π-π interactions with the adsorbent, which showed high affinity for the active sites of the adsorbent via FTIR. In addition, the sorption isotherms of trimethoprim followed a Langmuir type isotherm, amoxicillin followed a Freundlich type isotherm, and enrofloxacin and sulfadiazine followed both. The antibiotics followed pseudo-second-order kinetics. Sulfadiazine and amoxicillin gave better performances in acidic conditions. By contrast, the sorption of trimethoprim was favored in basic environments. Variations of pH had a negligible effect on the removal of enrofloxacin.

Do membrane filtration systems in drinking water treatment plants release nano/microplastics?

Drinking water treatment plants (DWTPs) are thought to be able to remove many micropollutants including nanoplastics (NPs) and microplastics (MPs). However, few studies have focused on the water treatment process itself producing NPs and/or MPs. This paper discussed the possibility of releasing NPs and MPs from organic membranes in drinking water treatment plants. The effects of physical cleaning, chemical agents, mechanical stress, aging, and wear on the possibility of membrane breach during long-term use were analyzed. Further analysis based on membrane aging mechanisms and material properties revealed that the membrane filtration systems could release NPs/MPs to drinking water supply networks. Although the toxicity of membrane materials to human body needs further study, the action that should be taken to treat the release of NPs/MPs in DWTPs cannot be ignored: (1) in-depth study of the generation and release mechanisms of NPs/MPs; (2) reconsideration of membrane life cycle design; (3) determination of NPs/MPs concentration limits in drinking water through toxicity assessment; (4) accelerating development of biomembrane and inorganic membrane materials; and (5) unification of NPs/MPs sampling and testing standard. Accordingly, more research needs to be conducted to investigate the release of NPs and/or MPs from DWTPs.

Occurrence and removal of sulfonamide antibiotics and antibiotic resistance genes in conventional and advanced drinking water treatment processes.

Sulfonamides (SAs) and sul antibiotic resistance genes (ARGs) have been extensively detected in drinking water sources and warrant further studies on the removal of them in different drinking water treatment processes (DWTPs). The prevalence of 13 SAs, sul1, sul2 and class I integrase gene intI1 in conventional and advanced processes was investigated using HPLC-MS/MS and real-time quantitative PCR (qPCR), respectively. The most abundant SA was sulfamethoxazole, with the maximum concentration of 67.27 ng/L. High concentration of sulfamethoxazole was also measured in finished water in both conventional (22.05 ng/L) and advanced (11.24 ng/L) processes. Overall, the removal efficiency of advanced process for each SA was higher than that of conventional process, except for sulfameter. The absolute concentrations of sul1, sul2 and intI1 in raw water ranged from 1.8 × 103 to 2.4 × 105 gene abundance/mL. After treatment, the residual sul ARGs and intI1 in finished water still remained at 102 - 104 gene abundance/mL. Conventional treatment units, including flocculation/sedimentation/sand filtration, played a more important role in removing sul1, sul2 and intI1 than oxidation (chlorination or ozonation) and granular activated carbon filtration treatments. Based on this work, more investigations are needed to help improve the removal of both antibiotics and ARGs in DWTPs.

Risk exposure assessment of per- and polyfluoroalkyl substances (PFASs) in drinking water and atmosphere in central eastern China.

We examined per- and polyfluoroalkyl substances (PFASs) in air from eight cities, and in water from six drinking-water treatment plants (DWTPs), in central eastern China. We analyzed raw and treated water samples from the DWTPs for 17 ionic PFASs with high-performance liquid chromatography/negative-electrospray-ionization tandem mass spectrometry (HPLC/(-)ESI-MS/MS), and analyzed the gas and particle phases of atmospheric samples for 12 neutral PFASs by gas chromatography-mass spectrometry (GC-MS). Perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) were the dominant compounds in drinking water, and fluorotelomer alcohols (FTOHs) dominated in atmospheric samples. Of all the compounds in the treated water samples, the concentration of PFOA, at 51.0 ng L-1, was the highest. Conventional treatments such as coagulation (COA), flocculation (FOC), sedimentation (SED), and sand filtration (SAF) did not remove PFASs. Advanced treatments, however, including ultrafiltration (UF) and activated carbon (AC), removed the majority of PFASs except for shorter-chain PFASs such as perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPA). We also investigated human exposure to PFASs via drinking water and the atmosphere and found that the mean daily intake of PFASs was 0.43 ng kg-1 day-1.

The occurrence and removal of selected fluoroquinolones in urban drinking water treatment plants.

Fluoroquinolones (FQs) are a widely prescribed group of antibiotics. They enter the aqueous environment, where they are frequently detected, and can lead to a threat to human health. Drinking water treatment plants (DWTPs) play a key role in removing FQs from potable water. This study investigated the occurrence and removal of four selected FQs (norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL)) in three urban DWTPs in China. The treatment efficacy for each system was simultaneously evaluated. Two of the examined DWTPs used conventional treatment processes. The third used conventional processes followed by additional treatment processes (ozonation-biologically activated carbon (ozonation-BAC) and membrane technology). The average concentrations of the four FQs in the source water and the finished water ranged from 51 to 248 ng/L and from <5 to 46 ng/L, respectively. Based on residual concentrations, the conventional treatment system had a low removal of FQs. In contrast, the addition of advanced treatment processes such as the ozonation-BAC and membranes, substantially improved the removal of FQs. The finding of this study has important implications: even though coagulation-sedimentation and chlorination treatment processes can remove most target FQs, the typical practice of advanced treatment processes is necessary for the further removal.

Analysis of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and its brominated analogues in chlorine-treated water by gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS).

A simple, selective and sensitive method for the analysis of the strong mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and its brominated analogues (BMXs) in chlorine-treated water has been developed. The method is based on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS), previous liquid-liquid extraction (LLE) of a smaller sample volume compared to other methods and on-line derivatization with a silylation reactive. GC-QqQ-MS/MS has been raised as an alternative easier to perform than gas chromatography coupled to high resolution mass spectrometry (GC-HRMS) for the analysis of MX and BMXs, and it allows to achieve low LODs (0.3 ng/L for MX and 0.4-0.9 ng/L for BMXs). This technique had not been previously described for the analysis of MX and BMXs. Quality parameters were calculated and real samples related to 3 drinking water treatment plants (DWTPs), tap water and both untreated and chlorinated groundwater were analyzed. Concentrations of 0.3-6.6 ng/L for MX and 1.0-7.3 ng/L for BMXs were detected. Results were discussed according to five of the main factors affecting MX and BMXs formation in chlorine-treated water (organic precursors, influence of bromide ions, evolution of MX and BMXs in the drinking water distribution system, groundwater chlorination and infiltration of water coming from chlorination processes in groundwater).