Important properties of anion exchange resins for efficient removal of PFOS and PFOA from groundwater

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) present in various water sources have raised a serious concern on their health risk worldwide. Anion exchange is known to be one of the effective treatment methods but the resin properties suitable for theses contaminants have not been fully understood. We examined four commercially available anion exchange resins with different properties (DIAION™ PA312, HPA25M, UBA120, and WA30) and one polymer-based adsorbent (HP20), for their PFOA and PFOS removal in the batch experiment. All or a part of the selected resins were further characterized for their functional group, surface morphology and pore size distribution. The 72 h batch experiment with the 100 mg/L PFOA or PFOS in the laboratory pure water matrix showed a superior capacity of the strong base anion exchange resins, the porous-type HPA25M and PA312, and the gel-type UBA120, for PFOA removal (92.6-97.9%). Among those resins, the high porous HPA25M was suggested most effective due to its remarkably high reaction rate and effectiveness to PFOS (99.9%). In the groundwater matrix, however, the performance of the those anion exchange resins was generally suppressed, causing up to 71% decrease in their removal rates. The least matrix impact was observed for PFOS removal by HPA25M, which indicated the resin's high selectivity to the contaminant. The physiochemical analysis indicated that the presence of relatively large pores (1 nm-10 nm) over HPA25M played an important role in the PFAS removal.

Reduction of SARS-CoV-2 by biological nutrient removal and disinfection processes in full-scale wastewater treatment plants

Detection of SARS-CoV-2 RNA in wastewater poses people's concerns regarding the potential risk in water bodies receiving wastewater treatment effluent, despite the infectious risk of SARS-CoV-2 in wastewater being speculated to be low. Unlike well-studied nonenveloped viruses, SARS-CoV-2 in wastewater is present abundantly in both solid and liquid fractions of wastewater. Reduction of SARS-CoV-2 in past studies were likely underestimated, as SARS-CoV-2 in influent wastewater were quantified in either solid or liquid fraction only. The objectives of this study were (i) to clarify the reduction in SARS-CoV-2 RNA during biological nutrient removal and disinfection processes in full-scale WWTPs, considering the SARS-CoV-2 present in both solid and liquid fractions of wastewater, and (ii) to evaluate applicability of pepper mild mottle virus (PMMoV) as a performance indicator for reduction of SARS-CoV-2 in WWTPs. Accordingly, large amount of SARS-CoV-2 RNA were partitioned in the solid fraction of influent wastewater for composite sampling than grab sampling. When SARS-CoV-2 RNA in the both solid and liquid fractions were considered, log reduction values (LRVs) of SARS-CoV-2 during step-feed multistage biological nitrogen removal (SM-BNR) and enhanced biological phosphorus removal (EBPR) processes ranged between>2.1-4.4 log and did not differ significantly from those in conventional activated sludge (CAS). The LRVs of SARS-CoV-2 RNA in disinfection processes by ozonation and chlorination did not differ significantly. PMMoV is a promising performance indicator to secure reduction of SARS-CoV-2 in WWTPs, because of its higher persistence in wastewater treatment processes and abundance at a detectable concentration even in the final effluent after disinfection.

Biological treatment of perfluorooctanesulfonic acid (PFOS) using microbial capsules of a polysulfone membrane

Perfluorooctanesulfonic acid (PFOS) is a persistent organic substance that has been extensively applied in many industries and causes severe, widespread adverse health impacts on humans and the environment. The development of an effective PFOS treatment method with affordable operational costs has been expected. This study proposes the biological treatment of PFOS using microbial capsules enclosing a PFOS-reducing microbial consortium. The objective of this study was to evaluate the performance of the polymeric membrane encapsulation technique for the biological removal of PFOS. First, a PFOS-reducing bacterial consortium, composed of Paracoccus (72%), Hyphomicrobium (24%), and Micromonosporaceae (4%), was enriched from activated sludge by acclimation and subsequent subculturing with PFOS containing media. The bacterial consortium was first immobilized in alginate gel beads, then enclosed in membrane capsules by coating the gel beads with a 5% or 10% polysulfone (PSf) membrane. The introduction of microbial membrane capsules could increase PFOS reduction to between 52% and 74% compared with free cell suspension, which reduced by 14% over three weeks. Microbial capsules coated with 10% PSf membrane demonstrated the highest PFOS reduction at 80% and physical stability for six weeks. Candidate metabolites including perfluorobutanoic acid (PFBA) and 3,3,3- trifluoropropionic acid were detected by FTMS, suggesting the possible biological degradation of PFOS. In microbial membrane capsules, the initial adsorption of PFOS on the shell membrane layer enhanced subsequent biosorption and biological degradation by PFOS-reducing bacteria immobilized in the core alginate gel beads. The 10%-PSf microbial capsules exhibited a thicker membrane layer with the fabric structure of a polymer network, which maintained longer physical stability than 5%-PSf microbial capsules. This outcome suggests the potential application of microbial membrane capsules to PFOS-contaminated water treatment.

Ammonia tolerance and microbial community in thermophilic co-digestion of sewage sludge initiated with lignocellulosic biomass

Rice straw is a useful lignocellulosic biomass for controlling ammonia inhibition in the thermophilic anaerobic digestion of sewage sludge. However, it is challenging to procure rice straw throughout the year because of its seasonal production. This study investigated methane production in a laboratory-scale digester by gradually decreasing rice straw addition to solid thermophilic sewage sludge digestion. The decrease in rice straw did not accumulate volatile fatty acids and stabilized methane production. Even with increased sludge concentration without rice straw, methane production continued under high ammonia conditions. Ammonia tolerance of the digested sludge of the experimental digester was higher than that of conventionally digested sludge. The cellulose-degrading bacteria Clostridia and high ammonia-resistant archaea Methanosarcina were dominant in the experimentally digested sludge. The community was maintained for over 200 days after discontinuing the rice straw supply. These findings suggest that anaerobic digestion initiation with rice straw is appropriate to facilitate ammonia-tolerant communities.

Removal performance of SARS-CoV-2 in wastewater treatment by membrane bioreactor, anaerobic-anoxic-oxic, and conventional activated sludge processes

The potential risk of SARS-CoV-2 in treated effluent from a wastewater treatment plant (WWTP) is concerned since SARS-CoV-2 is contained in wastewater during the COVID-19 outbreak. However, the removal of SARS-CoV-2 in WWTP has not been well investigated. The objectives of this study were (i) to clarify the removal performance of SARS-CoV-2 during wastewater treatment, (ii) to compare the removal performance of different secondary treatment processes, and (iii) to evaluate applicability of pepper mild mottle of virus (PMMoV) as a performance indicator for the reduction of SARS-CoV-2 RNA in wastewater treatment. Influent wastewater, secondary-treatment effluent (before chlorination), and final effluent (after chlorination) samples were collected from a WWTP from May 28 to September 24, 2020, during the COVID-19 outbreak in Japan. The target WWTP had three parallel treatment systems employing conventional activated sludge (CAS), anaerobic-anoxic -oxic (A2O), and membrane bioreactor (MBR) processes. SARS-CoV-2 in both the liquid and solid fractions of the influent wastewater was concentrated and quantified using RT-qPCR. SARS-CoV-2 in treated effluent was concentrated from 10 L samples to achieve a detection limit as low as 10 copies/L. The log reduction value (LRV) of SARS-CoV-2 was 2.7 ± 0.86 log₁₀ in CAS, 1.6 ± 0.50 log₁₀ in A2O, and 3.6 ± 0.62 log₁₀ in MBR. The lowest LRV observed during the sampling period was 2.8 log₁₀ in MBR, 1.2 log₁₀ in CAS, and 1.0 log₁₀ in A2O process, indicating that the MBR had the most stable reduction performance. PMMoV was found to be a good indicator virus to evaluate reduction performance of SARS-CoV-2 independent of the process configuration because the LRV of PMMoV was significantly lower than that of SARS-CoV-2 in the CAS, A2O and MBR processes.

Selection of surrogate viruses for process control in detection of SARS-CoV-2 in wastewater

Since SARS-CoV-2 RNA in wastewater is often present at low concentration or under detection limit, ensuring the reliability of detection processes using appropriate process controls is essential. The objective of this study was to evaluate applicability and limitations of candidate surrogate viruses as process controls under combinations of different virus concentration and RNA extraction methods. Detection efficiency of SARS-CoV-2 spiked in wastewater was compared with those of candidate surrogate viruses of bacteriophage ϕ6, pepper mild mottle virus (PMMoV), F-specific coliphage (F-phage), and murine norovirus (MNV). After inactivated SARS-CoV-2 and ϕ6 were spiked in two different wastewaters, the viruses in solid and liquid fractions of wastewater were concentrated by centrifuge and polyethylene glycol (PEG) precipitation, respectively. Viral RNA was extracted by using QIAamp Viral RNA Mini Kit and 3 other commercially available extraction kits, then quantified by reverse transcription-quantitative PCR using CDCN1 assay. Regardless of extraction kits, SARS-CoV-2 was consistently detected with good efficiency from both liquid (11-200%) and solid fractions (7.1-93%). Among the candidate process controls, PMMoV was widely detected at good efficiencies from both liquid and solid fractions regardless of selection of RNA extraction kits. F-phage and MNV also showed good detection efficiencies in most combinations of wastewater fractions and RNA extraction kits. An enveloped virus ɸ6 was found often undetected or to have very low detection efficiency (0.1-4.2%) even when SARS-CoV-2 spiked in wastewater was detected with good efficiency. Consequently, PMMoV is widely applicable as process control for detection of SARS-CoV-2 either in liquid fractions concentrated by PEG precipitation, or in solid fractions concentrated by centrifuge.

Transcriptomic response of HepG2 cells exposed to three common anti-inflammatory drugs: Ketoprofen, mefenamic acid, and diclofenac in domestic wastewater effluents

The biological impacts of residual pharmaceuticals in the complex wastewater effluents have not been fully understood. Here, we investigated changes in the transcriptomic responses of hepatobrastoma (HepG2) cells exposed to a single or partially combined three common non-steroidal anti-inflammatory drugs (NSAIDs); ketoprofen (KPF), mefenamic acid (MFA) and diclofenac (DCF), in domestic wastewater effluents. After 48 h sub-lethal exposure to single compounds, the DNA microarray analysis identified 57-184 differently expressed genes (DEGs). The hierarchical clustering analysis and GO enrichment of the DEGs showed that gene expression profiles of the NSAIDs were distinct from each other although they are classified into the same therapeutic category. Four maker genes (i.e., EGR1, AQP3, SQSTM1, and NAG1) were further selected from the common DEGs, and their expressions were quantified by qPCR assay in a dose-dependent manner (ranging from μg/L to mg/L). The results revealed the insignificant induction of the marker genes at 1 μg/L of KPF, MFA, and DCF, suggesting negligible biological impacts of the NSAIDs on gene expression (early cellular responses) of HepG2 at typical concentration levels found in the actual wastewater effluents. Based on the quantitative expression analysis of the selected marker genes, the present study indicated that the presence of wastewater effluent matrix may mitigate the potentially adverse cellular impacts of the NSAIDs.

Initial behaviors and removal of extracellular plasmid gene in membrane bioreactor

Extracellular antibiotic resistance genes (eARG) are considered to play an important role in spread of antimicrobial resistance (AMR) in wastewater treatment and water environment. Membrane bioreactor (MBR) reportedly has better removal of ARGs in wastewater than conventional activated sludge process. However, removal of eARG is possibly limited because eARG is small to pass through microfiltration (MF) membranes. To evaluate potential removal of eARG in MBR, this study aimed to understand the initial behaviors of eARG received in MBR. The recombinant plasmid with artificial marker gene was spiked in lab-scale MBR to trace fate of eARG in MBR. Among 10 ¹⁰ copies/L of the spiked gene, 2.6 × 10⁹ copies/L was adsorbed on sludge particles at 6 h after spiking, while only 2.2 × 10⁸-3.6 × 10⁸ copies/L of the spiked gene was remained but constant in sludge liquid phase from 6 until 48 h. This result suggests that adsorption on sludge particles served as the main mechanism to govern the initial fate of eARG in MBR. Meanwhile, the spiked gene concentrations in membrane permeate was lower than sludge liquid phase and decreased overtime, suggesting retention of eARG in membrane filtration. Total LRV of the spiked extracellular gene were 3.4 ± 0.8 log at 48 h after spiking. LRV by adsorption corresponded to 1.7 ± 0.7 log constantly since 3 h after spiking, while LRV by membrane filtration increased from 0 to 1.7 ± 0.6 log. Linear correlation of LRV by membrane filtration with transmembrane pressure (TMP) suggested that foulant deposition on membrane governs removal of eARG by membrane filtration in MBR.

Detection of SARS-CoV-2 in wastewater in Japan during a COVID-19 outbreak

The presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater samples has been documented in several countries. Wastewater-based epidemiology (WBE) is potentially effective for early warning of a COVID-19 outbreak. In this study, presence of SARS-CoV-2 RNA in wastewater samples was investigated and was compared with the number of the confirmed COVID-19 cases in the study area during COVID-19 outbreak in Japan. In total, 45 influent wastewater samples were collected from five wastewater treatment plants in Ishikawa and Toyama prefectures in Japan. During the study period, the numbers of confirmed COVID-19 cases in these prefectures increased from 0.3 and 0 to >20 per 100,000 people. SARS-CoV-2 ribonucleic acid (RNA) in the samples was detected using several PCR-based assays. Of the 45 samples, 21 were positive for SARS-CoV-2 according to at least one of the three quantitative RT-PCR assays. The detection frequency increased when the number of total confirmed SARS-CoV-2 cases in 100,000 people exceeded 10 in each prefecture; however, SARS-CoV-2 could also be detected at a low frequency even when the number was below 1.0. SARS-CoV-2 in wastewater could be detected in the early stage of the epidemic, even if the number of confirmed cases potentially underestimates the actual numbers of cases. This suggests that WBE approach can potentially act as an early warning of COVID-19 outbreaks in Japan.

A bioelectrochemical-system-based trickling filter reactor for wastewater treatment

A bioelectrochemical system (BES)-based trickling filter (TF) reactor was utilized for wastewater treatment. At a COD load of 1.0 g-COD/L/day, effluent chemical oxygen demand (COD) and total nitrogen (TN) were 115 and 108 mg/L, respectively, which were allowed for discharge. Superior performance was achieved at 0.5 g-COD/L/day with a circulation rate of 8 L/h, and both COD and TN removal were >98%. Coulombic efficiency was 11% at 1.0 g-COD/L/day and at most 16% at 0.5 g-COD/L/day. COD removal decreased when the BES was removed, demonstrating that BES improved COD removal capability. In anodic biofilms, exoelectrogenic, facultative, nitrifying, and sulfate-reducing bacteria could coexist. Geobacter for current generation grew inside the biofilm, and bacteria in the middle and outer layers consumed oxygen and degraded organic matter and nitrogen. This BES-based TF reactor may be used for efficient and cost-effective COD and TN removal at high loads without excess sludge removal.

Transcriptomic analysis of HepG2 cells exposed to fractionated wastewater effluents suggested humic substances as potential inducer of whole effluent toxicity

We performed a transcriptome-based bioassay (TSB assay) using human hepatoma HepG2 cells to evaluate the potential toxicity of whole wastewater effluents from two membrane bioreactors (MBRs) and a conventional activated sludge process (AS). The biologically active agent(s) in the wastewater effluents were characterized based on expression of the marker genes (i.e., CYP1A1, AKR1B10, GCLM and GPX2) selected by DNA microarray analysis, after the wastewater effluent samples were concentrated by a reverse osmosis (RO) membrane and further fractionated by various manipulations. The qPCR assay of marker genes demonstrated that the induction of CYP1A1 and GPX2 was mitigated after passing through C18 and chelate columns. In addition, clear induction of CYP1A1 was observed in the smallest size fraction with 1 k Da or smaller organic molecules in all the tested effluents. These results together with the water quality data of the fractionated samples suggested that responsible constituents for potentially adverse and abnormal transcriptomic responses in HepG2 could have hydrophobic nature and act with metal-dissolved organic matter (DOM) complexes in 1 k Da or smaller size fraction. Although DOM is known to play two contradictory roles as a protector and an inducer of toxicants, our present study indicated the DOM in wastewater effluent, particularly humic substances with acidic nature, functioned as a toxicity inducer of residual chemicals in the effluents. This study provided a new insight into the nature of "toxic unknowns" in the wastewater effluents, which should be monitored whole through the reclamation process and prioritized for removal.

Candidates of quorum sensing bacteria in activated sludge associated with N-acyl homoserine lactones

This study aimed to explore candidates of microbial groups which is associated with quorum sensing in activated sludge. Activated sludge samples were collected from three wastewater treatment plants (WWTP) to analyze N-acyl homoserine lactone (AHL) by Fourier-transform mass spectrometry (FTMS) and 16S rRNA-based microbial community. Among activated sludge samples taken at 3 WWTPs in different seasons, 2 AHL species of N-3-hydroxyoctanoyl-l-homoserine lactone and N-3-hydroxydecanoyl-l-homoserine lactone were detected in the range of ranged of 0.1 ng/L to 1.6 ng/L. The detected AHL species were not dependent on treatment systems nor seasons. From microbial community analysis, population abundance of one strain in Verrucomicrobia and two strains in Holophagaceae had high correlation with AHL concentration in activated sludge. Comamonadaceae had also moderately correlated population with AHL concentrations among quorum sensing bacteria reported previously.

Multiple-endpoints gene alteration-based (MEGA) assay: A toxicogenomics approach for water quality assessment of wastewater effluents

Wastewater effluents contain a significant number of toxic contaminants, which, even at low concentrations, display a wide variety of toxic actions. In this study, we developed a multiple-endpoints gene alteration-based (MEGA) assay, a real-time PCR-based transcriptomic analysis, to assess the water quality of wastewater effluents for human health risk assessment and management. Twenty-one genes from the human hepatoblastoma cell line (HepG2), covering the basic health-relevant stress responses such as response to xenobiotics, genotoxicity, and cytotoxicity, were selected and incorporated into the MEGA assay. The genes related to the p53-mediated DNA damage response and cytochrome P450 were selected as markers for genotoxicity and response to xenobiotics, respectively. Additionally, the genes that were dose-dependently regulated by exposure to the wastewater effluents were chosen as markers for cytotoxicity. The alterations in the expression of an individual gene, induced by exposure to the wastewater effluents, were evaluated by real-time PCR and the results were validated by genotoxicity (e.g., comet assay) and cell-based cytotoxicity tests. In summary, the MEGA assay is a real-time PCR-based assay that targets cellular responses to contaminants present in wastewater effluents at the transcriptional level; it is rapid, cost-effective, and high-throughput and can thus complement any chemical analysis for water quality assessment and management.

Toxicity assessment of chlorinated wastewater effluents by using transcriptome-based bioassays and Fourier transform mass spectrometry (FT-MS) analysis

Effects of chlorination on the toxicity of wastewater effluents treated by activated sludge (AS) and submerged membrane bioreactor (S-MBRB) systems to HepG2 human hepatoblastoma cells were investigated. In addition to the cytotoxicity and genotoxicity assays, the DNA microarray-based transcriptome analysis was performed to evaluate the change in types of biological impacts on HepG2 cells of the effluents by chlorination. Effluent organic matter (EfOM) and disinfection by-products (DBPs) were also characterized by using Fourier transform mass spectrometry (FT-MS). Although no significant induction of genotoxicity was observed by chlorination for both effluents, the chlorination elevated the cytotoxicity of AS effluent but reduced that of S-MBRB effluent. The FT-MS analyses revealed that more DBPs including nitrogenated DBPs (N-DBPs) were formed in the AS effluent than in the S-MBRB effluent by chlorination, supporting the increased cytotoxicity of AS effluent. The lower O/C ratio of S-MBRB EfOM suggests that a large number of organic molecules were detoxified by chlorination, which consequently decreased the cytotoxicity of S-MBRB effluent. Integration of all the results highlights that both cytotoxicity and biological impacts of chlorinated wastewater effluents were clearly dependent on the EfOM characteristics such as DBPs and O/C ratio, namely, on types of treatment systems.

Evaluation of whole wastewater effluent impacts on HepG2 using DNA microarray-based transcriptome analysis

DNA microarray-based transcriptome analysis with human hepatoma HepG2 cells was applied to evaluate the impacts of whole wastewater effluents from the membrane bioreactors (MBRs) and the activated sludge process (AS). In addition, the conventional bioassays (i.e., cytotoxicity tests and bioluminescence inhibition test), which were well-established for the evaluation of the overall effluent toxicity, were also performed for the same samples. Transcriptome analysis revealed that 2 to 926 genes, which were categorized to 0 to 225 biological processes, were differentially expressed after exposure to the effluents and the raw wastewater. Among the tested effluents, the effluent from a MBR operated at a relatively long solid retention time (i.e., 40 days) and small membrane pore size (i.e., 0.03 μm) showed the least impacts on the HepG2 even at the level comparable to tap water. The observed gene expression responses were in good agreement with the results of cytotoxicity tests, and provided additional molecular mechanistic information on adverse effects occurred in the sublethal region. Furthermore, the genes related to "lipid metabolism", "response to endogenous stimulus", and "response to inorganic substance" were selected as potential genetic markers, and their expression levels were quantified to evaluate the cellular impacts and treatability of wastewater effluents. Although the harmful impacts and innocuous impacts could not be distinguished at present, the results demonstrated that the DNA microarray-based transcriptome analysis with human HepG2 cells was a powerful tool to rapidly and comprehensively evaluate impacts of whole wastewater effluents.