In the study and management of ozonation, a model that describes ozone (O3) concentration dynamics is a fundamental framework. However, the conventional initial O3 demand/pseudo-first-order model (IPM) is strongly dependent on the O3 dose and consequently constrains both basic and applied research. Therefore, we propose a new model that expands IPM by representing O3 consumption with two distinct second-order reactions. Using this model, O3 exposure was successfully predicted with a median absolute relative error (MdARE) of 4.8% for various combinations of water temperature and O3 dose within the calibrated range. Coupling our model with an existing hydroxyl radical (& centerdot;OH) model accurately reproduced the decay of p-chlorobenzoic acid (a & centerdot;OH probe compound) with a MdARE of 3.2%. Simulations using the new model revealed that (i) the O3 dose required for the removal of Cryptosporidium parvum oocysts is governed by water temperature rather than dissolved substances, (ii) the O3/& centerdot;OH contribution ratio to cis-1,2-dichloroethene oxidation is practically independent of O3 dose, and (iii) the removal efficiency of p-chlorobenzoic acid can be estimated with a MdARE of 14% through real-time monitoring of the O3 consumption rate. This study provides a versatile kinetic framework for mechanistic studies and practical applications in treatment operations.

Algal-bacterial aerobic granular sludge (AB-AGS) systems have been regarded as efficient and sustainable technologies for wastewater treatment, providing superior biomass characteristics and nutrient removal. However, their response to mixed antibiotic-containing wastewater remains insufficiently understood. This study compared granule characteristics, treatment performance, and microbial dynamics of AB-AGS and bacterial aerobic granular sludge (AGS) reactors operated in parallel under mixed antibiotic exposure containing tetracycline (TC), sulfamethoxazole (SMX), ciprofloxacin (CIP), and erythromycin (ERY) at concentrations up to 200 mu g/L. Both systems achieved successful granulation, yet AB-AGS developed denser and more stable granules. Across the experimental period, AB-AGS exhibited higher treatment efficiencies, with average removals of 95.2 f 0.5% chemical oxygen demand (COD), 72.2 f 0.7% total nitrogen (TN), 99.3 f 0.0% ammonia nitrogen (NH4+-N), and 90.6 f 0.3% total phosphorus (TP), compared with 93.2 f 0.6%, 66.7 f 1.0%, 98.7 f 0.0%, and 85.2 f 0.6% in AGS, respectively. Antibiotic removal was more stable in AB-AGS, achieving > 90% for TC, CIP, and ERY, and 64% for SMX during the antibiotic-loading phases. Metagenomic analysis showed Chlamydomonas as the dominant eukaryote in AB-AGS. Relative to the inoculum, AB-AGS exhibited lower enrichment of antibiotic resistance genes (ARGs) (0.46-fold) and mobile genetic elements (MGEs) (0.2-0.6-fold) than AGS, suggesting altered resistance-related system responses and reduced mobility-associated genetic elements. These results highlight that AB-AGS maintains stable treatment performance and distinct resistance-related responses under mixed antibiotic exposure.

Septic systems are major on-site sanitation facilities used in many developing countries to treat domestic wastewater. Climate change concerns have prompted efforts to reduce greenhouse gas (GHG) emissions; nonetheless, septic systems contribute to emissions of GHGs, such as methane. The present study investigated modifications to improve the operating conditions of septic systems to minimize methane emissions by evaluating the oxidation reduction potential (ORP) as an operating parameter using laboratory-scale biodegradation experiments. To investigate the influence of ORP on methane emissions, dog food and potassium nitrate were used as representatives of blackwater and alternative electron acceptors to oxygen, respectively, under various biodegradation conditions. The experimental results suggest that methane emission is suppressed at a critical ORP level (-350 to -450 mV vs. Ag/AgCl). They also showed that ORP can be used as a monitoring signal to better understand methane-producing conditions in septic systems. The proposed modifications to improve septic system operating conditions are to shorten the desludging period and provide sufficient oxygen to the septic tank, considering the critical ORP to prevent anaerobic conditions.

Mainstream anammox faces challenges in adapting to non-optimal temperatures and managing greenhouse gas emissions. This study investigates nitrogen removal and N2O emissions in attached-growth anammox reactors subjected to rapid temperature shifts (15-55 degrees C). Temperature reductions to 15-25 degrees C had minimal impact on the anammox bacterial populations, with nitrogen removal rates of 0.37 +/- 0.11 gN/(L & sdot;d) and 0.88 +/- 0.10 gN/(L & sdot;d) at 15 degrees C and 25 degrees C, respectively. In contrast, increasing temperatures to 45-55 degrees C significantly diminished both anammox biomass and bioactivity. The reactor at 35 degrees C exhibited the lowest N2O emissions (< 1.0 mgN/(L & sdot;d)), while emissions rose to approximately 5.0 mgN/(L & sdot;d) at 15 degrees C and 3.4 mgN/(L & sdot;d) at 55 degrees C (during 295-395 d), primarily due to denitrification performed by coexisting ammonia-oxidizing bacteria and denitrifying microbes. This study provides insights into temperature adaptability and N2O emission risks, supporting mainstream anammox applications.

Phosphorus (P) recovery from wastewater streams using electrochemical precipitation has attracted increasing interest. Herein, electrochemical precipitation of P from a sludge-separated liquid was conducted using an anode covered with the shells of various bivalves (oyster, scallop, clam and corbicula). Moreover, the precipitation process and the characteristics of the recovered solids, including the precipitates, were investigated. The dissolution of each bivalve shell by the hydrogen ions generated from the anode resulted in the release of calcium ions and the accumulation of hydroxide ions generated from the cathode, creating high super-saturation conditions and enhancing calcium phosphate (CaP) precipitation in the water phase. The oxygen gas generated from the anode caused the original and dissolved shell fillings to transfer from the anode case to the water phase and to immix in the CaP precipitates, reducing the P content in the recovered solids. Because the densities of the calcite-based oyster and scallop shells were lower than those of the aragonite-based clam and corbicula shells, the P content in the recovered solids from the experiments involving oyster and scallop shells was considerably lower, negatively affecting the utilisation of the recovered solids for P reuse. Covering the upper side of the anode case with a material that prevents the escape of the original shells and filling the area above the anode with shells successfully prevented the immixture of shells in the CaP precipitates. Thus, bivalve shells can be used as valuable materials to enhance P precipitation and subsequent reuse.

The algal-bacterial aerobic granular sludge (AB-AGS) system, which combines microalgae with aerobic granular sludge, is a sustainable and promising wastewater treatment method. The algae embedded in the aerobic granulation process allow for the algal and bacterial cells in the sludge to interact and form granular flocs, which increases the treatment efficiency and helps separate the treated wastewater from the biomass. Additionally, AB-AGS biomass can be harvested for the extraction of biolipids and alginate-like exopolymers, contributing to resource recovery. This study reviews the applications and resource recovery potential of the AB-AGS system, highlighting its proven effectiveness in treating a range of wastewaters, from low-strength municipal to high-strength leachate. Keyword co-occurrences analysis further revealed pollutant removal, extracellular polymeric substances, the microbial community, and wastewater treatment as research hotspots. Research trends indicated by the keywords with the most recent publication year focused on system application and granulation factors. Additionally, an increasing number of studies regarding AB-AGS for saline and antibiotic-containing wastewater have also been reported. This review also identifies several research gaps and suggests directions for future investigations in this field.

The prevalence of antibiotic-resistant bacteria (ARB) poses a significant threat to public health. In particular, increases in multi-drug-resistant bacteria, such as extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) and carbapenemase-producing Enterobacteriaceae (CPE), limit treatment options for bacterial infections, underscoring the urgent need for robust surveillance of antibiotic resistance. In response to this need, we surveyed wastewater at 33 municipal sewer access sites in a city in Japan during January 2022 to March 2024 to assess the current antibiotic resistance status there. Concentrations of antibiotic-resistant E. coli and of antibiotics were quantified, urban land-use zones of the sewer catchments were summarized, and whole-genome sequencing was used to investigate genetic characteristics of ESBL-EC and CPE. Sewer samples shared similar antibiotic resistance profiles with the influent of five downstream wastewater treatment plants. Antibiotic-resistant E. coli concentrations were related positively with the relative abundance of residential zone and negatively with that of industrial zone. Levofloxacin and sulfamethoxazole concentrations were correlated positively with antibiotic-resistant E. coli concentrations in the sewer system. ESBL-EC were pooled in the city, where sequence type (ST) 38 and ST131 were prevalent and the blaCTX-M-14 and blaCTX-M-27 genes were predominant. CPE were identified in several sewer access sites, where E. coli carrying blaNDM-5 were the most prevalent CPE. blaGES-24 was frequently detected in Enterobacter kobei, Klebsiella michiganensis, and Klebsiella quasipneumoniae. Moreover, two novel blaGES alleles (i.e., blaGES-63 and blaGES-64) were identified in Raoultella ornithinolytica.

Due to the widespread appearance of viruses, antibiotic-resistant bacteria (ARBs), and antibiotic resistance genes (ARGs) in the aquatic environment, more powerful oxidation processes such as ozonation are needed to enhance the efficiency of their inactivation and removal during wastewater treatment. However, information is lacking on the elimination rates of viruses, ARBs, cell-associated ARGs (ca-ARGs), and cell-free ARGs (cf-ARGs) during ozonation. This study examined the kinetics and dose-dependent inactivation of a virus (MS2 coliphage) and an ARB (Ampicillin-resistant [AmpR] E. coli) and the removal of ca- and cf-ARGs (plasmid-encoded blaTEM) by ozonation in a filtered secondary effluent (SE) of a municipal sewage treatment plant (STP). In addition, the ozonation kinetics of carbamazepine (CBZ) and metoprolol (MTP)—ubiquitous organic micropollutants with different removal rate constants—were also investigated in order to monitor their effectiveness as indicators for the abovementioned biological risk factors. Our results showed that ozonation was an efficient way to remove MS2, AmpR E. coli, ARGs, CBZ, and MTP. We investigated the kinetics of their inactivation/removal with respect to exposure in terms of CT (dissolved ozone concentration C and contact time T) value, and found their inactivation/removal constants were in the following order: MS2 (8.66 ×103 M−1s−1) ≈ AmpR E. coli (8.19 ×103 M−1s−1) > cf-ARG (3.95 ×103 M−1s−1) > CBZ (3.21 ×103 M−1s−1) > ca-ARG (2.48×103 M−1s−1) > MTP (8.35 ×102 M−1s−1). In terms of specific ozone dose, > 5-log inactivation of MS2 was observed at > 0.30 mg O3/mg DOC, while > 5-log inactivation of AmpR E. coli was confirmed at 1.61–2.35 mg O3/mg DOC. Moreover, there was almost no removal of ca-ARG when the specific ozone dose was < 0.68 mg O3/mg DOC. However, 2.86–3.42-log removal of ca-ARG was observed at 1.27–1.31 mg O3/mg DOC, while 1.14–1.36-log removal of cf-ARG was confirmed at 3.60–4.30 mg O3/mg DOC. As alternative indicators, > 4-log removal of CBZ was observed at > 1.00 mg O3/mg DOC, while > 2-log removal of MTP was confirmed at > 2.00 mg O3/mg DOC. Thus, it was observed that inactivation of E. coli needs a greater ozone dose to achieve the same level of inactivation of AmpR E. coli; for ARGs, cf-ARG can persist longer than ca-ARG if low dosages of ozone are applied in the filtrated SE, CBZ might act as an indicator with which to monitor the inactivation of viruses and ARBs, while MTP might act as an indicator with which to monitor removal of ARGs. Moreover, cf-ARG cannot be neglected even after ozonation due to the possibility that ca-ARGs can become cf-ARGs during ozonation and be discharged with the final effluent, posing a potential risk to the receiving environment.

N-nitrosomorpholine (NMOR), its important precursor (morpholine, MOR) and formation potential (NMOR FP) were detected in effluents with concentrations of up to 15 ng/L, 1.62 mu g/L, and 24.1 ng/L, respectively. The photodegradation of NMOR can produce the non-photodegradable MOR, regenerating NMOR by chloramine, and different concentrations of NMOR (50, 100, 200, 500 mu g/L) can be completely photodegraded within 60 min with generation of MOR with range from 2 to 14 mu g/L. In this study, a TiO2 based photocatalytic ceramic membrane system was designed and developed for removing MOR and NMOR FP in water environment. Microfiltration membrane with pore size of 100 nm can control the loss of TiO2 by the flat membrane pores, while TiO2 of 4-40 g/m2 accumulated to form a TiO2 layer generating hydroxyl radicals (& sdot;OH) sufficiently under 8.93 mW/cm2 of ultraviolet irradiation. Moreover, MOR (10, 100, and 1000 mu g/L) and NMOR FP showed effective removal by TiO2 based photocatalytic membrane system with removal efficiency up to 60 %. In addition, although NMOR had different precursors, the near removal efficiency between MOR and NMOR FP indicated that MOR was the main precursor of NMOR. Furthermore, the designed system achieved recycling of the catalyst to avoid the risk on release of the catalyst into water environment.

The combination of microalgae cultivation and anaerobic co-digestion of sewage sludge and microalgae is a promising system for increased energy efficiency in sewage treatment plants. This study proposed an innovative separation and recovery technology for microalgae from liquid media after culturing using combined heating and co-sedimentation with activated sludge. Sedimentation and anaerobic digestion experiments were conducted using Euglena gracilis cultures and activated sludge. Combining heating at 40 degrees C and co-sedimentation resulted in a maximum recovery of 92 %. Activated sludge adsorbed E. gracilis at a ratio of 0.644 mu g-Chl. a/mg-MLSS. In anaerobic digestion experiments, no adverse effects such as fermentation inhibition were caused by mixing the activated sludge and E. gracilis. Total energy balance was evaluated assuming a sewage treatment plant with a capacity of 50,000 m3/day. The proposed system is shown to be energy efficient, and increase methane recovery by 24 %.

In this study, the reduction in the abundance of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) and the fertilizer potential of liquid products from hydrothermally treated cattle manure were investigated. Hydrothermal treatment (HTT) was conducted under different reaction temperatures (125, 150, 175 and 200 °C) and retention times (60, 90 and 120 min). The total organic carbon (TOC) and total nitrogen (TN) of the liquid product increased with increasing reaction temperature. The germination index (GI), a measure of the percentage of germination, exceeded 90 % at 125, 150, and 175 °C in diluted samples, while it decreased to 18 % at 200 °C. Although a longer retention time contributed to an increase in TOC of liquid products, it did not increase the GI values. The liquid product should be diluted or adjusted before use as fertilizer to prevent phytotoxicity. In our analysis of ARB and ARGs, E. coli and antibiotic-resistant E. coli were completely reduced after HTT, except for the operating conditions of 125 °C and 60 min. Although both a higher reaction temperature and longer retention time tended to be better for the reduction of ARGs and intI1, it was found that the longer retention time is much more effective than the higher reaction temperature. The reduction of target ARGs and intI1 was 2.9-log under175 °C and 120 min. Comprehensively considering the fertilizer potential of liquid product and the reduction of ARB and ARGs, 175 °C of reaction temperature and 120 min of retention time of operating conditions for HTT were recommended.

Antibiotics are extensively used as medicine for humans and also in livestock for growth promotion, disease prevention, and treatment. However, the pervasive usage of antibiotics has led to a critical global challenge raising issues regarding antibiotic-resistant bacteria and antibiotic-resistant genes. The presence of antibiotic-resistant bacteria and antibiotic-resistant genes poses a growing threat impacting the effectiveness of treatments for infectious diseases. Projections suggest that by 2050, there could be over 10 million deaths attributed to pathogens carrying antibiotic resistance genes. Consequently, there is a pressing need for methods that target the removal of residual antibiotics, eradication of antibiotic-resistant bacteria, and elimination of antibiotic-resistance genes specifically in wastewater treatment and livestock waste management before their release into the environment. This remediation approach aims to diminish the selective pressure on native bacteria in nature caused by antibiotics and mitigate the emergence of potential antibiotic-resistant strains. This review paper aims to outline the current status and significance of antibiotic control. Various contemporary strategies are employed to eliminate antibiotic residues, combat antibiotic-resistant bacteria, and counteract antibiotic-resistant genes. This review also evaluates the environmental impact assessment regarding antibiotic residues and antibiotic resistance genes on public health and the environment. The contribution of this review would provide insights into the multifaceted dimensions of antibiotic management and its implications for both human health and the ecosystem.

下水処理場の流入水NH4-Nの連続計測を3年間実施し,計測結果を使用した運転計画を立案して省エネ施策やN2O抑制施策,能動的管理を下水処理場シミュレータにより評価した.流入水NH4-Nの季節変動では,冬場のほうが高い傾向であり,最小値と最大値の幅も大きかった.日間変動では早朝に最小値となり,午前中に最大値となる典型的な変動パターンが年間を通じて見られ,最小値と最大値では2倍以上の差があり,運転管理上の考慮が必要と考えられた.シミュレーションを利用した運転計画として,省エネ施策で流入水窒素負荷の低い時間帯のDO設定値を下げると曝気風量が5.2%削減され,処理場全体GHG排出量は0.5%削減された.水処理N2O生成抑制施策として負荷の高い時間帯の汚泥返送率を2倍とすると,N2O排出量は12.0%抑制された.能動的管理では窒素供給量が5%の増加となり,電力消費CO2は58%の削減となっていた.流入水質を連続計測し運転計画を立案することにより,現状プロセスの運転管理の工夫でGHG排出量の削減が期待できることが確認できた.

Escherichia coli has been used as an indicator of fecal pollution in environmental waters. However, its presence in environmental waters does not provide information on the source of water pollution. Identifying the source of water pollution is paramount to be able to effectively reduce contamination. The present study aimed to identify E. coli microbial source tracking (MST) markers that can be used to identify domestic wastewater contamination in environmental waters. We first analyzed wastewater E. coli genomes sequenced by us (n = 50) and RefSeq animal E. coli genomes of fecal origin (n = 82), and identified 144 candidate wastewater-associated marker genes. The sensitivity and specificity of the candidate marker genes were then assessed by screening the genes in 335 RefSeq wastewater E. coli genomes and 3318 RefSeq animal E. coli genomes. We finally identified two MST markers, namely W_nqrC and W_clsA_2, which could be used for detection of wastewater-associated E. coli isolates. These two markers showed higher performance than the previously developed human wastewater-associated E. coli markers H8 and H12. When used in combination, W_nqrC and W_clsA_2 showed specificity of 98.9 % and sensitivity of 25.7 %. PCR assays to detect W_nqrC and W_clsA_2 were also developed and validated. The developed PCR assays are potentially useful for detecting E. coli isolates of wastewater origin in environmental waters, though users should keep in mind that the sensitivity of these markers is not high. Further studies are needed to assess the applicability of the developed markers to a culture-independent approach.

Considering the reciprocating processes of nitrogen gas (N2) fixation to ammonia (NH4-N) and NH4-N removal to N2 through nitrification and denitrification during wastewater treatment, a microaerobic activated sludge process (MAS) is proposed in this study as a pretreatment to retain NH4-N from high-strength nitrogenous wastewater for further NH4-N recovery through membrane technology, that is, inhibit nitrification, with sufficient removal of total organic carbon (TOC). With DO and pH control, the 3-reactor bench-scale MAS systems successfully realized an NH4-N retention rate of over 80 %, with TOC removal rates of over 90 %. In addition, the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) during MAS were evaluated. The total N2O emissions were 407 and 475 mg-N/day when pH was controlled at 6.2 (S1) and 6.8 (S2), respectively, with average emission factors to total nitrogen load over 2 % in both systems. Also, the global warming potential of N2O is one order of magnitude larger than that of CO2, indicating the significance of N2O in the MAS process. Therefore, the mechanisms of N2O emission from each reactor were investigated. The first reactor, where most of the TOC was adsorbed, emitted only 1.98 % (S1) and 2.43 % (S2) of the total N2O emissions through the denitrification of nitrite and nitrate (NOx) from the return sludge. The second reactor emitted 79.9 % (S1) and 69.0 % (S2) of the total N2O with the emission rates the same order of magnitude as the NOx production rates. Multiple pathways were considered to contribute to the high N2O emissions, and biotic NH2OH oxidation was one potential pathway at pH 6.2. Finally, the third reactor emitted 9.98 % (S1) and 16.8 % (S2) of the total N2O by nitrifier denitrification. Overall, this study showed that the large N2O emissions under nitrification-inhibiting conditions of the MAS process owed to the incomplete nitrification under acidic conditions and large abundances of denitrifiers. On the other hand, the lower N2O emissions at pH 6.2 evidenced the potential N2O mitigation under slightly more acidic conditions, underlining the necessity of further study on N2O mitigation when adapting to the trend of NH4-N recovery.

In the composting process, hydrothermal pretreatment (HTP) can be appropriate for improving fertilizer potential and reducing the presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in compost. Here, we investigated the optimum operating conditions of HTP in terms of both fertilizer potential and reduction in the abundance of ARB and ARGs. The total organic carbon (TOC) and total nitrogen (TN) of the liquid product increased with increasing reaction temperature. The germination index (GI) of diluted samples exceeded 90% at 125, 150, and 175℃, while it decreased to 18% at 200℃. Although a longer retention time contributed to an increase in TOC in the liquid product, it did not increase the GI values. The liquid product should be diluted or adjusted before use as fertilizer to prevent phytotoxicity. In our analysis of ARB and ARGs, E. coli and antibiotic-resistant E. coli in the solid phase were completely removed during HTP, except under operating conditions of 125 ℃ and 60 min. In addition, a higher reaction temperature and longer retention time tended to be better for removing ARGs and intI1. There was a 2.9-log reduction at a reaction temperature of 175 ℃ and a retention time of 120 min. Considering the fertilizer potential of liquid products and the load of target ARB and ARGs in solid products, 175 ℃ would be the optimum reaction temperature and 120 min the optimum retention time.