Shallow wells are common source of drinking water in low-resource countries; however, they are highly vulnerable to fecal contamination. Here, we assessed the microbial quality and antibiotic susceptibility patterns of enteric bacteria recovered from shallow wells situated near sanitation facilities in four security-challenged areas of Katsina State, Nigeria. A total of 45 water samples were collected from 15 wells. Bacterial isolation and identification were performed using standard microbiological procedures and the analytical profile index (API) 20E kit. Antibiotic susceptibility testing was performed using the disk diffusion method, and Pearson’s correlation was performed to determine associations between risk factors and microbial contamination. Total coliform counts exceeded the World Health Organization-recommended limits. Klebsiella pneumoniae (25.0%) was the most frequently isolated species, followed by Salmonella species (20.83%) and Escherichia coli (16.67%). Notably, 86.5% of isolates exhibited multidrug-resistant phenotypes. Well distance relative to sanitation structures did not establish a causal relationship between sanitary risk scores and total coliform counts (r = 0.32, p = 0.47). Improved sanitation, regular water disinfection, and routine surveillance of groundwater is recommended to protect vulnerable communities in these security-challenged areas. A limitation of this study is its relatively small sample size and reliance on phenotypic methods, which may limit the comprehensiveness of the analyses.
Water quality in semi-arid reservoirs is vulnerable to drought, yet impacts remain poorly quantified. This study assesses meteorological drought effects on Boukerdane Dam, Tipaza, Algeria, from 2019 to 2023 using high-resolution weekly physicochemical sampling and daily volume records. Drought severity was measured using Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Water quality was evaluated via the Water Quality Index (WQI) and irrigation indices Sodium Adsorption Ratio, Residual Sodium Carbonate, Magnesium Ratio, and Magnesium Hazard. Results revealed strong negative correlations between drought indices and key parameters: drought increased conductivity, nitrate, and turbidity, while decreasing dissolved oxygen and volume. SPEI showed marginally stronger correlations than SPI for physicochemical parameters, highlighting evaporation’s role. Trend analysis confirmed a significant drying trend coupled with declining water quality. A stepwise degradation pattern was identified, where post-drought recoveries were incomplete. Principal Component Analysis retained six components explaining 72.3% variance, identifying salinity and temperature as primary drivers. Although WQI remained stable, irrigation indices indicated rising sodium hazards. The study concludes that drought degraded water quality, heightening risks of salinization and nutrient pollution. Parameter-specific monitoring is recommended over aggregate indices for effective management under climate change.
This study assessed the relative contributions of selected nitrogen sources to nori cultivation in Mikawa Bay using nitrogen stable isotope ratios (δ15N) and a Bayesian isotope mixing model (MixSIAR). The analysis considered three potential nitrogen sources: Yahagi River water, sewage effluent, and offshore subsurface oceanic nitrate. Water samples were collected between November 2024 and February 2025, and dried nori produced across eight districts in the bay were also sampled during this period. The δ15N–NO3∁Evalues in sewage effluent (15.6 E1.3‰, n = 6) were substantially higher than those in Yahagi River water (7.1 E.2‰, n = 6) and offshore water (5.6 E.3‰, n = 4). By comparing these isotopic signatures with the δ15N values of dried nori (12.8 ± 1.8‰, n = 48), we evaluated the relative importance of nitrogen sources using MixSIAR. The results suggest that wastewater-derived nitrogen may account for a relatively large proportion of the nitrogen in cultivated nori, particularly near the sewage treatment facility, with a detectable influence extending to the bay mouth (16 km from the river mouth). Given the limitations of single-tracer isotope mixing models, these results should be interpreted as semi-quantitative estimates under the assumptions of the present study.
We developed a novel modeling framework that forecasts nutrient load inputs to coastal waters at site-specific resolution by integrating demographic change, industrial activity, and operational conditions at sewage treatment plants. This framework quantifies the controllable range of nutrient inflows achievable through anthropogenic interventions and supports evaluation of management strategies addressing both eutrophication and oligotrophication. In the model, the coastal zone is divided into subregions, and chemical oxygen demand, total nitrogen, and total phosphorus loads originating from sewage are predicted using explanatory variables including resident population, numbers of manufacturing employees, and manufactured-goods shipment values. Predicted loads showed strong agreement with observations (r > 0.9), confirming model validity. By incorporating variable nutrient removal efficiencies at treatment plants, the model enables scenario-based estimation of discharged nutrient loads under alternative management and socioeconomic conditions. Application of the model to two adjacent but contrasting systems—eutrophic Osaka Bay and increasingly oligotrophic Harima-nada—demonstrated its ability to resolve region-specific load dynamics and future trajectories. This integrated framework provides essential input information for decision support in adaptive and region-specific nutrient management by quantifying feasible ranges of nutrient inflow adjustments; when coupled with hydrodynamic–ecosystem models, it can support the evaluation of restoration, aquaculture, and water-quality improvement strategies.
The degradation of Allura Red azo dye using niobium pentoxide (Nb2O5) as a catalyst and hydrogen peroxide (H2O2) as an oxidant was studied in a slurry batch reactor at 30 degrees C. The effects of H2O2 concentration (45-180 mM), catalyst loading (0.25-0.75 wt%), and pH (3-11) were analyzed for 2 h. The highest color removal (81%) was achieved with 0.5 wt% Nb2O5, 180 mM H2O2, and pH 11. At pH 5, suitable for real effluents, removal efficiency reached 68% after 6 h. Hydroxyl radicals, responsible for degradation, were confirmed using a 2-propanol quenching test. The apparent activation energy was 56.3 kJ center dot mol-1, and the data followed a pseudo-first-order kinetic model. The catalyst remained active after three cycles. Nb2O5 with H2O2 appears to be a promising system for azo dye removal in aqueous solutions.
In this study, ammonium was separated from water samples using a diffusion technique and oxidized to nitrate. Nitrate was then denitrified and analyzed for isotopic values using isotope ratio mass spectrometry. Each step was carefully examined, particularly oxidation, which was conducted under a near-neutral pH through the addition of a buffer. This precaution was critical because highly acidic or alkaline conditions can lead to nitrogen loss during high-temperature and high-pressure oxidation. The results indicate that the employed ammonium diffusion technique combined with the optimized oxidation process can yield precise and reproducible delta N-15 values for low-concentration NH4+ water samples. Notably, our method requires only 10 & micro;g of NH4+ for both diffusion and isotope analyses, which is a notable improvement over conventional diffusion techniques, which typically require 50-150 & micro;g. To evaluate potential matrix interferences, we conducted recovery tests by spiking ammonium standards into three different hot spring samples, which often contain low ammonium concentrations and high concentrations of other ions. The results of recovery tests showed robust performance of the proposed method, with recovery rates ranging from 87% to 102%. These results confirm that our method is unaffected by high ion concentrations in complex natural matrices. Additionally, comparison with a previously reported technique revealed no significant difference in the isotope results (paired t-test, p > 0.05). We analyzed several natural hot spring samples across Japan using the proposed method, with the obtained results clarifying the origin of ammonium in the natural hot springs at the investigated locations. Therefore, our analytical method is efficient and highly sensitive for the analysis of ammonium isotopes in environmental water samples with low ammonium concentrations; furthermore, it enables the processing of large numbers of samples in a short time. The delta(NH4+)-N-15 results contributed to elucidating the NH4+ sources and transport mechanisms at the study locations.
To recover soluble nitrogen and phosphorus from the anaerobic digestate liquor in crystallisation, sets of batch experiments were conducted with varied dosing of liquid phosphoric acid and powdered Mg(OH)2. Both nutrients were recovered from the liquor by 90% within about 20 minutes when the initial molar ratios of Mg/N and P/N were set at 1.6 and 0.95, respectively. A high initial Mg/N ratio accelerated the reaction, whereas a low initial P/N ratio resulted in a lowered nitrogen recovery. The crystals obtained at the end of the experiment were composed of struvite (91 w/w%), Mg-PO4 species (1.0 w/w%), and remaining Mg(OH)2 (8.0 w/w%), where about 15 mmol L-1 of magnesium was present in a soluble form. Struvite was the species to capture the nitrogen and phosphate, whilst the formation of Mg-PO4 crystal minimised the soluble phosphate. To reuse the remaining Mg(OH)2, a sequential batch operation was examined without withdrawing the solids, where the Mg(OH)2 dosing was intentionally reduced in the consecutive runs. The experiment indicated that a total of 3-5 cycles of slurry reuse seemed to be of interest because of saving magnesium addition by 0.3 mol-Mg mol-N-1 in an acceptably short reaction time with about 40 min per cycle.
Nitrite-oxidizing bacteria (NOB) can be inhibited by high concentrations of heavy metals; however, trace elements (TE) are critical for their growth and sustained activity. In this first time report, the long-term impacts of limiting Ni(II), Co(II), and Zn(II) on nitrite oxidation were separately evaluated using a continuous test system, wherein NOB was immobilized on polyvinyl alcohol gel carriers. Even under Ni(II)- and Co(II)-limited conditions, a high nitrite oxidation rate (NOR) of 1.2 kg-N m-3 d-1 was maintained for three months without these TE supplementation, suggesting that continuous addition of Ni(II) or Co(II) is not strictly necessary. In contrast, Zn(II) limitation suppressed NOR to 0.8 kg-N m-3 d-1. Supplementation with 1 & micro;g L-1 Zn(II) initiated NOR recovery, and 2 & micro;g L-1 fully restored activity. Under all limitation conditions and during Zn(II) recovery, microbial community analysis focusing on NOB revealed that Nitrospira consistently accounted for only a few percent, whereas Nitrobacter showed a relatively high abundance of approximately 20%. These findings highlight the essential role of Zn(II) in maintaining optimal nitrite oxidation and demonstrate that minimal TE supplementation can be crucial for stable nitrification performance in nitrogen wastewater treatment systems, particularly where background TE concentrations are inadequate.
This study explores the potential of lanthanum-modified sugarcane bagasse-derived hydrochar (SBH-La) as an effective biosorbent for phosphorus elimination from aqueous solutions. The hydrochar was fabricated under optimal hydrothermal carbonization conditions (solid-to-liquid ratio of 1:15, 200 degrees C, 4 h) using 0.3 M lanthanum(III) chloride as the modifying agent. To clarify the adsorption mechanisms, isotherm, kinetic, and thermodynamic experiments were conducted by varying the initial phosphorus concentrations (40-500 mg/L), adsorption time (0-24 h), and temperature (298, 303, 313, and 323 K). Comprehensive characterization was also performed on the raw sugarcane bagasse (SB) and SBH-La. The results revealed that the SBH-La exhibited a significantly higher maximum phosphorus adsorption capacity (82.82 mg/g) than SB and many conventional biosorbents. The adsorption behavior was well-described by the Langmuir isotherm and Pseudo-second-order kinetic models, indicating that chemisorption was the dominant removal pathway. Thermodynamic analysis confirmed that the phosphorus adsorption onto SBH-La was spontaneous, feasible, and endothermic. Characterization results validated the successful integration of La(III) into SB to form hydrochar and notable improvements in surface area, pore volume, and pore diameter of SBH-La compared to raw SB. These findings provide valuable insights into the adsorption mechanisms, enabling the design of viable treatment systems for phosphorus-contaminated wastewater.
The spread of antimicrobial-resistant bacteria (ARB) has become one of the major threats to human health worldwide, and migratory birds are potentially contributing to the spread of ARB in the environment. This study investigated Escherichia coli and antibiotic-resistant E. coli in Ishizuchi Pond and Tochi River in Kochi Prefecture, Japan, where migratory birds congregate, as well as in mallard (Anas platyrhynchos) feces. We examined the number of E. coli and antibiotic resistance patterns and estimated the source of E. coli isolates. At Ishizuchi Pond, E. coli counts increased during the bird migratory period, suggesting that migratory birds may serve as a source of E. coli contamination. In contrast, Tochi River, which receives septic tank effluent, showed no significant seasonal variation in E. coli counts throughout the year. Antibiotic-resistant E. coli counts in mallard feces were approximately 1/100 to 1/300 of total E. coli counts, indicating high E. coli abundance but relatively low antibiotic-resistant E. coli presence. Phylogenetic analysis revealed similar trends between E. coli isolates from Ishizuchi Pond and mallards, with comparable positive rates for chicken-specific markers, supporting the potential contribution of migratory birds to E. coli loads in the pond.
The utilization of liquid dairy biomass (LDB) as an energy source has attracted growing attention, but its high organic content can hinder anaerobic digestion (AD) efficiency. This study investigated the effects of conductive materials on AD performance under high organic loading rates (OLR). After batch screening, granular activated carbon (GAC) and bamboo biochar (BBC) were introduced into continuous stirred tank reactors. At an OLR of 4.80 kg-COD/m3/d, BBC showed the highest methane yield (0.141 m3/kg-COD), outperforming GAC and the control. Microbial analysis revealed that BBC enriched Methanomassiliicoccaceae and altered hydrogen utilization pathways, indicating a shift in methanogenic metabolism. These results suggest that conductive materials, particularly BBC, significantly enhance the efficiency and stability of AD for LDB treatment, making them promising additives to improve LDB processing.
Freshwater raphidophytes occasionally proliferate and release high concentrations of trichloroacetic acid (TCAA) precursors into drinking water sources, which have been identified as phenolic glycosides. However, the environmental factors driving the production of these precursors remain unclear. This study investigated the growth behavior and disinfection byproduct formation potentials, including TCAA formation potential (TCAAFP), of three raphidophyte species (Merotricha bacillata, Gonyostomum latum, and Gonyostomum semen) under different cultivation conditions (i.e., a standard culture medium (AF-6) and environmental water supplemented with the same nutrients as AF-6 (AF-6-Env)). Algal growth was similar across all tested species, with no large differences observed between AF-6-Env and AF-6 media. However, TCAAFPs were consistently higher in AF-6-Env than in AF-6, suggesting that dissolved components in environmental water promote the production of TCAA precursors. Furthermore, the addition of dissolved organic matter (DOM) extracted from the environmental water using solid-phase extraction (SPE) cartridges to G. latum cultures in AF-6 medium resulted in increased TCAAFP. In contrast, no algal growth was observed in AF-6 medium containing the fraction not retained by the SPE cartridges. These results indicate that DOM in environmental waters plays a critical role in TCAA precursors production by raphidophytes.
Denitrification is an important process for water quality control in recirculating aquacultural systems. Denitrifying granular sludge reactors, such as upflow sludge blanket (USB) reactors, can achieve a high NO3--N removal efficiency under a short hydraulic retention time. These biological reactors require the seeding of anaerobic granular sludge and an extended start-up period, thereby limiting their use in denitrifying granular sludge reactors. Herein, a rapid granular sludge formation method was developed by increasing nitrate and total organic carbon concentrations up to 500 mg-N.L-1 and 500 mg.L-1, respectively, in the influent substrate of the USB reactor. High sludge concentration (31.8 g-mixed liquor suspended solids (MLSS).L-1) and denitrification activity (2.6 mg-N.g-MLSS-1.h(-1)) were observed in the denitrifying granular sludge on Day 20. Analysis of 16S rRNA amplicon sequencing indicated that Colwellia sp., a type of bacteria renowned for synthesizing extracellular polymeric substances, was the most abundant in granular sludge. Therefore, increasing the NO3--N and organic concentrations is effective for forming denitrifying granular sludge.
Antimicrobial resistance in human, veterinary, and agricultural sectors is a pressing global health threat. Wastewater surveillance is a promising approach to comprehensively evaluate the prevalence of antimicrobial-resistant bacteria and antimicrobial resistance genes in urban areas. Although cefotaxime-resistant E. coli and class 1 integron integrase gene (intI1) were proposed as key indicators of AMR, their levels in wastewater in Japan remain unknown. This study quantified these parameters in wastewater samples collected every two months from two cities (A and B) in Japan. Cefotaxime-resistant E. coli and intI1 genes were consistently detected in wastewater from both cities, with relative abundances of cefotaxime-resistant E. coli/total E. coli ranging from 0.3%-2.5% in City A and 1.2%-2.5% in City B, and intI1/16S rRNA gene ratios ranging from 1.0 x 10(-2)-3.3 x 10(-2) in City A and 3.0 x 10(-3)-2.2 x 10(-2) in City B. The cefotaxime-resistant E. coli isolates harbored extended-spectrum beta-lactamase genes including bla(CTX-M-1) group, bla(CTX-M-9) group, and bla(TEM). Metagenomic analysis with hybrid capture enrichment identified dominant genes conferring resistance to tetracyclines, aminoglycosides, beta-lactams, and macrolides. The relative abundances of some extended-spectrum beta-lactamase, carbapenemase, and colistin resistance genes was higher in wastewater samples from City B than those in City A.
The fiberboard industry generates significant amounts of wastewater laden with heavy metals and organic pollutants, necessitating the development of effective and sustainable treatment solutions. This study investigates the physicochemical characteristics of wastewater from fiberboard processing and evaluates the potential of oil palm petiole- derived activated carbon (OPP-AC) for heavy metal adsorption. The wastewater exhibited elevated concentrations of manganese (14.5 mg/L), iron (53.9 mg/ L), and zinc (7.68 mg/L), alongside an acidic pH of 4.6. OPP-AC was synthesized and characterized for its lignocellulosic composition, thermal stability, surface morphology, porosity, and functional groups. Adsorption studies indicated that samples 10KOH480 and 15HNO480, prepared at 480 degrees C using KOH and HNO3 as activating agents respectively, were effective in adsorbing heavy metals. In particular, 10KOH480 showed excellent performance, achieving removal efficiencies of 97.02% for Mn, 91.05% for Fe, and 81.1% for Zn under optimal conditions. Adsorption behavior followed the Freundlich isotherm model and pseudo-second-order kinetics, suggesting multilayer adsorption and chemisorption processes. These findings demonstrate that OPP-AC is a promising, low-cost, and eco-friendly adsorbent for treating heavy metal-contaminated industrial effluent.
Nitrous oxide (N2O) is a potent greenhouse gas emitted from bioreactors in sewage treatment plants. Quantifying emissions from uncovered reactors remains challenging because of methodological and operational limitations. This study aimed to characterize the three-dimensional spatial distribution of atmospheric N2O concentrations around a full-scale, uncovered Carrousel reactor under various conditions, as a step toward reliable non-invasive quantification methods. Atmospheric gas samples were collected using combined manual and drone-based techniques at multiple heights and locations. The agitator functioned as the primary emission source of high N2O concentrations, and atmospheric N2O levels tended to be elevated near the reactor surface. The emitted N2O was dispersed into the atmosphere under the influence of wind, creating asymmetric and complex vertical patterns. As distance from the emission source increased, concentrations decreased and quantification became more difficult, whereas elevated concentrations were observed near the source even under low wind. These findings demonstrate that atmospheric N2O analysis is a promising non-invasive approach for quantification and may serve as a robust foundation for emission monitoring. Additional data—especially under diverse environmental conditions—are needed to refine and generalize this methodology for practical application.
The dynamics of surface-groundwater interaction (SGI) in the alluvial Gangetic plains are critically analyzed using multivariate statistical techniques (MST) applied to major and trace ion chemistry of river water (RW) and groundwater (GW) samples. The study reveals an unusual decline in SGI, even in typically stable alluvial zones. A higher saturation index for RW indicates increasing risks in critical regions, suggesting disruption in natural recharge-discharge processes. Probability exceedance plot highlights an inverse relationship between contaminant concentrations and the likelihood of exceeding regulatory thresholds. RW is contaminated by both domestic and industrial wastewater, while GW remains largely unaffected, as shown by lower total organic carbon levels. Hydrogeochemical analyses indicate that RW generally contains higher levels of micropollutants such as arsenic (As) and lead (Pb) compared to GW. A novel integration of Q and R-mode hierarchical clustering with heat mapping is applied for the first time to assess SGI in the Mid-Gangetic Plain, enabling clearer differentiation of RW and GW and revealing complex geogenic-anthropogenic interactions. The altered ionic associations identified through MST require further investigation to understand their hydrogeochemical implications and potential risks to ecosystem health. Immediate action is recommended as rapid hydrogeologic change threatens sustainable water management.
Many children suffer from diarrhea in low-income settlements. However, little information is available on the microbial contamination related to waterborne diseases. Microbial contamination of five environmental media (groundwater, tap water, stored household water, drinking cups, dish sponges) was investigated in Chawama ward, Lusaka, Zambia. Escherichia coli was measured by culture method. Seven waterborne pathogens (rotavirus A, norovirus GII, Shigella spp., Vibrio cholerae, enterotoxigenic E. coli (ETEC), Campylobacter jejuni, Cryptosporidium spp.) and fecal genetic markers (human, pig, chicken) were detected by quantitative PCR. The concentrations of E. coli in groundwater and tap water were under 5 colony forming unit (CFU)/100 mL. High concentrations of E. coli were observed in 3 of 20 stored water samples (> 100 CFU/100 mL) and on 5 of 20 cups (> 1,000 CFU/media). Rotavirus A, Shigella spp. and ETEC were detected on cups. Presence of I1 genotype of human rotavirus A was identified by nested PCR and amplicon sequencing for a partial region of the VP6 gene. C. jejuni and a chicken-associated genetic marker were detected from tap water, stored water, cups and sponges, suggesting that chicken would be the main cause of microbial contamination. These results indicate the various transmission routes of enteric pathogens in this area.
The colony size expansion and the reduction of cell density of wild Microcystis were attempted to accelerate its buoyancy. Culture experiments of Microcystis exhibited that the colony size expansion was observed after 24 h preculture with higher Ca2+ concentration (1,000 mg L-1) in medium, while the preculture with the addition of tightly-bound extracellular polysaccharides (TB-EPS) extracted from cyanobacterial blooms into the same medium did not largely expand the colony size compared to the Ca2+ added medium. Surface analysis of TB-EPS indicated the presence of negatively charged carboxy groups, and the added TB-EPS and the EPS originally surrounding Microcystis would be repulsed, causing prevention of colony size expansion. The floating velocity of Microcystis precultured with light exposure for 24 h was 8.19 x 10(-3) cm s(-1) at Ca2+ = 1,000 mg L-1, which was 1.4 times higher than that in the control. Furthermore, in case of the preculture without light exposure, the velocity had a remarkable acceleration (5.49 x 10(-2) cm s(-1)), which was ca. 9.1 and 5.7 times greater than the control with and without light exposure, respectively (p < 0.05). These results suggest that the reduction of cell density of Microcystis by respiration in dark would further enhance the buoyancy of Microcystis.
This study investigated the spatiotemporal dynamics of benthic diatoms and terrestrial plants as food sources for benthic animals in Imazu Tidal Flat, using fatty acid biomarkers and stable isotope analysis. The sediments of estuarine sites exhibited higher terrestrial fatty acids and depleted delta C-13 values, reflecting riverine organic inputs, while sediments of outer flats showed marine-dominated signatures linked to benthic diatoms. The decrease in benthic diatom contribution during winter may be associated with reduced productivity under lower water temperature. Benthic diatom-derived 20:5.3 (Eicosapentaenoic acid) dominated benthic diets annually (82-100% contribution), but winter elevated the contribution of terrestrial plants due to plant decay and reduced tidal flushing. Food source of terrestrial plants for Polychaetes (e.g., Heteromastus sp.) increased significantly in winter, which underscored the changes in the consumption of some benthic animals due to the increase in the relative contribution of allochthonous food sources. The observed seasonal interaction between riverine organic matter and benthic diatom availability, influenced by temperature, suggests potential flexibility in the tidal flat food web. This highlights the importance of understanding spatial-temporal variation in food sources when considering land-sea ecosystem connectivity.
