Nitrate prediction in groundwater of data scarce regions: The futuristic fresh-water management outlook.

Nitrate contamination in groundwater poses a significant threat to water quality and public health, especially in regions with limited data availability. This study addresses this challenge by employing machine learning (ML) techniques to predict nitrate (NO3--N) concentrations in Mexico's groundwater. Four ML algorithms-Extreme Gradient Boosting (XGB), Boosted Regression Trees (BRT), Random Forest (RF), and Support Vector Machines (SVM)-were executed to model NO3--N concentrations across the country. Despite data limitations, the ML models achieved robust predictive performances. XGB and BRT algorithms demonstrated superior accuracy (0.80 and 0.78, respectively). Notably, this was achieved using ∼10 times less information than previous large-scale assessments. The novelty lies in the first-ever implementation of the 'Support Points-based Split Approach' during data pre-processing. The models considered initially 68 covariates and identified 13-19 significant predictors of NO3--N concentration spanning from climate, geomorphology, soil, hydrogeology, and human factors. Rainfall, elevation, and slope emerged as key predictors. A validation incorporated nationwide waste disposal sites, yielding an encouraging correlation. Spatial risk mapping unveiled significant pollution hotspots across Mexico. Regions with elevated NO3--N concentrations (>10 mg/L) were identified, particularly in the north-central and northeast parts of the country, associated with agricultural and industrial activities. Approximately 21 million people, accounting for 10 % of Mexico's population, are potentially exposed to elevated NO3--N levels in groundwater. Moreover, the NO3--N hotspots align with reported NO3--N health implications such as gastric and colorectal cancer. This study not only demonstrates the potential of ML in data-scarce regions but also offers actionable insights for policy and management strategies. Our research underscores the urgency of implementing sustainable agricultural practices and comprehensive domestic waste management measures to mitigate NO3--N contamination. Moreover, it advocates for the establishment of effective policies based on real-time monitoring and collaboration among stakeholders.

Mixed-culture polyhydroxyalkanoate production from olive oil mill pomace.

Polyhydroxyalkanoate (PHA) was produced in bench-scale sequencing batch reactors (SBRs) fed olive pomace fermentate containing a mixed microbial consortium. Initial anaerobic fermentation in a sequencing batch fermentor (SBF) produced soluble carbon compounds, mainly organic acids. SBF effluent was centrifuged, removing solids, and fed into a SBR where intracellular PHA was produced. Buffer pre-treatment of diluted olive pomace increased organic acid production 75% in SBF fermentate over no pre-treatment. Hydraulic retention time (HRT), solids retention time (SRT), pomace concentration/dilution, and aerobic operation vs. anoxic/oxic cycling were studied to improve PHA formation. Maximum %PHA achieved was 39% (on a dry-weight cell basis), and the highest volumetric productivity was 0.042 g PHA/L-day under fully aerobic conditions. The highest PHA conversion yield was 0.3625 g PHA/L fermentate.

Viruses in nondisinfected drinking water from municipal wells and community incidence of acute gastrointestinal illness.

BACKGROUND: Groundwater supplies for drinking water are frequently contaminated with low levels of human enteric virus genomes, yet evidence for waterborne disease transmission is lacking. OBJECTIVES: We related quantitative polymerase chain reaction (qPCR)-measured enteric viruses in the tap water of 14 Wisconsin communities supplied by nondisinfected groundwater to acute gastrointestinal illness (AGI) incidence. METHODS: AGI incidence was estimated from health diaries completed weekly by households within each study community during four 12-week periods. Water samples were collected monthly from five to eight households per community. Viruses were measured by qPCR, and infectivity assessed by cell culture. AGI incidence was related to virus measures using Poisson regression with random effects. RESULTS: Communities and time periods with the highest virus measures had correspondingly high AGI incidence. This association was particularly strong for norovirus genogroup I (NoV-GI) and between adult AGI and enteroviruses when echovirus serotypes predominated. At mean concentrations of 1 and 0.8 genomic copies/L of NoV-GI and enteroviruses, respectively, the AGI incidence rate ratios (i.e., relative risk) increased by 30%. Adenoviruses were common, but tap-water concentrations were low and not positively associated with AGI. The estimated fraction of AGI attributable to tap-water-borne viruses was between 6% and 22%, depending on the virus exposure-AGI incidence model selected, and could have been as high as 63% among children < 5 years of age during the period when NoV-GI was abundant in drinking water. CONCLUSIONS: The majority of groundwater-source public water systems in the United States produce water without disinfection, and our findings suggest that populations served by such systems may be exposed to waterborne viruses and consequent health risks.

The role of the microbial stringent response in excess intracellular accumulation of phosphorous in mixed consortia fed synthetic wastewater.

Four bench-scale sequencing batch reactors (SBRs) seeded with activated sludge were operated under either fully oxic or anoxic/oxic conditions and fed synthetic wastewater containing either peptone or acetate. The function of each reactor was assessed through the measure of (i) soluble chemical oxygen demand, orthophosphate, ammonia, and nitrate; and (ii) biomass concentrations of phosphorus, polyhydroxyalkanoate, guanosine tetraphosphate, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate. In all four reactors, the biomass concentration of phosphorous was correlated statistically with the biomass concentration of ppGpp. The microbial consortia in all four reactors removed an appreciable quantity of phosphorous from solution (67-99%), and the net quantity of phosphorous removed from solution corresponded to the net increase in the biomass concentration of phosphorous. Hence, the microbial stringent response (MSR) was associated with excess intracellular accumulation of phosphorous in mixed microbial consortia fed synthetic wastewater. With recognition of the potential role of the MSR in the removal of soluble phosphorous from wastewater, additional research may lead to further optimization of treatment technologies and the development of new treatment systems for the biological removal of phosphorus from wastewater.

Effect of anaerobic HRT on biological phosphorus removal and the enrichment of phosphorus accumulating organisms.

The purpose of this research was to develop a better understanding of the dynamic effects of anaerobic hydraulic retention time (HRT) on both enhanced biological phosphorus removal (EBPR) performance and enrichment of phosphorus accumulating organisms (PAOs). The research was conducted using laboratory-scale sequencing batch reactors inoculated with mixed microbial consortia and fed real wastewater. Exposing microorganisms to extended anaerobic HRTs is not recommended for EBPR configured systems. In this research, however, longer anaerobic exposure did not negatively affect performance even if volatile fatty acids were depleted. Further, extended anaerobic HRTs may positively affect phosphorus removal through enhanced aerobic uptake. The EBPR consortia also appear to maintain reserve energetic capacity in the form of polyphosphate that can be used to survive and grow under variable operational and environmental conditions. Finally, the tested EBPR systems yield mixed microbial consortia enriched with PAOs (specifically Candidatus Accumulibacter phosphatis) at approximately 7.1 to 21.6% of the total population.

Concentration of enteroviruses, adenoviruses, and noroviruses from drinking water by use of glass wool filters.

Available filtration methods to concentrate waterborne viruses are either too costly for studies requiring large numbers of samples, limited to small sample volumes, or not very portable for routine field applications. Sodocalcic glass wool filtration is a cost-effective and easy-to-use method to retain viruses, but its efficiency and reliability are not adequately understood. This study evaluated glass wool filter performance to concentrate the four viruses on the U.S. Environmental Protection Agency contaminant candidate list, i.e., coxsackievirus, echovirus, norovirus, and adenovirus, as well as poliovirus. Total virus numbers recovered were measured by quantitative reverse transcription-PCR (qRT-PCR); infectious polioviruses were quantified by integrated cell culture (ICC)-qRT-PCR. Recovery efficiencies averaged 70% for poliovirus, 14% for coxsackievirus B5, 19% for echovirus 18, 21% for adenovirus 41, and 29% for norovirus. Virus strain and water matrix affected recovery, with significant interaction between the two variables. Optimal recovery was obtained at pH 6.5. No evidence was found that water volume, filtration rate, and number of viruses seeded influenced recovery. The method was successful in detecting indigenous viruses in municipal wells in Wisconsin. Long-term continuous filtration retained viruses sufficiently for their detection for up to 16 days after seeding for qRT-PCR and up to 30 days for ICC-qRT-PCR. Glass wool filtration is suitable for large-volume samples (1,000 liters) collected at high filtration rates (4 liters min(-1)), and its low cost makes it advantageous for studies requiring large numbers of samples.

PCR detection of specific pathogens in water: a risk-based analysis.

The relative concentration of pathogens in water samples collected from storm drains and adjacent surfaces was evaluated using established PCR-based protocols. Out of the 58 samples collected from 21 different storm drains, 22% were PCR positive for Escherichia coli ETEC, Salmonella, or adenovirus. The risk of swimming related illnesses associated with detection of E. coli ETEC and Salmonella ranged from 0.39 to 30:100 000 and 0.3-25:1000, respectively. The detection limit corresponding to a negative-PCR result was evaluated in reference to water quality standards developed using a risk-based approach that integrates human dose-response data with acceptable levels of risk promulgated by the U.S. EPA for recreational contact. The percent of samples with an acceptable detection limit ranged from 0% for Giardia lamblia and Shigella to 100% for E. coli ETEC. The principal factor influencing the detection limit of G. lamblia and Shigella was sample volume. The principal factor influencing the detection limit of the remaining bacteria and protozoa, including E. coli O157:H7, Salmonella, and Cryptosporidium parvum, was the presence of inhibitory compounds in the purified nucleic acid extracts. Both recovery and inhibition adversely impacted the detection limit of viruses. Ambient water quality standards based on the occurrence of specific pathogens enumerated with PCR-based assays could serve as a method of evaluating the biological quality of water but only after significant improvements in filtration and purification protocols. The risk-based methodology developed in this study can be used to evaluate future improvements in filtration and purification protocols.