Microbial fuel cells (MFC) are an alternative for electric power production based on the oxidation of organic matter, for that reason waste waters are been considered as source of organic matter which can be transformed by microorganisms with the capacity of generating electric power. Therefore, the use of this technology, allows fulfilling two objectives, electricity production and pollutant reduction. In this work, a two-chamber MFC was assembled and operated in discontinuous mode to evaluate the parameters of electricity production and COD reduction in a synthetic waste water (with an invariant nutritional composition), using Escherichia coli and Pseudomonas aeruginosa strains. Carbon cloth and graphite were employed as electrodes, and methylene blue as a mediator. The initial pH values of the synthetic wastewater used as a substrate were variated in the tests. According to the operating conditions described above, a maximum average value of 464 mV was obtained for the voltage in open circuit and a potential density of 3.98 mW/m2, using Escherichia coli with a pH value of 6.5, a mediator, and with graphite as the material for electrodes. Additionally, a significant decrease in chemical oxygen demand (COD) was achieved with 11.53% for E. coli being the highest one. Lastly, microbial quantification was done, obtaining a lower growth time also for Escherichia coli.

Groundwater recharge estimation in arid and semi-arid southern Africa is reviewed based on four decades of recharge investigation in the region. This paper updates an earlier review by incorporating emerging and grey literature from a wide range of research sectors in southern Africa, collected during the past decade. For ease of comparison, methods commonly used are critically reviewed with a rating provided in terms of accuracy, application and costs. These include, but are not limited to, the methods of chloride mass balance (CMB), rainfall infiltration breakthrough (RIB), Extended model for Aquifer Recharge and moisture Transport through unsaturated Hardrock (EARTH), water-table fluctuation (WTF), water balance in the saturated zone (including equal volume spring flow (EVSF) and saturated volume fluctuation (SVF)), and groundwater modelling (GM). As the methods based on mass balance and relationships between rainfall, water-level fluctuations and abstraction are proven to have the potential to simulate and forecast groundwater recharge, the EVSF and CMB methods are highly recommended for use in the southern African region according to this review. Caution on the uncertainty associated with error input and propagation for all the methods is advised, based on a case study in South Africa. The review provides an updated source of references related to recharge estimation in arid and semi-arid regions of Sub-Saharan Africa in general and to ongoing projects for the implementation for Resource Directed Measures (part of the National Water Resources Strategy) in South Africa in particular.

The processes of microplastic fiber pollution in groundwater are unknown. The recent research on this contaminant threat is generally focused on surface waters (mainly oceans and rivers), while aquifer contamination is only marginally mentioned as an issue needing further investigation. Synthetic microfibers can be introduced into soils in different ways (e.g. wastewater treatment plants or greywater discharge, septic tank outflows, direct injection of contaminated water in cases of managed aquifer recharge, losing streams, etc.), and can thus reach aquifer systems due to leaching or infiltration in soil pores. Microfibers can then adsorb persistent bioaccumulative and toxic chemicals, which include persistent organic pollutants and metals, and become a carrier of harmful substances in the aquifer system, hence contributing to the overall contamination in both urban and rural areas. For this reason, it is of paramount importance, not only to assess the occurrence and fate of microplastic fibers in groundwater, but also to study the role of microplastics as carriers of contaminants within the aquifer and to advance standardization and organization of monitoring campaigns. Only by addressing these key challenges can hydrogeologists contribute to the state of the art on microplastic pollution and ensure that groundwater is not neglected in the environmental assessments tackling this contaminant of emerging concern.

Excess nitrate (NO₃⁻) is a critical problem in agricultural land-use areas, causing eutrophication and hypoxia in surface waters. Diversion of agricultural runoff into saturated buffer zones reduces NO₃⁻ loading. This study seeks to understand nitrate concentration, [NO₃⁻], and environmental factor variability in a saturated buffer zone (~0.007 km²) at a site in the USA on a diurnal scale within and among seasons. Between September 2016 and August 2017, groundwater samples were collected hourly for 24 h from an unconfined aquifer 1.5 m below the surface in the saturated buffer zone. Mean daily [NO₃⁻-N] ranged from 2.18 mg/L in the fall to 4.63 mg/L in the summer and varied by a statistically significant difference from spring to fall and from summer to fall. Differences between 24-h maximum and minimum [NO₃⁻-N] were statistically significant within spring, summer, fall, and winter. The occurrence of a sinusoidal [NO₃⁻-N] trend where the timing of maximum and minimum [NO₃⁻-N] coincide with photoperiod indicates that vegetation uptake is a controlling process. NO₃⁻ leaching, evapotranspiration, and nitrification were identified as processes controlling [NO₃⁻-N] increases over the 24-h period. The magnitude of difference between daily maximum and minimum [NO₃⁻-N] displayed no correlation with daily average air temperature, solar intensity, or mean daily water temperature. This study demonstrated that variation in [NO₃⁻] exists on seasonal and diurnal time scales; the fluctuations are driven by multiple processes consistent over the 24-h period.

The need for regional-scale integrated hydrological models for the purpose of water resource management is increasing. Distributed physically based coupled surface-subsurface models are usually complex and contain a large amount of spatio-temporal information that leads to a relatively long forward runtime. One of the main challenges with regard to regional-scale inverse modeling relates to parameterization and how to adequately exploit the information embedded in the existing observational data while avoiding parameter identifiability issues. This study examined and compared the calibration of a “highly parameterized” model with a “classical” unit-based parameterization scheme in which the dominant geological features were assumed to be known. The physically based coupled surface-subsurface model MIKE SHE was used for conducting the study of five river basins (4,900 km²) in central Jutland in Denmark, characterized by heterogeneous geology and a considerable amount of groundwater flux across topographical catchment boundaries. The results indicated that introducing more flexibility in the parameter estimation process through a regularized approach significantly improved the model performance, in particular head and water balance errors. The highly parameterized calibration results additionally provided very useful insights into the model deficiencies in terms of conceptual model structure and incorrectly imposed boundary conditions. Furthermore, the results from data-worth analysis indicated that the highly parameterized model has more effectively utilized the information in the dataset compared to a traditional unit-based calibration approach.

Based on a five-town case-study cohort in Kenya, a conceptual framework has been developed to enable the formulation of holistic and effective strategies that encompass the national aspirations and regional to global sustainability agendas, and which can be used to monitor progress in achieving set objectives. The approach is flexible, scalable and transferrable, so that it can be applied in different contexts and using different indicators, based upon the same construct. Insufficient technical knowledge of urban aquifers and their interplay with the wider social-ecological system constrains the development of holistic, effective and robust management systems to ensure their sustainability for intended uses. The objective was to consider governance and management solutions that could promote water security for urban towns in Kenya through the sustainable use of groundwater in the context of its complex hydrogeology, water access disparities, competing uses and future risks. The in force national and county water policies, strategies, and plans for the case study areas were critically reviewed. The status of aquifer knowledge, water access disparities, competing uses, and risks was evaluated from critical literature reviews and data compilation, fieldwork, and analysis of indicator datasets from the Kenya 2009 census. Key aquifers need urgent characterisation to reverse the current situation whereby development proceeds with insufficient aquifer knowledge. Private sector and public participation in management should be enhanced through decentralised management approaches. Water infrastructure and technologies should be fit-for-purpose in application and scale, and the pro-poor focus should be underpinned by appropriately focused management regimes.

Weathered crystalline bedrock aquifers sustain water supplies across the tropics, including East Africa. Although well yields are commonly <1 L s⁻¹, more intensive abstraction occurs and provides vital urban and agricultural water supplies. The hydrogeological conditions that sustain such high abstraction from crystalline bedrock aquifers remain, however, poorly characterised. Five sites of intensive groundwater abstraction (multiple boreholes yielding several L s⁻¹ or more) were investigated in Uganda and Tanzania. Analysis of aquifer properties data indicates that the sites have transmissivities of 10–1,000 m² day⁻¹, which is higher than generally observed in deeply weathered crystalline bedrock aquifers. At four of the five sites, weathered bedrock (saprolite) is overlain by younger superficial sediments, which provide additional storage and raise the water table within the underlying aquifer. Residence-time indicators suggest that: (1) abstracted water derives, in part, from modern recharge (within the last 10–60 years); and (2) intensive abstraction is sustained by recharge occurring over several decades. This range of encountered residence times indicates a degree of resilience to contemporary climate variability (e.g. short-term droughts), although the long-term sustainability of intensive abstractions remains uncertain. Evidence from one site in Tanzania (Makutapora) highlights the value of multi-decadal groundwater-level records in establishing the long-term viability of intensive groundwater abstraction, and demonstrates the influence of intra-decadal climate variability in determining the magnitude and frequency of recharge.

El Ministerio de Salud de Costa Rica (MINSA), como ente rector en materia de salud y prevención de la contaminación producida por la humanidad cuenta con distintas funciones, entre ellas monitorear el cumplimiento legal de una gran cantidad de empresas que impactan la salud y el ambiente. Desde la óptica de su afectación por generación de aguas residuales, dichas empresas analizan y reportan, ante este Ministerio, la calidad de sus aguas vertidas provenientes de sus procesos productivos. | En Costa Rica, se ha venido presentando en los últimos años un problema grave con el manejo y vertido de aguas residuales sin control en nuestros diferentes ríos y acequias. El Ministerio de Salud mediante la aplicación del decreto No 33601- MINAE-S a través de sus Área Rectoras de Salud realizan una vigilancia sobre esta problemática, no obstante el esfuerzo es insuficiente ya que dicho control se basa únicamente en la revisión de cumplimiento de los parámetros universales de vertido y no toman en cuenta la carga contaminante que llevan estas aguas a los cuerpos, lo que provoca un consecuente impacto ambiental ya que se están vertiendo sustancias que son ajenas al río alterando su composición. En la problemática de la carga contaminante antes mencionada, en este proyecto se elaboraron dos índices para aguas residuales, que permite a las Áreas Rectoras de Salud valorar tanto el cumplimiento normativo, como la cantidad de carga contaminante vertidas a los ríos y acequias procurando, que por medio del Ministerio de Salud y estos entes generadores (empresas) realicen acciones en mejoramiento del ambiente y la salud de la población.

Several methodologies exist for the design of optimal groundwater monitoring networks. Those that employ geostatistical techniques are usually dependent on a variogram. In practice, different variograms for an environmental variable can be fitted depending on the number of available data, their spatial distribution, and their variability. For this reason, in most cases, it is difficult to get an adequate variogram. This report evaluates the influence of the groundwater level data available in the construction of a product-sum spatiotemporal variogram model and its consequences on a geostatistical-based methodology that uses the Kalman filter for the design of optimal spatiotemporal monitoring networks. Additionally, a sensitivity analysis is carried out to determine the variations in the optimal number of wells and monitoring frequency for the monitoring network, depending on the selected spatiotemporal variogram model. The results show the importance of getting a good quality spatiotemporal variogram when designing optimal groundwater-level monitoring networks using geostatistical-based methodologies.