Application of an improved global-scale groundwater model for water table estimation across New Zealand

Many studies underline the importance of groundwater assessment at the larger, i.e. global, scale. The groundwater models used for these assessments are dedicated to the global scale and therefore not often applied for studies in smaller areas, e.g. catchments, because of their simplifying assumptions. In New Zealand, advanced numerical groundwater flow models have been applied in several catchments. However, that application is piecemeal: only for a limited amount of aquifers and through a variety of groundwater model suites, formats, and developers. Additionally, there are large areas where groundwater models and data are sparse. Hence, an inter-catchment, inter-regional, or nationwide overview of important groundwater information, such as the water table, does not exist. The investment needed to adequately cover New Zealand with high-resolution groundwater models in a consistent approach would be significant and is therefore not considered possible at this stage. This study proposes a solution that obtains a nationwide overview of groundwater that bridges the gap between the (too-)expensive advanced local models and the (too-)simple global-scale models. We apply an existing, global-scale, groundwater flow model and improve it by feeding in national input data of New Zealand terrain, geology, and recharge, and by slight adjustment of model parametrisation and model testing. The resulting nationwide maps of hydraulic head and water table depths show that the model points out the main alluvial aquifers with fine spatial detail (200 m grid resolution). The national input data and finer spatial detail result in better and more realistic variations of water table depth than the original, global-scale, model outputs. In two regional case studies in New Zealand, the hydraulic head shows excellent correlation with the available groundwater level data. Sensitivity and other analyses of our nationwide water tables show that the model is mostly driven by recharge, model resolution, and elevation (gravity), and impeded by the geology (permeability). The use of this first dedicated New Zealand-wide model can aid in provision of water table estimates in data-sparse regions. The national model can also be used to solve inconsistency of models in areas of trans-boundary aquifers, i.e. aquifers that cover more than one region in New Zealand. Comparison of the models, i.e. the national application (National Water Table model: NWT) with the global model (Equilibrium Water Table model: EWT), shows that most improvement is achieved by feeding in better and higher-resolution input data. The NWT model still has a bias towards shallow water tables (but less than the EWT model because of the finer model resolution), which could only be solved by feeding in a very high resolution terrain model that incorporates drainage features. Although this is a model shortcoming, it can also be viewed as a valuable indicator of the pre-human water table, i.e. before 90 % of wetlands were drained for agriculture since European settlement in New Zealand. Calibration to ground-observed water level improves model results but can of course only work where there are such data available. Future research should therefore focus on both model improvements and more data-driven, improved estimation of hydraulic conductivity, recharge, and the digital elevation model. We further surmise that the findings of this study, i.e. successful application of a global-scale model at smaller scales, will lead to subsequent improvement of the global-scale model equationsThis research has been part of a PhD study of the lead author at the University of Waikato, New Zealand, supervised by Moira Steyn-Ross. It has been performed as part of the Smart Aquifer Characterisation (SAC) Programme, funded by the Ministry of Business, Innovation and Employment, New Zealand. This project has received co-funding from the European Union's Seventh Framework Programme for Research and Technological Development under grant agreement no. 603608, eartH2Observe. We furthermore would like to thank the reviewers for their valuable comments, Waikato Regional Council and Environment Canterbury for their ground-observed data used in the results section, and Jeremy White (GNS Science) for his advice on the sensitivity analysesS

Capturing the Lost Phosphorus

Minable phosphorus (P) reserves are being depleted and will need to be replaced by recovering P that currently is lost from the agricultural system, causing water-quality problems. The largest two flows of lost P are in agricultural runoff and erosion (∼46% of mined P globally) and animal wastes (∼40%). These flows are quite distinct. Runoff has a very high volumetric flow rate, but a low P concentration; animal wastes have low flow rates, but a high P concentration together with a high concentration of organic material. Recovering the lost P in animal wastes is technically and economically more tractable, and it is the focus for this review of promising P-capture technologies. P capture requires that organic P be transformed into inorganic P (phosphate). For high-strength animal wastes, P release can be accomplished in tandem with anaerobic treatment that converts the energy value in the organic matter to CH4, H2, or electricity. Once present as phosphate, the P can be captured in a reusable form by four approaches. Most well developed is precipitation as magnesium or calcium solids. Less developed, but promising are adsorption to iron-based adsorbents, ion exchange to phosphate-selective solids, and uptake by photosynthetic microorganisms or P-selective proteins

Total Value of Phosphorus Recovery

Phosphorus (P) is a critical, geographically concentrated, nonrenewable resource necessary to support global food production. In excess (e.g., due to runoff or wastewater discharges), P is also a primary cause of eutrophication. To reconcile the simultaneous shortage and overabundance of P, lost P flows must be recovered and reused, alongside improvements in P-use efficiency. While this motivation is increasingly being recognized, little P recovery is practiced today, as recovered P generally cannot compete with the relatively low cost of mined P. Therefore, P is often captured to prevent its release into the environment without beneficial recovery and reuse. However, additional incentives for P recovery emerge when accounting for the total value of P recovery. This article provides a comprehensive overview of the range of benefits of recovering P from waste streams, i.e., the total value of recovering P. This approach accounts for P products, as well as other assets that are associated with P and can be recovered in parallel, such as energy, nitrogen, metals and minerals, and water. Additionally, P recovery provides valuable services to society and the environment by protecting and improving environmental quality, enhancing efficiency of waste treatment facilities, and improving food security and social equity. The needs to make P recovery a reality are also discussed, including business models, bottlenecks, and policy and education strategies

The silicon trypanosome

African trypanosomes have emerged as promising unicellular model organisms for the next generation of systems biology. They offer unique advantages, due to their relative simplicity, the availability of all standard genomics techniques and a long history of quantitative research. Reproducible cultivation methods exist for morphologically and physiologically distinct life-cycle stages. The genome has been sequenced, and microarrays, RNA-interference and high-accuracy metabolomics are available. Furthermore, the availability of extensive kinetic data on all glycolytic enzymes has led to the early development of a complete, experiment-based dynamic model of an important biochemical pathway. Here we describe the achievements of trypanosome systems biology so far and outline the necessary steps towards the ambitious aim of creating a , a comprehensive, experiment-based, multi-scale mathematical model of trypanosome physiology. We expect that, in the long run, the quantitative modelling enabled by the Silicon Trypanosome will play a key role in selecting the most suitable targets for developing new anti-parasite drugs

Repeatable use assessment of silicon carbide as permanent susceptor bed in ex situ microwave remediation of petroleum-impacted soils

Efficiency of microwave-enabled ex situ soil remediation can be improved by dielectric susceptors. Cost, and environmental burden of these susceptors can be minimized if they are used repeatedly in a permanent bed set-up. In this study, carbon nanofibers, activated carbon, magnetite, and silicon carbide were tested at the lab scale for repeated use in permanent microwave-induced thermal soil remediation. Despite their superior ability to convert microwaves into heat, carbon nanofibers experienced electrokinesis and activated carbon partially combusted in the microwave cavity, which complicates their pragmatic use in remediation applications. Magnetite was also able to convert microwaves into heat effectively and it was relatively more stable; however, repeated heating/and cooling cycles changed its physicochemical properties, which was attributed to oxidation of iron oxides at the air-soil interface. Silicon carbide, on the other hand, was an efficient heating agent and was stable during repeatable heating and cooling cycles. Through 25 heating/cooling cycles, an average peak temperature of 329 ± 55°C was achieved for a 29 cm3 sample and analysis of dielectric properties after every 10th and 25th cycle indicated that there were no significant losses in thermal conductivity or permittivity of the material. Subsequent remediation experiments with silicon carbide demonstrated that between 89 and 97% of the total petroleum hydrocarbons were removed from soil including a marked fraction of heavy hydrocarbons when 20.2 kJ g−1 of microwave energy was introduced. In addition, post-treatment experiments demonstrated that soil conditions were capable of supporting seed germination indicating that some conditions of soil were recovered after microwave remediation

Metal and nanoparticle occurrence in biosolid-amended soils

Metals can accumulate in soils amended with biosolids in which metals have been concentrated during wastewater treatment. The goal of this study is to inspect agricultural sites with long-term biosolid application for a suite of regulated and unregulated metals, including some potentially present as commonly used engineered nanomaterials (ENMs). Sampling occurred in fields at a municipal and a privately operated biosolid recycling facilities in Texas. Depth profiles of various metals were developed for control soils without biosolid amendment and soils with different rates of biosolid application (6.6 to 74 dry tons per hectare per year) over 5 to 25 years. Regulated metals of known toxicity, including chromium, copper, cadmium, lead, and zinc, had higher concentrations in the upper layer of biosolid-amended soils (top 0–30 cm or 0–15 cm) than in control soils. The depth profiles of unregulated metals (antimony, hafnium, molybdenum, niobium, gold, silver, tantalum, tin, tungsten, and zirconium) indicate higher concentrations in the 0–30 cm soil increment than in the 70–100 cm soil increment, indicating low vertical mobility after entering the soils. Titanium-containing particles between 50 nm and 250 nm in diameterwere identified in soil by transmission electron microscopy (TEM) coupled with energy dispersive x-ray spectroscopy (EDX) analysis. In conjunctionwith other studies, this research shows the potential for nanomaterials used in society that enter the sewer system to be removed at municipal biological wastewater treatment plants and accumulate in agricultural fields. The metal concentrations observed herein could be used as representative exposure levels for eco-toxicological studies in these soils

Scaling up photoelectrocatalytic reactors: A TiO2 nanotube-coated disc compound reactor effectively degrades acetaminophen

Multiple discs coated with hierarchically-organized TiO2 anatase nanotubes served as photoelectrodes in a novel annular photoelectrocatalytic reactor. Electrochemical characterization showed light irradiation enhanced the current response due to photogeneration of charge carriers. The pharmaceutical acetaminophen was used as a representative water micropollutant. The photoelectrocatalysis pseudo-first-order rate constant for acetaminophen was seven orders of magnitude greater than electrocatalytic treatment. Compared against photocatalysis alone, our photoelectrocatalytic reactor at <8 V reduced by two fold, the electric energy per order (EEO; kWh m-3 order-1 for 90% pollutant degradation). Applying a cell potential higher than 8 V detrimentally increased EEO. Acetaminophen was degraded across a range of initial concentrations, but absorbance at higher concentration diminished photon transport, resulting in higher EEO. Extended photoelectrocatalytic reactor operation degraded acetaminophen, which was accompanied by 53% mineralization based upon total organic carbon measurements. This proof of concept for our photoelectrocatalytic reactor demonstrated a strategy to increase photo-active surface area in annular reactors

Photoelectrocatalytic degradation of 2,4-dichlorophenol in a TiO2 nanotube-coated disc flow reactor

Photoelectrocatalytic (PEC) water treatment is a promising technology for organic pollution abatement. Much of the prior research focused on material discovery and optimization. However, challenges exist in scaling-up PEC processes and are associated with designing reactors with effective light irradiation on electrode surfaces and, simultaneously, efficient electrode configurations. We design and demonstrate key reactor design principles, which influence reaction mechanisms, for a reactor using a TiO2 nanotube-coated disc flow reactor. Degradation of organochlorinated 2,4-dichlorophenol was studied as representative carcinogenic micropollutant. The synergistic photoelectrocatalytic process showed 5-fold faster degradation kinetics than solely electrocatalytic treatment or a greater than 2-fold enhancement over photocatalysis alone. Applicability of photoelectrocatalytic treatment was demonstrated over a wide range of micropollutant concentrations with almost complete abatement even at concentrations up to 25 mg L-1 of 2,4-dichlorophenol. Mechanistically, the increase in applied current density efficiency for degradation of 2,4-dichlorophenol was due to stabilization of charge carriers and higher oxidants production rates in the PEC system. Carboxylic acids were identified as the main by-products formed from cleavage of the phenolic ring moieties in 2,4-dichlorophenol. However, very importantly we achieved dehalogenation photoelectrocatalysis with evidence of chlorine heteroatoms released as innocuous chloride anions. Overall, this research demonstrates the importance of PEC reactor design and how properly orientated TiO2 nanotube-coated disc flow reactors leverage both novel material designs and reactor architectures to achieve pollutant degradation

Portable point-of-use photoelectrocatalytic device provides rapid water disinfection

Portable water purification devices are needed to provide safe drinking water in rural communities, developing communities with low quality centralized water distribution, and military or recreational applications. Filtration, ultraviolet light, or chemical additives provide a spectrum of alternatives to remove pathogens from water. For the first time, we design, fabricate and demonstrate the performance of a small portable photoelectric point-of-use device, and document its performance on pathogen inactivation. The device utilizes a commercial teacup from which TiO2 nanotube photoanodes were produced in-situ and, with a small rechargeable battery powered 365 nm light emitting diode, was able to achieve 5-log inactivation of Escherichia coli in 10 s and 2.6-log of Legionella in 60 s of treatment in model water samples. Treatment of natural water achieved a 1-log bacteria inactivation after 30 s due to matrix effects. The electro-photocatalytic disinfection reactor in a kup (e-DRINK) can provide a feasible and affordable solution to ensure access to clean water. More broadly, this work demonstrates the potential for illumination to improve the efficiency of electrocatalytic surfaces