K.G. Zuurbier

The impact of low-temperature seasonal aquifer thermal energy storage (SATES) systems on chlorinated solvent contaminated groundwater: Modeling of spreading and degradation

Groundwater systems are increasingly used for seasonal aquifer thermal energy storage (SATES) for periodic heating and cooling of buildings. Its use is hampered in contaminated aquifers because of the potential environmental risks associated with the spreading of contaminated groundwater, but positive side effects, such as enhanced contaminant remediation, might also occur. A first reactive transport study is presented to assess the effect of SATES on the fate of chlorinated solvents by means of scenario modeling, with emphasis on the effects of transient SATES pumping and applicable kinetic degradation regime. Temperature effects on physical, chemical, and biological reactions were excluded as calculations and initial simulations showed that the small temperature range commonly involved (ΔT<15 °C) only caused minor effects. The results show that a significant decrease of the contaminant mass and (eventually) plume volume occurs when degradation is described as sediment-limited with a constant rate in space and time, provided that dense non-aqueous phase liquid (DNAPL) is absent. However, in the presence of DNAPL dissolution, particularly when the dissolved contaminant reaches SATES wells, a considerably larger contaminant plume is created, depending on the balance between DNAPL dissolution and mass removal by degradation. Under conditions where degradation is contaminant-limited and degradation rates depend on contaminant concentrations in the aquifer, a SATES system does not result in enhanced remediation of a contaminant plume. Although field data are lacking and existing regulatory constraints do not yet permit the application of SATES in contaminated aquifers, reactive transport modeling provides a means of assessing the risks of SATES application in contaminated aquifers. The results from this study are considered to be a first step in identifying the subsurface conditions under which SATES can be applied in a safe or even beneficial manner.

Identification of potential sites for aquifer storage and recovery (ASR) in coastal areas using ASR performance estimation methods

Performance of freshwater aquifer storage and recovery (ASR) systems in brackish or saline aquifers is negatively affected by lateral flow, density effects, and/or dispersive mixing, causing ambient groundwater to enter ASR wells during recovery. Two recently published ASR performance estimation methods are applied in a Dutch coastal area, characterized by brackish-to-saline groundwater and locally high lateral-flow velocities. ASR performance of existing systems in the study area show good agreement with the predicted performance using the two methods, provided that local vertical anisotropy ratios are limited (<3). Deviations between actual and predicted ASR performance may originate from simplifications in the conceptual model and uncertainties in the hydrogeological and hydrochemical input. As the estimation methods prove suitable to predict ASR performance, feasibility maps are generated for different scales of ASR to identify favorable ASR sites. Successful small-to-medium-scale ASR varies spatially in the study area, emphasizing the relevance of reliable a priori spatial mapping.RésuméLa performance des dispositifs de stockage souterrain et récupération (ASR) d’eau douce dans les aquifères salés ou saumâtres est pénalisée par l’écoulement latéral, les effets de densité et/ou le mélange dispersif, ce qui cause l’intrusion d’eau connée dans les puits d’ASR pendant la récupération. Deux méthodes d’estimation de la performance de l’ASR récemment publiées sont appliquées à une zone côtière de Hollande caractérisée par des eaux souterraines saumâtres à salées et localement des vitesses d’écoulement latérales élevées. La performance ASR de dispositifs existants dans la zone d’étude montre un bon accord avec la performance prévue avec les deux méthodes, tant que les rapports d’anisotropie verticale locale sont limités (<3). Les écarts entre la performance ASR prévue et observée pourraient avoir pour origine des simplifications du modèle conceptuel et des incertitudes dans les paramètres d’entrée hydrogéologiques et hydrochimiques. Comme les méthodes d’estimation sont adaptées à la prévision de la performance de l’ASR, des cartes de faisabilité sont établies pour des dispositifs d’ASR de différents volumes afin d’identifier des sites ASR favorables. Les dispositifs d’ASR de petit à moyen volume efficaces varient dans le domaine de la zone d’étude, ce qui souligne la pertinence d’une cartographie spatiale préalable fiable.ResumenEl rendimiento de los sistemas de recuperación y almacenamiento (ASR) de acuíferos de agua dulce en acuíferos salobres o salino es negativamente afectado por el flujo lateral, los efectos de densidad y / o mezcla dispersiva, lo cual causa que el agua subterránea ambiente entre a pozos ASR durante la recuperación. Se aplican dos métodos de estimación de rendimiento ASR recientemente publicados a un área costera holandesa., caracterizada por agua subterránea salobre a salina y altas velocidades locales de flujo lateral. Los rendimientos ASR de sistemas existentes en el área de estudio muestran un buen acuerdo con el rendimiento predicho usando los dos métodos, siempre y cuando que las tasas anisotropía vertical local sean limitadas (<3). Las desviaciones entre los rendimientos reales y los predichos por ASR pueden originarse a partir simplificaciones en el modelo conceptual e incertidumbres en las entradas hidrogeológicas e hidroquímicas. Como los métodos de estimación muestran apropiados rendimientos predichos por ASR, se generan mapas de factibilidad para distintas escalas de ASR para identificar sitios ASR favorables. Los ASR exitosos de media a pequeña escala varían espacialmente en el área de estudio, enfatizando la relevancia de un mapeo espacial confiable a priori.摘要淡水含水层的存储和恢复(ASR)系统在微咸水或咸水含水层中受到侧向流、密度的影响和/或分散混合的负面影响,在恢复中造成周围地下水进入ASR井。在荷兰沿海地区,最近发表的两篇有关ASR性能估算法应用于微咸到咸水地下水和局部高侧向流动速度的地区。在研究区内,现有系统的ASR性能显示与预测的性能一致,在当地垂直各向异性率不超过 < 3的条件下。实际的与预测的性能之间的偏差可能源自简化概念模型以及在水文地质、水化学输入的不确定因素。随着评估法可以预测ASR性能,不同比例尺的ASR可行性地图可帮助识别好的ASR场地。在研究区内,成功的小型 -中型的ASR场地空间的变化,强调可靠的先天的特殊标测的相关性。ResumoO desempenho de sistemas de armazenamento e recuperação de água doce em aquíferos (ASR) salobros ou salinos é afetado negativamente por fluxo lateral, efeitos de densidade e/ou mistura dispersiva, causando a entrada de água subterrânea ambiente nos poços ASR durante a extração. Dois métodos de estimação de desempenho do ASR recentemente publicados foram aplicados numa área costeira holandesa, caraterizada por água subterrânea salobra a salina e, localmente, por velocidades elevadas de fluxo lateral. O desempenho do ASR dos sistemas existentes na área de estudo mostram uma boa correlação com o desempenho previsto quando se usam os dois métodos, desde que os índices de anisotropia vertical sejam limitados (<3). Os desvios entre os desempenhos de ASR reais e os previstos podem ter origem nas simplificações do modelo concetual e nas incertezas dos dados hidrogeológicos e hidrogeoquímicos iniciais. Como os métodos de estimação provam ser adequados para prever o desempenho do ASR, mapas de viabilidade são gerados para diferentes escalas de ASR, a fim de identificar locais favoráveis ao ASR. O sucesso a pequena a média escala varia espacialmente na área de estudo, enfatizando a importância de um mapeamento espacial confiável feito a priori.

Enabling Successful Aquifer Storage and Recovery of Freshwater Using Horizontal Directional Drilled Wells in Coastal Aquifers

AbstractAquifer storage and recovery (ASR) of freshwater surpluses can reduce freshwater shortages in coastal areas during periods of prolonged droughts. However, ASR is troublesome in saline coastal aquifers as buoyancy effects generally cause a significant loss of injected freshwater. The use of a pair of parallel, superimposed horizontal wells is proposed to combine shallow ASR with deep interception of underlying saltwater. A shallow, fresh groundwater lens can thereby be enlarged and protected. This freshmaker setup was successfully placed in a coastal aquifer in The Netherlands using horizontal directional drilling to install 70-m-long horizontal directional drilled wells (HDDWs). The freshmaker prototype aims to inject a specific volume of freshwater and abstract the same volume of water (consisting of injected water and ambient native groundwater) within the targeted water quality. Groundwater transport modeling preceding ASR operation demonstrates that this set up is able to abstract a water volu...

How Subsurface Water Technologies (SWT) can Provide Robust, Effective, and Cost-Efficient Solutions for Freshwater Management in Coastal Zones

Freshwater resources in coastal zones are limited while demands are high, resulting in problems like seasonal water shortage, overexploitation of freshwater aquifers, and seawater intrusion. Three subsurface water technologies (SWT) that can provide robust, effective, and cost-efficient solutions to manage freshwater resources in the subsurface are evaluated using groundwater modelling and validation at field-scale: (1) ASR-coastal to store freshwater surpluses in confined brackish-saline aquifers for recovery in times of demand, (2) the Freshkeeper to counteract salinization of well fields by interception and desalination of upconing brackish groundwater, and (3) the Freshmaker to combine ASR and Freshkeeper to enlarge the volume of natural freshwater lenses for later abstraction. The evaluation indicates that SWT can be used in various hydrogeological settings for various hydrogeological problems like seawater intrusion, upconing, and bubble drift during ASR and have significant economic benefits. Although only sporadically applied to date, we foresee that SWT will stimulate (cost-)efficient and sustainable exploitation of various freshwater sources (like groundwater, rainwater, treated waste water, surface water) in coastal zones. Prolonged SWT testing in the current pilots, replication of SWT in other areas worldwide, and the development of technical and non-technical support tools are required to facilitate potential end-users in investment decision making and SWT implementation.