Bradley Patterson

Managed aquifer recharge of treated wastewater: Water quality changes resulting from infiltration through the vadose zone

Secondary treated wastewater was infiltrated through a 9 m-thick calcareous vadose zone during a 39 month managed aquifer recharge (MAR) field trial to determine potential improvements in the recycled water quality. The water quality improvements of the recycled water were based on changes in the chemistry and microbiology of (i) the recycled water prior to infiltration relative to (ii) groundwater immediately down-gradient from the infiltration gallery. Changes in the average concentrations of several constituents in the recycled water were identified with reductions of 30% for phosphorous, 66% for fluoride, 62% for iron and 51% for total organic carbon when the secondary treated wastewater was infiltrated at an applied rate of 17.5 L per minute with a residence time of approximately four days in the vadose zone and less than two days in the aquifer. Reductions were also noted for oxazepam and temazepam among the pharmaceuticals tested and for a range of microbial pathogens, but reductions were harder to quantify as their magnitudes varied over time. Total nitrogen and carbamazepine persisted in groundwater down-gradient from the infiltration galleries. Infiltration does potentially offer a range of water quality improvements over direct injection to the water table without passage through the unsaturated zone; however, additional treatment options for the non-potable water may still need to be considered, depending on the receiving environment or the end use of the recovered water.

Behaviour and fate of nine recycled water trace organics during managed aquifer recharge in an aerobic aquifer

The fate of nine trace organic compounds was evaluated during a 12month large-scale laboratory column experiment. The columns were packed with aquifer sediment and evaluated under natural aerobic and artificial anaerobic geochemical conditions, to assess the potential for natural attenuation of these compounds during aquifer passage associated with managed aquifer recharge (MAR). The nine trace organic compounds were bisphenol A (BPA), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR), carbamazepine, oxazepam, iohexol and iodipamide. In the low organic carbon content Spearwood sediment, all trace organics were non-retarded with retardation coefficients between 1.0 and 1.2, indicating that these compounds would travel at near groundwater velocities within the aquifer. The natural aerobic geochemical conditions provided a suitable environment for the rapid degradation for BPA, E2, iohexol (half life <1day). Lag-times for the start of degradation of these compounds ranged from <15 to 30days. While iodipamide was persistent under aerobic conditions, artificial reductive geochemical conditions promoted via the addition of ethanol, resulted in rapid degradation (half life <1days). Pharmaceuticals (carbamazepine and oxazepam) and disinfection by-products (NDMA and NMOR) did not degrade under either aerobic or anaerobic aquifer geochemical conditions (half life >50days). Field-based validation experiments with carbamazepine and oxazepam also showed no degradation. If persistent trace organics are present in recycled waters at concentrations in excess of their intended use, natural attenuation during aquifer passage alone may not result in extracted water meeting regulatory requirements. Additional pre treatment of the recycled water would therefore be required.

Benzotriazoles in the Aquatic Environment: a Review of Their Occurrence, Toxicity, Degradation and Analysis

Benzotriazoles (BTs) are an emerging class of environmental pollutants used in a wide range of industrial applications. Benzotriazole (BTri) and 5-methylbenzotriazole (5-MeBT) have recently been detected in water supplies around the world, and are thus attracting the attention of many environmental researchers. The focus of this review is on assessing contemporary methods to detect BTs using high-performance liquid chromatography (HPLC), and providing information regarding their occurrence, degradation and toxicity within the environment.

Fate of N-nitrosomorpholine in an anaerobic aquifer used for managed aquifer recharge: A column study

The fate of N-nitrosomorpholine (NMOR) was evaluated at microgram and nanogram per litre concentrations. Experiments were undertaken to simulate the passage of groundwater contaminants through a deep anaerobic pyritic aquifer system, as part of a managed aquifer recharge (MAR) strategy. Sorption studies demonstrated the high mobility of NMOR in the Leederville aquifer system, with retardation coefficients between 1.2 and 1.6. Degradation studies from a 351 day column experiment and a 506 day stop-flow column experiment showed an anaerobic biologically induced reductive degradation process which followed first order kinetics. A biological lag-time of less than 3 months and a transient accumulation of morpholine (MOR) were also noted during the degradation. Comparable half-life degradation rates of 40-45 days were observed over three orders of magnitude in concentration (200 ng L(-1) to 650 μg L(-1)). An inhibitory effect on microorganism responsible to the biodegradation of NMOR at 650 μg L(-1) or a threshold effect at 200 ng L(-1) was not observed during these experiments.

Aquifer residence times for recycled water estimated using chemical tracers and the propagation of temperature signals at a managed aquifer recharge site in Australia

A prerequisite for minimizing contamination risk whilst conducting managed aquifer recharge (MAR) with recycled water is estimating the residence time in the zone where pathogen inactivation and biodegradation processes occur. MAR in Western Australia’s coastal aquifers is a potential major water source. As MAR with recycled water becomes increasingly considered in this region, better knowledge of applied and incidental tracer-based options from case studies is needed. Tracer data were collected at a MAR site in Floreat, Western Australia, under a controlled pumping regime over a distance of 50xa0m. Travel times for bromide-spiked groundwater were compared with two incidental tracers in recycled water: chloride and water temperature. The average travel time using bromide was 87u2009±u20096xa0days, whereas the estimates were longer based on water temperature (102u2009±u200917xa0days) and chloride (98u2009±u200960xa0days). The estimate of average flow velocity based on water temperature data was identical to the estimate based on bromide within a 25-m section of the aquifer (0.57u2009±u20090.04xa0mxa0day−1). This case study offers insights into the advantages, challenges and limitations of using incidental tracers in recycled water as a supplement to a controlled tracer test for estimating aquifer residence times.RésuméUne condition pour réduire le risque de contamination pendant la réalisation d’une opération de gestion d’aquifère par recharge par des eaux recyclées est l’estimation du temps de résidence dans la zone où ont lieu les phénomènes d’inactivation des pathogènes et de biodégradation. La gestion des aquifères par recharge sur le littoral occidental australien constitue une ressource en eau potentielle majeure. Comme la gestion des aquifères par recharge avec des eaux recyclées est de plus en plus envisagée dans cette région, une meilleure connaissance, à partir d’études de cas, des options appliquées et accessoires basées sur les traceurs est nécessaire. Les données de traçage ont été recueillies sur un site de gestion d’aquifère par la recharge à Floreat, Ouest de l’Australie, sous un régime de pompage contrôlé sur une distance de 50xa0m. Les temps de transfert des eaux souterraines déterminés à partir d’un traçage au bromure ont été comparés avec deux traceurs associés aux eaux recyclées: les chlorures et la température de l’eau. Le temps de transfert moyen d’après les bromures est de 87u2009±u20096xa0jours, les estimations d’après la température de l’eau (102u2009±u200917xa0jours) et les chlorures (98u2009±u200960xa0jours) sont quant à elles plus élevées. L’estimation de la vitesse moyenne d’écoulement d’après les données de température de l’eau est identique à celle basée sur les bromures dans une section de 25xa0m de l’aquifère (0.57u2009±u20090.04xa0m/jour). Cette étude de cas présente une analyse approfondie des avantages, des enjeux et des limites d’utilisation des traceurs associés aux eaux recyclées en tant que complément à un essai de traçage contrôlé destiné à évaluer les temps de résidence en aquifère.ResumenUn prerrequisito para minimizar el riesgo de contaminación mientras se realiza la recarga de gestionada en un acuífero (MAR) con agua reciclada consiste en estimar el tiempo de residencia en la zona donde ocurren procesos de inactivación de patógenos y biodegradación. El MAR en acuíferos costeros de Australia occidental es una fuente potencial importante de agua. Puesto que el MAR con agua reciclada está teniendo cada vez más importancia en esta región, es necesario un mejor conocimiento de las opciones basadas en trazadores tanto aplicados como incidentales a partir de casos de estudio. Se recolectaron datos de trazadores en un sitio MAR en Floreal, Australia Occidental, bajo un régimen de bombeo controlado sobre una distancia de 50xa0m. Los tiempos de tránsito para el agua subterránea con picos de bromuro se compararon con dos trazadores incidentales en el agua de reciclado: cloruro y temperatura del agua. El tiempo de tránsito promedio usando bromuro fue de 87u2009±u20096xa0días, mientras que las estimaciones fueron mayores basadas en la temperatura del agua (102u2009±u200917xa0días) y cloruro (98u2009±u200960xa0días). La estimación de la velocidad media del flujo basada en los datos de temperatura del agua fue idéntica a la estimación basada en el bromuro dentro de una sección de 25xa0m del acuífero (0.57u2009±u20090.04xa0m día−1). Este caso de estudio ofrece un conocimiento profundo sobre las ventajas, desafíos y limitaciones de usar trazadores incidentales en agua reciclada como un suplemento a una prueba de trazador controlado para estimar los tiempos de residencias en el acuífero.摘要采用循环水对管理的含水层进行补给中,减少污染风险的先决条件是估算循环水在出现病原体失活和生物降解过程地带的滞留时间。澳大利亚西部沿海含水层中的管理的含水层补给是一个潜在的主要水源。随着本地区管理的含水层补给采用循环水越来越多,就需要更加了解研究实例中基于实用的、随机的示踪剂选项。在澳大利亚西部Floreat地区一个管理的含水层补给地,收集了控制的抽水条件下50米距离外的示踪剂资料。比较了添加溴化物的地下水和循环水中两种随机示踪剂的运移时间:氯化物和温度。采用溴化物平均运移时间为87u2009±u20096天,而根据温度(102u2009±u200917天)和氯化物(98u2009±u200960天)获得的运移时间较长。根据水温度资料得出的平均水流速度与含水层25米长距离内溴化物得出的水流速度一致(0.57u2009±u20090.04 米天)。采用循环水中随机示踪剂可作为对控制的示踪剂实验的补充,以估算含水层滞留时间,这个研究实例可深入了解其优点、挑战和局限。ResumoUm pré-requisito para minimizar o risco de contaminação enquanto se efetua recarga artificial de aquíferos (RAA) com águas residuais é a estimação dos tempos de residência na zona onde ocorrem processos de inativação e biodegradação de agentes patogénicos. A RAA é uma origem potencial de água importante em aquíferos costeiros da Austrália Ocidental. Como nesta região a RAA com águas residuais é cada vez mais considerada, é necessário ter um melhor conhecimento das opções baseadas em traçadores aplicados e incidentais provenientes de estudos de caso. Em Floreat, Austrália Ocidental, reuniram-se dados de traçadores num local de RAA sob um regime de bombeamento controlado ao longo de uma distância de 50xa0m. Compararam-se os tempos de circulação da água subterrânea marcada com brometo com dois traçadores incidentais de água residual: cloreto e temperatura da água. O tempo médio de circulação utilizando brometo foi de 87u2009±u20096xa0dias, ao passo que as estimativas baseadas na temperatura da água (102u2009±u200917xa0dias) e no cloreto (98u2009±u200960xa0dias) foram superiores. A estimativa da velocidade média de fluxo com base nos dados de temperatura foi idêntica à estimativa baseada em brometo, dentro de uma seção de 25xa0m no aquífero (0.57u2009±u20090.04xa0m dia−1). Este estudo de caso demonstra as vantagens, os desafios e as limitações do uso de traçadores incidentais em águas residuais, de forma complementar aos ensaios de traçadores controlados, para estimar tempos de residência em aquíferos.

Bacterial community and groundwater quality changes in an anaerobic aquifer during groundwater recharge with aerobic recycled water

Managed aquifer recharge offers the opportunity to manage groundwater resources by storing water in aquifers when in surplus and thus increase the amount of groundwater available for abstraction during high demand. The Water Corporation of Western Australia (WA) is undertaking a Groundwater Replenishment Trial to evaluate the effects of recharging aerobic recycled water (secondary treated wastewater subjected to ultrafiltration, reverse osmosis, and ultraviolet disinfection) into the anaerobic Leederville aquifer in Perth, WA. Using culture-independent methods, this study showed the presence of Actinobacteria, Alphaproteobacteria, Bacilli, Betaproteobacteria, Cytophaga, Flavobacteria, Gammaproteobacteria, and Sphingobacteria, and a decrease in microbial diversity with an increase in depth of aquifer. Assessment of physico-chemical and microbiological properties of groundwater before and after recharge revealed that recharging the aquifer with aerobic recycled water resulted in elevated redox potentials in the aquifer and increased bacterial numbers, but reduced microbial diversity. The increase in bacterial numbers and reduced microbial diversity in groundwater could be a reflection of an increased denitrifier and sulfur-oxidizing populations in the aquifer, as a result of the increased availability of nitrate, oxygen, and residual organic matter. This is consistent with the geochemical data that showed pyrite oxidation and denitrification within the aquifer after recycled water recharge commenced.

Soil gas carbon dioxide probe: Laboratory testing and field evaluation

An automated semi-continuous on-line instrument has been developed to measure CO2 gas concentrations in the vadose zone. The instrument uses semi-permeable polymer tubing (CO2 probe) for diffusion based sampling, coupled to an infra red sensor. The system operated automatically by intermittently purging the CO2 probe, which was installed in the vadose zone, with a non-CO2 gas at a low flow rate. The gas exiting the CO2 probe was monitored at the ground surface using a miniature infra red sensor and the response related to the vadose zone soil gas CO2 concentration. The in situ CO2 probes provided a reliable monitoring technique under long-term (18 months) aggressive and dynamic field conditions, with no interference observed from non-CO2 gases and volatile organic compounds. The probes provided data that were comparable to conventional grab sampling techniques without the labour-intensive sample collection and processing associated with these conventional techniques. Also, disturbance to vadose zone CO2 profiles from repeated grab samples during long-term semi-continuous monitoring could potential be reduced by using the diffusion based sampling technique.