Water Recycling via Aquifers for Sustainable Urban Water Quality Management: Current Status, Challenges and Opportunities

Aquifer storage and recovery (ASR) refers to injecting freshwater into an aquifer and later withdrawing it. In brackish-to-saline aquifers, density-driven convection and fresh-saline water mixing lead to a reduced recovery efficiency (RE, i.e., the volumetric ratio between recovered potable water and injected freshwater) of ASR. For a layered aquifer, previous studies assume a constant hydraulic conductivity ratio between neighboring layers. In order to reflect the realistic formation of layered aquifers, we systematically investigate 120 layered heterogeneous scenarios with different layer arrangements on multiple-cycle ASR using numerical simulations. Results show that the convection (as is reflected by the tilt of the fresh-saline interface) and mixing phenomena of the ASR system vary significantly among scenarios with different layer arrangements. In particular, the lower permeable layer underlying the higher permeable layer restricts the free convection and leads to the spreading of salinity at the bottom of the higher permeable layer and early salt breakthrough to the well. Correspondingly, the RE values are different among the heterogeneous scenarios, with a maximum absolute RE difference of 22% for the first cycle and 9% for the tenth cycle. Even though the difference in RE decreases with more ASR cycles, it is still non-negligible and needs to be considered after ten ASR cycles. The method to homogenize the layered heterogeneity by simply taking the arithmetic and geometric means of the hydraulic conductivities among different layers as the horizontal and vertical hydraulic conductivities is shown to overestimate the RE for multiple-cycle ASR. The outcomes of this research illustrate the importance of considering the geometric arrangement of layers in assessing the feasibility of multiple-cycle ASR operations in brackish-to-saline layered aquifers.

Section: Introductionmentioning

confidence: 99%

Aquifer Storage and Recovery in Layered Saline Aquifers: Importance of Layer-Arrangements

2021

“…In addition, the infiltrated water might eventually recharge a local or regional groundwater body. From a water management perspective, this process includes significant advantages, such as groundwater level stabilization [3], creating hydraulic barriers against potential seawater intrusion [4], and no need for surface water reservoirs prone to evaporation [5], as well as algae growth [5] or providing breeding ground for mosquitos [6]. Finally, the recharged water can be recovered either on a long-time scale, on a seasonal base, or in case of emergencies [3].…”

Section: Introductionmentioning

confidence: 99%

Numerical and Laboratory Investigations of Closely-Spaced and Joint Infiltration of Precipitation and Treated Waste Water

Händel

Fichtner

Graeber

2019

The closely-spaced infiltration of treated waste water and precipitation water may have advantages when compared to the single infiltration, such as reduction of construction costs and space requirements. Recent numerical works showed the theoretical applicability of this approach. A physical tank experiment has been set-up to study the processes in more detail and provide real data on the water flow as well as the purification potential during infiltration. Various scenarios of treated waste water infiltration with and without precipitation events have been technically realized. These data have then been used to implement a numerical model that supported the review of criteria for a proof of the principal applicability. A joint infiltration set-up is proposed and analyzed after successful evaluation of the closely-spaced, but separated infiltration of treated waste water and precipitation water. Again, both the laboratory and numerical works show the principal applicability of the proposed technique.

“…Stormwater can transport pathogens, nutrients, such as nitrogen, and other contaminants from these surfaces to surrounding water bodies if not properly managed [2]. Engineered infiltration systems (EIS) can promote groundwater recharge and reduce the concentration of contaminants through physical filtration, chemical reactions and biological transformations [3,4]. Biotransformation of nutrients and removal of pathogens is influenced by microbial communities colonizing engineered infiltration systems (EIS), and these processes are not well understood [5].…”

Section: Introductionmentioning

confidence: 99%

Dynamics and Functional Potential of Stormwater Microorganisms Colonizing Sand Filters

Fraser

Yue

Sakowski

et al. 2018

Stormwater management is increasingly relying on engineered infiltration systems (EIS) to reduce the volume and improve the quality of managed stormwater. Yet, EIS in the field will be colonized by a diverse array of environmental microorganisms that change the physiochemical properties of the EIS and provide a habitat for microorganisms with harmful or beneficial qualities. Understanding factors influencing the composition and stability of microbial communities could open up strategies for more efficient management of stormwater. Here, we analyzed the potential pathogenic and metabolic capabilities of stormwater microorganisms colonizing idealized EIS (i.e., sand columns) under laboratory conditions over time. The diversity of microbial communities was analyzed using 16S rRNA gene sequencing, and potential pathogens and denitrifying microbes were identified from taxonomic match to known species. Denitrification potential as determined by nosZ abundance was also assessed with quantitative polymerase chain reaction PCR. Our findings demonstrate that replicate microbial communities colonizing sand columns change in a similar way over time, distinct from control columns and the source community. Potential pathogens were initially more abundant on the columns than in the stormwater but returned to background levels by 24 days after inoculation. The conditions within sand columns select for potential denitrifying microorganisms, some of which were also potential pathogens. These results demonstrate that a diverse suite of stormwater microorganisms colonize sand filters, including a transient population of potential pathogens and denitrifiers. Manipulating the inoculating microbial community of EIS could prove an effective mechanism for changing both potential pathogens and denitrifying bacteria.