Pretreatment approaches to minimize clogging during managed aquifer recharge with drywells

Authors: EKAMPARAM, ARAVINTH SIVA - Oregon State University; Bradford, Scott; SASIDHARAN, SALINI - Oregon State University

Submitted to: Colloids and Surfaces A: Physicochemical and Engineering Aspects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2025
Publication Date: 7/29/2025
Citation: Ekamparam, A.S., Bradford, S.A., Sasidharan, S. 2025. Pretreatment approaches to minimize clogging during managed aquifer recharge with drywells. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 726(2). Article 137891. https://doi.org/10.1016/j.colsurfa.2025.137891.
DOI: https://doi.org/10.1016/j.colsurfa.2025.137891

Interpretive Summary: The performance of Managed Aquifer Recharge (MAR) is adversely impacted when clays in water clog soil surfaces. Column-scale studies were initiated to better understand and mitigate the influence of various concentrations of clay on clogging in sand. Clogging of the sand was strongly impacted by the concentration of clays in water, with higher clay concentrations producing more rapid clogging and little transport of clay. Replacement of the top sand layer was found to be effective to reduce clogging. Conversely, low clay concentrations produced slow clogging at greater depths. In this case, significant clay transport occurred and sand replacement and flow reversal were not effective approaches to mitigate clogging. Results highlight the need for concentration dependent management practices for clogging. This information will be of interest to scientists, engineers, and managers concerned with controlling clogging during MAR.

Technical Abstract: Managed Aquifer Recharge (MAR) using drywells (DWs) is a promising strategy for groundwater replenishment in arid and semi-arid regions. However, clogging caused by suspended particles (SPs) reduces infiltration efficiency and necessitates effective pretreatment strategies. This study investigates clogging mechanisms and mitigation approaches under constant head conditions (148 cm) using two column configurations: (i) quartz sand only (15 cm) and (ii) quartz sand (9 cm) over gravel (6 cm). Kaolin clay was used as a model SP at three turbidity levels (250, 750, and 1500 FNU) over five cycles. At high turbidity (1500 FNU), straining and hydrodynamic bridging caused severe surface clogging, leading to rapid permeability loss, requiring frequent top-layer replacement. At moderate turbidity (750 FNU), straining and blocking contributed to a gradual permeability decline as retention sites became saturated. Hydrodynamic bridging was also present but less significant than at the highest turbidity. Backflushing was moderately effective but declined in efficiency over repeated cycles. At low turbidity (250 FNU), fine particles migrated deeper into the porous media rather than accumulating at the surface. Electrostatic repulsion limited attachment, but hydrodynamic forces facilitated deeper infiltration, resulting in slow, long-term clogging. These findings highlight the need for turbidity-specific pretreatment strategies. For high turbidity (>750 FNU), frequent surface-layer replacement is necessary. For moderate turbidity (~750 FNU), periodic backflushing can delay clogging but loses effectiveness over time. For low turbidity (~250 FNU), optimized filtration media are essential to prevent deep clogging. This study provides insights for enhancing MAR filtration design and reducing maintenance costs.