Managed aquifer recharge is an effective strategy for urban stormwater management. Chemical ions are normally retained in stormwater and groundwater and may accelerate clogging during the recharge process. However, the effect of water chemistry on physical clogging has not previously been investigated. In this study, we investigated the hydrogeochemical mechanism of saturated porous media clogging in a series of column experiments. The column was packed with river sand and added suspensions of kaolinite particles. Calcium chloride and sodium chloride are used as representative ions to study chemical effects. We found that an increase in ionic strength resulted in retention of kaolinite solids in the column, with a breakthrough peak of C/C0 value of 1 to 0.2. The corresponding hydraulic conductivity decreased with increased solids clogging. Divalent cations were also found to have a greater influence on kaolinite particle clogging than monovalent cations. The enhanced hydrochemical-related clogging was caused by kaolinite solids flocculating and increasing the deposition rate coefficient by 1 to 2 times in high ionic strength conditions. Three clogging mechanisms of kaolinite solids are proposed: surface filtration, inner blocking, and attachment. This study further deepens the understanding of the mechanisms of solids clogging during aquifer recharge and demonstrates the significance of ionic strength on recharge clogging risk assessments.
Abstract Managed aquifer recharge (MAR) is increasingly being adopted to improve water security internationally. However, clogging during MAR remains one of the greatest challenges for sustainable operations. This study examines the effects of iron on biological clogging processes using column experiments and suggests management options. The results indicated that the presence of iron limits the transport of bacteria through the column, and that concentrations <10 mg/L are correlated with increased bacterial growth. Conversely, the increased viscosity of biofilm subsequently limits the transport of iron through the column. Fourier transform infrared spectroscopy and x‐ray photoelectron spectroscopy indicated that large iron‐ Pseudomonas sp. flocs formed which occupied the sand pore spaces. The effect of iron induced chemical clogging was most notable in the initial stage of the experiment while bio‐clogging dominated later. There are many recommended values of iron concentration in water recharge, most of them are advised from the point of pollution perspective. Based on these laboratory results, iron concentrations in recharge water for MAR should be <0.3 mg/L to mitigate clogging effects. Furthermore, using non‐corrodible materials for bore screen and pumps, and avoiding external oxidant inputs should be considered to prevent iron related chemical and biological clogging.
Abstract Many microorganisms are naturally occurring in both recharging water and porous media, and microorganisms will grow and clog the pores of porous media. Porous media show different clogging depth and rate, which depends on the carbon source concentration. The bioclogging depth limit and rate under the effect of the nutrient concentration can be disentangled through column experiments and numerical simulation approaches. We use the TOUGHREACT method‐based on the monod equation of microbial growth to explore the process of microbial growth and permeability change, and correct with experimental results. The experimental results show the influence of nutrient concentration (glucose) on microbial growth and clogging of porous medium, and leads to clogging of porous medium. The clogging rate was defined as the rate of change of hydraulic conductivity with time for quantitative study of bioclogging in our study. Simulated results found that the clogging rate increases 0.035 and 0.00673 (m/d/min) respectively in the glucose concentration range of 0.045–0.6 and 0.6–5 mmol/L, simultaneously, the ultimate clogging depth decreases 18.2 and 1.7 mm respectively in the glucose concentration range of 0.045–0.6 and 0.6–5 mmol/L. The aim of this study was to evaluate the effects of nutrient concentrations on bioclogging and shed light on the establishment of nutrient concentration standards for recharge water during groundwater artificial recharge.
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