Mechanism of chemical-biological composite clogging of aquifer caused by Al(III) and bacteria

This study investigated the chemical-biological clogging problem caused by the combined effect of aluminum trivalent [Al(Ⅲ)] and bacteria during artificial recharge processes. Laboratory-scale percolation experiments were conducted to explore the composite clogging mechanism of aquifers under the coexistence of bacteria and Al(Ⅲ) at the concentration of 0.05, 0.20, and 0.60 mg/L. The results indicate that Al(III) in the recharge water could modify the surface morphology of quartz sand and promote the chemical precipitation of aluminum-containing compounds. The formation of Si—O—Al bonds proves that the addition of Al(III) can cause chemical clogging of the aquifer. Different concentrations of Al(III) in the recharge water have different effects on clogging. Low Al(III) concentrations of 0.05 and 0.20 mg/L alleviate bioclogging by inhibiting effect on bacterial activity, reducing bacterial aggregation, and overall decreasing the proportion of bacterial genera that contribute significantly to bioclogging. In contrast, high Al(III) concentrations of 0.60 mg/L can stimulate bacteria to produce extracellular polymers (EPS), which bridge most dispersed bacteria and aggravate bioclogging. Flake deposits of aluminum-containing compounds and bacterial morphology were observed on quartz sand surface, further proving the role of Al(III) on chemical-biological complex clogging during the recharge processes. This study provides a theoretical basis for optimizing the design and management of the recharge process by improving our understanding of the relationship between Al(III), bacteria, and clogging effects, thus ensuring the sustainable utilization of groundwater.