Effect of fulvic acid and Cu(II) on the suspended particles clogging of porous media during artificial recharge

Artificial recharge is an effective technology to solve the problem of groundwater over-exploitation. Clogging of porous media is the bottleneck affecting groundwater recharge. Most studies have focused on the clogging of suspended particles. Few studies focus on the effects of heavy metal ions and humus in recharge water on the physical clogging. This study conducts sand column experiment to explore the influence of fulvic acid, Cu(II) and their coexistence on the suspended particles clogging of porous media. Kaolin (SS group), fulvic acid + kaolin (SS+FA group), fulvic acid + Cu(II) + kaolin (SS+FA+Cu group) are added to recharge water, respectively. The results show that (1) the relative hydraulic conductivity (K’) of SS group, SS+FA group and SS+FA+Cu group decrease to 0.233, 0.095 and 0.182, respectively. The K’ of SS group and SS+FA+Cu group in 0−7.50 cm decrease to below 0.28, while the K’ in the bottom layer (7.50−10.50 cm) decrease to about 0.45, which indicates that 0−7.50 cm of the porous media in SS group and SS+FA+Cu group are severely clogged (0<K’<0.30) and the bottom layer is moderately clogged (0.30<K’<0.60). TheK' of the porous media in SS+FA group among different layers (0−10.50 cm) decrease to below 0.18, which shows that the porous media of SS+FA group in different layers are severely clogged. Compared with the other two experimental groups, the suspended particles in SS+FA group are more likely to migrate into the deeper layer in the sand column. (2) Fulvic acid and Cu(II) can change the particle size, charge and internal hydrogen bonding of the suspended particles, thus affect the clogging process. (3) Compared with SS group, fulvic acid aggravates the clogging of the porous media. The clogging degree of the porous media in SS+FA+Cu group is slighter than that in SS+FA group, which indicates that Cu(II) would alleviate the aggravating effect of fulvic acid on clogging. Exploring the influence mechanism of fulvic acid and Cu(Ⅱ) on porous media clogging can provide a theoretical and scientific basis for the prevention and treatment of porous media clogging in the process of artificial recharge.