Influence of Humic Acid on the Transport and Deposition of Colloidal Silica under Different Hydrogeochemical Conditions

Abstract

Abstract:The transport and deposition of colloids in aquifers plays an important role in managed aquifer recharge (MAR) schemes. Here, the processes of colloidal silica transport and deposition were studied by displacing groundwater with recharge water. The results showed that significant amounts of colloidal silica transport occurred when native groundwater was displaced by HA solution. Solution contains varying conditions of ionic strength and ion valence. The presence of humic acid could affect the zeta potential and size of the colloidal silica, which led to obvious colloidal silica aggregation in the divalent ion solution. Humic acid increased colloidal silica transport by formation of non-adsorbing aqueous phase silica-HA complexes. The experimental and modeling results showed good agreement, indicating that the essential physics were accurately captured by the model. The deposition rates were less than 10 −8 s −1 in deionized water and monovalent ion solution. Moreover, the addition of Ca 2+ and increase of IS resulted in the deposition rates increasing by five orders of magnitude to 10 −4 s −1 . In all experiments, the deposition rates decreased in the presence of humic acid. Overall, the promotion of humic acid in colloidal silica was strongly associated with changes in water quality, indicating that they should receive greater attention during MAR.

Influence of Proteins on Transport of Ferrihydrite Particles Formed during Recharge of Groundwater Containing Fe with Reclaimed Water

“…The Fe-OH groups on the surface of the ferrihydrite were deprotonated at a neutral condition to complex with the organic matter, such as the protein-and humic-like compounds. In addition, most of the protein-and humic-like compounds exhibited negative charges in water [13,36]. Thus, the positively charged ferrihydrite had high affinity to the negatively charged organic matter via electrostatic attraction, resulting in the decrease of COD in the effluent.…”

“…Tosco et al [10] reported that ferrihydrite particles with mean hydrodynamic radius of 106.7 ± 15.5 nm were transported from 5 m to 30 m at an ionic strength of 2-5 mM in European aquifers. Humic acids were abundant in both groundwater and reclaimed water [11], which considerably increased the moving distances of ferrihydrite particles in sand column due to its ready adsorption of humic acids via enhanced electrostatic and steric forces [12,13]. Protein-like compounds, which are a typically dissolved organic matter in reclaimed water [11], have amino groups that bind positively charged particles, thereby enhancing the repelling forces between ferrihydrite particles and porous medium [14].…”

Water Quality Considerations on the Rise as the Use of Managed Aquifer Recharge Systems Widens

“…Such insight can be supported by field monitoring, e.g., by using isotopes to assess the relative contribution of different water types to the recovered water in mixed source MAR systems [20], reveal the mobilization of chromium during infiltration of a desert dune sand aquifer [2], to assess retention times [30], or to study factors that affect clogging by, e.g., air bubbles [19]. Laboratory experiments allow one to focus on specific MAR aspects under well controlled conditions, e.g., to study the factors that affect the extent of removal of emerging compounds such as pharmaceuticals [31], or to assess the conditions that affect the risk of colloid-facilitated contaminant transport [32,33] or industrially produced nano-particles in the infiltrated source water. In addition, numerical modeling allows the assessment of water quantity and quality aspects for a wide range of MAR conditions, which can support the feasibility, design and optimization of MAR application [34].…”

Stability of Artificial Nano‐Hydroxyapatite in the Presence of Natural Colloids: Influence of Steric Forces and Chargeability

“…When ionic strength is increased in solution, nanoparticles are more likely to aggregate due to reduced repulsive forces, which are caused by the compression of the electrical double layer. The effect of divalent cations on nanoparticle stability is greater than that of the monovalent cations, due to higher adsorption and stronger screening effects of divalent cations (Tang and Cheng, 2018; Zhou et al, 2016). Natural dissolved organic matter (DOM) is an important component of soil organic colloids.…”