Role of Soil Biofilms in Clogging and Fate of Pharmaceuticals: A Laboratory-Scale Column Experiment

Abstract

Contamination of groundwater with pharmaceutical active compounds (PhACs) increased over the last decades. Potential pathways of PhACs to groundwater include techniques such as irrigation, managed aquifer recharge, or bank filtration as well as natural processes such as losing streams of PhACs-loaded source waters. Usually, these systems are characterized by redox-active zones, where microorganisms grow and become immobilized by the formation of biofilms, structures that colonize the pore space and decrease the infiltration capacities, a phenomenon known as bioclogging. The goal of this work is to gain a deeper understanding of the influence of soil biofilms on hydraulic conductivity reduction and the fate of PhACs in the subsurface. For this purpose, we selected three PhACs with different physicochemical properties (carbamazepine, diclofenac, and metoprolol) and performed batch and column experiments using a natural soil, as it is and with the organic matter removed, under different biological conditions. We observed enhanced sorption and biodegradation for all PhACs in the system with higher biological activity. Bioclogging was more prevalent in the absence of organic matter. Our results differ from works using artificial porous media and thus reveal the importance of utilizing natural soils with organic matter in studies designed to assess the role of soil biofilms in bioclogging and the fate of PhACs in soils.

Natural attenuation of pharmaceuticals and personal care products percolating through rocky substrates – an example based on the Káraný waterworks

“…The importance of biotransformation and sorption as the most important mechanisms for the natural attenuation of PPCPs is confirmed by several studies (Schaffer et al 2012;Regnery et al 2017). Muñoz-Vega et al (2023) describe the influence of soil biofilms on hydraulic conductivity, reduction and fate of three pharmaceuticals with different physicochemical properties: carbamazepine, diclofenac, and metoprolol; PPCPs that were also recorded in the current study. They observed enhanced adsorption and biodegradation of all pharmaceuticals in the system, with high biological activity both in batch and column experiments.…”

Assessing the Fate of Benzophenone-Type UV Filters and Transformation Products during Soil Aquifer Treatment: The Biofilm Compartment as Bioaccumulator and Biodegrader in Porous Media

“…Biotraps consisted of sandbags packed into a protective plastic mesh. The siliceous sand was the same as the aquifer and was previously muffled for 5 h at 600 °C to remove all sedimentary organic matter (SOM) and to ensure that any observed retention of UVFs in the biotraps was solely attributed to the biofilm, as little interaction with the silica sand was anticipated . Biotraps were installed one month before the test to promote bacterial growth and biofilm formation.…”

“…The siliceous sand was the same as the aquifer and was previously muffled for 5 h at 600 °C to remove all sedimentary organic matter (SOM) and to ensure that any observed retention of UVFs in the biotraps was solely attributed to the biofilm, as little interaction with the silica sand was anticipated. 28 Biotraps were installed one month before the test to promote bacterial growth and biofilm formation. UVFs concentration, bacterial density, and EPS (as an amount of biofilm measurement) were determined in the biotrap samples (see Section 2.3 and S6 in the SI).…”

“…Biodegradation occurs mainly inside the biofilms, which are an assemblage of microorganisms comprising microbial species attached to a surface and encased in a self-synthesized matrix with water and extracellular polymeric substances (EPS). They can act as active sorbents to organic compounds in porous media. , EPS is both positively and negatively charged, favoring the retention of anionic and cationic species. There are also lipids that promote the retention of lipophilic compounds.…”

“…They can act as active sorbents to organic compounds in porous media. 28 , 29 EPS is both positively and negatively charged, favoring the retention of anionic and cationic species. There are also lipids that promote the retention of lipophilic compounds.…”