Use of column experiments to investigate the fate of organic micropollutants – a review

Abstract

Abstract. Although column experiments are frequently used to investigate the transport of organic micropollutants, little guidance is available on what they can be used for, how they should be set up, and how the experiments should be carried out. This review covers the use of column experiments to investigate the fate of organic micropollutants. Alternative setups are discussed together with their respective advantages and limitations. An overview is presented of published column experiments investigating the transport of organic micropollutants, and suggestions are offered on how to improve the comparability of future results from different experiments. The main purpose of column experiments is to investigate the transport and attenuation of a specific compound within a specific sediment or substrate. The transport of (organic) solutes in groundwater is influenced by the chemical and physical properties of the compounds, the solvent (i.e. the groundwater, including all solutes), and the substrate (the aquifer material). By adjusting these boundary conditions a multitude of different processes and related research questions can be investigated using a variety of experimental setups. Apart from the ability to effectively control the individual boundary conditions, the main advantage of column experiments compared to other experimental setups (such as those used in field experiments, or in batch microcosm experiments) is that conservative and reactive solute breakthrough curves can be derived, which represent the sum of the transport processes. There are well-established methods for analyzing these curves. The effects observed in column studies are often a result of dynamic, non-equilibrium processes. Time (or flow velocity) is an important factor, in contrast to batch experiments where all processes are observed until equilibrium is reached in the substrate-solution system. Slight variations in the boundary conditions of different experiments can have a marked influence on the transport and degradation of organic micropollutants. This is of critical importance when comparing general results from different column experiments investigating the transport behavior of a specific organic compound. Such variations unfortunately mean that the results from most column experiments are not transferable to other hydrogeochemical environments but are only valid for the specific experimental setup used. Column experiments are fast, flexible, and easy to manage; their boundary conditions can be controlled and they are cheap compared to extensive field experiments. They can provide good estimates of all relevant transport parameters. However, the obtained results will almost always be limited to the scale of the experiment and not directly transferrable to field scales as too many parameters are exclusive to the column setup. The challenge for the future is to develop standardized column experiments on organic micropollutants in order to overcome these issues.

Occurrence of Pharmaceuticals in Wastewater and Their Interaction with Shallow Aquifers: A Case Study of Horní Beřkovice, Czech Republic

“…Banzhaf et al [14] studied surface water and groundwater interaction and classified selected pharmaceuticals as mobile and sorbing/degradable. According to some studies, the natural attenuation of pharmaceuticals is greatly affected by temperature, redox potential, mineralogy, and sorption ability [15]. Laboratory experiments indicated that sorption is the main attenuation process for pharmaceuticals rather than degradation [16].…”

Design and Construction of Repacked Soil Columns for Measuring Solute Transport, Plant Growth and Soil Biota

“…Soil columns are used widely in studies on the fate and transport of nutrients, pesticides, microbes, and heavy metals (Lewis and Sjöstrom, 2010). Specifically, soil columns have been used in several studies including leaching of pharmaceuticals (Oppel et al, 2004), response of root growth to soil compaction levels (Tracy et al, 2012), dissolved organic carbon and nitrate fluxes (Eykelbosh et al, 2015), fate of organic micropollutants (Banzhaf and Hebig, 2016), and modelling of micropollutants to simulate riverbank filtration (Bertelkamp et al, 2016).…”