Research in Arizona has thrown more light on what happens to pharmaceutically active compounds (PACs) in reused wastewater which is used for groundwater aquifer recharge via a recharge basin.
Clinton F Williams and JET McLain from the US Arid-Land Agricultural Research Center studied soils at a 28.3 ha facility in Gilbert, Arizona, designed to recharge 15,150 m³/d through recharge basins constructed on native soil.
In a paper to be published in the Journal of Environmental Quality (September/October 2012), the researchers say they targeted their research on ibuprofen, caffeine, carbamazepine, and lincomycin. These compounds can be influential in the build-up of antibiotic resistance in the population.
Colonies of bacteria exposed to PhACs in nature can develop into resistant strains over time, leading to diseases requiring more expensive and toxic medication. PhACs have also been linked to endocrine disruption in humans, affecting hormone glands regulating reproductive growth, metabolism and other essential body functions.
The Gilbert facility averages an infiltration rate of >5 cm/d, resulting in the potential of pharmaceutical compounds leaching to groundwater. One 4 ha basin was selected for spatial sampling of the four PhACs.
The anti-inflammatory compound ibuprofen was measured as below detection limits in all samples. Lincomycin, an antibiotic, showed no net accumulation over the three-year study but had significantly higher concentrations closest to the surface. And the stimulant caffeine, exhibited net accumulation throughout the study, with its greatest concentrations also near the surface.
Carbamazepine is a drug used to treat epilepsy and bipolar disorders. It showed accumulation over the course of the study similar to caffeine, yet had the lowest concentration of the four compounds at a depth of 0-5 cm.
In an article summarizing the research, the US Society of Agronomy quotes Williams’ reaction: “You can look, and you can find these compounds everywhere at very low concentrations. But I’m mostly interested in what we saw happen with carbamazepine. There’s something going on at the surface and that’s what I want to figure out.”
Understanding the low carbamazepine concentrations at the soil surface holds the answers to processes responsible for degrading PhACs leftover from wastewater. This could allow scientists to further increase the sustainability of wastewater reuse for groundwater recharge purposes, while at the same time protecting human health.