Pharma residues from treated municipal wastewater can contaminate groundwater, study finds

A recent study by US Geological Survey (USGS) reveals that pharmaceuticals and other contaminants from treated municipal wastewater can reach shallow groundwater after they are released in the streams.

The report, ‘Riverbank filtration potential of pharmaceuticals in a wastewater-impacted stream’, has been published in the international journal Environmental Pollution.

USGS conducted the study in Iowa at Fourmile Creek, which is a small, wastewater-dominated stream near Des Moines.

The water samples for the study were collected during October and December 2012, during which the creek was facing dry conditions.

While 99% of the stream’s flow comprised wastewater in October, it was reduced to 71% in December.

After analysing samples for 110 pharmaceutical compounds and chemicals, such as personal care products and hormones, the research team found that the dissolved compounds can move around to adjacent groundwater and contaminate the systems.

During the two periods of study, the researchers found that 48 and 61 different pharmaceuticals were present in the stream, downstream of the wastewater discharge point, with concentrations of 7,810 parts-per-trillion.

In addition, the groundwater samples collected at a distance of approximately 20m from the stream bank contain between seven and 18 pharmaceuticals with concentrations as high as 87 parts-per-trillion.

Lead author for the study Paul Bradley said: "Water level measurements obtained during this study clearly show that stream levels drive daily trends in groundwater levels.

"Combined with the detection of pharmaceuticals in groundwater collected several metres away from the stream, these results demonstrate that addition of wastewater to this stream results in unintentional, directed transport of pharmaceuticals into shallow groundwater.

"This research has important implications for the application of bank filtration for indirect water reuse."

Bank filtration is the engineered process of water movement between surface water bodies and wells at short distance. It is usually used to treat surface water for drinking water supply or as a final polishing step before releasing treated wastewater.