Emerging Contaminant Migration Between Surface and Subsurface Waters

Low-quality groundwater or a reduction in groundwater supply is causing many states to turn to alternative water sources, including reclamation of stormwater runoff for irrigation and artificial aquifer recharge. However, as with reuse of treated municipal wastewater, a major consideration in the use of stormwater runoff is the potential presence of Pharmaceutically Active Compounds (PhACs), Endocrine Disrupting Compounds (EDCs), and other emerging contaminants. PhACs and EDCs are present in both human and animal waste, and can be transported to stormwater systems through agricultural and municipal operations (e.g., the use of manure as fertilizer, animal-based farming operations using antibiotics, and application of sludge from wastewater treatment plants to land).

 It has been demonstrated that when stormwater management practices are not in place or are not constructed properly (e.g. insufficient depth to groundwater), the quality of receiving surface waters is impacted. Where surface water is discharging to groundwater, groundwater impacts may also be observed. Studies on bank filtration and on-site wastewater treatment systems (e.g. septic systems) have demonstrated the subsurface transport of these compounds, and publications on risks to groundwater quality from urban stormwater infiltration have recommended the use of proper pretreatment. Similarly, if impacted stormwater is reused for irrigation or aquifer recharge, PhACs and EDCs can be released to groundwater, and thus have the potential for discharge to surface water. For these reasons, best stormwater management practices will consider not only potential surface water impacts, but also potential groundwater impacts, and groundwater-surface water interactions.

 In evaluating stormwater management and the potential for stormwater reuse, consideration should be given to the mobility and persistence of PhACs and EDCs, as well the potential for transport from surface water to groundwater and vice versa.