Can the Results of Modeling ASR Systems Answer Long-Term Viability Issues?

Abstract

A recent AWWWA survey indicated that there are over 60 aquifer storage and recovery (ASR) projects nation-wide, albeit many of those are in the test phase and not currently operational. Most of the systems are in areas where freshwater is injected into aquifer zones of relatively fresh native water. The limitations for such systems are mostly related to geo-chemical concerns. However, where the freshwater is injected into brackish water, ASR technology is not as well understood as some believe. Questions about the effects of buoyancy on the migration of the water, how well the system will operate over large injection horizons and the effects of the aquifer formation are all issues of concern. The current groundwater modeling software base (MODFLOW) is not sufficient to model ASR systems in brackish environments. As a result the authors have used SEAWAT, a USGS density driven model to look at these effects on some specific ASR systems: Collier County and Ft. Lauderdale in south Florida. Modeling ASR systems successfully can provide a tool for engineers and policy -makers for answering more extensive questions on non-potable ASR systems that might use surface waters or wastewater effluent. These ASR systems will need to answer concerns about nutrients, pathogens and potentially more exotic public health concerns such as endocrine disruptors. Using current Congressional directives to US EPA, may pose serious concerns in the near future despite the current analytical techniques not being available to detect the pharmaceuticals and viruses. The results of the modeling will shed light on limitations identified by the authors over the past several years, and provide some guidance as to their solutions.