Optimization and use of various recharge techniques for reclaimed wastewater at a sensitive site in Glendale, Arizona

摘要

A "leading-edge" aquifer recharge facility (ARF) was designed, permitted, and constructed for the City of Glendale, Arizona to bank reclaimed wastewater for future use. Mounding of water in the shallow aquifer and/or on underlying perching layers and nitrate impacts to groundwater were concerns associated with aquifer quality and operations of nearby facilities (solid waste landfill, gravel mine, and water supply wells). In June 2000, a two-year pilot study began that to date has tested two separate recharge methods: recharge basins and seepage trenches. Provision has also been made for testing vadose zone injection wells. Reclaimed wastewater was delivered at a rate of 16 ML/d and each recharge method was tested and monitored individually and/or collectively to assess the efficiency and sustainability of each method. Nearly 20 monitoring wells and piezometers were installed to measure the rise of the mound beneath the ARF, monitor soil treatment, and track water quality changes. Pilot study results also showed that seepage ponds were effective in returning effluent to the aquifer. The big problem with trenches and vadose zone injection wells is clogging. They may save space, but they may not produce much recharge. Through efficient water level and water quality monitoring, and calibration of a groundwater flow model, the ARF could be utilized to its full capacity (26ML/d) while maintaining a high-level of protection of the aquifer quality and operations of the surrounding facilities.