NYC’s groundwater system incorporates over 60 wells with a historic capacity in the range of 60-80 mgd. The aquifers below Queens, NY were subject to the impact of a variety of VOCs from decades of industrial activities common in older cities. Although groundwater sampling and modeling has been performed, water quality at each well remains uncertain. Selecting treatment that is appropriate for the anticipated water quality range, maximizes well usage, is cost effective, and provides operations consistency were all considered.
A study was conducted to identify appropriate treatment and the most cost-effective way to bring the inactive wells online to augment the existing water supply when necessary. Treatment for VOCs, iron and manganese, and nitrate may be necessary. GAC adsorption was compared with air stripping to address variable levels of VOCs. GAC was selected because of low capital costs and increased water quality flexibility. Filtration or sequestration was selected to treat iron and manganese. Nitrate will be controlled with blending.
Lessons learned from this large-scale project with more than 60 wells will be valuable to utilities as they grapple to make the most of existing supplies and infrastructure. The treatment methods selected maximize use of existing facilities and historic methods along with flexible processes to produce safe water to augment NYC's existing supplies.
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