SUSTAINING DEVELOPMENT, WHILE MINIMIZING GROUNDWATER WITHDRAWALS BY CONVERTING EXISTING PRODUCTION WELLS TO AQUIFER STORAGE AND RECOVERY

In the Atlantic Coastal Plain Province, conversion of a conventional production well to Aquifer Storage and Recovery (ASR) can enhance sustainable development by extending the service life of the well, mitigating severe water quality problems (salinity, radionuclides, iron,), while minimizing environmental concerns related to groundwater withdrawals. ASR is feasible in many older wells effected by water quality problems. Conversion of problem wells to ASR increases the reliability and security of water supplies, while maintaining the system's original capital investment in the well. Costs of converting production wells to ASR equate to one tenth the cost of installing a new production well or expanding surface water supplies. Conversion of production wells to ASR is useful in addressing water quality problems like elevated salinity or radionuclides. In aquifers exhibiting brackish or saline water, treated drinking water recharged through the ASR well drives the native groundwater away from the well, forming a storage zone of fresh water. After several test cycles, typically 100 percent of the stored water can be recovered with constituents less than the local or Federal standards. Conversion of production wells to ASR affected by elevated iron concentrations offers benefits in the recovery of water with negligible concentrations. Wells at Mount Laurel, Moorestown, and Toms River, New Jersey have been converted to ASR to mitigate problems related to elevated iron concentrations. Pretreatment of recharge water with oxidizing (dissolved oxygen, permanganate) and pH adjustment agents stabilizes iron bearing minerals by developing a ferric oxyhydroxide coating on iron-bearing mineral surfaces. The coating isolates the mineral from reactions with the aquifer environment. Further, the coating is highly sorptive of free iron ions migrating in the groundwater. With the large sorptive capacity of a conditioned storage zone, recovery volumes can exceed recharge volumes by three to six times with low iron (iron < 0.3 mg/L) concentrations.