Recycling of Salt-Contaminated Stormwater Runoff for Brine Production at Virginia Department of Transportation Road-Salt Storage Facilities

摘要

A large part of the Virginia Department of Transportations (VDOTs) maintenance effort comprises the implementation of its snow removal and ice control program. Earlier research confirmed that VDOT captures significant volumes of salt-laden stormwater runoff at its 300+ salt storage facilities throughout the state and that the disposal options for this water are limited and costly. Although VDOT is implementing recommended management options to reduce the quantity of salt water captured, this research was undertaken to determine the possibility of recycling salt-contaminated stormwater runoff for the purpose of producing brine that can be used for pre-wetting of granular NaCl and direct application. Laboratory and field tests were conducted using bench-scale brine generation equipment. In the laboratory phase, brine was produced using tap water while hydraulic retention times and water temperatures were varied to determine how these changes would affect the quantity and quality of brine production. Stormwater runoff from a storage pond without any previous treatment was used in the field phase to allow a better estimate of the potential effects of stormwater on the quality of the brine generated. Results showed that the optimum conditions for brine production were low hydraulic retention time (high flow rates) and high temperatures. The total suspended solids present in the stormwater runoff did not diminish the quality of the brine in the field tests. Based on historic precipitation and chemical application data, VDOT appears to capture sufficient volumes of water to meet the majority of its potential brine production needs. Further, significant economic benefits can be obtained by applying this recycling strategy, with the greatest benefits resulting from generating brine for both direct application and pre-wetting. Assuming average stormwater volume collection and average total NaCl application, VDOT can save approximately $3 million each year by generating brine for pre-wetting only versus approximately $6.5 million each year by generating brine for the combination of pre-wetting and direct application.