Salinity Removal Cost Curves for Small to Medium Size Water Wells and Wastewater Effluents
Authors: Mackey, Erin D.; Seacord, Tom; Stringfield, David; Carlo, Penny
Source: Proceedings of the Water Environment Federation, Technology 2005 , pp. 539-557(19)
Publisher: Water Environment Federation
Abstract:Cost curves were developed to evaluate reverse osmosis (RO) vs. electrodialysis reversed (EDR) (0.1 to 2 mgd) followed by thermal brine concentration and evaporation ponds (10 to 600 gpm). The design conditions that have a significant impact on implementation cost were provided as variables in the cost curves to allow flexibility in case-specific applications of the alternatives.The desalting options were evaluated assuming maximum TDS concentration of 600 mg/L in the groundwater or effluent. The limiting factor for RO recovery was anticipated to be silica. Silica species have limited solubility and can precipitate from the concentrate stream, irreversibly fouling an RO membrane. Silica concentrations were grouped into two categories, <33 mg/L and <55 mg/L, with corresponding RO recoveries of 85% and 70%. The limiting factor for EDR is calcium (dissolved silica is not ionic and so is not removed by EDR). With acid and scale inhibitor added to inhibit calcium carbonate precipitation, EDR is expected to operate at a recovery of 93% with a finished water quality of approximately 65-85 mg/L of TDS, 33-55 mg/L of which would be silica.Specific case studies are presented to determine the most appropriate desalting technology and brine disposal process using the cost curves developed. The results of this effort indicate that although EDR is more expensive to build and operate, the high recovery rates associated with EDR results in a lower project net present value due to the concentrate volume reduction that can be achieved. This is because brine disposal presents the most significant cost for the entire project.
Document Type: Research article
Publication date: 2005-01-01
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