Permeate quality, advanced oxidation process treatability, and cost for two concentrate treatment technologies to enhance recovery for potable reuse
Han Gu, Julio A. Polanco, Kenneth P. Ishida, Megan H. Plumlee, Michael L. Boyd, Erik Desormeaux, Graham Juby, Mojtaba Farrokh Shad
Abstract
Abstract Closed circuit reverse osmosis (CCRO) and forward osmosis-RO (FO-RO) were evaluated at a pilot scale to generate additional permeate from RO concentrate – achieving a recovery of 61% for CCRO and 35% for FO-RO – at a full-scale advanced water purification facility. This study assessed permeate water quality, suitability of the permeate for treatment by an ultraviolet-advanced oxidation process (UV-AOP), and cost/footprint for a conceptual 10- or 20-mgd system. Both technologies demonstrated inorganic, organic, and microbiological constituent removal suitable for blending with primary RO permeate. Virus challenge testing with MS coliphage demonstrated ≥3.7-log removal by both technologies. Pilot-scale UV/hydrogen peroxide AOP treatment of CCRO or FO-RO permeate yielded similar performance (∼1.4-log N-nitrosodimethylamine removal and ∼0.5-log 1,4-dioxane removal) as the full-scale UV-AOP that treats the RO permeate from the purification facility. The estimated full-scale total unit cost (capital plus operation and maintenance costs) of product water produced by the two technologies was estimated to range from $0.91 to $1.12 per cubic meter, depending on the design flow rate of RO concentrate treated, and is estimated to be similar between the two technologies given the +50%/–30% expected accuracy of the Class 5 cost estimate.