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Managing brackish RO concentrates
In response to increasing demand for potable water and maximisation of traditional fresh sources of water several public water utilities in South Florida have turned to brackish water desalination with RO (reverse osmosis). The associated challenges with concentrate disposal can limit the use of alternative water sources in inland and coastal communities. The desalination capacity shall be increased by a factor of 2.5 until 2025, and increased recovery efficiency from the current average of 75 percent to about 95 percent will make more water available for use through more effective concentrate management. A study was performed for recommendations for concentrate minimisation of scale forming compounds and for identification of affordable and sustainable treatment technologies. Key components of the study included source water modelling for 14 plants, characterisation and evaluation of treatment schemes, examination of technical and implementation factors, and cost and benefits estimation of the recommended improvements, followed by a pilot study to demonstrate technology feasibility and provide data on costs. Four concentrate minimisation approaches were studied, distillation in a brine concentrator followed either by an evaporation pond or by solids crystallisation, multiple step recovery of pure salts for sale as byproducts, and precipitate softening before secondary RO. Precipitative softening was followed by secondary RO was considered favourable due to lower capital cost and energy consumption. The concentrate from the primary RO was very saline with 11,900 mg/l TDS (total dissolved solids), and contained significant calcium hardness (1,310 mg/l as CaCO3) and magnesium hardness (1,942 mg/l as CaCO3). Stable softening was achievable with lime-soda softening by addition of supplemental soda ash. The secondary RO process demonstrated stable hydraulic performance over a 1-month operation, and no significant decline of the normalised permeate flux was observed, and thus no chemical cleaning was required in this period.
Managing brackish RO concentrates
In response to increasing demand for potable water and maximisation of traditional fresh sources of water several public water utilities in South Florida have turned to brackish water desalination with RO (reverse osmosis). The associated challenges with concentrate disposal can limit the use of alternative water sources in inland and coastal communities. The desalination capacity shall be increased by a factor of 2.5 until 2025, and increased recovery efficiency from the current average of 75 percent to about 95 percent will make more water available for use through more effective concentrate management. A study was performed for recommendations for concentrate minimisation of scale forming compounds and for identification of affordable and sustainable treatment technologies. Key components of the study included source water modelling for 14 plants, characterisation and evaluation of treatment schemes, examination of technical and implementation factors, and cost and benefits estimation of the recommended improvements, followed by a pilot study to demonstrate technology feasibility and provide data on costs. Four concentrate minimisation approaches were studied, distillation in a brine concentrator followed either by an evaporation pond or by solids crystallisation, multiple step recovery of pure salts for sale as byproducts, and precipitate softening before secondary RO. Precipitative softening was followed by secondary RO was considered favourable due to lower capital cost and energy consumption. The concentrate from the primary RO was very saline with 11,900 mg/l TDS (total dissolved solids), and contained significant calcium hardness (1,310 mg/l as CaCO3) and magnesium hardness (1,942 mg/l as CaCO3). Stable softening was achievable with lime-soda softening by addition of supplemental soda ash. The secondary RO process demonstrated stable hydraulic performance over a 1-month operation, and no significant decline of the normalised permeate flux was observed, and thus no chemical cleaning was required in this period.
Managing brackish RO concentrates
Seacord, Thomas (author) / MacNevin, David (author) / Akpoji, Ashie (author) / An, Jeff Huren (author) / Sethi, Sandeep (author) / Munce, Lyle (author) / Elsner, Mark (author)
2010
11 Seiten, 5 Bilder, 4 Tabellen, 15 Quellen
Conference paper
Storage medium
English
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