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Table 7 summarizes 50th and 90th percentile flux and recovery values for the two RO trains for 2012, indicating that they were generally operated at reasonable flux and recovery values. Analysis of sparingly soluble salts indicated that calcium carbonate, calcium phosphate, barium sulfate, and silica were supersaturated in the RO concentration at 75% recovery for both the 50th and 90th percentile feed water concentrations, but this was controlled by anti-scalant addition (GWF 2012). Analysis of feed water data indicated some concern related to iron precipitation. An analysis of normalized product flow, normalized differential pressure, and normalized salt passage for the entire period of operation (2010 through 2012) indicated little evidence of fouling or increased salt passage (GWF 2012), although it was decided to clean the membranes with both sodium hydroxide and citric acid in mid-2011 to facilitate commissioning of the RO cleaning systems. Biofouling of the RO membranes is controlled by continuous dosing of chloramines which acts to suppress biological growth within the RO system.

Table 7

RO operating conditions for 2012

 50th %tile
90th %tile
TrainFlux (L/m2-hrRecovery (%)Flux (L/m2-hr)Recovery (%)
Train A stage 1 18.1 51.0 19.3 54.0 
Train A stage 2 17.0 49.5 19.1 53.1 
Train A overall 17.8 75.3 19.2 77.8 
Train B stage 1 18.4 53.7 19.9 56.3 
Train B stage 2 16.3 52.1 18.3 53.1 
Train B overall 17.7 77.2 19.1 78.5 
 50th %tile
90th %tile
TrainFlux (L/m2-hrRecovery (%)Flux (L/m2-hr)Recovery (%)
Train A stage 1 18.1 51.0 19.3 54.0 
Train A stage 2 17.0 49.5 19.1 53.1 
Train A overall 17.8 75.3 19.2 77.8 
Train B stage 1 18.4 53.7 19.9 56.3 
Train B stage 2 16.3 52.1 18.3 53.1 
Train B overall 17.7 77.2 19.1 78.5 

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