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A detailed summary of RO influent quality is presented in Table 6 for the period of January through October 2012, compared to the specified design influent quality. Both 50th and 90th percentile values are presented. Influent values exceeding the specified design values are indicated in bold. The principal issues indicated by these data are iron and manganese (because of potential oxidation and fouling of the RO membranes), and nitrogen and phosphate species (because of the stringent reclaimed water discharge standards and potential for precipitation of calcium phosphate within the second stage of the RO system). Actual total dissolved solids (TDS) values were significantly less than the design value. Even considering that operating temperatures were generally lower than the 90th percentile design value of 26 °C, the head on the RO feed pumps was more than sufficient to achieve the specified flux and recovery at the observed TDS values.

Table 6

Comparison of RO feedwater quality for 12 January through 22 October 2012 compared to specified design values

 Design
Actual
Parameter, mg/L50th %tile90th %tile50th %tile90th %tile
Ca 20.1 29.7 24.1a 28.1 
Mg 6.6 9.5 7.4 8.9 
Na 161 190 121.6 138 
21.6 31.2 15 16.9 
Ba 0.07 0.12 < 0.01 < 0.01 
Sr 0.08 0.08 < 0.01 0.1 
Al 0.04 0.04 NMb NM 
Fe 0.07 0.11 0.2 0.37 
Mn 0.06 0.06 0.26 0.35 
Alkalinity as CaCO3 146 192 127 151 
Bicarbonate as CaCO3 178 234 155 184 
Cl 158 190 100 117 
SO4−2 72.2 94.4 55.0 65.9 
Fl 0.95 0.95 0.22 0.28 
Br 0.00 0.00 0.26 0.42 
NH3-Nc 0.18 0.18 1.24 2.46 
NO2-N 0.39 0.45 0.00 0.09 
NO3-N 0.70 1.43 0.78 2.19 
Organic nitrogen 2.06 1.27 1.89 1.94 
TN 3.33 3.33 3.91 6.68 
PO4-P 1.00 1.00 2.00 4.45 
TP 1.00 1.00 2.70 4.75 
Si 17.1 17.27 NM NM 
0.22 0.23 NM NM 
Conductivity, uS/cm 1006 1247 758 859 
TDS 644 804 485 554 
Total hardness, as CaCO3 66 111 91 107 
pH, units 7.01 7.00 7.18 7.53 
Temperature, deg C 19 26 17.1 21.2 
Turbidity, NTU NEd NE 0.030 0.080 
SDI, 15-min NE NE 2.4 3.28 
TOC NE NE 13.3 19.5 
Total carbon NE NE 52.6 63.8 
Colour, Pt Co NE NE 51.5 77.1 
UV254, 1/cm NE NE 0.35 0.50 
Chloramines, as NH2Cl 3.0 3.0 1.52 2.14 
Chloramines, as NH3 0.82 0.82 0.50 0.71 
 Design
Actual
Parameter, mg/L50th %tile90th %tile50th %tile90th %tile
Ca 20.1 29.7 24.1a 28.1 
Mg 6.6 9.5 7.4 8.9 
Na 161 190 121.6 138 
21.6 31.2 15 16.9 
Ba 0.07 0.12 < 0.01 < 0.01 
Sr 0.08 0.08 < 0.01 0.1 
Al 0.04 0.04 NMb NM 
Fe 0.07 0.11 0.2 0.37 
Mn 0.06 0.06 0.26 0.35 
Alkalinity as CaCO3 146 192 127 151 
Bicarbonate as CaCO3 178 234 155 184 
Cl 158 190 100 117 
SO4−2 72.2 94.4 55.0 65.9 
Fl 0.95 0.95 0.22 0.28 
Br 0.00 0.00 0.26 0.42 
NH3-Nc 0.18 0.18 1.24 2.46 
NO2-N 0.39 0.45 0.00 0.09 
NO3-N 0.70 1.43 0.78 2.19 
Organic nitrogen 2.06 1.27 1.89 1.94 
TN 3.33 3.33 3.91 6.68 
PO4-P 1.00 1.00 2.00 4.45 
TP 1.00 1.00 2.70 4.75 
Si 17.1 17.27 NM NM 
0.22 0.23 NM NM 
Conductivity, uS/cm 1006 1247 758 859 
TDS 644 804 485 554 
Total hardness, as CaCO3 66 111 91 107 
pH, units 7.01 7.00 7.18 7.53 
Temperature, deg C 19 26 17.1 21.2 
Turbidity, NTU NEd NE 0.030 0.080 
SDI, 15-min NE NE 2.4 3.28 
TOC NE NE 13.3 19.5 
Total carbon NE NE 52.6 63.8 
Colour, Pt Co NE NE 51.5 77.1 
UV254, 1/cm NE NE 0.35 0.50 
Chloramines, as NH2Cl 3.0 3.0 1.52 2.14 
Chloramines, as NH3 0.82 0.82 0.50 0.71 

aBold values represent measured values that exceed corresponding design values.

bNM, not measured.

c50th and 90th percentile NH3-N levels in MBR filtrate prior to ammonia dosing were 0.20 and 3.6 mg/L, respectively.

dNE, none established.

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