Sodium Chloride Removal - WateReuse

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Good variability of salt passage with recycle. Trends are similar to model results but lower sodium calcium high recycle medium recycle low recycle model w/.
Sodium Chloride Removal July 2015

Where we are

TODAY

Many utilities’ ability to reclaim water for irrigation is being adversely impacted by elevated sodium and chloride levels. Brown and Caldwell

2

Local Urban Water/Salt Balance

Comparison of Potable and Reclaimed Water Major Anions and Cations (mg/L) 400 WTP Finished Water

350

WRP MF Effluent

300 250 200 150 100 50 0 HCO3

Cl

SO4

Na

Mg

Ca

Traditional Treatment Approach

Traditional Treatment Approach Benefit

Challenge Reliable, well understood process

Recovery limited by precipitates of carbonates, sulfates, phosphates and silica

Good removal of ions

Must add chemical or blend to re-stabilize product water

Good removal of organics, including emerging contaminants

High TDS concentrate stream that is difficult to treat

What could be… Alternative treatment configurations that: Reduce sodium and chloride levels Reduce cost of chemical addition Reduce cost of concentrate management

Hybrid NFRO

Pilot Test of NF

Salt Passage Characteristics

1

Take advantage of different rejection of multivalent vs. monovalent ions in NF membrane

2

Enrich waste with sodium and chloride

3

Retain hardness, sulfates for re-blending

Pilot Study Set Up

3 membranes tested

with multiple recovery and recycle rates

Membrane B Results 50.0%

Membrane B Cation Salt Passage model w/ recycle

40.0%

high recycle medium recycle

model w/ plug flow

30.0%

sodium

low recycle

20.0%

10.0%

calcium 0.0%

55%

60%

65%

70%

Recovery

75%

80%

Good variability of salt passage with recycle Trends are similar to model results but lower

Membrane C Results Membrane C Cation Salt Passage

Provides adequate sodium and chloride passage but Calcium and Magnesium passage higher than expected

120% 110% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

55%

60%

65%

70%

Recovery

75%

80%

Average Concentrations Constituent

Feed A

Permeate B

C

TOC

2.3

< 0.5