This study evaluated regeneration efficiency and optimization in suspended ion exchange (SIX) systems by quantifying resin blinding and its effects on contaminant removal. Researchers investigated the impacts of salt concentration and contact time on desorption during regeneration. Key findings include that higher salt concentrations and longer contact times improved desorption of anions from the resin, and that resin blinding decreased nitrate removal capacity but could be reversed with more thorough regeneration. The results provide insight into optimizing salt use during regeneration of SIX systems for more sustainable water treatment.

1. • Salt consumption during regeneration and the resulting waste
brine have important environmental and economic impacts, thus
requiring a better understanding of chloride use in SIX system
Investigation of Regeneration in Suspended Ion Exchange –
Sustainable Alternative to Conventional Coagulation
Jihyon Im and Dr. James Malley, University of New Hampshire - Erik Koreman, PWN Technologies, Netherlands
Objectives
Background Information
1) Resin Blinding & Its Effects on Removal Performance
Conclusions
1) Evaluate current regeneration efficiency by quantifying resin
blinding and studying its effects on removal performance
2) Investigate optimization of the regeneration process by testing
the effects of salt concentration and contact time
Treatment: anion contaminants are
adsorbed on resin and take the
place of chloride on exchange sites
Regeneration: anions are desorbed
and chloride is forced on resin by a
high salt concentration solution
Resin
Water
DOC, NO3
-
SO4
2-, HCO3
-Cl-
2) Effects of Salt Concentration & Contact Time on Desorption
Future Work
• This research was conducted at and is being applied to a 32 mgd
SIX WTP: Andijk III, PWN Water Company, the Netherlands
• Suspended ion exchange (SIX) can achieve desirable removal of
organic precursors (NOM) and nitrate and thus provide an
alternative to sludge-producing coagulants
• Resin blinding is caused by accumulation of organics and colloidal
matter on resin and can lead to slower removal kinetics and
clogging of the pores
SIX pilot (left); Bench Scale Jar Test & Column Set-ups (right)
SIX Reactors
Lamella
Separator
Regeneration
Vessels
36.2%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 1 2 3 4 5 6 7 8 9 10111213
%Desorption
TotalDesorbedConcentration(g/L)
Regeneration Cycle
DOC Desorption
-10%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
12 g/L 16 g/L 20 g/L
Nitrate %Removal Efficiency
85.3%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
0.8
1.6
2.4
3.2
4
4.8
0 1 2 3 4 5 6 7 8 9 10111213
%Desorption
TotalDesorbedConcentration(g/L)
Regeneration Cycle
Sulfate Desorption
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
12 g/L 16 g/L 20 g/L
DOC %Removal Efficiency
Virgin Pilot Optimized
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 30 60 90 120 150 180
Desorbed(g-DOC/L)
week 1-2
0 30 60 90 120 150 180
week 3-4
0 30 60 90 120 150 180
week 5-6
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30
UVT%
Time (minute)
DOC Desorption vs. Time
16 g Cl-/L (KCl)
16 g Cl-/L (NaCl)
31 g Cl-/L (KCl)
31 g Cl-/L (NaCl)
62 g Cl-/L (KCl)
63 g Cl-/L (NaCl)
DOC Desorption vs. Salt Concentrations
Initial Cl- Concentration (g/L)
• Regenerant volume required for maximum desorption =
SO4
2- < HCO3
- < NO3
- < DOC
• Resin blinding especially deteriorates nitrate removal capacity of resin,
but this effect is reversible through a higher degree of regeneration
• Salt consumption is a key sustainability issue in ion exchange
• This research examined important aspects of SIX and chloride
use including anion desorption preference and resin blinding
• The results from studying operation parameters such as salt
concentration and contact time can assist in efficient salt use
during regeneration
• Influential factors in desorption, such as seasonal
variation and matrix effect, should be further
investigated
• Issues of resin blinding must be addressed for
long-term SIX operation
• Cation exchange should be further tested for
softening to increase overall salt use efficiency