• 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 desorbedand chloride is forced on resin by a high salt concentration solution

Resin

Water

DOC, NO3-

SO42-, 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 mgdSIX 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

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Sulfate Desorption

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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 =

SO42- < 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