0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

0 100 200 300 400

Ca

2+

Dis

pla

ced

(m

g/L

as

Ca

CO

3)

Regenerant Concentration Relative to IX Capacity

NaCl KCl

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

0 100 200 300 400

NO

3 d

isp

lace

d (

mg

/L-N

)

Concentration of Regenerant Relative to IX capacity

KCl NaCl

Overcoming the Challenge of Managing Ion Exchange ResidualsGabe Maul, Treavor Boyer, Environmental Engineering Sciences

Conventional IX Residuals Management Experimental DesignCompare alternative regenerants KHCO3, KCl, and NaHCO3, to NaCl in regeneration and

treatment of a wide variety of contaminants using combined ion exchange.Hypothesis: Ion exchange resins will be regenerated by K+ similarly to Na+, and regenerated by HCO3

- similarly to Cl-.

Expected Contribution to Water Treatment

Improve the sustainability and viability of ion exchange process

Demonstrate synergistic advantages of alternative regeneration and combined ion exchange

Uncover operational challenges with combined ion exchange regeneration

Alternative IX Residuals Management

Remaining Questions1. Combined Ion Exchange Regeneration Pilot

2. Biodegradation with K+ and HCO3-

3. Vegetative tolerance with K+ and HCO3-

Combined Ion Exchange

Treatment Adv.

• Selectively remove

complimentary

anion & cation pairs

• Co-removal when

contaminants

interact: 70% DOC

& 55% hardness

• Easy retrofit

Regeneration Adv.

• Fully utilize

regenerant

• Generate as low

as 50% less

residuals

compared to

individual

• Easy retrofit

+

Treatment:

Ca2+ & NO3-

Na+

Ca2+

Cation IX

_ ___

__++

+

++

+

++

+

NO3-

Cl-Anion IX +++

+++

__

__

_

__ _

_

Na+

Alternative RegenerationK+

Na+ HCO3-

K+ HCO3-

Cl- Na+

Cl- 1. KCl - #1 source of potassium for agricultural crops

2. NaHCO3 – less harmful to humans and ecosystems;

reduced corrosion

3. KHCO3 – combination of benefits

Novel Approach

Results

IX Resin Resin DoseRegeneration

Capacity

Contaminant

Removal Capacity

Cation 0.45 mL/L 0.9 meq/L 45 mg/L Ca as CaCO3

Anion 1.0 mL/L 0.9 meq/L 12.6 mg/L as N

Fig. 2: Regenerant concentrations varying

1x - 300x the resin IX capacity. (For NaCl,

ranges from ~50 – ~15,000 mg/L)

Table 1: IX Dose and Removal Capacity for Regenerating Ca2+/NO3-

exhausted resin

1. Arbitrary resin dose

selected of 1.0 mL/L

3. Check: removal

capacities reasonable

Min. resin capacity

Min. resin capacity

2. Cation dose based

on equivalent

regeneration capacityFig. 1: Start with resin

exhausted with Ca2+ and NO3-

NO3-

+++

+++

NO3-

NO3-

NO3-

NO3-

NO3-

NO3-

Ca2+

_ ___

__

Ca2+

Ca2+Ca2+

Ca2+

Ca2+Ca2+

Do not

interact

Fig. 3: Regeneration Efficiency of NaCl and KCl on

Ca2+ Resin

Fig. 4: Regeneration Efficiency of NaCl and KCl on

NO3- Resin

• ↑ regenerant concentration, ↑ regeneration

• 300x was not concentrated enough to displace all Ca2+

• K+ regenerated Ca2+ resin slightly better than Na+

• Treatment efficiency of K+ expected slightly worse

• 100x was sufficient to displace most NO3-

• Cl- regenerated NO3- similarly with both regenerants

• Fully regenerated resin displaced 20% more NO3 than

minimum capacity � test capacity

• 100x regenerant (5,000 mg/L) will regenerate all NO3- resin, but only 70% of Ca2+ resin

• Can dose higher NO3- resin than Ca resin with similar regeneration

1. Compare regeneration efficiency of HCO3-

to Cl- (with Ca2+/NO3- resin pair)

Upcoming Experiments and Challenges

HCO3- Cl-

CaCO3 (or Ca(HCO3)2) precipitation

• Acidify samples before Ca titration

HCO3- Ca2++

2. Determine treatment efficiency of resin

K+ and HCO3- compared to Na+ and Cl-

_ ___

__

K+

K+

K+K+

K+

K+

K+

+++

+++HCO3

-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

Analyzing K+ and HCO3-

• IC (K+) and either DIC or alkalinity (HCO3-)

Simulate precipitation?

3. Repeat for more contaminants:

Ions Interact: Toxic Pair:

Ca2+/NOM- Cd2+/ClO4-

Cover robustness of IX?

Base on IX functional groups?

• Anion: quaternary ammonium,

phosphonium, sulfonium

• Cation: sulfonic acid, carboxylic acid

Or on major types of contaminants?

• Oxyanions, salts, organics, metals

Experiment Challenge

4. Aquatic toxicity with K+ and HCO3-

5. HCO3 loading to wastewater treatment plant

6. Regenerant reuse after precipitation