Heavy metal removal using ion exchange processes

- research projects, approval and application in Germany -

Envirowater 2009

Stellenbosch (04.03.2009)

Dieter Stetter

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Contents

BackgroundHeavy metal removal in drinking water treatmentSelective ion exchangePilot plantsBreakthrough curves + Operating capacityRegenerationApprovalSummary

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Reasons for Nickel Problems

Mobilization of Nickel from subterraneous minerals due to low pH (caused e.g. by acidic rain)

Oxidation of Ni-containing Pyrite (FeS2) in reduced groundwaters by Nitrate (from agricultural fertilizers) an release of Nickel-Ions

Oxidation of Ni-containing Pyrite (FeS2) in mining dump by Oxygen combined with acidification and release of heavy metal ions

Waste water from metal industry (eg. electroplating) contamination surface water

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Oxidation of Pyrite (FeS2) by nitrate

OH52N

57SO2FeH

54NO

514FeS 22

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232 +++⇒++ −++−

Processes in aquifer:

→ Mobilisation of Fe, SO4 and minor Pyrite components (Ni, Co)→ Oxidation and Precepitation of Iron Fe(II) → Fe(III)

Consequences on Water Quality:→ Increase of sulfate concentration→ Increase of heavy metal concentration (Ni, Co)

O2NO3

- SO42- , SM, Fe2+SO42-, SM, H+ SO42- , Ni, Co, As

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Heavy metal guideline values (MCL)

guideline values in µg/l WHO US EPA EC GermanyNickel 70* (20) - 20 20Lead 10 15 10 10Cadmium 3 5 5 5

* revised in 2005

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Nickel in groundwater in the province ofNorth Rhine-Westphalia

Munich

Berlin

Hamburg

Water protectionareas

Cologne

Düsseldorf

IWWMülheim

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Options for Heavy Metal Removal inDrinking Water Treatment

Precipitation / Combined Precipitation-AdsorptionHydroxide, Carbonate / Softening (not specific)Manganese Removal + Adsorption of heavy metals by Manganese Oxides (specific for cations2+)

Membrane processes (not specific)(Nanofiltration, Reverse Osmosis, Electrodialysis)

Sorption processesdifferent sorbentsIon exchange with chelating functional goups(specific for cations2+ )

Ion Exchange with selective resins doesn‘t affect the main ionic composition of drinking water !!

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Ion Exchange Resinfor selective heavy metal removal

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Selective Ion Exchange Resin

Functional group: iminodiacetic acid (e.g. Lewatit TP 207)

resin selectivity (order of removal):copper > lead > nickel > zinc > cadmium > iron(II) > beryllium >

manganese(II) > calcium > magnesium > strontium > barium

R CH2 NCH2COO-

CH2COO-

+ Ni 2+ R CH2 N

CH2COO

CH2COO

NiCa2+ Ca2+

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Pilot Plant using drinking water as feed

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Pilot Plant Scheme (good feed quality)

feed

drinking waterpH = 7.8c(Ni) = 21 µg/Lc(Ca) = 70 mg/L

nickel-dosage

effluent

column1

individualdosage(Ca2+ , H+

Pb2+, Cd2+)

c(Ni): 100 µg/L

c(Ni): < 5 µg/L

column2

Technical data of the pilot plant Columns type 1 Columns type 2OperationResin Bed Dephts (single column)Column Diameter 10 cm (3.9 '') 25 cm (9.8 '')Resin Volume 7.5 Liter (2 gal) 45 Liter (12 gal)Flow rate in bedvolumes per hour 30 - 70 BV/h 35 - 70 BV/hFlow rate in Liters per hour 225 - 525 L/h 1500 - 3150 L/h

downflow, 2 columns in series95 cm (37 '')

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Feed Water Quality

Parameter Unit Drinkingwater

Afterspiking

Temperature °C 10.5

pH-value - 7.8 6.5*

Alkalinity mmol/L 1.9

Calcium mg/L 69 120*

Magnesium mg/L 10

Iron µg/L 3

Manganese µg/L 6

Zinc µg/L 28 110*

Nickel µg/L 21 100**

Cadmium µg/L <1 20*

Lead µg/L <1 20*

*only for selected filter runs, ** for most filter runs

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Break Through Curve (2 columns in series)

0

20

40

60

80

100

120

0 40000 80000 120000 160000

Treated Volume in BV (Bed Volumes)

FeedColumn 1

EffluentColumn 1

Effluentcolumn 2

c(N

i) in

µg/

l

"Breakthrough" at 5 µg/L Ni

Resin Type: Lewatit TP 207Flow rate: 70 BV/h (Bed Volumes per hour)

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Operating Capacity

0,20

0,30

0,40

0,50

0,60

0,70

0,80

30 40 50 60 70 80

Flowrate - Bedvolumes per hour (BV/h)

Ope

ratin

g C

apac

ityeq

per

LR

esin

200 µg/L Ni+ 70 mg/L Ca

100 µg/L Ni+ 70 mg/L Ca

100 µg/L Ni+ 120 mg/L Ca

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Pilot Plants using slightly turbid feed

mud coating of the resin

backwash necessary (each column) remixing the resin per column

lower filtration velocity and lower specific flow in BV/h

EDTA in the feed water (some µg/L)

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Pretreatment and feed water quality

Essen Kettwig : Flocculation/Sedimenation as first step

Essen Überruhr: Flocculation/MSF as first step

Mülheim Styrum: Slow Sand Filtration as first step (manganese)

IWW – Lab: Same ionic composition / no turbidity

Simulating low level pre treatment (low level drinking water quality)

Plant Essen-Kettwig Essen-Überruhr Mülheim-Styrum IWW-Lab

Turbidity ~ 2 FNU ~ 1 FNU 0,1 FNU 0,05 FNUc(EDTA) ~ 7 µg/l ~ 8 µg/l ~ 8 µg/l ~ 3 µg/lBackwash 2 - 3 per week 1 per week 2 per year noBackwash water/air water/air water -

Feed Pilot Plant

DrinkingWater

Effluent Flocculator

Effluent MSF after Ozone Treatment

Effluent Slow Sand Filtration

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Pilot Plants using slightly turbid feed

0,000

0,100

0,200

0,300

0,400

0,500

0 20.000 40.000 60.000 80.000 100.000 120.000

troughput in bedvolumes (BV)

Nic

kel-c

once

ntra

tion

in m

g/l

WTP Kettwig effluent column 1 WTP Kettwig effluent column 2 drinking water effluent column 1 drinking water column 2

c(Ni) feed: 500 µg/l

specific flow: 20 BV/h

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Pilot Plants using slightly turbid feed

Effluent column 1:Nickel leaching from start, slow and constant rising of the concentration up to 0,5 mg/L Nickel

Effluent column 2:Minimum Nickel leaching from start (~ 10 µg/L); further breakthrough not till 100.000 BV

runtime: ~ 7 months or ~ 100,000 BV

oprerating capacity: ~ 0,5 eq/L

Minimum permanent Nickel breakthrough of 10 µg/L caused by EDTA

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Investigation‘s main results

Main influencing factors: Flow rate (BV/h)

Nickel Feed Concentration

Calcium Feed Concentration

complexing agents

Operating time per run: 4 weeks - 8 monthOperating capacity per run: 0.3 - 0.9 eq/LResin

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Further results from special research steps

No increase of the bacterial count of theeffluent

No migration of organics into drinkingwater

Cadmium, lead and zinc are removed in a similar way like nickel

Treatment costs of around 4 - 10 €cent/m³depending on main boundaries

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Regeneration

Backwash

Regeneration (acid)

Neutralization and Conditioning fromH+- to Ca2+-Loading usingCa(OH)2 or NaOH followed by CaCl2

Rinsing to neutral pH

→ Handling of Chemicals→ heavy metal containing

(acidic) brine solution(liquid waste for disposal or treatment)

→ The use of transportable columns and centralized regeneration ist possible for small plants

0

2

4

6

8

10

12

0,0 1,0 2,0 3,0 4,0 5,0

Durchgesetztes spezifisches Volumen in BV

c(N

i) in

g/l

c(Ni)

Bed Volumes of hydrochloric acid (5 %)

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Process steps for Regeneration

Service CycleUptake of

heavy metal ions

Ion Exchanger

Regenerationwith acid / base

Waste

Regeneratecontaining heavy

metals

Disposale.g. hydroxide

sludge

Wastewater

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Mobile columns for external Regeneration

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Established in Leipzig /Eastern Germany

The first small full-scale DWTP in Germany is operatedwith iminodiacetic ion exchangers for nickel removal

regeneration off site

2 x 700 L resin(Lewatit TP 207)

max. 40 m3/h

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Approval Process

IWW and Germany‘s EPA (Umweltbundesamt)accompanied the initial operation phase of 1 year in Leipzig

intensively with a lot of regulated documentation

The results complied with all legal stipulationsGerman drinking water requirements and approval regulations

Selective Ion Exchange is an approved technologie for the removal of nickel in Germany

It is the only specific process being able to remove nickel and otherheavy metals from concentrations far above 100 µg/l down to below 5 µg/l

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Approved Technology

Ion exchange using functional Iminodiacetic Acid groups is now approved in germany as technology for the removal of nickel in drinking water treatment

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Summary

Chelating ion-exchange is a suitable and very efficient process for selective heavy metal removal in drinking water treatment

Very long adsorber runs with high nickel capacity of the resin are possible

Liquid waste volume ≤ 0,01 % of treated volume

No migration of organics into drinking water

No increase of bacterial count in the effluent

The research was funded bythe german ministry of educationand research

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Get in Contact with IWW

IWW Rhenish-Westphalian Institute for Water Research

Moritzstrasse 26D-45476 Muelheim an der Ruhr, Germany

Phone: (+49) (0)208 40303-0, Fax -80 E-Mail: info@iww-online.deInternet: http://www.iww-online.ded.stetter@iww-online.de