heavy metal removal using ion exchange processes - envirowater
TRANSCRIPT
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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
24
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: [email protected]: http://[email protected]