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Possibilities for Reuse of Calcium Carbonate Pellets from Drinking Water Softening
Camilla Tang, PhD student
Laure Lopato (HOFOR), Sally Nyberg Kornholt (HOFOR) & Hans-Jørgen Albrechtsen (DTU)
Danish Water Forum
Annual meeting
January 30th 2017
30/01/2017 Danish Water Forum Annual Meeting 2 DTU Environment, Technical University of Denmark
Central Drinking Water Softening
• Mitigate negative effects from water hardness:
– Chemical consumption (soap, detergent)
– Energy consumption and longer lifespan of appliances
• Studies conclude that there are both socio-economic and environmental benefits in households from central drinking water softening
COWI (2011) Deloitte (2015a,b) Godskesen et al. (2012) COWI (2015a,b)
30/01/2017 Danish Water Forum Annual Meeting 3 DTU Environment, Technical University of Denmark
Design of the Softening Process
Quartz sand
Limestone
Garnet sand
Na2CO3
Ca(OH)2
NaOH
Waste? Resource?
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Methodology
• Literature review
• Study trip to the Netherlands
• Pellet analyses
30/01/2017 Danish Water Forum Annual Meeting 5 DTU Environment, Technical University of Denmark
Possibilities for reuse
Reactivity
Particle size Quartz
Heavy metals
Iron
Color
30/01/2017 Danish Water Forum Annual Meeting 6 DTU Environment, Technical University of Denmark
Pellet samples
Hoogeveen
Lindved Brokilde
Brøndbyvester DalumBefore aeration DalumAfter filtration
De Beitel
FrederiksbergSand FrederiksbergLimestone
Marbjerg Regnemark
Seppe
Weesperkarpel
Søndersø
Lejre ThorsbroSolhøj ThorsbroHavdrup
FrederiksbergAfter filtration FrederiksbergAfter aeration
30/01/2017 Danish Water Forum Annual Meeting 7 DTU Environment, Technical University of Denmark
Chemical Composition
• A number of ions precipitate with calcium carbonate in the pellets
• Concentrations depend on influent water quality
• Iron concentration: 22 – 9.300 mg/kg dry matter
• Manganese concentration: < 1 – 996 mg/kg dry matter
Guideline Concentration
Measured Concentration
[mg/kg dry matter] [mg/kg dry matter]
Cadmium (Cd) 3 < 0.05 – 0.09
Chromium (Cr(VI)) 2 < 0.1
Mercury (Hg) 2 < 0.01
Nickel (Ni) 120 < 1 – 24
Lead (Pb) 150 < 2 – 0.84
Arsenic (As) 60 < 1 – 0.99
30/01/2017 Danish Water Forum Annual Meeting 8 DTU Environment, Technical University of Denmark
Surface Area and Reactivity
0
10
20
30
40
50
60
70
80
Reactivity [
%]
Commercial limestone
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Optimizing pellet quality
The pellet quality can be optimized by:
• Implementing softening after filtration (99 % less iron and manganese)
• Replacing quartz sand with crushed pellets or limestone as seeding material
Seeding material:
Sand Seeding
material:
crushed pellets
30/01/2017 Danish Water Forum Annual Meeting 10 DTU Environment, Technical University of Denmark
Perspectives – Optimizing softening is complex
By-product reuse
Capital costs
Environmental effects
Technology choice
Implementation in waterworks
Building footprint
Health effects
Corrosion
Process design Chemical consumption
Water quality
Operational costs
30/01/2017 Danish Water Forum Annual Meeting 11 DTU Environment, Technical University of Denmark
Perspectives – Decision Support System
hej
Design parameters
• Technology choice
• Process design
• Implementation in waterworks
• By-product reuse
• Etc.
Decision Support
Effects
• Economy
• Environment
• Health
• Corrosion
• Water quality
• Etc.
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Conclusions
• Pellets are not waste
• Pellet reuse should be included in the design of the softening process
• A systematic approach for optimizing the softening process is lacking
30/01/2017 Danish Water Forum Annual Meeting 13 DTU Environment, Technical University of Denmark
Thank you!
COWI (2011). Central Blødgøring af Drikkevand. Naturstyrelsen.
COWI (2015a). Miljøvurdering af blødgøring af vand. Nordvand
COWI (2015b). Samfundsøkonomisk screening af blødgøring af vand på Nordvands anlæg. Nordvand
Deloitte (2015a). Samfundsøkonomisk analyse af central blødgøring af vand på Forsyning Ballerups værker – konsekvenser for husholdninger. Forsyning Ballerup
Deloitte (2015b). Samfundsøkonomisk analyse af central blødgøring af vand på Forsyning Ballerups værker – screening af konsekvenser for virksomheder. Forsyning Ballerup
Godskesen, B.; Hauschild, M.; Rygaard, M.; Zambrano, K.; and Albrechtsen, H.-J. (2012). Life cycle assessment of central softening of very hard drinking water. Journal of Environmental Management. 105:83–89.
References
Camilla Tang
E-mail: [email protected]
