Possibilities for Reuse of Calcium Carbonate Pellets from Drinking Water Softening

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1 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 30 th 2017

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

2 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) Godskesen et al. (2012) COWI (2015a,b) Deloitte (2015a,b) 2 DTU Environment, Technical University of Denmark

3 Design of the Softening Process Quartz sand NaOH Limestone Ca(OH) 2 Garnet sand Na 2 CO 3 Waste? Resource? 3 DTU Environment, Technical University of Denmark

4 Methodology Literature review Study trip to the Netherlands Pellet analyses 4 DTU Environment, Technical University of Denmark

5 Possibilities for reuse Particle size Iron Quartz Reactivity Heavy metals Color 5 DTU Environment, Technical University of Denmark

Pellet samples De Beitel Weesperkarpel Thorsbro Solhøj Thorsbro Havdrup Lejre Hoogeveen Seppe Brøndbyvester Dalum Before aeration Dalum After filtration Lindved Marbjerg

6 Pellet samples De Beitel Weesperkarpel Thorsbro Solhøj Thorsbro Havdrup Lejre Hoogeveen Seppe Brøndbyvester Dalum Before aeration Dalum After filtration Lindved Marbjerg Regnemark Brokilde Søndersø Frederiksberg Sand Frederiksberg Limestone Frederiksberg After filtration Frederiksberg After aeration 6 DTU Environment, Technical University of Denmark

7 Chemical Composition A number of ions precipitate with calcium carbonate in the pellets Concentrations depend on influent water quality Iron concentration: mg/kg dry matter Manganese concentration: < mg/kg dry matter Guideline Concentration [mg/kg dry matter] Measured Concentration [mg/kg dry matter] Cadmium (Cd) 3 < Chromium (Cr(VI)) 2 < 0.1 Mercury (Hg) 2 < 0.01 Nickel (Ni) 120 < 1 24 Lead (Pb) 150 < Arsenic (As) 60 < DTU Environment, Technical University of Denmark

8 Reactivity [%] Surface Area and Reactivity Commercial limestone DTU Environment, Technical University of Denmark

Optimizing pellet quality The pellet quality can be optimized by: Implementing softening after filtration (99 % less iron and manganese) Replacing quartz sand

9 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 9 DTU Environment, Technical University of Denmark

10 Perspectives Optimizing softening is complex Capital costs Building footprint Process design Water quality Technology choice Chemical consumption Implementation in waterworks Corrosion By-product reuse Operational costs Environmental effects Health effects 10 DTU Environment, Technical University of Denmark

11 Perspectives Decision Support System Design parameters Technology choice hej Process design Implementation in waterworks By-product reuse Etc. Effects Economy Environment Health Corrosion Water quality Etc. Decision Support 11 DTU Environment, Technical University of Denmark

12 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 12 DTU Environment, Technical University of Denmark

13 Thank you! Camilla Tang References 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: DTU Environment, Technical University of Denmark

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