1 Reuse of softening pellets for remineralizing desalinated water Li Gao MSc Thesis Presentation

2 Department of Water Management Section Sanitary engineering Contents 1. Introduction 2. Theory 3. Materials and methods 4. Results and discussion 5. Practical consideration 6. Conclusions and recommendations

3 Department of Water Management Section Sanitary engineering 1. Introduction Desalination Membrane filtration process (RO) Thermal processes (MSF)

4 Department of Water Management Section Sanitary engineering Desalinated water pH < 6 Ca 2+ concentration< 0.1mmol/L HCO 3 - concentration< 0.2mmol/L Corrosive and Instable SI= -4<0

5 Department of Water Management Section Sanitary engineering Remineralization Drinking Water Guidelines: <SI< <pH< mmol/L<Ca 2+ <2mmol/L 2. 1mmol/L<HCO Global Water Research Coalition

6 Department of Water Management Section Sanitary engineering Remineralization Alternatives: 1. Dosing chemical solution CaCl 2 and NaHCO 3 CaCl 2 +2NaHCO 3 Ca(HCO 3 ) 2 +2NaCl

7 Department of Water Management Section Sanitary engineering Remineralization Alternatives: 2. Mixing with other water sources Groundwater Desalinated water

8 Department of Water Management Section Sanitary engineering Remineralization Alternatives: 3. Dissolving calcium rich filter material by CO 2 Shell Limestone Softening pellet

9 Department of Water Management Section Sanitary engineering Reuse of softening pellet (1) Pellet softening process Ca 2+ +CO 3 2- CaCO 3

10 Department of Water Management Section Sanitary engineering Reuse of softening pellet (1) Pellet softening process (2) Pellet

11 Department of Water Management Section Sanitary engineering Reuse of softening pellet (1) Pellet softening process (2) Pellet (3) Alternatives ① Dissolution process ② Filtration process

12 Department of Water Management Section Sanitary engineering Reuse of softening pellet (1) Pellet softening process (2) Pellet (3) Alternatives ① Dissolution process ② Filtration process Softening pellet

13 Department of Water Management Section Sanitary engineering Reuse of softening pellet (1) Pellet softening process (2) Pellet (3) Alternatives ① Dissolution process ② Filtration process Softening pellet ③ Combination of dissolution process and filtration process Softening pellet

14 Department of Water Management Section Sanitary engineering 2. Theory (1). Calcium carbonic acid equilibrium

15 Department of Water Management Section Sanitary engineering (2). SI (Saturation Index) SI=0Equilibrium SI<0Corrosion SI>0Scaling

16 Department of Water Management Section Sanitary engineering (3). Henry’s law

17 Department of Water Management Section Sanitary engineering (4). Kinetics of CaCO 3 dissolution process K=0.005 K=0.002

18 Department of Water Management Section Sanitary engineering 3. Materials and methods (1). For dissolution experiments

19 Department of Water Management Section Sanitary engineering (1). For dissolution experiments Bottle of CO 2 Pressure vessel Stirrer

20 Department of Water Management Section Sanitary engineering (1). For dissolution experiments

21 Department of Water Management Section Sanitary engineering (2). For filtration experiments

22 Department of Water Management Section Sanitary engineering (2). For filtration experiments Column Mixing point Pressure vessel

23 Department of Water Management Section Sanitary engineering 4. Results and discussion (1). Results of theoretical calculation Water quality of the chemical solution

24 Department of Water Management Section Sanitary engineering (1). Results of theoretical calculation Water quality of the directly mixed solution

25 Department of Water Management Section Sanitary engineering (1). Results of theoretical calculation Water quality of the directly mixed solution Water quality of the mixed solution in equilibrium state

26 Department of Water Management Section Sanitary engineering (2). Results of dissolution experiments ①. Different diameters lead to limited difference in reaction constant ②. Different pressures do not lead to difference in reaction constant ③. Different dosages of pellets lead to big difference in reaction constant

27 Department of Water Management Section Sanitary engineering (3). Results of filtration experiments

28 Department of Water Management Section Sanitary engineering (3). Results of filtration experiments

29 Department of Water Management Section Sanitary engineering 5. Practical consideration (1). Application of dissolution process (2). Application of filtration process

30 Department of Water Management Section Sanitary engineering (3). Process scheme Sea waterDesalinated water CO 2 Drinking water Limestone Existing: Sea waterDesalinated water CO 2 Ca 2+ HCO 3 - Drinking water Limestone Alternatives: Sea waterDesalinated water CO 2 Ca 2+ HCO 3 - Drinking water Softening pellet

31 Department of Water Management Section Sanitary engineering 6. Conclusions and recommendations (1). Softening pellets can be reused in dissolution process (2). Softening pellets can be reused in filtration process Conclusions Recommendations (1). Investigating the influences of impurities and nuclear sand of softening pellets (3). Kinetics of reaction constants (2). Reuse of chemical solution and nuclear sand in other application

32 Department of Water Management Section Sanitary engineering Thank you for your attention!