Aquatic chemistry for engineers

Transcription

1 Water treatment in PHREEQC - Lab December 2011 Peter de Moel - TU Delft Delft University of Technology Challenge the future

2 Course program Introduction Phreeqc (lecture) PHREEQC PHREEQCI - IPHREEQC Drinking water (lab 1a PHREEQC / lab 1b+c Excel)) Chemistry: SI / CCPP / Buffercapacity / Corrosion Engineering: Ionic balance / Conductivity / Mixing Gases in water (lab 2a+b+c Excel) Chemistry: solubility O 2, N 2, CO 2, CH 4 etc Engineering: P*V/T = R / Biodegradation wastewater Hardness and ph (lab 3a+b Excel) Chemistry: acid/base, solubility CaCO 3, FeCO 3, etc Engineering: ph control / Neutralization / Softening 2

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4 Folder Lab 1a Double click Lab 1a.pqi 4

5 Click on Run... On Start On Dismiss 5

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7 Close the application 7

8 What happened? PHREEQC has : Filled the input file (Lab 1a.pqi) with the default database (phreeqc.dat) Created an output file (Lab 1a.pqo) Created an log-file (phreeqc.log) 8

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10 Folder Lab 1a Double click.pqi again Type in Input section: Solution End Click on Run... On Start On Dismiss 10

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13 Folder Lab 1a Double click.pqi again Click on Solution icon 13

14 Folder Lab 1a Double click.pqi again Click on Individual element input Click on Solution icon 14

15 Individual element input Fill in the Solution data Default units: mg/l Alkalinity 188 as HCO3 Ca 38 Cl 28 Mg 5 Na 48 O In tab General ph 7.8 Temperature 11 Click OK 15

16 Look to the input data... You might modify this data direct in this input screen 16

17 and Run this input (file) Click on Run... On Start On Dismiss 17

18 PHREEQC output Input data: mg/l to Molality (mol/kgw) and Moles.. Molality [ ] for Equilibrium HCO 3 - < -- > H + + CO 3 2- K 2 = {H + } {CO 3 2- } / {HCO 3- } { X } = γ [ X ] γ (gamma) = f ( ion, ionic strength ) Moles for Mass balance in input: 1 kg water calculated from Molality 18

19 PHREEQC output.. Description of solutions / Redox couples.. 19

20 PHREEQC output.. Distribution of species.. C(4) = Total CO2 CO2 = 1.26 E-4 = * 44 = 5.5 mg/l HCO3 = 3.02 E-3 = 3.02 * 61 = 184 mg/l Molality ( +log) Activity ( +log) Gamma = Activity coeff. 20

21 PHREEQC output.. Saturation indices Solids SI = log(iap/ks) SI calcite = (precipitate) SI aragonite = (dissolve) Gases SI = log(pa) po2 = 10^SI = 10^-0.68 = 0.21 atm CO2 = atm H2O = p vapour = 0.01 atm 21

22 PHREEQC output In- and output in txt-files (pqi / pqo) Input = *.pqi Output = *.pqo + Log-file = empty (if OK) = errors and messages (if not OK) 22

23 Questions? 23

24 Folder Lab 1b Double click Lab_1b.xlsm requires IPHREEQC COM installed phreeqc_wt.dat in same folder (or other.dat file) macros enabled in Excel 24

25 Module : Drinking water O 2 > 0.1 mg/l No CH 4, no H 2 S All other parameters (in phreeqc_wat.dat) Data from Lab 1a + Conductivity EC / EGV 25

26 Run Control Input Chemistry database Input options File (external) Excel sheet (name) Output options Excel sheet (name) Full output file (T/F) Selected output file (T/F) 26

27 Input 1 - Output control PRINT Alkalinity SELECTED_OUTPUT for table output parameters USER_PUNCH for table output special parameters CALCULATE_VALUES Basic statements 27

28 Input 2 Simulations SOLUTION water quality EQUILIBRIUM_PHASES electron (pe) solids gases REACTION adding chemicals REACTION_TEMPERATURE other temperature 28

29 Output Simulations table output 29

30 phreeqc.out Import of full output-file (to combine all PHREEQC data) 30

31 Results Relevant results Calculations Requirements Graphics 31

32 Drinking water What causes the charge difference? Cations: 4.36 meq/kgw Anions: 3.87 meq/kgw Difference: 0.52 meq/kgw I give you 5 minutes... 32

33 Drinking water What causes the charge difference? Answer: 33

34 Drinking water What causes the charge difference? Missing anion Cation > Anion 0.52 meq/kgw EC measured = 31.2 ms/m > EC calculated = 28.3 ms/m Extra anions 0.52 meq/kgw = NO mmol/kgw 32 mg/l 30.7 ms/m SO mmol/kgw 25 mg/l 30.4 ms/m F mmol/kgw 10 mg/l 30.1 ms/m Most probably: SO4 only 16% of max. content for drinking water 34

35 Drinking water Further output values on Excel Drinking water regulations (Netherlands / SM / CEN) Overall parameters (Cation / Anion / Total hardness / EC etc) Redox conditions (O 2 / pe / redox potential) Analysis correctness checks, acc. Standard Methods 1030E Carbon equilibrium TIC : CO 2 / HCO 3 / CO 3 bufferindex / dph 0.1 mmol HCl/kgw Calcite equilibrium SI calcite, phs CCPP (actual temp / 60 C /90 C) SI of other scaling solids Corrosion indices Major species 35

36 Conclusions - Lessons learned Engineers versus Researchers Engineers use PHREEQC in predesigned Excel versions no PHREEQC programming skills required easy input with normal units etc. additional relevant output data provided Researchers use PHREEQC in predesigned Excel versions in Excel with own program lines in Excel for addional graphs developing Excel for Engineers Original PHREEQCI only for input help / online manual 36

37 Drinking water What causes the charge difference? Further problem: Drinking water P&P: page 225 Note: Cations and Anions are smaller in PHREEQC due to ion-pairs 37

38 Questions? 38

39 Module : Mixing of water (Lab 1c) What is the ph of mixed water? ph : =??? SI : = < 0 Application Drinking water : hard water + soft water Sewerage / wastewater: rain water + domestic wastewater 39

40 Folder Lab 1c Double click Lab_1c.xlsm requires IPHREEQC COM installed phreeqc_wt.dat in same folder (or other.dat file) macros enabled in Excel 40

41 Module : Mixing of water 1: Soft water Ca = 8 mg/l = 0.2 mmol/kgw ph = 9.33 / Alk = 0.4 meq/kgw 2.: Hard water Ca = 80 mg/l = 2 mmol/kgw ph = 7.36 / Alk = 4 meq/kgw Calculate ph and SI: A: 1 = 100% B: 2 = 100 % C: 1 = 2 = 50% I give you 3 minutes... 41

42 Module : Mixing of water Answers 42

43 Module : Mixing of water A: ph = 9.33 / SI = 0 (input 1) B: ph = 7.36 / SI = 0 (input 2) C: ph = 7.45 (not 8.35) SI = (aggressive) CCPP = mmol/kgw CCPP = - aggressive CO 2 aggressive CO 2 = 0.11 mmol/kgw pe not reliable (no redox elements) 43

44 Module : Mixing of water Code for output PRINT SELECTED OUTPUT USER PUNCH CALCULATE_VALUES SOLUTION 1 / 2 / 3 (= math) electron balance MIX # 0.5 of Solution 1 (= mass) # 0.5 of Solution 2 (= mass) EQUILIBRIUM_PHASES (for CCPP) - PHREEQC code 44

45 Conclusions - Lessons learned Redox state Funny pe results PHREEQC and REDOX change in water quality reactions to redox equilibrium To do include a redox couple O 2 for aerobic water CH 4 for anaerobic water Check your PHREEQC results What happend? 45

46 Questions? 46

47 Water treatment in PHREEQC - Lab December 2011 Peter de Moel - TU Delft Delft University of Technology Challenge the future