USER_GRAPH and EQUILIBRIUM_PHASES

[NicolevJ]

Hi,

To show and calculate the phosphorus removal by P precipitation in waste waters I want to create two different graphs using the keywords Phases, Reaction, Equilibrium_phases and User_Graph.

Graph 1: Showing the SI values vs the pH
Graph 2: Showing the SI values vs the pH while Equilibrium_Phases are defined.

With the following script my Graph 1 takes into account the equilibrium_phases defined later (incorrect graph). If I were to not implement Equilibrium_Phase and the second graph the plot does turn out like desired.

Is there a way to exclude equilibrium phases from my first graph and then include it in my second graph?

I understand that one might think why don't you use the attached graphs as your desired result, but I would like to apply the similair script for different variables and water compositions.

Thank you in advance,
Nicole

Script:

TITLE Nicole Black Water pH Effect
#Black water composition as defined by De Graaff 2010.

PHASES
# Defining phases that are not in the phreeqc.dat database:

ATCP      # Amorphous tricalcium phosphate: Ca3(PO4)2(am2)   from minteq database (from Smith 2003 NIST database, see Gustafsson 2008)
Ca3(PO4)2 = 3 Ca+2 + 2 PO4-3
log_k   -28.25
delta_h   -87       # kJ/mol

TCP      #Via Maņas, NSIT Database 2011
   Ca3(PO4)2 = 3Ca+2 + 2PO4-3
    log_k -32.69
END

SOLUTION  1 Black Water  @De Graaff 2010
-units   mg/l
-temp   20         #
pH      4.8        # 8.8
P       25         # 25 mgPO4-P/l
Amm     286        # 286 mgN/l
K       116        # 116 mg/l
Na      221        # 221 mg/l
Mg      24         # 24 mg/l  = 0.504mmoles
S(6)    31.6      # 31.6
Cl   246      # 246
N(5)   11.4      # 11.4
Ca      54.6       # 54.6 mg/l
Alkalinity    1525  as HCO3    # as HCO3, (is HCO3+CO3- mg/l)

REACTION 1
NaOH
1.4 in 18 steps    #
END
 
USE Solution 1
USE Reaction 1
USER_GRAPH 1   
    -headings       pH TCP Hydroxyapatite ATCP   
    -axis_titles            "pH" "SI"
    -chart_title            "Saturation Index vs. pH"
    -initial_solutions      false
    -axis_scale x_axis       auto auto   # X pH
     -axis_scale y_axis       auto auto     # Y SI
    -connect_simulations    true
-start
10 pH = -LA("H+")
20 GRAPH_X pH
30 GRAPH_Y SI("TCP")
40 GRAPH_Y SI("Hydroxyapatite")
50 GRAPH_Y SI("ATCP")
  -end
END
 
EQUILIBRIUM_PHASES 
ATCP         0 0
Hydroxyapatite        0 0
TCP          0 0 
  USER_GRAPH 2
    -headings               pH TCP Hydroxyapatite  ATCP %P-removal
    -axis_titles            "pH" "SI" "P removal %"
    -chart_title            "Saturation Index vs. pH"
    -initial_solutions      true
    -axis_scale x_axis       auto auto        # pH
    -axis_scale y_axis       auto auto       # SI 
    -axis_scale sy_axis     0 100          # %P removal
    -connect_simulations    true
  -start
 10 pH = -LA("H+")
110 GRAPH_X pH
120 GRAPH_Y SI("TCP")
130 GRAPH_Y SI("Hydroxyapatite")
160 GRAPH_Y SI("ATCP")
180 P0  = 8.081e-04            # initial P concentration
190 GRAPH_SY     ((P0-tot("P"))/P0)*100,    # %P removal
  -end
END

[dlparkhurst]

I don't see anything wrong with your file. If you leave the "END" after USER_GRAPH 1, you get the SIs with USER_GRAPH 1 when there are no reactions with EQUILIBRIUM_PHASES. All SIs monotonically increase.

If you comment the END (#END) then EQUILIBRIUM_PHASES is used and USER_GRAPH 1 shows just the SIs, and USER_GRAPH 2 also shows the percent removal. At pH above 6 TCP form and its SI stays constant at 0.0. The other mineral SIs evolve accordingly with ATCP remaining constant and undersaturated and hydroxyapatitie increasing in SI, but remaining undersaturated.

[NicolevJ]

Hi,

I realized I oversimplified my script I shared (some keywords before USER_GRAPH 2 were missing).
The problem that actually arose when using the non simplified script was that Graph 1 was using the input of Graph 2 as well. Causing double lines in Graph 1 where I didn't want it to do so. I found out that by adding

USER_GRAPH 1
-detach

After the END of USER_GRAPH 1 the double lines don't occur anymore.

I have added the 'correct' simplified script in the attachment.
So future users might benefit from it as well. :)

Have a nice day :)
Nicole

ps: 'correct' being as correct as my knowledge can value