SPREADSHEET PROGRAM FOR CALCULATING THE
pH - COAGULANT DOSAGE RELATIONSHIP
Project : EXAMPLE
Date : 01/06/21 Coagulant: Alum
1. INPUT: INSERT INPUT IN DOUBLE-LINED CELLS
Raw Water Characteristics
Specific Alkalinity
Initial Conductance Temp. (mg/L as
pH (µmho/cm) (°C ) CaCO3)
8.2 100 20 100
Commercial Coagulant Solution Characteristics
Basicity Sulfuric Acid Metal Coagulant Use the following concentration (mg metal per microlit
(%) (%) Content Soln. Specific to determine the required volume when adding
(%) Gravity commercial strength coagulant with a microdispenser
0 0 4.3 1.33 mg metal/µL 0.0572
Type of Coagulant (For Fe put 0 in cell, for Al put 1) 1
Calculated Effective Acid Content (EAC) of the Coagulant Solution 0.111 (meq/mg Al)
Flowrate of Water to be Treated
Flowrate (gallons per minute)
694 1 MGD = 694 gpm
Target
pH
8.20 <---------------- INITIAL pH
8.10 (1) Enter interval between pH values, e.g., 0.1 units
8.00 (2) 0.1
7.90 (3)
7.80 (4)
Closed System pH (no exchange of CO2 with atmosphere)
8.5
8.0
7.5
Closed System pH (no exchange of CO2 with atmosphere)
7.70 (5)
7.60 (6) 8.5
7.50 (7)
8.0
7.40 (8)
7.30 (9) 7.5
7.20 (10)
7.10 (11) 7.0
pH
7.00 (12) 6.5
6.90 (13)
6.80 (14) 6.0
6.70 (15)
5.5
6.60 (16)
6.50 (17) 5.0
6.40 (18)
4.5
6.30 (19)
6.20 (20) 4.0
0 2 4 6 8 1
Coagulant dosage (mg metal/L)
2. OUTPUT
Table 1: Coagulant Concentration in Treated Water and Coagulant Solution Feedrate
Coagulant Solution
Target Concentration Feedrate
pH (meq/L) (mg metal/L) (mM) (gal/min) (gal/MG)
-------------- ------------------ ------------------------- -------------- -------------- ---------------
8.20 0.000 0.000 0.000 0.000 0.0
8.10 0.011 0.097 0.004 0.001 1.7
8.00 0.023 0.207 0.008 0.003 3.6
7.90 0.037 0.334 0.012 0.004 5.8
7.80 0.054 0.484 0.018 0.006 8.5
7.70 0.074 0.664 0.025 0.008 11.6
7.60 0.098 0.882 0.033 0.011 15.4
7.50 0.127 1.144 0.042 0.014 20.0
7.40 0.162 1.461 0.054 0.018 25.5
7.30 0.205 1.841 0.068 0.022 32.2
7.20 0.255 2.294 0.085 0.028 40.1
7.10 0.314 2.828 0.105 0.034 49.5
7.00 0.383 3.451 0.128 0.042 60.3
6.90 0.463 4.165 0.154 0.051 72.8
6.80 0.552 4.970 0.184 0.060 86.9
6.70 0.651 5.858 0.217 0.071 102.4
6.60 0.758 6.819 0.253 0.083 119.2
6.50 0.870 7.831 0.290 0.095 136.9
6.40 0.986 8.872 0.329 0.108 155.1
6.30 1.102 9.914 0.367 0.120 173.4
6.20 1.215 10.931 0.405 0.133 191.1
Table 2: Volume of Coagulant Solution
Operational period of: 30 days
Target Volume in Volume in
pH Liters Gallons
------------------- ------------------------- --------------
8.20 0 0.0
8.10 193 51.0
8.00 411 108.5
7.90 663 175.1
7.80 961 253.9
7.70 1,318 348.3
7.60 1,749 462.2
7.50 2,270 599.8
7.40 2,899 765.8
7.30 3,653 965.1
7.20 4,552 1,202.6
7.10 5,612 1,482.8
7.00 6,847 1,809.1
6.90 8,264 2,183.4
6.80 9,861 2,605.2
6.70 11,624 3,071.2
6.60 13,530 3,574.6
6.50 15,539 4,105.4
6.40 17,604 4,651.0
6.30 19,672 5,197.5
6.20 21,690 5,730.6
3. INTERMEDIATE OUTPUT - CHEMISTRY RESULTS
TABLES WITH HYDROGEN ION ACTIVITY {H+}, ESTIMATED IONIC STRENGTH (I),
ACTIVITY COEF. (R), HYDROGEN ION MOLAR CONCENTRATION [H+],
EQUILIBRIUM CONSTANTS (Kw, Ka1, Ka2), IONIZATION FRACTIONS (a1, a2), INITIAL
INORGANIC CARBON CONC. (CT), AND ACID CONCENTRATION NEEDED
TO REACH EACH TARGET pH.
{H+} I R [H+] Kw
-------------- ------------------- ------------------ ------------------------- --------------
6.31E-09 0.0016 0.916 6.89E-09 6.76E-15
-------------- ------------------- ------------------ ------------------------- --------------
Ka1 Ka2 a1 a2 CT (M)
-------------- ------------------- ------------------ ------------------------- --------------
4.03E-07 4.19E-11 0.9782 0.0065 2.02E-03
-------------- ------------------- ------------------ ------------------------- --------------
Acid
Acid Required
New Alk. Required (mg/L as
New {H+} New [H+] New a1 New a2 (eq/L) (meq/L) CaCO3)
-------------- ------------------- ------------------ ------------------------- -------------- -------------- ---------------
6.31E-09 6.89E-09 0.9782 0.0065 2.00E-03 0.000 0.00
7.94E-09 8.67E-09 0.9756 0.0051 1.99E-03 0.011 0.54
1.00E-08 1.09E-08 0.9718 0.0041 1.98E-03 0.023 1.15
1.26E-08 1.37E-08 0.9666 0.0032 1.96E-03 0.037 1.86
1.58E-08 1.73E-08 0.9597 0.0025 1.95E-03 0.054 2.69
2.00E-08 2.18E-08 0.9509 0.0020 1.93E-03 0.074 3.69
2.51E-08 2.74E-08 0.9398 0.0016 1.90E-03 0.098 4.90
3.16E-08 3.45E-08 0.9261 0.0012 1.87E-03 0.127 6.36
3.98E-08 4.35E-08 0.9092 0.0010 1.84E-03 0.162 8.12
5.01E-08 5.47E-08 0.8887 0.0007 1.80E-03 0.205 10.23
6.31E-08 6.89E-08 0.8641 0.0006 1.75E-03 0.255 12.74
7.94E-08 8.67E-08 0.8350 0.0004 1.69E-03 0.314 15.71
1.00E-07 1.09E-07 0.8009 0.0003 1.62E-03 0.383 19.17
1.26E-07 1.37E-07 0.7617 0.0003 1.54E-03 0.463 23.14
1.58E-07 1.73E-07 0.7176 0.0002 1.45E-03 0.552 27.61
2.00E-07 2.18E-07 0.6687 0.0001 1.35E-03 0.651 32.55
2.51E-07 2.74E-07 0.6159 0.0001 1.24E-03 0.758 37.88
3.16E-07 3.45E-07 0.5602 0.0001 1.13E-03 0.870 43.51
3.98E-07 4.35E-07 0.5030 0.0001 1.01E-03 0.986 49.29
5.01E-07 5.47E-07 0.4456 0.0000 8.98E-04 1.102 55.08
6.31E-07 6.89E-07 0.3897 0.0000 7.85E-04 1.215 60.73
centration (mg metal per microliter)
red volume when adding
oagulant with a microdispenser
0.0572
ge of CO2 with atmosphere)
ge of CO2 with atmosphere)
6 8 10 12
osage (mg metal/L)
