The document describes a unique treatment scenario at the Tempe Water Treatment Plant caused by a historic September monsoon that dropped 3.29 inches of rain. The large rainfall caused acidic runoff which lowered the pH and alkalinity of the raw water source. To address this, plant operators performed lime shock feeding and adjusted lime dosing to carefully raise the pH within regulatory limits. They also implemented a split alum feeding to optimize chemical dosing and precipitation given the low alkalinity and high turbidity of the raw water during this event. Proper calculation and testing of alkalinity and chemical feeding was crucial to effectively manage the water's acidity without overdosing.

1. Phoenix Historic September Monsoon
Rainstorm Causes Unique Treatment
Scenario at Tempe Water Treatment Plant

2. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
2014
6.34"
1984
9.56"
1955
5.99"
1951
6.96"
1946
7.45"
1943
6.15"
1939
7.30"
1911
9.31"
1897
6.03"
1896
7.20"
7th Highest on
Record

3. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
0
0.5
1
1.5
2
2.5
3
3.5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
September 2014 Precipitation
Inches
Trace
3.29”

4. Unique Treatment Scenario at Tempe JGM Water Treatment Plant

5. 0
10
20
30
40
50
9/6/14 9/7/14 9/8/14 9/9/14 9/10/14 9/11/14
Raw Water Quality
NTU
NTU
Unique Treatment Scenario at Tempe JGM Water Treatment Plant
7.3
7.4
7.5
7.6
7.7
7.8
7.9
8
8.1
8.2
9/6/14 9/7/14 9/8/14 9/9/14 9/10/14 9/11/14
Raw Water Quality – Midnights
pH
0
20
40
60
80
100
120
140
160
180
9/6/14 9/7/14 9/8/14 9/9/14 9/10/14 9/11/14
Raw Water Quality - Midnights
Alkalinity
Mg/L

6. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Lime Shock Feeding
Lime Shock Feeding

7. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Alkalinity
ml/g
pH
September 9, 2014
105.6
86.4
73
43
104
87.2
88
71
8.3
8.8
9.3
9.75
9.43
8.49Maximum SDWA pH Level
Time (AM)

8. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Chemical Feeding
Lime shock feeding
Alum feeding:
Normal dose @ dosing
channel - 37 mg/L
Split feed:
35 mg/L @ flume
45 mg/L @ dosing channel


Lime
37-45 mg/L

9. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Managing acidity through adjusting Lime
7.5
8
8.5
9
9.5
10
8:30 8:40 9:00 9:40 10:30 13:30
September 9, 2014
pH Response to Lime Adjustment
pH Maximum SDWA pH Level
Maximum SDWA pH Level
pH
pH
Time (AM)

10. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Preferable Method

11. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Split Feeding
60 NTUs therefore
80 mg/L Alum
required
Split Feed



12. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Given:
 Normal Alum Dose Alum dose  45 mg/L Alum
 Turbidity of 60 NTUs require  80 mg/L Alum
 Residual Alkalinity required for precipitation  30 mg/L

13. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Alkalinity and Alum Efficiency
1 ppm Alum Consumes 0.45 ppm Alkalinity
43 mg/L 180-200 mg/LVs.

14. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Raising Alkalinity

15. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
Managing acidity by calculating Alkalinity & Lime feeding
1. Jar Test / Alkalinity Test
2. Alkalinity Required?
3. Total Alkalinity Required?
4. Alkalinity to Add
5. Lime to Feed?

16. Unique Treatment Scenario at Tempe JGM Water Treatment Plant
What did we learn?
 3.29” rain fell on September 8, 2014
 Little turbidity / Acid rain
 Successfully managed acidity through adjusting lime
 Preferable to perform jar test and calculate alkalinity/lime feeding to
prevent overdosing