125
No Legionella detected
No Legionella detected
100
75
50
Legionella count (CFU/L) Legionella limit (CFU/L)
25
0
1
3
5
7
9
11 13
15 17
19 21 23 25 27 29 31 33 35 37
39
Number of weeks
Figure 2 Zero Legionella counts before and after implementation of the ClearPoint programme. The dashed green line indicates the beginning of the new programme
refinery could meet its goal of implementing circular water usage solutions and could use grey water consistently as make-up water for cooling and other processes. The first objective, noted in Table 1, was to reduce hypochlorite consumption and decrease the number of times the chemistry needed to be fed to the wastewater system. The KPI for this objective showed outstanding results: hypochlorite consumption in the wastewater treat- ment plant was reduced by 80%, and overall product con- sumption for tertiary treatment was reduced by 75%. Previously, hypochlorite was typically delivered monthly in bulk to a large storage tank, and the unloading process posed a safety risk to employees and the environment. Also, prior to implementing the new programme, hypochlo- rite was fed continuously, resulting in the need for frequent restocking of the storage tank. By decreasing hypochlorite consumption, handling risks decreased, and overall plant safety increased. Figure 1 shows an immediate and contin- uous decrease in hypochlorite consumption after the imple- mentation of the new programme. Improving water quality and increasing the consistency of its quality was the second objective of this application. Water quality was assessed by measuring and tracking
Legionella, e-coli, and total bacteria counts in the make-up water. This refinery had not experienced any issues with Legionella prior to implementing the new programme, and the new specialty chemical team did not measure any positive Legionella counts during this application (see Figure 2 ). Figure 3 shows the total plate counts for the tertiary water at 22°C and 37°C (71.6°F and 98.6°F); most meas- urements were within the specified limits. During a three- week period, indicated by blue shading, the refinery faced operational problems in the clarifier of the wastewater plant that reduced the water quality. When the problem in the clarifier first occurred, total plate counts increased; however, after the team adjusted the biocide dosage, total plate counts quickly decreased. The analyser alerted the refinery personnel and specialty chemical team when a measurement was reported out of bounds so an appropriate adjustment could be made in a timely manner. This rapid response allowed refinery engi- neers to maintain the quality of the wastewater reused as make-up water even during operational problems with the clarifier, which had not been possible previously when the refinery used only hypochlorite. The reduction in
100 , 000
10 , 000
TPC aerobic 22˚C (CFU/mL) TPC aerobic 37˚C (CFU/mL) TPC limit (CFU/mL)
1 , 000
100
10
0
1
3
5
7
9
11 13
15 17
19 21 23 25 27 29 31 33 35 37
39
Number of weeks
Figure 3 Total plate counts from the tertiary system. The dashed green line indicates the beginning of the new biofilm detection and control programme. The blue shaded area denotes issues in the clarifier
47
PTQ Q2 2025
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