cooling tower treatment

1. PT. Supreme Energy
Supreme-Energy Rantau Dedap Cooling Tower
pH Drop Troubleshoot
Rantau Dedap Geothermal Power Plant April 11th 2024

2. Purpose, Process
and Pay Off
 Purpose
Updating the existing condition of pH drop troubleshoot
 Process
Present in SERD site & sent the document to the SERD
team, and Q & A by the Ecolab Team & SEML team
 Pay Off
• Determined the existing & next plan of pH drop
troubleshoot till the pH back to the normal ( pH 6 – 7)
2
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3. CHEMICAL SELECTION
3
Program Type Function
N-7330 Chemistry Control all bacterias, algae and fungi
NON OXIDIZING BIOCIDE = SLOW KILLING BIOCIDE
REQUIRED AT LEAST MAINTAIN IN > 40 PPM FOR 7 HOURS IN SYSTEM

4. CHEMICAL SELECTION
4
Program Type Function
Purate Chemistry Control SOB (sulfur oxidizing bacteria) and minimize sulfur deposition
NEED TO INJECTED AS FAST AS POSSIBLE INTO THE SYSTEM
DOSE WILL REDUCE ONCE THE SOB GROWTH IS MAINTAINED LOW
SPECIFIC SOB TREATMENT PURPOSE

5. CHEMICAL SELECTION
5
Program Type Function
GEO966 Chemistry Enhance biocide penetration and disperse sulfur deposits
NON FOAMING DISPERSANT (DIRECT CONTACT)

6. COOLING TOWER UNIT 1 UP TO DATE WATER CHEMISTRY TREND
6

7. COOLING TOWER UNIT 1 UP TO DATE WATER CHEMISTRY TREND
7
Remarks
 On 3 April 2024, the Blowdown changes from bottom basins opened & the intake
water still to continue filling to the Cooling Tower. From the 3D Trasar 24/7 data
record (update 4 March 2024), the pH level trend start to increasing, conductivity
& ORP start to decreasing. On 1 – 3 April 2023, caustic injection majority focus
supplied into CT Unit 2.
 On 5 April 2024 till now, the pH stable and able to control in desired level as the
KPI target (6.0 – 7.0) and the ORP already back to the normal level in < 200 mV.
 In purpose to keep the good quality of CT water along the operation, the N7330
will be injected regularly to keep the TAB level < 3000 CFU/mL. The purate
injection will be considered if the sulfate increased and the bottom sulfate higher
than the surface sulfate but the dose will be adjusted (low dose) since the
system is majority still cleaned from sludge (as SOB growth media).
 The pH probe 3D Trasar need replacement so the 3D Trasar for pH reading on 9
April 2024 error reading (pH 0.0). The new probe as soon as possible will be sent
ot the site (approximately 20 – 25 April 2024).
 The update manual analysis on 11 April 2024 (10:00 a.m.) are:
 pH portable : 6.54 (Surface), 6.70 (Bottom)
 pH Trasar : - (probe need replacement)
 pH online : 6.52
 Conductivity : 545 us/cm
 TDS : 272 ppm
 Turbidity : 0.18 NTU
 Sulfate: 146 ppm (Surface), 148 ppm (Bottom)
 Nitrate : 0.7 ppm (Surface), 0.5 ppm (Bottom)

8. COOLING TOWER UNIT 2 UP TO DATE WATER CHEMISTRY TREND
8

9. COOLING TOWER UNIT 2 UP TO DATE WATER CHEMISTRY TREND
9
Remarks
 The CT-02 had planned to overflow & water intake filling 2 days (stop on 7 April
2024) but it cannot proceed as planned since the intake line has some problem.
Therefore, along 7 – 10 April 2024 the overflow and water intake filling proceed
with unstable condition (sometimes proceed & sometimes postponed). However,
the normalization of water quality not smooth as CT-01 in previous week. But,
the sulfate level already stop to increase and stagnate in 100 ppm. Regarding
this condition, it not recommended operated CT with low pH in long term, and
the caustic injection should be injected as soon as possible to check the pH
already able to adjust or not yet.
 The caustic already injected today (11 April 2024) and the pH gradually incerases
& will be monitored later tomorrow.
 It recommended to injected the N7330 to control TAB level in CT-02 since it
already more than a week already running without treatment. The purate
injection will be considered if the sulfate increased and the bottom sulfate higher
than the surface sulfate but the dose will be adjusted (low dose) since the
system is majority still cleaned from sludge (as SOB growth media).
 The update manual analysis on 11 April 2024 (10:00 a.m.) are:
 pH portable : 2.79 (Surface), 2.72 (Bottom)
 pH Trasar : 2.77
 pH online : 3.21
 Conductivity : 796 us/cm
 TDS : 398 ppm
 Turbidity : 0.20 NTU
 Sulfate: 100 ppm (Surface), 100 ppm (Bottom)
 Nitrate : 1.0 ppm (Surface), 1.5 ppm (Bottom)

10. MONITORING ANALYSIS & NEXT PLAN RECOMMENDATION
10
MONITORING ANALYSIS
 On 5 April 2024 till now, the pH in CT-01 stable and able to control in desired level as
the KPI target (6.0 – 7.0) and the ORP already back to the normal level in < 200 mV.
 The CT-02 had planned to overflow & water intake filling 2 days (stop on 7 April 2024)
but it cannot proceed as planned since the intake line has some problem. Therefore,
along 7 – 10 April 2024 the overflow and water intake filling proceed with unstable
condition (sometimes proceed & sometimes postponed). However, the normalization
of water quality not smooth as CT-01 in previous week. But, the sulfate level already
stop to increase and stagnate in 100 ppm.
 The caustic in CT-02 already injected today (11 April 2024) and the pH gradually
increases & will be monitored later tomorrow.
NEXT PLAN RECOMMENDATION
 Regarding CT-02 condition, it not recommended operated CT with low pH in long
term, and the caustic injection should be injected as soon as possible to check the
pH already able to adjust or not yet.
 In purpose to keep the good quality of CT01 & CT02 water along the operation, the
N7330 will be injected regularly to keep the TAB level < 3000 CFU/mL. The purate
injection will be considered if the sulfate increased and the bottom sulfate higher
than the surface sulfate but the dose will be adjusted (low dose) since the system is
majority still cleaned from sludge (as SOB growth media).
 With the method proper operation setting & chemical injection method and dose
that adjusted by the new condition of CT basin & water after overhaul, we are
optimistic the pH & other related issue will be able to prevented to occurs or at
least when it occurs the mitigation process already available to maintain back to
the normal condition.

12. APPENDIX

13. WHAT MAKES GEOTHERMAL
COOLING SYSTEM UNIQUE?
13
 MakeUp
 Condensed Geothermal steam – either direct or
indirect
 Presence of H2S, Ammonia, CO2, other
 Quantity of dissolved gases entering tower depends on
quantity of gases in steam and design of NCG removal
system
 Other than dissolved gases, very little other
dissolved salts
 Often have “excess makeup”
 Low cycle of concentration and HTI

14. SULFUR CYCLE IN GEOTHERMAL
COOLING TOWER
14
Sulfur Cycle in Cooling Tower
Chemical Oxidation Biological Oxidation
2H2S+ O2→2S0+2H2O
2S+ 3O2+2H2O→2H2SO4
Naturally occurred & can’t be controlled
S0 is solid insulative material that can hinder the heat
transfer in cooling tower filler by reducing heat transfer
surface area
Acidic in
Nature
Acidic in
Nature
Will also produced biofilm that will also hinder the
heat transfer

15. IMPACT OF UNCONTROLLED SULFUR
CYCLE
15
1C increase in approach temperature ~ 0.017
kg/s/MW increase in specific steam consumption

16. GEOTHERMAL COOLING WATER
TREATMENT STRATEGY
16
Chemical Oxidation Biological Oxidation
Disperse S0 to prevent deposition in
cooling tower filler
Suppress SOB growth
Non-foaming sulfur dispersant Apply correct biocide
Continuous lagging & leading indicator monitoring

17. CHALLENGES IN EXISTING
BIOCONTROL PROGRAM
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Type Issues Impact
Isothiazoline React and deactivated by reduced sulfur
compounds
In-effective to control SOB (rich
enviroment of sulfur)
DBNPA React and deactivated by reduced sulfur
compounds
Not persistent
In-effective to control SOB (rich
enviroment of sulfur)
High treatment cost
Glutaraldehyde React and deactivated by ammonia
High dosage and high cost
In-effective to control bacteria in high
ammonia environment
High treatment cost
Quatamine Foaming High dosage lead to plant performance
issue

18. INTRODUCING PURATE®
18
 Purate® is patented technology of Nalco Water – a precusor, unique blend of salts.
 This technology, when applied to geothermal CT, will act as an enzyme inhibitor for
SOB which affects their assimilation of either H2S, elemental sulfur and sulfate as food.
 Nalco Water Purate® may also consume sulfuric acid in the system from the SOB.

19. NALCO WATER GEOTHERMAL COOLING
TOWER CHEMISTRY SOLUTION
19
Program Function
N-7330 Control all bacterias, algae and fungi
Purate Control SOB (sulfur oxidizing bacteria) and
minimize sulfur deposition
GEO966 Enhance biocide penetration and disperse sulfur
deposits

20. GEOTHERMAL COOLING WATER
MONITORING STRATEGY
20
Lagging Indicator Leading Indicator
Offline Monitoring
Online Monitoring
Water Chemistry
Bacteria Population
Residual dispersant
Approach temperature
Online Monitoring
Specific steam consumption

21. NALCO WATER SULFUR CONTROL
21
Disperse
the Sulfur
Inhibit Bio
Growth
Automation
Non foaming sulfur
dispersant (GEO966) –
Traced & Tagged HSP2
(PURATETM) and
Isothiazoline
3D TRASAR Performance

22. NALCO WATER GEOTHERMAL COOLING
TOWER TOTAL SOLUTION
22
Program Type Function
N-7330 Chemistry Control all bacterias, algae and fungi
Purate Chemistry Control SOB (sulfur oxidizing bacteria) and minimize sulfur deposition
GEO966 Chemistry Enhance biocide penetration and disperse sulfur deposits
3D TRASAR Automation Provide leading indicator for overall treatment & control logic