TL;DR
Algae and biofilm grow when biocide levels drop below effective concentration. Perform a shock biocide dose, clean the basin, and review the ongoing chemical dosing schedule with your water treatment provider.
What you might see
- green or brown slime visible in basin
- increased pressure drop across fill
- slippery surfaces on tower internals
- elevated turbidity in circulating water
Likely causes
Inadequate or lapsed biocide dosing program allowing microbial growth
High basin temperature and sunlight exposure accelerating algae growth
Nutrient-rich makeup water not treated adequately
Long intervals between blowdown, allowing microorganism concentration to climb
Required tools
- Water test kit (pH, conductivity, biocide residual)
- Chemical splash goggles and face shield
- Nitrile gloves and chemical-resistant apron
- LOTO kit
- Basin cleaning tools (squeegee, brushes)
Safety first
- Legionella bacteria thrive in poorly treated cooling towers. Follow your facility Legionella water management plan.
- Wear chemical splash goggles and nitrile gloves when handling concentrated biocide. Never mix oxidizing and non-oxidizing biocides.
- Check local regulations before discharging chemically treated water to drain.
Procedure
- 1
Notify your water treatment provider before any chemical addition. Follow local regulations for biocide use and discharge.
Warning: Biocide chemicals are hazardous. Wear chemical splash goggles, nitrile gloves, and a face shield when handling concentrated biocide. - 2
Test the current circulating water: measure pH, conductivity, and free biocide residual.
- 3
Lock out the system if a basin cleanout is needed. Drain the basin and remove accumulated sludge and debris manually.[1]
- 4
Flush the fill, basin, and internal surfaces with clean water to remove loosened biofilm.
- 5
Refill the basin and add a shock dose of an approved non-oxidizing biocide per your water treatment provider's recommendation.
- 6
Re-establish the continuous or alternating biocide program. Typical target: maintain measurable biocide residual at all times.
- 7
Increase blowdown rate temporarily to reduce conductivity and flush residual biofilm from the system.[1]
- 8
Retest the circulating water every 24 hours for the next 3 days and confirm biocide residual is within the target range.
Sources
Marley NC Cooling Tower User Manual, Marley Cooling (SPX Cooling Technologies)
Marley NC Cooling Tower Installation, Operation and Maintenance manual, water treatment and basin maintenance procedures (general)
View source
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