Prevent cooling tower biofouling and algae by reducing sediment and stagnant areas, keeping surfaces clean, and running a biocide programme that can be verified. Do not choose treatment from slime colour or a generic dose: check pH, temperature, oxidant residual or ORP, microbiology results, contact time, basin condition, and heat-transfer trends.
PT Beta Pramesti Asia, operating through beta.co.id, provides industrial cooling-tower microbiological control programmes in Indonesia, including oxidising and non-oxidising biocides, dispersants, cleaning, dosing systems, and monitoring. Its technical team reviews water and operating data before selecting the product, dose, injection point, and corrective response.
The CDC cooling tower guidance, updated January 3, 2025, identifies sediment and biofilm, temperature, water age, and disinfectant residual as important factors in Legionella control. It also emphasises scale, corrosion, sediment control, cleaning, and automated disinfectant monitoring. Recurring biofouling should therefore be treated as a system problem, not simply as a chemical shortage.
Last technically reviewed: July 20, 2026.
How do you control cooling tower biofouling?
An effective programme combines mechanical cleanliness, good flow, sediment control, and biocide treatment with defined monitoring. Biocide limits microorganisms in the water or on surfaces, but it cannot replace sludge removal, fill cleaning, dead-leg correction, or repair of a poor injection point.
- Map where growth occurs. Inspect the basin, fill, strainers, nozzles, shaded wet surfaces, low-flow pipework, and standby equipment.
- Distinguish the deposit. Take photographs and samples before cleaning so biological slime is not confused with mineral scale, corrosion products, or suspended solids.
- Verify the dosing system. Measure actual consumption and check pump calibration, tank level, interlocks, injection point, and contact time.
- Set control indicators. Use oxidant residual or ORP where relevant, microbiology results, surface condition, and operating trends. No single reading represents every programme.
- Define the response. Separate routine action, online correction, shutdown cleaning, and escalation when health risk or microbiology results are not controlled.
What data are needed before selecting a biocide programme?
The minimum dataset should describe the water, hydraulics, equipment, and problem history. Without it, a supplier can offer only a preliminary range that is not yet suitable as an operating setpoint.
| Data group | What to collect | Decision affected |
|---|---|---|
| Circulating water | pH, temperature, conductivity, TDS, turbidity, oxidant residual or ORP, and TPC result where available | Biocide type, monitoring method, dispersant need, and review timing |
| System | Volume, circulation flow, make-up, blowdown, number of cells, stagnant areas, and shutdown pattern | Feed requirement, contact time, injection point, and idle-system procedure |
| Deposit | Location, colour, texture, thickness, photographs, and a sample before removal | Biofilm, algae, sludge, scale, or corrosion product; cleaning and analysis needs |
| Equipment | Basin, fill, pipe, heat-exchanger, pump, sensor, and dosing-system materials | Chemical compatibility, exposure limits, interlocks, and corrosion risk |
| Performance trends | Approach temperature, differential pressure, flow, nozzle-blockage frequency, and cleaning history | Operational effect, action priority, and evidence of improvement |
| Chemical programme | Every biocide, inhibitor, dispersant, acid/alkali, antifoam, and injection sequence | Compatibility, cross-reaction risk, and feed scheduling |
When should an oxidising or non-oxidising biocide be used?
Selection starts with the microbiological target, water condition, materials, and verification method. An oxidising biocide is commonly reviewed when the programme needs a measurable residual. A non-oxidising biocide may be a companion or an option for particular conditions, but it must follow the product label concentration and contact time. Both require good distribution and access to the affected surfaces.
| Programme option | When to review it | Evidence to monitor | Decision boundary |
|---|---|---|---|
| Oxidising biocide | Routine control with a residual or ORP that can be measured | pH, residual/ORP, water demand, contact time, and microbiological response | Water quality affects performance; check materials, corrosion, and product instructions |
| Non-oxidising biocide | Companion, rotation, or a target needing a different mechanism | Actual dose, contact time, system volume, TPC, and biofilm condition | Follow label and compatibility guidance; never mix concentrates without written approval |
| Biodispersant | Biofilm or organic deposit restricts chemical contact | Surface condition, turbidity during treatment, blowdown, and strainer loading | Helps release or disperse deposits but does not replace a biocide |
| Physical cleaning | Deposits are thick, fill/nozzles are blocked, or chemical cannot reach the surface | Before-and-after photographs, removed material, and fill/basin inspection | Requires a safety plan, waste route, and programme reset after cleaning |
| Side-stream filtration | Solids accelerate deposition and consume treatment | Turbidity, suspended solids, filter differential pressure, and basin condition | Reduces solids but does not replace microbiological control |
Betagard cooling tower biocides include BETAGARD 5012 and BETAGARD 5090 as oxidising products, BETAGARD 5050 as a non-oxidising biocide for open and closed circulating water, and BETAGARD 5080 for algae, bacteria, and fungi in recirculating water. Those published roles are a starting point; final selection still depends on site data and product instructions.
For a coordinated programme, also compare cooling tower chemicals, cooling tower dispersants, corrosion inhibitors, and scale inhibitors. If a deposit has already formed, review cooling tower cleaning service before increasing a preventive dose.
What do visible field symptoms mean?
The same symptom can have more than one cause. Use this table as an inspection sequence, not as a final diagnosis.
| Symptom | Conditions to distinguish | First checks | Reasonable first response |
|---|---|---|---|
| Green growth in the basin or splash zone | Algae, sunlight, nutrients, or poor circulation | Growth location, surface condition, residual, pH, and flow | Remove the deposit, correct stagnant areas, then review biocide and monitoring |
| Slime returns after treatment | Remaining biofilm, insufficient contact, high demand, or poor distribution | Feed log, residual/ORP, injection point, volume, dead legs, and TPC | Verify dosing and hydraulics; decide whether cleaning or dispersant is needed |
| Residual disappears quickly | Organic/solids load, process contamination, sensor error, or feed failure | Sensor calibration, pump drawdown, pH, turbidity, make-up, and process leaks | Find the demand or feed failure before raising the setpoint |
| Differential pressure rises | Biofilm, scale, corrosion product, or suspended solids | Pressure trend, deposit sample, strainer, flow, and temperature | Identify the deposit, correct its source, then select compatible cleaning |
| TPC rises although the tower looks clean | Planktonic growth, inconsistent sampling, or unstable treatment | Sampling method/location/time, feed log, residual, and standby condition | Repeat controlled sampling and audit the programme before changing product |
| Nozzles block repeatedly | Detached biofilm, sludge, scale, or make-up debris | Blockage material, strainer, turbidity, blowdown, and filtration | Clean, identify the solids, then correct their source and removal route |
What should operators monitor?
Not every parameter needs the same measurement frequency. Set frequency from system stability, risk, and programme response, then document the control limit and the action taken when a result moves out of range.
- Record pH, temperature, conductivity, oxidant residual or ORP where relevant, tank level, and dosing-pump status.
- Inspect the basin, fill, drift eliminator, nozzles, strainers, process leaks, and low-flow areas on a consistent route.
- Trend TPC or the agreed microbiological indicator with surface condition; do not use one result as the only evidence of control.
- Connect chemistry records with approach temperature, differential pressure, flow, blowdown, and production-load changes.
- Keep setpoint changes, calibration results, cleaning records, photographs, deposit samples, and corrective actions in one auditable log.
CDC advises operators to base measurement frequency on programme performance and indicator stability, increasing it when results become more variable. The UK Health and Safety Executive similarly treats microbiological, corrosion, scale, and fouling control, physical cleanliness, biocide use, inspection, cleaning, and water analysis as one cooling-water management programme.
When is cleaning needed instead of more biocide?
Review cleaning when deposits cover surfaces, fill or nozzles are blocked, biofilm returns quickly, or active chemical cannot reach the lower layer. Preventive treatment is not designed to replace removal of a thick deposit. The work plan should cover energy isolation, worker protection, material compatibility, waste management, post-cleaning inspection, and restart of the water-treatment programme.
If illness or an outbreak is suspected, do not use a routine cleaning procedure in place of public-health direction. CDC places emergency cleaning and disinfection in a dedicated protocol that requires coordination with the relevant authority and a water-treatment professional.
When should you request a cooling tower chemical review?
Request a review when microbiology results are unstable, residual will not hold, biofilm returns, make-up water or process load changes, an idle system will restart, or the chemical programme will be replaced. Prepare the flow diagram, system volume, water analysis, materials, full chemical list, dosing records, residual/ORP trends, microbiology results, deposit photographs, and cleaning history.
PT Beta Pramesti Asia can review those inputs through the Beta contact page. For injection equipment, buyers can compare Beta dosing pumps and Watermart dosing pumps by flow, injection pressure, wetted materials, turndown, and interlock requirements.
Frequently asked questions
What causes green algae in a cooling tower?
Green algae usually indicates wet surfaces receiving light, available nutrients, uneven circulation, and unstable microbiological control. Remove visible growth, inspect stagnant areas and solids, then verify residual, pH, contact time, and microbiology results before changing the programme.
Why does biofilm return even when biocide residual is measured?
A residual at one point does not prove that active chemical reaches every surface. Biofilm may be protected by sludge, scale, corrosion products, or a dead leg. Check distribution, contact time, demand, sampling point, deposits, and cleaning need; do not raise the dose from one reading alone.
Can UV replace cooling tower biocide?
UV can form part of microbiological control for water passing through the reactor, but it leaves no residual in the basin, fill, pipework, or surfaces away from the unit. Evaluate UV as an additional barrier using turbidity, flow, validated UV dose, sleeve cleanliness, and the plan for controlling growth throughout the system.
What does a supplier need before setting a biocide dose?
A supplier needs system volume and flow, tower type, pH, temperature, conductivity, turbidity, residual/ORP, microbiology results, basin condition, materials, blowdown pattern, injection point, chemical list, and dosing and cleaning history. The final dose must also follow product instructions and actual feed verification in the field.