{"id":5954,"date":"2026-03-18T15:23:54","date_gmt":"2026-03-18T08:23:54","guid":{"rendered":"https:\/\/amco.co.th\/?p=5954"},"modified":"2026-07-20T14:27:48","modified_gmt":"2026-07-20T07:27:48","slug":"legionella-cooling-tower-side-stream-filtration","status":"publish","type":"post","link":"https:\/\/amco.co.th\/en\/legionella-cooling-tower-side-stream-filtration\/","title":{"rendered":"Legionella in Cooling Towers: How We Drove It to Non-Detect \u2014 Honestly"},"content":{"rendered":"\n

Legionella<\/em> is the bacterium behind Legionnaires’ disease, and a warm, scaled cooling tower<\/a> is one of its favourite homes. Most water-treatment vendors will promise to “kill” it with a headline percentage. We’re going to be more careful than that \u2014 because the honest mechanism is both more durable and easier to prove. This guide explains why cooling towers grow Legionella<\/em>, why chemicals alone struggle, and what a real 73-day field trial actually measured: Legionella<\/em> 930 CFU\/mL \u2192 non-detect<\/strong> \u2014 alongside exactly what did not<\/em> change.<\/p>\n\n\n\n

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Table of contents<\/h3>\n\n\n\n
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  1. Why cooling towers grow Legionella<\/li>\n\n\n\n
  2. Why biocide alone struggles<\/li>\n\n\n\n
  3. The honest approach: remove the habitat, then filter<\/li>\n\n\n\n
  4. What the field trial measured<\/li>\n\n\n\n
  5. What this does not<\/em> do<\/li>\n\n\n\n
  6. Is your tower at risk?<\/li>\n\n\n\n
  7. Frequently asked questions<\/li>\n<\/ol>\n\n\n\n
    \n\n\n\n

    1. Why cooling towers grow Legionella<\/h3>\n\n\n\n

    A cooling tower is warm, aerated, and \u2014 over time \u2014 lined with scale and biofilm<\/a>. That combination is close to an ideal Legionella<\/em> habitat. The bacteria don’t live freely in clean water so much as they shelter inside the biofilm and porous scale on tower fill and heat-exchanger surfaces. So the real question isn’t “what chemical kills them in the water?” \u2014 it’s “how do we remove the place they live<\/em>?”<\/p>\n\n\n\n

    2. Why biocide alone struggles<\/h3>\n\n\n\n

    An open cooling tower needs a residual biocide, and it does real work. But biocide is dosed into the water<\/em>, and Legionella<\/em>‘s stronghold is inside<\/em> the scale and biofilm, where dosed chemical penetrates poorly. You can knock down the free-floating organisms and still leave the sheltered population intact to re-seed the loop. That’s why a chemicals-only programme can show good water samples one week and a Legionella<\/em> rebound the next: the habitat was never removed.<\/p>\n\n\n\n

    3. The honest approach: remove the habitat, then filter<\/h3>\n\n\n\n

    The AMCO approach pairs an Aragon APEF field with an AVC self-cleaning side-stream filter. It attacks the habitat rather than promising a field “kill”:<\/p>\n\n\n\n

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    1. Loose formation.<\/strong> The APEF field encourages scale to form as tiny particles suspended in the flowing water<\/em> rather than hardening onto surfaces \u2014 so less new habitat is laid down.<\/li>\n\n\n\n
    2. Filtration.<\/strong> The AVC filter, on a small side loop, continuously captures those particles \u2014 this is where the material (and the organisms riding it) is actually removed<\/strong> from the system.<\/li>\n\n\n\n
    3. Descaling.<\/strong> As the water carries less scale, older scale and its biofilm gradually dissolve back into the water and are filtered out too. The habitat leaves with it.<\/li>\n<\/ol>\n\n\n\n

      A residual biocide stays in the programme. The point is that filtration + habitat removal do the heavy lifting, and the biocide now works on a much cleaner system instead of fighting a sheltered population. We cover the full mechanism in our pillar guide, side stream filtration for cooling towers<\/a>.<\/p>\n\n\n\n

      4. What the field trial measured<\/h3>\n\n\n\n
      \"Field-measured<\/figure>\n\n\n\n

      We ran an APEF + AVC bundle on a live cooling tower for 73 days<\/strong> (circulation 275 m\u00b3\/h, a 20 m\u00b3\/h side stream through an AVC 16L2 filter on a 50-micron screen) and logged the water throughout.<\/p>\n\n\n\n

      Measure<\/th>Before<\/th>After<\/th>Tier<\/th><\/tr><\/thead>
      Legionella<\/em><\/td>930 CFU\/mL<\/td>Not detected<\/td>Measured<\/td><\/tr>
      Suspended solids (TSS)<\/td>136 mg\/L<\/td>~1\u20135 mg\/L<\/td>Measured<\/td><\/tr>
      Turbidity<\/td>29.1 NTU<\/td>0.82 NTU<\/td>Measured<\/td><\/tr>
      Chemical dosing<\/td>baseline<\/td>\u221235% to \u221250%<\/td>Measured<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

      Two honesty notes matter more than the headline:<\/p>\n\n\n\n