{"id":722,"date":"2026-04-20T21:09:49","date_gmt":"2026-04-20T21:09:49","guid":{"rendered":"https:\/\/maritech.org\/?page_id=722"},"modified":"2026-04-20T22:53:14","modified_gmt":"2026-04-20T22:53:14","slug":"threats-legionella-algae-corrosion","status":"publish","type":"page","link":"https:\/\/maritech.org\/?page_id=722","title":{"rendered":"Threats: Legionella, Algae & Corrosion"},"content":{"rendered":"\t\t
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6.Threats: Legionella, Algae & Corrosion<\/span><\/h2>

6.1 Legionella Pneumophila<\/span><\/h3>

Background<\/span><\/h4>

Legionella pneumophila<\/em>\u00a0is a gram-negative, aerobic, rod-shaped bacterium (1\u20132 \u00b5m) and the causative agent of Legionnaires’ disease \u2014 a severe and potentially fatal form of pneumonia \u2014 and the milder Pontiac fever. More than 50 Legionella species are known;\u00a0L. pneumophila<\/em>\u00a0accounts for the majority of human cases.<\/span><\/p>

Legionella is naturally present in surface water and soil, but becomes a public health threat when it colonises man-made water systems where conditions are favourable for explosive growth. The Philadelphia epidemic of July 1976 first brought the bacterium to public attention.<\/span><\/p>

Growth characteristics<\/span><\/h4>
Parameter<\/span><\/th>Value \/ Detail<\/span><\/th><\/tr><\/thead>
Optimal growth temperature<\/span><\/td>32\u201335\u00b0C<\/span><\/td><\/tr>
Growth range<\/span><\/td>20\u201345\u00b0C<\/span><\/td><\/tr>
Inactivation temperature<\/span><\/td>> 60\u00b0C (immediate above 70\u00b0C)<\/span><\/td><\/tr>
Doubling time<\/span><\/td>Approximately 2 hours under optimal conditions<\/span><\/td><\/tr>
Primary infection route<\/span><\/td>Inhalation of contaminated aerosols<\/span><\/td><\/tr>
High-risk groups<\/span><\/td>Elderly, immunocompromised, transplant patients, smokers<\/span><\/td><\/tr>
Survival strategy<\/span><\/td>Protected within biofilm and amoeba hosts<\/span><\/td><\/tr><\/tbody><\/table>

High-risk environments<\/span><\/h4>
  • Cooling towers and HVAC systems in power stations, factories, hotels and hospitals<\/span><\/li>
  • Hot and cold water distribution in large buildings \u2014 particularly dead-end branches<\/span><\/li>
  • Public showers and shower systems not used for extended periods<\/span><\/li>
  • Jacuzzis, spa pools and steam rooms (ideal temperature and aerosol generation)<\/span><\/li>
  • Hospital water systems (particularly high risk for immunocompromised patients)<\/span><\/li>
  • Exhibition and trade fair venues that undergo periodic refurbishment<\/span><\/li>
  • Sediment at the base of tanks and heat exchangers \u2014 calcium scale provides shelter<\/span><\/li><\/ul>

    Conventional control methods and their limitations<\/span><\/h4>
    • Thermal shock disinfection (65\u201370\u00b0C for prescribed durations): energy-intensive; does not reach dead legs; biofilm insulates bacteria<\/span><\/li>
    • Continuous chlorination (3\u20134 mg\/L): suppresses but does not eliminate growth; generates chlorinated by-products; corrosive to some materials<\/span><\/li>
    • UVC irradiation (254 nm): effective for planktonic bacteria; cannot penetrate biofilm<\/span><\/li>
    • Chemical shock disinfection (sodium hypochlorite, hydrogen peroxide, chlorine dioxide): costly; generates disinfection by-products; corrosive at effective concentrations<\/span><\/li><\/ul>

      Physical treatment approach<\/span><\/h4>

      Biofilm formation is the primary mechanism enabling Legionella colonisation in engineered water systems. By eliminating the biofilm substrate, Maritech’s technologies remove the protected environment that allows Legionella to survive, and disinfect by way of copper ionization.<\/span><\/p>

      Supporting research: NCBI studies 19854466 and 19962336; European ECDC Legionella guidelines.<\/span><\/p>

      “Prevention is the key to an effective solution.” \u2014 A reactive approach to Legionella is always more costly and disruptive than a continuous physical prevention strategy.<\/span><\/p><\/blockquote>

      6.2 Algae<\/span><\/h3>

      Overview<\/span><\/h4>

      Algae are photosynthetic microorganisms that have existed for over 3.8 billion years. With over 300,000 known species (of which only ~30,000 have been studied), they represent extraordinary biological diversity. While algae are valuable as a potential biofuel and oxygen-producing resource, uncontrolled growth in industrial and recreational water systems is a serious problem.<\/span><\/p>

      Classification by pigment<\/span><\/h4>
      Type<\/span><\/th>Scientific name<\/span><\/th>Notes<\/span><\/th><\/tr><\/thead>
      Green algae<\/span><\/td>Chlorophyceae<\/span><\/td>Most common in freshwater systems<\/span><\/td><\/tr>
      Brown algae<\/span><\/td>Phaeophyceae<\/span><\/td>Macroalgae (seaweeds) \u2014 up to 30 m length<\/span><\/td><\/tr>
      Red algae<\/span><\/td>Rhodophyceae<\/span><\/td>Can cause ‘red tide’ events<\/span><\/td><\/tr>
      Blue-green algae<\/span><\/td>Cyanobacteria<\/span><\/td>Toxic; produces Microcystis. Swimming prohibited above 20 \u00b5g\/L<\/span><\/td><\/tr>
      Black algae<\/span><\/td>Various<\/span><\/td>Pigmented secretions; highly adherent to surfaces<\/span><\/td><\/tr>
      Yellow-green algae<\/span><\/td>Xanthophyta \/ Tribophyta<\/span><\/td>Common in soils and freshwater<\/span><\/td><\/tr><\/tbody><\/table>

      Growth requirements<\/span><\/h4>
      • Light (photosynthesis is the primary energy source)<\/span><\/li>
      • Carbon (CO\u2082 from water or atmosphere)<\/span><\/li>
      • Nitrogen (nitrate, ammonia, urea)<\/span><\/li>
      • Minerals: magnesium, potassium, calcium, phosphate<\/span><\/li>
      • Trace elements: aluminium, zinc, copper, iron<\/span><\/li><\/ul>

        Optimal water temperature range: 15\u201335\u00b0C. Algae consume atmospheric CO\u2082 (carbon sequestration) and produce oxygen, making them ecologically important \u2014 but this same metabolic activity makes them problematic in closed or semi-closed water systems.<\/span><\/p>

        Problem environments<\/span><\/h4>
        • Ornamental and fish ponds \u2014 toxin risk and pH fluctuations<\/span><\/li>
        • Man-made swimming pools and natural ponds \u2014 aesthetic problems<\/span><\/li>
        • Cooling water circuits \u2014 industrial installations \/ cooling towers<\/span><\/li>
        • Rainwater collection and recirculation systems \u2014 filter blockage and contamination<\/span><\/li>
        • Open reservoirs used in agriculture and horticulture \u2014 dripper blockage risk<\/span><\/li><\/ul>

          6.3 Corrosion in Water Systems<\/span><\/h3>

          Forms of corrosion<\/span><\/h4>
          Type<\/span><\/th>Mechanism<\/span><\/th>Risk level<\/span><\/th><\/tr><\/thead>
          Uniform (general) corrosion<\/span><\/td>Even surface dissolution \u2014 predictable and measurable<\/span><\/td>Moderate \u2014 manageable with coatings<\/span><\/td><\/tr>
          Pitting corrosion<\/span><\/td>Localised deep attack, often invisible until failure<\/span><\/td>High \u2014 can cause sudden pipe rupture<\/span><\/td><\/tr>
          Galvanic corrosion<\/span><\/td>Electrochemical reaction between dissimilar metals<\/span><\/td>Medium \u2014 preventable by material selection<\/span><\/td><\/tr>
          Crevice corrosion<\/span><\/td>In narrow gaps where stagnant liquid collects<\/span><\/td>High \u2014 common in flanged joints and fittings<\/span><\/td><\/tr>
          Microbiologically Influenced Corrosion (MIC)<\/span><\/td>Driven by specific bacteria within biofilm<\/span><\/td>Very high \u2014 accelerated and unpredictable<\/span><\/td><\/tr><\/tbody><\/table>

          Microbiologically Influenced Corrosion (MIC)<\/span><\/h4>

          MIC is the most insidious form of corrosion in water systems because it is driven by microbial activity within established biofilm. Sulphate-reducing bacteria (SRB) produce hydrogen sulphide (H\u2082S) as a metabolic by-product, which attacks steel directly and accelerates electrochemical corrosion. The result is localised pitting that can penetrate pipe walls far faster than general corrosion models predict.<\/span><\/p>

          The conventional response \u2014 increasing chemical dosing \u2014 can be counterproductive: many biocides are themselves corrosive at the concentrations required to penetrate biofilm. Physical biofilm prevention eliminates the primary condition for MIC without chemical risk.<\/span><\/p>

          A word on frequencies<\/span><\/h4>

          Not all ultrasonic frequencies produce the same effects. Our systems are engineered to deliver specific frequencies and combinations that simultaneously target multiple mechanisms: cell wall resonance (algae destruction), acoustic cavitation (microbubble generation), and mechanical stress induction. Frequency selection is critical \u2014 a single-frequency system cannot replicate the multi-functional effect of properly combined broad-spectrum transducers.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

          6.Threats: Legionella, Algae & Corrosion 6.1 Legionella Pneumophila Background Legionella pneumophila\u00a0is a gram-negative, aerobic, rod-shaped bacterium (1\u20132 \u00b5m) and the causative agent of Legionnaires’ disease \u2014 a severe and potentially fatal form of pneumonia \u2014 and the milder Pontiac fever. More than 50 Legionella species are known;\u00a0L. pneumophila\u00a0accounts for the majority of human cases. Legionella […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-722","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/maritech.org\/index.php?rest_route=\/wp\/v2\/pages\/722","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/maritech.org\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/maritech.org\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/maritech.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/maritech.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=722"}],"version-history":[{"count":7,"href":"https:\/\/maritech.org\/index.php?rest_route=\/wp\/v2\/pages\/722\/revisions"}],"predecessor-version":[{"id":789,"href":"https:\/\/maritech.org\/index.php?rest_route=\/wp\/v2\/pages\/722\/revisions\/789"}],"wp:attachment":[{"href":"https:\/\/maritech.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=722"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}