Bacteria Growth in Pipelines
Bacterial growth in process pipelines happens when operating and material conditions allow microorganisms to attach, survive, and multiply (often as biofilms). The main causes can be grouped as follows:
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1️⃣ Water & Nutrient Availability (Primary Cause)
Bacteria need water + food to grow.
Presence of water or moisture (especially stagnant or low-flow zones)
Organic matter (oils, hydrocarbons, sugars, proteins)
Inorganic nutrients (iron, sulfur, nitrogen, phosphorus)
Dissolved oxygen (for aerobic bacteria) or sulfates (for SRB)
📌 Even “clean” water can support bacteria if nutrients are present at low levels.
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2️⃣ Flow Conditions
Poor hydraulic conditions strongly promote growth.
Low flow velocity
Dead legs, blind branches, unused connections
Stagnant zones (shutdowns, batch operation)
Laminar flow instead of turbulent flow
➡ These allow bacteria to settle and attach to pipe walls.
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3️⃣ Pipe Material & Surface Condition
Some materials promote attachment more than others.
Carbon steel & cast iron → rough surface, iron acts as nutrient
Corroded or pitted pipes
Weld seams and gaskets
Rubber liners and elastomers
🦠 Rough surfaces make it easier for bacteria to form biofilms.
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4️⃣ Temperature Range
Most process bacteria thrive in:
20–45 °C → ideal for many bacteria
<60 °C → biofilm still possible
>70 °C → many bacteria die (not all)
⚠ Thermophilic bacteria can survive at higher temperatures in some systems.
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5️⃣ Chemical Conditions
Certain chemistry favors bacterial growth:
Low disinfectant residual (chlorine, biocide, ozone)
Neutral pH (6–8) → optimal
Low salinity (some bacteria tolerate high salinity)
Sulfates → support sulfate-reducing bacteria (SRB)
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6️⃣ Lack of Proper Disinfection / Biocide Control
No continuous or periodic biocide dosing
Incorrect biocide type or concentration
Poor mixing or contact time
Biocide neutralized by organic load
➡ Bacteria adapt and form resistant biofilms.
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7️⃣ Oxygen Conditions
Different bacteria dominate depending on oxygen presence:
Aerobic bacteria → oxygen present
Anaerobic bacteria → oxygen-free zones (dead legs, deposits)
Sulfate-reducing bacteria (SRB) → major cause of MIC corrosion
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8️⃣ Contamination Sources
Bacteria can be introduced from:
Makeup water
Poorly cleaned new pipes
Maintenance activities
Open tanks and vents
Recycled or reused process water
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9️⃣ Deposits & Fouling
Sediments, scale, corrosion products
Sludge and oil films
These shield bacteria from disinfectants and create micro-environments.
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⚠ Consequences of Bacterial Growth
Microbiologically Influenced Corrosion (MIC)
Flow restriction and pressure drop
Product contamination
Heat transfer loss
Bad odor (H₂S)
Reduced pipe life
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✅ Typical Prevention Measures
Eliminate dead legs
Maintain minimum flow velocity
Proper material selection (e.g., stainless steel, plastics)
Regular pigging / flushing
Correct biocide selection & dosing
Maintain disinfectant residual
Control nutrients and deposits