1a. Distinguish clearly between biodegradation and biodeterioration. b. Write a short note on biodeterioration highlighting specifically (i) types (ii) classification and (iii) cost and implications. c. Briefly state how microbes colonize concrete.

Biodegradation refers to the breakdown of organic materials by microorganisms into simpler, non-toxic substances such as carbon dioxide, water, and minerals. It is a natural, beneficial process often used in environmental remediation, waste treatment, and composting.

Biodeterioration, on the other hand, is the undesirable degradation of materials (organic or inorganic) by microorganisms, leading to physical, chemical, or aesthetic damage. Examples include microbial corrosion of metals, spoilage of food, and cracking of concrete.

Key differences:

• Purpose/Impact: Biodegradation is beneficial and environmentally friendly; biodeterioration is harmful, causing economic loss and material failure.
• Materials affected: Biodegradation targets pollutants and wastes; biodeterioration affects useful materials like fuels, paints, textiles, and buildings.
• Outcome: Biodegradation results in mineralization; biodeterioration leads to weakening or destruction.

Biodeterioration is the microbial-mediated deterioration of industrial materials, reducing their utility, safety, or value.

Specific types (i):

• Metals: Sulphur-oxidizing bacteria (e.g., Thiobacillus) produce H$_2$SO$_4$, causing biocorrosion (MIC - microbially influenced corrosion).
• Concrete: Acid-producing microbes (e.g., Acidithiobacillus) dissolve calcium, leading to cracking and spalling.
• Fuels: Hydrocarbon-utilizing bacteria/fungi cause sludge formation and fuel degradation.
• Textiles/Paints: Cellulolytic fungi degrade fabrics; moulds discolour paints.
• Wood: Fungi (e.g., brown/white rot) and bacteria degrade lignin/cellulose.

Cost and implications (ii):

• Economic cost: Global annual loss exceeds billions (e.g., $100 billion in US for MIC alone); includes repair, replacement, and downtime.
• Implications:
  • Safety hazards (e.g., structural failures in bridges/buildings).
  • Health risks (e.g., mycotoxins from mouldy materials).
  • Environmental impact (e.g., increased waste from deteriorated products).
  • Reduced lifespan of infrastructure, necessitating biocides and protective coatings.

Microbial colonization of concrete occurs in stages: