Biological attack on cooling tower wood affects the

• A. lignin
• B. cellulose
• C. natural extractives
• D. chemicals that cement the cellulose fibres together

Answer: (B)

Biological attack on wood primarily targets the cellulose—the main structural carbohydrate that forms the strong fibrous framework of the wood. Fungi and other decay organisms secrete enzymes, like cellulases, that break down cellulose into sugars, causing the wood to lose its stiffness and strength. Lignin, though it can be degraded, is more resistant, so it isn’t the main component affected in typical decay of cooling tower wood. Natural extractives may help resist decay but are not what the attack acts on directly, and the idea of “chemicals that cement the cellulose fibres together” isn’t a distinct structural component—the binding involves lignin and hemicellulose, so weakening the cellulose is the key consequence of the biological attack.