Read the passage excerpt:
'Desalination through reverse osmosis (RO) is indispensable for municipal freshwater supply in hyper-arid coastal territories. In this process, pretreated seawater is forced under high hydrostatic pressure—exceeding natural osmotic pressure—across semipermeable polyamide membranes that selectively permit water molecules to pass while rejecting dissolved ions. A critical environmental challenge, however, remains the safe disposal of hypersaline effluent (brine), which can induce thermal and chemical stratification in local marine benthic habitats if discharged without diffuse outfall designs.'
What physiological mechanism governs the reverse osmosis desalination process?
Answer and explanation
Correct answer: C. Forcing seawater under high hydrostatic pressure across a semipermeable membrane
- Step 1: The excerpt explains: 'pretreated seawater is forced under high hydrostatic pressure, exceeding natural osmotic pressure, across semipermeable polyamide membranes...'
- Step 2: High hydrostatic pressure overcoming osmotic equilibrium is the defining mechanism.
Answer
Forcing seawater under high hydrostatic pressure across a semipermeable membrane.
Why not the others: 'Boiling seawater in pressurized chambers...' describes thermal distillation (MSF or MED); 'Freezing surface water...' describes freeze desalination; 'Passing electrical currents...' describes water electrolysis, which destroys water rather than purifying it.
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