State one condition that favours denitrification.

Explain the consequences of releasing raw sewage and nitrate fertilizer into rivers.

denitrification is favoured by anaerobic conditions in soil;
poor drainage/waterlogged soils;
slightly alkaline;
suitable temperature;
the presence of denitrifying bacteria/Pseudomonas (denitrificans);

pH changes;
raw sewage often contains pathogens that cause disease;
increase in nutrients/nitrates (from fertilizer) leads to eutrophication;
decomposition of organic matter releases ammonia into water;
ammonia is converted into nitrate;
nitrate causes algal bloom;
bacteria that feed on sewage cause high BOD/lack of (dissolved) oxygen;
lack of oxygen may kill fish/other aquatic life;
as algae release oxygen into water via photosynthesis, water recovers downstream;

In F3 (a) most candidates were able to achieve marks but few fully explained their answers as required in the command term.

N/A