WAEC Biology 2015 Theory — Question 8

Model answer

(i) Sewage simply refers to used water and waste substances that are produced by human bodies, and which are carried away from houses and factories through special pipes/drains. (ii) Effects of releasing untreated sewage into a stagnant water body: it poses danger to the lives of aquatic organisms; it reduces the oxygen content of the water body; it produces repugnant odour; it causes rapid growth of algae, thereby clogging up the water body; and it renders the water unfit for human consumption.