Explain the process of eutrophication of water, limited to: - increased availability of nitrate and other ions - increased growth of producers - increased decomposition after death of producers - increased aerobic respiration by decomposers - reduction in dissolved oxygen - death of organisms requiring dissolved oxygen in water

Explain the importance of the following in controlling the spread of disease: (a) a clean water supply (b) hygienic food preparation (c) good personal hygiene (d) waste disposal (e) sewage treatment (details of the stages of sewage treatment are not required)