Fertilization algal production

The activity of chlorine as a bactericide is decreased by the presence of large quantities of algal slimes and certain process leaks (for example, hydrogen sulfide from petrochemical industries, ammonium compounds from fertilizer production, or citrates from the bioengineering manufacture of citric acid, but not hydrocarbon oil leaks from an oil refinery). 

Excessive use of phosphate and artificial nitrogen fertilizer, again part of the quest to increase yields, is another cause of water-quality decline. It may result in cultural eutrophication, notably a substantial increase in the nutrient content of fresh and salt water, which encourages algal growth and an eventual overall decline in biodiversity (see Section 6.3.1). The problem is widespread in coimtries where intensive industrialized crop production is prevalent and is a major problem in enclosed seas such as the Mediterranean. Industry and domestic uses of water also exact a toll. For example, in parts of the USA, Canada and Europe acid rain , caused by the burning of sulphur-rich fossil fuels, has acidified catchments and reduced water pH below the levels tolerated by most fish species algal and microbial populations have also altered. Acidification is likely to spread substantially as industrialization continues in China, India etc. The issue is discussed in Sections 5.5 and 7.7. 

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