Are population centres polluting waters?

Wastewaters produced by cities and other population centres are today treated efficiently. Do they continue to pollute waters? What about in sparsely populated areas?

Efficient treatment of wastewaters generated by population centres began in the 1970s, dramatically reducing emissions of organic matter and phosphorus, in particular. Phosphorus is a key plant nutrient which causes eutrophication in lakes and coastal areas and, among other things, algal blooms.

The reduction in emissions has helped waters near population centres to recover. The fact that wastewaters are often treated at larger plants further away from population centres has also contributed to improving the condition of waters locally. Lakes and coastal waters near many population centres and cities are today clean enough for bathing.

While the share of population centres in the total influx of pollutants into waters is today small in Finland, agriculture is the biggest culprit when it comes to emissions into waters. Population centres nevertheless continue to produce emissions of nitrogen, in particular. Nitrogen is another key plant nutrient that has adverse impacts, especially on the marine environment.

Appropriate treatment of wastewaters from sparsely populated areas is a recent improvement. Up till now, these emissions have been considerably large when calculated per resident and also had local impacts on the status of lakes, coastal areas and groundwaters. On the national scale, sparsely populated areas have in recent years equalled population centres as a source of pollution.

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