In a concentrated form, it is both a caustic and hazardous substance and is toxic to both fish and other aquatic organisms. It can also overstimulate plant growth or cause algal blooms, leading to a drastic reduction in the oxygen needed to support aquatic life. If not addressed, an over-abundance of ammonia can be catastrophic, killing off aquatic life, and rendering streams, rivers and lakes lifeless.
For this reason, ammonia therefore needs to be closely monitored, with levels higher than around 0.1 mg/L indicating a polluted water source. Ammonia can enter the aquatic environment via direct means such as municipal effluent discharges, industrial processes and agricultural run-off, and indirect means such as nitrogen fixation and the excretion of nitrogenous wastes from animals.
When it comes to potable water, although ammonia in drinking water is not considered to be an immediate risk to human health, it is nevertheless desirable to keep it under control. Excess concentrations can reduce the efficiency of the disinfection processes, form nitrites in distribution systems, cause manganese filters to fail and lead to taste and odour problems.
A rising problem
Whilst significant inroads have been made in reducing emissions of other environmentally harmful substances, ammonia has been bucking the trend, with emissions levels rising or not reducing as quickly as desired.
In OECD countries, emissions of ammonia decreased in the period between 2003 and 2015. However, this was lower than between 1993 and 2005[1]. Much of this is attributable to agriculture, which has used organic and inorganic fertilisers in growing quantities.
Although there are a number of sources, the agricultural sector accounts for around 80-90 per cent of total global ammonia emissions[2].
For example, in the EU, agricultural activities resulted in the emission of 3.6 million tonnes of ammonia in 2013. Although this was a decline of almost 30 per cent compared with 1990, agriculture was still responsible for over 93 per cent of total ammonia emissions in the EU-28 in 2013[3].