3. Biological treatments

nitrate-reducing bacteria reduce nitrates to various nitrogen compounds, including nitrogen gas in the final stage. In contrast, nitrifying bacteria oxidize ammonia into various forms of nitrogen.

These bacteria each thrive under different optimum conditions, but in general they grow better at medium-high temperatures of 15 to 25°C than at low temperatures below 10°C.

Bacteria also degrade organic matter and eliminate elements such as iron and manganese.