3. Nutrient Removal from Variable Stormwater Flows

When nutrient loads are discharged into surface waters with variable stormwater and wastewater flows, surface water pollution is impaired. Nutrients can lead to oxygen depletion and eutrophication of surface waters, including excessive plant and algae growth. Popular examples of structures harmed by excessive nutrient inflow are the Baltic Sea or the Great Barrier Reef in Australia. Hence, removing nutrients, especially nitrogen and phosphorus compounds, is a major target when variable flows should be treated. This chapter gives an overview of the available removal mechanisms and the potential efficiencies of different treatment facilities. While particle-bound nutrients can be removed via sedimentation processes, dissolved nitrogen and phosphorus compounds cannot as they differ in their biochemical degradation: the adsorption capacity for nitrogen compounds is often renewable, whereas the uptake of phosphorus compounds is limited over time. Hence, treatment facilities need to be able to address the different requirements.