Stormwater pollution varies from place to place and it is highly dependent on the surrounding environment. While urban areas have high litter pollution, the agricultural areas can have high nutrient pollution, whereas the industrial regions can have a high metal concentration in the stormwater.
Due to the spraying of pesticides and fertilisers on the agricultural fields, these fields tend to have a high concentration of nutrients like nitrogen and phosphorous. The stormwater on contact with these fields and can have a very high concentration of nutrients. This nutrient-rich stormwater can be very troublesome downstream to the receiving waterbody and can lead to eutrophication, which can, in turn, affect the marine ecosystem and aquatic life within that system. Therefore, nutrient removal from stormwater can be very vital for the marine ecosystem balance to be maintained.
Stormwater nutrient removal is a part of tertiary treatment which is the final stage of treatment train. Therefore, it is one of the last safeguards for treating stormwater before it enters waterways.
The stormwater nutrient removal can either be done with the utilisation of proprietary treatment devices (a filter or a combination of filters) that can absorb these nutrients or a biofilter can be designed to remove the nutrients to the desired standard limits or the limits set by the guidelines. Various materials have been studied and utilised as filters for nutrient removal in the past, like sand and soil-based water filter, high flow media etc. These proprietary treatment devices can be very effective for the removal in areas with a shortage of land since biofilters require large areas.