Fate and removal of nutrients in bioretention systems

Phosphorus and nitrogen in different forms are the primary concern in surface water bodies nowadays since it causes eutrophication. A bioretention system, an example of green stormwater infrastructures reduces nutrients through biological processes such as plant uptake and microbial conversion of nitrogen known as bioremediation. In this study, the performance of two types of bioretention system in managing nutrients from urban stormwater runoff was investigated. Total phosphorus (TP) was reduced by 85% up to 86% in both bioretention types while total nitrogen (TN) was reduced by 49 and 55% in type A and type B bioretention, respectively. Among the plants species used in the study, Rhododendron indicum Linnaeus was identified as the most appropriate plant that should be used in bioretention systems considering factors such as number of flower per plants, plant decay rate, cost of plant, number of plant per reactor, and TN and TP uptake by plants. Based on the results, 25–32% of TN and 47–59% of the TP load were absorbed by the soil medium. This finding signified that filtration was the main removal mechanism for nutrients in bioretention.