The Nutrient Removal Aspect of the ABC Waters Programme: A Case Study of the Kallang River at Bishan-Ang Mo Kio Park

Abstract

Singapore faces several water management challenges because of its urbanized environment, and these problems include elevated nutrient and sediment concentrations, as well as quick and high peak runoff discharges during a storm event. The Active, Beautiful and Clean (ABC) Waters programme was implemented to help solve these problems. Effective removal of pollutants by ABC Waters projects can help to decrease the amount of problems associated with urban runoff. In this thesis, an ABC Waters project that underwent river restoration, the Kallang River at Bishan-Ang Mo Kio Park (BAMKP) was studied. Water samples from the river and drain inlets feeding the river were collected and analysed to understand the nutrient and sediment levels in the BAMKP catchment, as well as to find out how efficiently a completed ABC Waters project removed pollutants in both baseflow and storm conditions. Nutrients and sediments (NO2,3, NH3, TN, PO4, TP, TSS) in water samples were analysed. Data from this study found that the drain inlets contributed a large proportion of nutrient loading into the Kallang River in BAMKP, with runoff from urban residential areas having the highest concentrations of nutrients. The overall removal efficiencies of this ABC Waters project were found to be 9.4% for nitrogen and 40.2% for phosphorus during baseflow conditions and -17% for nitrogen and 25% for phosphorus during storm events, with larger storms having lower removal efficiencies than smaller storms. This is a cause for concern as the ABC Waters design guidelines aim for a removal efficiency of 45% for each of nitrogen and phosphorus respectively.