The role of tropical shrub with enhanced bioretention media in nutrient rich runoff treatment

Nor Azazi Zakaria, Chun Kiat Chang, Tze Liang Lau, Keng Yuen Foo, Hui Weng Goh

Friday 3 july 2015

14:45 - 15:00h at South America (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment

Parallel session: 16J. Environment - Wetlands

Bioretention systems with sedges as vegetation for the system are one of the popular Best Management Practices (BMPs) in temperate countries. However, there are lack of studies using shrub in tropical countries, which has been used widely as landscape plants. In recent years, use of additives for nutrient removal from water bodies has been proven to be successful in various applications but the potential of using waste material as additives in bioretention has not been fully discovered. In this study, the effect of tropical shrub with enhanced bioretention media, which contain 4 different types of additives from waste materials (cockle shell, newspaper, coconut husk and printed paper) was examined. Natural runoff with high pollutant concentration (more than 5 times of normal urban runoff concentration) was used in this study. Comparison between 20 bioretention mesocosm planted with and without Red Hot Chinese Hibiscus (Hibiscus rosa-sinensis) showed that tropical shrub with well developed root systems played an important role in maintaining hydraulic conductivity within the range stated in various guidelines. Results show that after 16 weeks of runoff test, mean of hydraulic conductivity for mesocosm without shrub has decreased 25%, whereby for mesocosm with shrub, the difference of hydraulic conductivity was maintain within 4%. For TSS and TP mass removal, both mesocosm with and without shrub for all types of additives performed well, with overall mean ranging from 93-96% and 90-91% respectively. For TN mass removal, mesocosm with shrub containing printed paper and cockle shell (69-72%) perform better compared to mesocosm without plant (54-58%), which proven that the combination of shrub with selected additives could improve TN removal of bioretention and at the same time maintain the hydraulic conductivity of the media. It was recommended that TSS and TP removal could be further improved by incorporating turf to the system to cover the soil media. Keywords: Additives, Best Management Practices (BMPs), Bioretention, Filter Media, Nutrient Removal