Urban Stormwater Treatment in Tropical Catchments Using Biofiltration Systems

Andreas Aditya Hermawan, Amin Talei, Ana Deletic, Babak Salamatinia, International Conference on Water Resources, 24-25 Nov 2015, Langkawi, Malaysia, 2015

Biofiltration systems are landscape depressions or shallow basins used to slow and treat on-site stormwater runoff and are considered as one of the important components of a sustainable drainage system. Biofilters generally consist of two components: a filtration media which is sand-dominant and a top vegetated soil layer. The efficiency of a bioinfiltration systems is normally assessed by two key parameters namely hydraulic conductivity and percentage removal of pollutants. To date, several studies have been done on development and maintenance of such systems; however, few have addressed the issues that such systems may face in tropical climates which normally receive intense rainfall. To address such issues, an experimental study has been set up to characterize the key components in designing biofiltration basins for pollutant removal and flow retention of stormwater under tropical conditions of Malaysia. The first phase of this study which is presented here aims to identify proper soil filter media based on local market availability. The target was finding a filter media which could be able to remove heavy metals from storm water efficiently while its hydraulic conductivity is reasonably high enough. For this, a soil column experimental set up were developed based on six different filter media. To assure the validity of the results for each proposed filter media three columns were prepared. All columns were watered several times by tap water until they reach their stable hydraulic conductivity. Then the capability of each column in heavy metal removal was tested by filtering the synthesized stormwater which was polluted by pre-defined concentration of heavy metals including Fe, Mn, Cu, Zn, Ni, and Pb. The runoff volume dosage and pollutant concentration in synthesized stormwater were chosen based on available rainfall and water quality data from Malaysian catchments. The water samples taken from columns’ outlet (after passing through the filters) were then tested in ICP-OES machine to find the percentage removal. Results showed that the proposed sand-based filter is able to achieve percentage removal of 89.7%, 92.3%, 98.9%, 96.1%, 93.9%, and 99.1% for Fe, Mn, Cu, Zn, Ni, and Pb, respectively. Moreover, it was found that adding 2% (weight percentage) fly ash can improve the performance removal to 96.9%, 99.5%, 98.9%, 100%, 96.7%, and 99.4% for Fe, Mn, Cu, Zn, Ni, and Pb, respectively. However, adding fly ash resulted in 23% decrease in hydraulic conductivity which could not be desirable in tropical areas where rainfall intensity is high.