The Influence of Filter Depths in Capturing Nutrient Contaminants for Non-Vegetated Bioretention Column: A Preliminary Study

Tze Liang Lau, Aminuddin Ab. Ghani, Nor Azazi Zakaria, Husna Takaijudin, How Tion Puay

Thursday 2 july 2015

11:00 - 11:15h at Asia (level 0)

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

Parallel session: 11G. Environment - Impact

The success of Best Mangement Practices (BMPs) mainly bioretention in treating stormwater pollutants are revealed through laboratory and fieldwork studies. Engineered filter media plays significant role in enhancing bioretention performance in terms of quantitative and qualitative aspects. Hence, this paper presents the preliminary study on the life span of hydraulic conductivity and examine the stormwater treatment efficiency for variation engineered filter depths. This study focused on the three (3) small-scale column namely C1,C2 and C3 with 74mm diameter and 700 mm height which varied the soil media depth ranged from 300 mm to 500 mm. Daily hydraulic conductivity (Ksat) were monitored over 12 weeks to observe the declination of this parameter over the time. Then, approximately 3.3 L collected stormwater sample during dry season were poured into each column. All samples were collected and tested. The results found that C3 has the greater Ksat (280.2±63.4mm/hr)throughout the daily observation due to having narrow depth of filter media. Thus,water can permeate easily through the soil. However, C1 (88.2±36.7mm/hr) and C2 (74.6±15.1mm/hr) has deeper depths compared to C3 which provide less permeability rates. According to the life span, it showed a reduction of Ksat up to 94% within 3 months of duration. On water quality aspects, C1with depth of 500 mm which has highest retention time was capable to remove TN pollutants ranged 35-72%. While TP contaminants was treated well in C2 with depth of 400mm by ranged of 67-90%.C2 also indicate better performance in TSS removal from 45-96% due to filtration process. It can be stated that C2 offers highest performance in treating contaminants through several processes mainly filtration and adsorption. Conversely, C3 proved that with the narrow depth of engineered soil media, it provide greater outflow volume but lesser treatment on stormwater pollutants due to insufficient retention time to soil microbes react with the contaminants. Thus, it concluded that engineered soil media capable to remove nutrient pollutants effectively with minimum depth of 400 mm which can assist on bioretention performance mainly during premature state. KEYWORD: nutrient pollutants, bioretention, column study, engineered soil media, hydraulic conductivity, treatment efficiency