Pusat Penyelidikan Kejuruteraan Sungai dan Saliran Bandar (REDAC) - Tesis

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Browsing Pusat Penyelidikan Kejuruteraan Sungai dan Saliran Bandar (REDAC) - Tesis by Author "Woon, Khee Ling"

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    Assessing the effects of vegetation, influent concentration, and design sizing in establishment of pollutant reduction perfomance curve for bioretention system
    (2024-02-01)
    Woon, Khee Ling
    Bioretention is one of stormwater best management practices (BMPs) that can treat water quantity and quality effectively. However, there is still a lack of studies regarding the effectiveness of bioretention in treating stormwater in a tropical context. Both experimental study and modelling were conducted to address the literature gap in bioretention research within a tropical context. One of the objectives of this study is to evaluate the hydrology and pollutant removal performance with the changes in planting conditions. A pilot-scale bioretention site was constructed in Universiti Sains Malaysia (USM), Engineering Campus with three plots: plot without vegetation (P1), single species (P2) and multispecies with tropical plants (P3). In Stage 1 experiment, the performance of bioretention was evaluated based on peak flow (Qpeak) reduction, pollutant outlet concentration and pollutant removal efficiency. P3 showed the best result in Qpeak reduction with 82%, followed by P2 (78.2%) and P1 (75.4%). The presence of vegetation improves the pollutants removal efficiency, especially total suspended solids (TSS) and total nitrogen (TN), with removal efficiency up to 95% and 85% respectively. For pollutant outlet concentration, bioretention with multispecies plants (P3) can treat TSS and chemical oxygen demand (COD) up to class II, based on the water quality index (WQI) classification. The result reflected that the plant diversity is important in bioretention systems as it showed better performance. Overall, the influent concentration showed positive correlation to pollutant removal (except COD and BOD). Stage 2 experiment was conducted to assess the effect of bioretention sizing on bioretention performance. As a result, the increase of incoming water promoted more exfiltration and affected the Qpeak at outlet with the increase of 22%, 14% and 0.3% for P1, P2 and P3 respectively. To achieve the third objective, bioretention model using MUSIC X was calibrated and validated based on the experiment data. For water quantity prediction, the model was evaluated based on Nash-Sutcliffe Efficiency (NSE), which has achieved 0.713 and 0.938 for the calibrated and validated model respectively. The performance rating for prediction of TSS, TN and TP removal based on percentage bias was ‘very good’ after the calibration of k-C* model in MUSIC X. Lastly, a pollutant reduction performance curve was established up to 5% of bioretention area to the impervious catchment area. This study provides insight regarding the importance of multispecies planting, proper sizing, and pollutant reduction performance curve establishment for the effective implementation of bioretention systems.