Author(s): Nur Emylia Johari; Chun Kiat Chang; Marfiah Ab. Wahid; Aminuddin Ab. Ghani; Suhaimi Abdul Talib
Keywords: Constructed wetland; Pollutant level; Stormwater runoff; Treatment media; Water quality index
Abstract: The acceleration of urbanization with variable land use and increasing population, the natural environment has consistently deteriorated especially river water. The climatic change will change the rainfall pattern as well as evaporation and evapotranspiration. Urban stormwater runoff is becoming important to be treated before discharge into the river water as pollutant was carried off and gave significant impact to aquatic ecosystem. The incoming pollutant concentration by stormwater runoff would be increasing the actual pollutant level in river water body. Constructed wetland as one of the best management practice has been potentially to overcome this problem. However, an assessment of how much the urban stormwater pollutant level reduction and water quality can be achieved is needed. Therefore, this study was conducted to evaluate the performance of water quality level in stormwater runoff through a constructed wetland under tropical climate. This study was conducted in actual constructed wetland according to the design criteria and requirement as specified in MSMA 2nd Edition located in Universiti Sains Malaysia (USM) Engineering Campus, Nibong Tebal, Penang, Malaysia. The parameters that investigated in this study were p H, temperature, dissolved oxygen (DO) ,biochemical oxygen demand (BOD) ,chemical oxygen demand (COD) ,ammoniacal nitrogen (AN) and total suspended solid (TSS) .This study was conducted for eight months and grab sampling method were applied for 14 sampling stations. The mean of water quality index (WQI) of the inlet constructed wetland was 79. 26±3. 94 indicated as slightly polluted at Class III with WQI ranged from 70. 22 to 85. 00. After passing through the treatment at constructed wetland, the mean of WQI of the outlet constructed wetland was 84. 49±3. 68 indicated as clean at Class II with WQI ranged from 74. 74 to89. 31. High and low intensity of rainfall event will affect the level of pollutant as the land used of catchment area was same. The results showed a reduction of pollutant level for TSS and AN with 72. 99%and 74. 06%of percentage reduction, respectively throughout the constructed wetland. These results may be explained further by the treatment media in constructed wetland. Therefore, an appropriate design of constructed wetland with the consideration of pollutant level in catchment area land used is necessary to be identified as the constructed wetland shown the high contribution of the stormwater runoff quality enhancement.