Water Quality Modelling of Constructed Wetlands in Malaysia. Case Study BIOECODS, USM
Constructed wetland is an essential component in BIOECODS. The objective of this research is to evaluate the capability of constructed wetland in removing pollutants and improving stromwater quality through data sampling and computer modeling. Data samplings were performed to determine whether the constructed wetland able to improve the quality of stormwater. Water quality parameters namely BOD, COD, DO, TSS, turbidity and copper were taken into consideration. The percentage pollutant removal for BOD was 9.7% to 80%, COD was 5.7% to 62.9%, DO was 6.5% to 17.8%, turbidity was 25.9% to 30%, TSS was 50% to 100% and TP was 24% to 46%. The sampled data were analyses using Paired Sample Test and the results are significant. Other than sampling data, this research also included the application of water quality model for constructed wetland and two models were chosen, namely PREWETT and WMod. Sensitivity analyses were conducted for both models to identify the model parameters. The model parameters of PREWET were Kr for BOD, TP to TTP ratio for TP and Vs for TSS. Biofilm uptake rate is the model parameter for WMOd. Furthermore, calibration process was conducted to identify model parameters values and evaluation process was also performed to obtain model which best represent actual condition. For PREWET model, model parameters values that are obtained through calibration process were 0.32 day-1 for BOD, 0.4 for TP and 0.3m/day for TSS and R2 obtained were 0.525 for BOD, 0.067 for TSS and 0.479 for TP. While for WMod, the model parameter value obtained was 0.02 for TP and R2 was 0.525. a model simulation was carried out to determine the design parameters which give effective removal efficiency of between 50-60%. The design parameters obtained were detention time of 14 days, length to width ratio of 11.7:1, depth of 0.5m and inflow of 0.05 m3/s. in a nut shell, the finding from this research can be used as a guideline to design an effective constructed wetland that produce an optimum removal efficiency of pollutant.