Search

Green roofs are a key component to building sustainable cities because of their multiple environmental benefits, but without the proper level of care, the leachate from green roofs might contain pollutants and become a new nonpoint pollution source in urban areas. Because its leachate quality is affected by the substrates and plants used, the objective of this study is to evaluate the effects of the substrates and plants with the aim of improving green roof applications. This study tested 3 materials – normal cultivated (C) substrate, commercial green roof (L) substrate, and mixed C and recycled glass (R) substrate – with a focus on using recycled glass materials in the green roof system. Recycled glass is a lightweight and porous material that improves pollutant absorption and water quality purification. Three different types of plants were tested: a sedum, a fern, and a shrub. Therefore, this study evaluated 9 combinations, each with 3 replicates. The differences in the substrates exerted significant effects on the chemical oxygen demand (COD) and phosphorous (P) concentrations. The nitrogen (N) concentrations were affected by differences in both the substrates and the plants. The changes in the observed water quality with time implied that compact substrates and mature plants reduced pollutant concentrations, except for N concentrations, in the outflow. The L substrate contained high levels of nutrients, and the plants grew better in this substrate than in the other two substrates; however, the L substrate also produced higher pollution concentrations. The R substrate, with recycled glass, performed well in the neutralization of acid rain but did not significantly reduce the levels of other pollutants. To enhance the purification ability of the recycled glass, the mixing ratio between the recycled glass and organic substances and the placement in the substrate are important factors.

Taiwan is located in the Circum-Pacific Belt and at the junction of the Philippine Sea Plate and the Eurasian Plate. The island is squeezed over a long period of time, so the frequency of the occurrence of earthquakes is very high. Changes of terrain due to seismic forces such as fault ruptures and surface uplifts could cause extensive damage to water pipeline networks. The 921 Ji-Ji earthquake was one of the most serious disasters in recent years in Taiwan, and it indeed resulted in the most severe damage of water supply systems. The urban water supply network is very important for municipal water management in Taiwan. If the water supply systems break down, hospitals and fire stations will not have enough water to carry out the rescue work, and the results may worsen the disasters. This study took the water supply system of the West District in Taipei City as an example. First, the metro-Taipei area was split into three hundred and twenty-seven 1 km by 1 km cells. Second, the location of a simulated earthquake was determined. Third, the Peak Ground Acceleration (PGA) value of each cell was calculated by an empirical formula. Fourth, the Repair Rate (RR) of each cell was calculated based on its PGA value. Fifth, using the GIRAFFE software developed by Cornell University, the Monte Carlo simulation method was used to simulate the possible damage to the water supply system. And finally, the EPANET program developed by the US Environmental Protection Agency was applied to compute the distribution of flow volumes and water pressures of the damaged water supply system. Results of the pipeline network under different scenarios of earthquake magnitudes are shown in this study, and they provide an evaluation basis to decision makers to improve the pipeline infrastructures for fire protection after major earthquakes.