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Sustainable construction and demolition waste (CDW) management have been widely discussed. For a city seeking urban renewal or transformation, aging houses are remodeled, which creates a large amount of CDW. Taiwan is located in an earthquake-prone area with many aging houses. Sustainable CDW management is extremely urgent for such cities or countries. This study presented the current CDW state in Taiwan and suggested possible management strategies. Material flow analysis was conducted to understand the use and distribution of the construction materials. This shows that 100% of the raw material of concrete is imported, whereas 100% of the raw material of brick is domestic. Half of recycled steel is used as a raw material in steel products. The predicted CDW from aging houses was calculated and could be a sustainable source for these materials. However, waste concrete and brick are currently mostly used as subgrade filling materials but are not recycled to produce new construction materials. There are three obvious challenges in CDW management: the lack of cost-effective recycling technology, the increasing quantity of CDW, and the limits of refilled land and landfill volume. However, three opportunities have also emerged: the high potential for reducing carbon emissions from CDW, improved recycling technology, and increasing awareness of the circular economy. This study concludes that reducing the amount of CDW, increasing the lifespan of buildings, increasing the use of reuse or recycled CDW, and proper management of final waste disposal help reduce waste and build a nearly zero-carbon-emission construction industry. [ABSTRACT FROM AUTHOR]

Drainage systems in urban areas are designed to collect and transport stormwater from citizen areas. However, the water in drainage systems might contain untreated, misconnected, or low-treated sewage and polluted runoff and potentially pollute neighboring urban rivers. In this study, the drainage waters in Taipei city, Taiwan, were investigated, and the impacts on water quality in the receiving Keelung River were assessed by the Water Quality Analysis Simulation Program (WASP) and five scenarios. If the drainage outlets were not intercepted but discharged to the river, the BOD and NH3-N in the Keelung River would increase by 5.7% and 2.9%, respectively. Moreover, the BOD concentration under low-flow conditions (Q75) increased by 30%, and the NH3-N increased by 37.6%. If all domestic wastewater is treated and zero point pollution sources in the drainage water in the future, the BOD could decrease by 55.4%, and the NH3-N could decrease by 44.8%. [ABSTRACT FROM AUTHOR]

Nonpoint source pollution control requires the implementation of best management practices (BMPs) at various locations in a watershed. One important aspect of the watershed strategy is to find the optimal placement and design of BMPs so that their combined effect is most cost-effective. An innovative method is presented for optimizing the placement and configurations of BMPs at the watershed scale. Heuristic optimization techniques are coupled with a watershed model, which is the agricultural Nonpoint Source Pollution model (AnnAGNPS) in this case, and BMP simulation module to find a least cost set of solutions that meet the pollutant load reduction requirements. An impoundment module imbedded in AnnAGNPS, and modified to address the sediment accumulation and resuspension effect, is used to provide the means of evaluating the long-term performance of detention ponds. A scatter search algorithm is applied to finding the least cost solution. The optimization framework developed herein provides a tool for stormwater management practitioners to examine and analyze the treatment efficiencies of stormwater control alternatives and to determine a robust and cost-effective design of stormwater treatment systems. CE Database subject headings: Stormwater management; Optimization; Detention basins; Configuration; Best management practice; Simulation models; Nonpoint pollution; Water pollution; Watershed management.