ABSTRACT
Aims: A personal computer version of the Stormwater Management Model (PCSWMM) was applied to seamlessly link urban runoff, sanitary flow, pump station operations, and a natural wastewater treatment wetland in Phnom Penh, Cambodia, as a step towards developing a planning tool that could be used to explore urban development or climate change scenarios. Study Design: PCSWMM was calibrated with measured flow and water quality data and used to estimate total phosphorus, total nitrogen, detergents, and E. coli levels at the outlet of the wastewater treatment wetland for the period May 15 to July 1, 2011. Place and Duration of Study: Phnom Penh, Cambodia; January, 2011 to March, 2012. Methodology: In support of model development, a limited water quality sampling program and bathymetric survey were conducted for the sewer and wetland system in both the dry and rainy seasons, 2011. Samples were analyzed for total nitrogen, total phosphorus, detergents, and E. coli. Sewer flow was measured continuously at 5 minute intervals to determine sanitary flow characteristics as input to the model and pump operation rules were determined through interviews with the pump operators and analysis of their data log books. Results: Consistent with past studies, the sampling showed that the wetland was effective in treating municipal waste, particularly with respect to E. coli (99% reduction from sewage inputs) and detergents (86% reduction from sewage inputs). A lower treatment efficiency was observed for total phosphorus, at around 31%, while the treatment efficiency for total nitrogen was around 71%. The wetland was divided into four zones and PCSWMM was run in continuous mode for the period May 2-July 1, 2011. The mean levels of E. coli, detergents, total phosphorus, and total nitrogen estimated by the model for that time period compared favorably with sample results from the field campaign in August, 2011. Conclusion: The naturally-occurring wetland treatment system in Phnom Penh is effective and fits well with the concepts of green infrastructure and eco-cities. PCSWMM is a useful decisionsupport and planning tool to explore various development and climate change scenarios in Phnom Penh.
ABSTRACT
Aims: In recent decades, Ho Chi Minh City, Vietnam, frequently has been affected by local floods and inundation from heavy rainfall. Conventional flood mitigation measures such as building flood gates and upgrading sewerage systems have been implemented but problems persist. The objective of this research is to assess another approach for flood control measures, namely Sustainable Urban Drainage Systems (SUDS), with application to the Nhieu Loc - Thi Nghe Basin, located in the central part of Ho Chi Minh City. Methodology: A combination of the Stormwater Management Model (PCSWMM) and interviews with 140 households was used to assess the efficacy and acceptability of four of the most popular SUDS: Rainwater harvesting, green roofs, urban green space and pervious pavement. Thirteen SUDS and urban build-out scenarios were simulated under 6 design storm conditions. Results: PCSWMM results showed that inundation from intense rainfall could be reduced with proper land-use control, specifically by maintaining imperviousness at 65% or less of the surface area. With respect to SUDS performance, green roofs were best at reducing peak runoff (22% reduction), followed by pervious pavement, urban green space, and rainwater harvesting systems. Regarding environmental improvements, as represented by reduction in total suspended solids load, urban green space was best with 20% of the solids load removed compared to the base case scenario, followed by green roofs, pervious pavement, and rainwater harvesting. The household interviews revealed the majority of people preferred pervious pavement to the other SUDS options and the least preferred option was green roof technology. Conclusion: Considering the combination of water quantity and water quality controls, it seems that green roof technology was the best performer for this area of Ho Chi Minh City, followed by urban green space, pervious pavement and rainwater harvesting. However, green roof technology also was the least favored option for the public and stakeholder acceptance will impact SUDS implementation.