Linking hydrological, hydraulic and water quality models for river water environmental capacity assessment.

The water environment of a river network can self-clean to a certain extent; however, when the wastewater discharge load exceeds a certain threshold, the balance of nature is disrupted, leading to water pollution. This emphasises the urgent need to evaluate river water environmental capacity (RWEC) as a necessary parameter for sustainable development. However, to quantify the RWEC, it is important to estimate the hydrological and hydrodynamic factors in the basin, leading to the linking of these models. The present investigation aims to propose an integrated framework, named RWEC, consisting of hydrological and hydrodynamic models, a database system, and GIS to evaluate the water environmental carrying capacity of the selected river network. The rain - runoff (RR), hydrodynamic (HD), ecological (ECO), and RWEC models were used. Groups of data, including meteorology, hydrology, and the environment, combined with topographic data and waste sources, were applied. Groups of models and data were integrated into a seven-step framework to calculate the RWEC. The case study is a basin in Binh Duong Province, Vietnam and four pollutants were selected: NH4+, BOD5, NO3-, PO43-. The flow and water quality factors in the river basin in the study area were measured based on hydraulic models, and the water quality was calibrated. The role of hydrological, hydraulic, and water quality models in the RWEC calculation was clarified. According to the baseline and forecast scenarios, the calculation of the RWEC for the scenarios was performed. In the baseline scenario, RWECNH4+ is in the range (-283, -22) kg/day, RWECBOD5 ranges from (143, 3126) kg/day, RWECNO3- is in the range (-778, 2166) kg/day, and RWECPO43- is in the range (-31, 46) kg/day. The dependence of RWEC on environmental factors, self-cleaning factors, and the difference between the baseline and forecast scenarios were clarified.

Integrated model for methane emission and dispersion assessment from landfills: A case study of Ho Chi Minh City, Vietnam.

Methane is considered to be one of the main causes of global warming. Quantifying methane emissions from landfills is the subject of many studies, especially emphasizing the role of two parameters: methane generation potential capacity (L0), methane generation rate (k). In this study, we propose a system of integrated environmental information and mathematical model named EnLandFill (ENvironmental information - model integrated system for air emission and dispersion estimation from LandFill) that allows calculation L0 from database and experimentally to determine optimal k. To perform experimental calculations, meteorological data were extracted from the WRF model and verified with real measurements. The novelty of this study lies in the inferred database system, the math model bank, especially the dispersion model, taking note account the complex topography, meteorological factors that change by the hour. EnLandFill was applied to Phuoc Hiep Landfill (PHLF) in Ho Chi Minh City as a case study, the results have identified the amount of methane released that is equal to 44,094,697.88 m3/year in 2019, but EnLandFill is designed to be general, applicable to other landfill entities.