The paper presents the current situation of the waste management system of the megacity Ho Chi Minh in Vietnam, and the options for waste and land recycling in a low income country. Generally, there is a large potential for circular economy in the city as the main proportion of the waste flows are recyclables. Due to the missing selective collection system, this potential is not used in the full extend yet, even if the collection of the entire waste volumes is envisaged in the National Waste Management Strategy by 2025. The waste stocks are the landfill locations in the region of Ho Chi Minh City (HCMC), two of them being in operation and two of them already being closed. A special focus is given to the landfill Gò Cát, which was subject to an option analysis in terms of waste and land recycling options. The results indicate that there are several reuse options: the use of the landfill material in a waste-to-energy process after landfill mining, the reuse of the re-gained land in case of landfill mining, the reuse of the capped landfill for energy crop cultivation, and the gasification in a biogas plant in case of a remaining landfill.

Urbanization processes in Asia are still ongoing; thus, aggregate demand is expected to increase in following years. Even though construction and demolition waste is a source for secondary building materials in industrialized countries, it is not yet an alternative construction material source in Vietnam as the urbanization process is still ongoing. Thus, there is a need for river sand and aggregates alternatives in concrete, namely manufactured sand (m-sand) from primary solid rock materials and secondary waste materials. The focus in the present study for Vietnam was on m-sand sand as alternative for river sand, and different ashes as alternatives for cement in concrete. The investigations comprised concrete lab tests according to the formulations of concrete strength class C 25/30 in accordance with DIN EN 206, followed by a lifecycle assessment study in order to identify the environmental impact of the alternatives. In total 84 samples were investigated, consisting of 3 reference samples, 18 samples with primary substitutes, 18 samples with secondary substitutes, and 45 samples with cement substitutes. This kind of holistic investigation approach comprising material alternatives and accompanying LCA was the first study for Vietnam, and even for Asia, and represents a substantial added value for future policy development in order to cope with resource scarcity. The results show that with the exception of metamorphic rocks, all m-sands meet the requirements for quality concrete. In terms of cement replacement, the mixes showed that a higher percentage of ash reduces the compressive strength. The compressive strength values of the mixes with up to 10% coal filter ash or rice husk ash were equivalent to the C25/30 standard concrete formulation. Higher ash contents up to 30% lead to the reduction of the concrete quality. The LCA study’s results highlighted the better environmental footprints across environmental impact categories in the 10% substitution material in comparison to the use of primary materials. The LCA analysis results showed that cement as a component in concrete holds the highest footprint. The use of secondary waste as alternative for cement provides significant environmental advantage.

Plastic pollution is one of the significant environmental concerns due to the threefold increase in global plastic waste. Marine microplastics, including petroleum-based plastic pieces and synthetic and artificial fibers smaller than 5 mm, are not only ubiquitous in natural water but also high in wastewater streams due to the direct discharge, transfer and breakdown of plastic items. This research aims to investigate the presence and dispersion of microplastics in the downtown area and coastal suburban area of Ho-Chi-Minh City by using Raman microscopy. As a result, the most common plastics (PE, PET, PA, PP, PVC, PS and PMMA) were detected, and most of them were fibrous shorter than 500 μm. The total microplastics decreased gradually from the urban waterborne (up to 220 MPs/L) via Can Gio UNESCO Mangrove Biosphere Reserve (10 MPs/L) and to the East Sea (3 MPs/L), which reveals the potential role of the mangrove in reducing marine contaminants including microplastics. This study provides important insights into microplastic pollution in the Western Pacific Region, especially the Saigon-Dong Nai river systems, supporting useful data for natural water resources management.

Municipal solid waste (MSW) management is a significant problem for developing countries due to lack of sufficient infrastructure, poor management capacity, and low level of waste treatment technology. This study proposes three main groups of criteria, i.e., social, economic, and environmental, that can be used as an effective tool to assess the sustainability of MSW treatment technologies, considering Ho Chi Minh City, Vietnam as a case study. The sustainability assessment criteria consist of a list of indicators which consider potential waste treatment plants. The indicators and technologies then undertake a selection process from identifying assessment goals and key aspects to data collection and consultation of experts. The findings from the previous phase will be used to select the most preferred waste technology through AHP and normalization approaches. As a result, 12 selected indicators are as follows: investment cost, treatment cost, operation and maintenance costs, revenue/benefits, job creation, community consensus, support policy, community health, air pollution, water pollution, greenhouse gas emissions, and land quota. Among three MSW facilities selected, i.e., landfill, compost, and waste-to-energy incineration, waste-to-energy is determined as the best alternative solution for Ho Chi Minh City in a given context of approximate 70% of landfilling being applied. The selection process and indicators found can guide decision-makers and policy on selecting MSW treatment technologies in developing countries. Additionally, Ho Chi Minh City’s governors benefit from finding the most appropriate waste technology. A technology adoption roadmap and its implementation plan should be thought thoroughly to address challenges in MSW management in the city.

Microalgae are promising feedstock for the production of biodiesel and diverse medium- and high-value products such as pigments and polyunsaturated fatty acids. The importance of strain selection adapted to specific environments is important for economical purposes. We characterize here two microalgal strains, isolated from wastewater of shrimp cultivation ponds in Vietnam. Based on the 18S rDNA-ITS region, one strain belongs to the Eustigmatophyceae class and is identical to the Nannochloropsis salina isolate D12 (JX185299.1), while the other is a Chlorophyceae belonging to the Desmodesmus genus, which possesses a S516 group I intron in its 18S rDNA gene. The N. salina strain is a marine and oleaginous microalga (40% of dry weight (DW) at stationary phase) whole oil is rich in saturated fatty acids (around 45% of C16:0) suitable for biodiesel and contains a few percent of eicosapentaenoic acid (C20:5). The Desmodesmus isolate can assimilate acetate and ammonium and is rich in lutein. Its oil contains around 40%–50% α-linolenic acid (C18:3), an essential fatty acid. Since they tolerate various salinities (10% to 35‰), both strains are thus interesting for biodiesel or aquaculture valorization in coastal and tropical climate where water, nutrient, and salinity availability vary greatly depending on the season.

Ninh Thuan is a coastal province in the central region of Vietnam and is characterized by a climate that is the hottest and driest in the country. Vietnam is also one of the top five countries most vulnerable to the effects of climate change worldwide. The objective of this study was a thorough evaluation of the quality of water supply sources and the impacts of water effluents from shrimp farms in Ninh Thuan province. The comprehensive evaluation was based on an understanding of the water–wastewater cycle employed in coastal shrimp cultivation. We combined qualitative and quantitative analyses in undertaking this study. Secondary data of groundwater and coastal water from the local periodic water quality monitoring program and national technical regulations were collected in the qualitative approach. We also integrated participatory rural appraisal techniques and field observations to understanding shrimp cultivation and the environmental and social impacts of shrimp farm effluents. The quantitative assessment consisted of measuring groundwater and wastewater contamination from shrimp ponds. As a result, four main reasons for water pollution issues were determined including extreme weather events, shrimp cultivation practices, degraded infrastructure, and mismanagement by local governance. Shrimp cultivation practices (feeding, using chemicals) have resulted in elevated levels of suspended solid (TSS, total Coliform), organic and carbon matter (BOD₅, COD), and excessive nutrients (total Nitrogen, NO₂-N, NO₃-N, PO₄-P). According to a local monitoring program, the coastal water and groundwater have experienced nutrient pollution. Groundwater sampling near the shrimp farms identified salinization elevated levels of Coliform from local domestic sewage sources. This study resulted in an integrated approach that evaluated the combined effects of extreme weather events and shrimp farming practices on the quality of coastal water. Also, the finding can be useful in recommending remedial water treatment technologies as a follow-on phase.