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This study evaluated nutrients removal from domestic wastewater by five plants in wetland roof systems (WR). The study plants include Arachis duranensis (1), Evolvulus alsinoides (2), Cosmos Bipinnuatus (3), Cyperus alternifolius Linn (4), and Philodendron hastatum (5). The WRs were acclimatized at hydraulic loading rates (HLR) of 220 m3/ha d and operated at HLR of 300 m3/ha d. The plants (1), (2), (4), and (5) had the ability to grow under the rooftop conditions with domestic wastewater as a nutrient source while the plant (3) was not suitable and dead after 20 d of operation. Generally, A. duranensis (1) and C. alternifolius Linn (4) were the most suitable plants treating domestic wastewater under the conditions of WR. The average phosphorus removal efficiencies of (1) and (4) were approximately 75 and 89%, respectively, while the average nitrogen removal efficiencies were 69 and 92%. The phosphorus accumulation in plants (1) and (4) during operation was 20.4 and 29.4%, respectively, while the n...

Wetland roof (WR) system was developed to apply for building terrace and top roof in the urbanized area of Ho Chi Minh City. This study aims to improve the green area of the city and to treat domestic wastewater through a shallow horizontal subsurface constructed wetland that is located in a household roof. The pilot-scale unit of horizontal subsurface flow WR system with Melampodium paludosum, an indigenous emerging plant in Vietnam, was experimented at the average hydraulic loading rate (HLR) of 338 m3/ha d (∼36 kg COD/ha d) corresponding to HRT of 18 h. The treatment performance was not significantly different for rainy and sunny days at various HLRs. It was observed that the average removal efficiency of COD was 77–78% or 20–28 kgCOD/ha d for both sunny and rainy days. It is apparent that nutrient removal was greatly achieved as indicated by TN removal efficiency of 88–91% or 17–20 kg TN/ha d. In addition, TP removal reached 72–78% or 1.6 kg TP/ha d for different HLRs. The treated effluent cou...

In the Plain of Reeds in the Mekong delta (Viet Nam) about 600,000 ha is covered by pyrite soils. At the beginning of the rainy season acidic material is leached from the soil to water in the canal system. Evaluation of water chemistry data indicate that jurbanite is the acidic mineral which is accumulated at the soil surface and subsequently leached to the canals during the early rains. The results obtained correspond well with published results for acidic soils in other areas. It has earlier been assumed that Fe(II) is the major acidic ion in the water and oxidized slowly. The measurements made in acidic canal indicate that Fe(II) is oxidized to Fe(III) according to a pseudo first-order reaction with a half-time of about 4 h and precipitated as hydroxide. Instead aluminium, produced by weathering, has proved to be the most acidic ion in the water.

A large area in the Mekong delta is covered by acidic sulphate soils. Arsenic (As) and selenium (Se) are two potentially harmful elements that may accumulate in such sulphidic environments. Mapping of the abundance and fate of these elements during reclamation was therefore initiated. Results indicate that the soils are slightly enriched with As, but not with Se. The solubility of As varied considerably within the soil profiles and was much influenced by the redox conditions. Drainage, therefore, resulted in a downward shift of the zone with the highest As solubility. Selenium appeared to be practically immobile in all horizons studied. It was concluded that the drainage of these soils may result in high initial As concentrations in the drainage water, but also that As becomes largely unavailable to plants.