Science & Technology Development Journal - Science of The Earth & Environment

Study on the proposal of a community of freshwater aquaculture and vegetable farming in An Giang

Thu Hong Anh Nguyen — 2020-04-05

In recent years, fish farming (Pangasianodon hypophthalmus) an important contribution to the economy of Vietnam in general and the Mekong Delta provinces in particular. However, along with economic development issues is the problem of environmental pollution and disease caused by waste from fish farming operations. The optimal solution to this problem is the wastewater treatment of aquaculture. To the aquaculture industry in general and the fish farming profession in particular sustainable development, and to protect the natural environment, the research group conducts a symsanitary models of livelihoods symbiosis between freshwater aquaculture operations and vegetable farming. This model functioned as a way to reuse water and nutrients discharged from aquaculture activities, which caters for vegetable farming. The efficiency of the model is to minimize a large amount of solid waste disregarded directly to the receiving source, which was 315.098 kg. The quality of wastewater had been improved after releasing it to the source. The total amount of carbon (TOC), nitrogen and phosphorus was 7.56%, 8.27% and 0.64% respectively, all of which meet the standard index of waste discarded directly into the environment. Thus, the wastewater treatment ponds with tree water morning glory contribute to reducing pollution to water sources but also contribute to reuse components of waste from fish pond provides nutrients for plant water morning glory, increased efficiency, and the metabolic component of fish feed. In addition, the model also brings additional income for households with 24.9 million VN dong after every fish breeding in comparison with the traditional farming model.

Assessing drought from satellite data to support agricultural production

Van Tran Thi — 2020-05-04

Drought is one of the disasters causing the problems to the economy and social life of people, especially where agriculture is the main source of income. The paper presents the results of studying the application of optical satellite images to investigate the drought situation for the southern part of Binh Phuoc province for perennial cropland, the main agricultural crop of the province. The image used is Landsat 8 of the dry season month 2015. The method of drought assessment is based on the relationship of surface temperature, and the Normalization Difference Vegetation Index (NDVI) integrated into the Temperature-Vegetation Dryness Index TVDI. In particular, the NDVI index is determined from the red and near-infrared bands, and the surface temperature is determined from the thermal infrared band of Landsat 8 images. The results show that the whole area of southern Binh Phuoc has drought area accounting for 54.9% of the total area, of which the majority is mild drought level 38.3%, high and serious level is 16.7%. About the area of perennial land has drought area accounted for 33.76% of the total area, of which Dong Xoai town has the highest percentage of drought-affected areas compare to other districts. The results of the study aimed to identify drought areas with different levels so that managers can promptly take measures to protect agricultural crops and to ensure people's livelihoods in the global climate change trend seriously affecting the localities today.

Study on the use of sludge farming of catfish as organic fertilizer and evaluate its effectiveness in agriculture

Huyen Khon Nguyen — 2020-04-05

The purpose of this study is to reuse fishpond sediment to produce organic fertilizer for planting maize. The sludge was mixed with rice husk and Composted under aerobic conditions. The effectiveness of Compost on planting maizes was assessed by adding to maizes with and without combination chemical fertilizers as different dosages as recommendations. The amounts of Compost adding for maizes were 10 and 20 tons/ha. Maize growth, characteristics of corn, and soil physical and chemical parameters such as bulk density, soil aggregate stability, the volume of moisture, and useful moisture of soil were measured and evaluated. The results showed that the quality of organic fertilizer produced from waste sludge met Vietnamese standard (QCVN:2018/BNNPTNT) for adding to crops. Applying organic fertilizer with the quantity of 20 tons/ha to combine with the recommendation of inorganic fertilizer amount for planting maizes increased the yield. Moreover, 20 ton/ha of organic fertilizer coupling with 50% of chemical fertilizer amount as a recommendation for planting maize also enhanced the yield to compare with the control (only using inorganic fertilizer as a recommendation). The maize yield of applying 20 tons/ha of organic fertilizer was higher than the maize yield of 10 tons/ha of organic fertilizer. Using organic fertilizer produced by fishpond sediment did improve not only the soil quality but also protected the canals and increased household income.

Photocatalytic treatment of volatile organic compounds emitted from mosquito repel incense burning

Nguyen Nhat Huy — 2020-05-24

Mosquito-repellent incense (MRI) is a widely used product in the household. Although the quality of MRI has been strictly managed, it still has certain health effects in practical use. This study investigated the level of volatile organic compounds (VOCs) in MRI smoke and its removal ability by photocatalysis. An online survey was conducted using Google form to select three typical types of MRI which are the most popular use in Vietnam (i.e., MOSFLY, RAID, and JUMBO VAPE) as well as their use level and condition. These types of MRIs were then burnt in a normal room for 8 h to determine the level of air pollution emission. Results from room test show that the tVOCs concentration emitted from one of the MRIs was as high as 1621 ppb, which was the highest pollution level among the three MRIs tested. This type of MRI was then employed as VOCs pollutant source for testing the treatment ability of a photocatalytic equipment in a closed chamber. The experimental treatment of emitted VOCs by the photocatalytic treatment equipment showed that titania nanotubes (TNTs) modified with metal salt and heat treatment achieved high removal efficiency. It has reached indoor air standards of ≤ 490 ppb after 180 min of treatment with an input concentration of about 1,600 ppb. By changing the conditions of TNTs modification and operation conditions, the highest treatment efficiency was achieved with 2 g of zinc doped TNTs at a Zn/Ti molar ratio of 0.5%, calcined at 500 ^oC, in which the treatment to meet the standard reached the shortest treatment time. The results in this study indicate that burning MRI could cause indoor air pollution that may affect human health and photocatalysis is a potential technology for treating VOCs from indoor MRI burning.