VNU Journal of Science: Earth and Environmental Sciences

Abstract

This paper presents the results of the benefit of biogas solution in wastewater treatment system and the application of mathematical statistical methods to evaluate the benefits of this method for pig groups in concentrated pig farms in Hanoi, Bac Giang, Hoa Binh, Nghe An and Ha Tinh. The results of 8 pig farms in those localities idicate the potential revenue benefits from the sale of greenhouse gas emissions credits, save money for electricity and reduce environmental protection fee for the waste water from each group of pigs at different stages of growth (pregnant sows, sows, piglets and porkers). The average annual value of pregnant sows is 146.611 ± 37.718 VND, 126.424±68.920 VND for sows, 155.405 ±64.414 VND for piglets and 122.680 ±61.217 VND for porkers (confident interval is 68.2%). The initial results of this study show that the statistical method was applied effectively to solve environmental problems, and also provide useful information to propose solutions to improve the efficiency of the biogas system inmanagement of waste and biogas use to reduce greenhouse gas emissions and save energy.

According to the World Health Organization (WHO), air pollution ranks 6th among the leading causes of death globally. The wet porous membrane filter has been widely used in dust removal, VOCs, and acid gas absorption. The wet filtration solutions need to ensure a low water activity that limits the release of moisture into the air, inhibits microbial growth, and can absorb dangerous gases. This study investigated the water activity of NaCl, NaNO3, K2CO3, KCl, K2SO4, Mg(NO3)2, MgCl2, and CaCl2 solutions at different concentrations to saturation at 25 °C. NaCl and NaOH solutions are not only investigated at different concentrations but also investigated the effect of temperature in the range of 0-40 °C. Some solution formulas are suggested that ensures the following properties: low water activity, antifungal, antibacterial and acid gas absorption.      

Vertical subsurface flow-constructed wetlands (VSF CW) are evaluated in this research as a potentially effective and cost-efficient solution for treating wastewater from Da Mai noodle handicraft village in Bac Giang province. Due to the high pollution load in this type of wastewater, there are concerns about clogging and the stability of the technology. In this study, we explored different sizes of limestone and gravel for the five medium composition formulas in the VSF CW system. The experiments were conducted over a period of three months. We used ANOVA, one-sample T-test, and Pearson correlation analysis methods to evaluate the experimental results, with statistical significance set at 0.05. The results showed a linear correlation between medium size, hydraulic conductivity, and treatment efficiency (p < 0.05). Smaller medium sizes had higher pollutant removal efficiency but lower porosity and hydraulic conductivity. For the same sizes, limestone demonstrated higher treatment efficiency compared to gravel (p < 0.05). The Cp5 formula (comprising sand, 1×2 cm limestone, and 3×5 cm gravel) was selected as the best filter medium for VSF CW, achieving COD, TSS, TN, and TP removal efficiencies of 86.02 ± 1.71%, 81.15 ± 2.24%, 64.46 ± 2.23%, and 69.76 ± 2.68%, respectively. After three months of operation, the treated wastewater consistently met QCVN 40:2011/BTNMT Column B standards, and there were no significant differences in hydraulic conductivity (p > 0.05), indicating stable operation of the VSF CW.

Due to the emergence of new and persistent pollutants in wastewater, various advanced oxidation processes (AOPs) such as ultrasonic technology and electrocoagulation have been developed and employed for pollutant degradation, removal, and recovery from wastewater. In this study, we investigated the principles, influencing factors, and practical applications of several methods combining ultrasound and electrocoagulation with catalysts and demonstrated the efficiency of each method. Additionally, we analyzed the challenges associated with these ultrasonic methods and electrocoagulation in removing antibiotics and recovering pollutants from aqueous solutions and suggested solutions to these problems. Materials recovered after treatment can be utilized to improve soil quality.

This research developed a WebGIS system for managing green spaces at the Thu Dau Mot University. The system utilizes PostgreSQL for data storage and GeoServer for spatial data sharing, enabling efficient communication of field data. The platform's user-friendly interface, combined with QGIS tools and PostGIS/PostgreSQL, allows for easy data visualization and management, even for users without GIS expertise. This cost-effective solution facilitates quick information sharing, fosters a shared understanding of the data, and enables more efficient and sustainable management of the university's green spaces.  

Abstract: Heavy metal (HM) contaminations in the topsoil around handicraft villages in the Red River Delta (RRD),Vietnam impose serious threats to the subsoil as well as to the groundwater quality. This work is to decrease the mobility of HM by applying Fe powder, the kaolinite, bentonite and vermiculite to soils.  Organo-clays produced by modifying these above clay minerals with surfactants HDPy and HDPyCl were tested for removing HM. Fe powder exposes a better sorption capacity for HM as compared to vermiculite and bentonite. Application of Fe in 1 w.% can enhance adsorption capacity of Cu up to 170%, while vermiculite and bentonite applied at 5 w.% can only enhance the adsorption capacity up to ~160% and ~140%, respectively. Low charged clays, which were modified with organic cations have shown be a high potential as adsorbents for Cu in these situations (partially ~220%). These tested materials can flexibly be applied for soil and wastewater remediations in order to step by step reduce the impact of HM pollution in the local area.Keywords: Heavy metal, availability, remediation, clay mineral, Fe powder.

The Gulf of Thailand is a semi-closed Gulf on the west and southwest side of the Indochina Penisula and experiences reversal monsoon.  The object of the present study is to investigate monthly and spatial distributions of the phytoplankton in the Gulf of Thailand during whole El Nino year 2002 by using remote-sensing measurements of chlorophyll-a (Chl-a) and surface wind vectors. Results show that monthly and spatial variations of the phytoplankton blooms are primarily associated with the monsoonal winds. In general, the average monthly Chl-a concentrations were quite low (<0.5 mg m-3) most area of the Gulf, with a belt of higher Chl-a concentrations along the coast during throughout year. Phytoplankton blooms extensively offshore in the near-coastal area of the Gulf in January and February, which is consistent with the winter northeast monsoon. In particular, one peak of Chl-a concentrations was observed in December. Areas with higher Chl-a concentrations along the coast were observed in both winter and summer monsoon months. Keywords: Phytoplankton blooms, Monsoon, Gulf of Thailand, El Nino.

Controlled slow release fertilizer (CRF) in this study was produced by mixing Silica-Biochar (SB), Bentonite (B), and Diatomite (D) at different ratios with N, P, K form customized crystal membrane to control the dissolution of N, P, K into water. Research results show that the mixing rate of SB and B significantly affects the pelleting process, decay rate, hardness, and air hygroscopicity of CRF fertilizer. The decay rate is more than 20% after 13 and 5 days and greater than 80% after 17 and 9 days, respectively with SB mixing ratio of 30 and 40%. The maximum hardness of CRF fertilizer was 3.2 kg/cm2 and the smallest was 1.6 kg/cm2 respectively with the SB used ratio of 30 and 40%. With the mixing rate of SB at 30%, the resulting CRF fertilizer has the smallest hygroscopicity. With the mixing rate of B at 5%, the resulting decay rate of CRF was the smallest. The mixing rate of B did not affect the air hygroscopicity of CRF fertilizers. The different mixing rates of diatomite used did not affect the decay rate, hardness, and air hygroscopicity of CRF fertilizers.  

Urban transportation infrastructure development projects usually act as a lever for real estate values. This research aims to assess the effects of some projects on urban land prices in three wards of Cau Giay District, namely Quan Hoa, Dich Vong, and Dich Vong Hau wards. With 161 samples surveyed, we established a multivariate linear regression model initially having 11 variables. As the result, six variables are identified as having significant effect on land prices in the study area. Among those, three variables are related to the local transportation infrastructure, namely: location of land parcels; distance to urban railway lines; and distance to public transport stations. Location of land parcels and distance to public transport stations are factors that have a significant influence in reality. Besides, the distance to the urban railway lines is the factor that has a positive impact on land prices, but it is only still a potential and should be extensively investigated in the future because the urban railway project is still in the implementation phase.