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

Application of GIS and remote sensing to build up a map of environmental geological suitability for residential buildings on Thi Vai river basin

Tuong Van Ngo Thi — 2019-05-21

Geological environment zonation is to divide the areas into relatively homogeneous units based on their natural factors such as hydrology, topography, geology, disasters... to create geoenvironmental units which suit a specific type of exploitation for the purpose of research or regional management. This study presents a process of integrating GIS and remotely sensed data to develop a map of environmental geological zonning for the planning of development of the efective and safety construction sites. Data used in this work include Landsat 8 satellite image classified by application of Fuzzy Logic method to build the map of land use status which includes construction sites, and the GIS data including geology, topography, engineering geology and hydrogeology. The result from this process of integration is the suitability maps of appropriate units for the development of construction sites on the Thi Vai river basin. This map shows 3 different levels of geological environmental condition for development of the construction sites. This result demonstrates the efficiency of the integration of GIS and remote sensing to build tools to assist for the environmental capacity management, for data analysis, and beyond, to identify and incorporate the influencing factors to the subjects of management or research.

An A2O-MBR system for simultaneous nitrogen and phosphorus removal from brewery wastewater

Van Nu Thai Thien — 2019-08-13

Anaerobic/Anoxic/Oxic – Membrane BioReactor (A₂O-MBR) system was used to enhance simultaneous removal of nitrogen and phosphorus from brewery wastewater. The A₂O unit containing microorganisms with short solids retention time (SRT) was employed mainly for removal of organic matter and phosphorus together with denitrification. The MBR containing microorganisms with long SRT was employed mainly for nitrification of NH4⁺-N and recirculation of NO₃^--N. The model of A₂O-MBR system made from polyacrylic with the capacity of 49.5 liters was operated with hydraulic retention times decreased from 24, 18 to 12 hours corresponding to organic loading rates increased from 0.50, 0.75 to 1.00 kg COD/m³.day. The results showed that the model not only treated organic matter well but also nearly completely removed both nitrogen and phosphorus. For all three loading rates, chemical oxygen demand (COD) concentration decreased significantly in the anaerobic and anoxic compartments of the A₂O unit, indicating that most of organic matter was utilized in the anaerobic and anoxic compartments for phosphorus release and denitrification, respectively. Nitrification in the MBR was almost perfectly completed, with average NH4 ⁺-N removal efficiencies of over 98%. Denitrification in the anoxic compartment happened as much as possible. Demands for the development of PAOs, which were responsible for enhanced biological phosphorus removal (EBPR) processes, could be provided. For loading rate of 0.75 kg COD/m³.day, treatment efficiencies of COD, NH₄⁺-N, total nitrogen (TN) and total phosphorus (TP) of the model were the highest as 95.4, 99.2, 86.7 and 84.6%, respectively. Output values of these parameters were within the limits of Vietnam National Technical Regulation on Industrial Wastewater (QCVN 40:2011/BTNMT), column A. The model of A2O-MBR system was capable of achieving effluents with very low nitrogen and phosphorus concentrations from brewery wastewater.

3D numerical modeling of flow and sediment transport in rivers and open channels

Le Song Giang — 2019-08-16

Numerical model is a useful tool in studying the flow and sediment transport, change in river bed and is built on solving governing differential equations. Numerical model has many different levels and three-dimensional model is the highest level, allowing detailed simulation of flow and sediment transport process in 3D space. The paper presents a method calculating three - dimensional flow and sediment transport in the open channel. Water level and flow velocity are solved from three-dimensional equations with hydrostatic hypothesis. Concentration of suspended sediment, bottom sediment and bottom evolution is solved from transport equations. The governing differential equations in the "sigma" transform coordinate system are solved by finite volume method on unstructured grid of quadrilateral elements. Boundary condition of water level or flow will be imposed on open boundary. For suspended sediment concentrations in the injected phase, suspended sediment concentrations are applied and the outflow phase applies free drainage conditions. This method of calculation was tested with the problem of curved channel sediment transport which was studied experimentally by Odgaard and Bergs. Calculation results are quite consistent with the measured data. In order to test the practical applicability, this method is also tested with the problem of sediment transport in Cu lao Pho islet on Dong Nai river. To solve the matter of hydraulic boundary condition of this problem, the model of Cu lao Pho islet is integrated into the Sai Gon - Dong Nai river system model. Results of the calculation of the river bed evolution of the Cu lao Pho islet on the Dong Nai river also show that this calculation method gives results consistent with the rule and can be used in practical research.

Chronic efffects of bisphenol an exposure on zebrafish (Danio rerio) at juvenile state

Mai Thi Ngo — 2019-08-19

Introduction: Bisphenol A (BPA) is an endocrine disrupting chemical, therefore some countries have banned the use of it in plastic containers for food storage and plastic toys for children. BPA can be found in natural waters with measured concentrations varying from ng/l to mg/l. However, in fact that the chronic ecotoxicology data obtained from aquatic animals for BPA exposure at these levels are quite few.

Methods: In this study zebrafish at 30 days of age were exposed to four variants 0, 1, 10 and 100 μg/l BPA along 60 days, which is the fasted growth period in zebrafish (Juvenile stage). At the end of the experiments, all fish weight and length were measured and their fresh livers were used for histological assessment.

Results: The results showed that weight and length of fish in 100 mg/l BPA group increased significantly as compared with that in the other experimental groups. Also only in this group, changes in hepatic morphology such as vacuolar number and size increasement, cytoplasmicand/or nuclear enlargement, glycogen reduction, lipid enhancement, were observed, but especially no significant inflammation. Fish in the other groups exposed to BPA concentrations <100mg/l had no change in all targeted endpoints as compared with that of the control.

Conclusion: Chronic exposure of 100mg/L BPA to zebrafish along the fast-growth period (Juvenile) caused increasement of weight and length, and altered morphology of hepatic cells, that may harm to liver functions.

Application of CANON-SBR process for ammonium removal from old municipal old landfill leachate

Le Thanh Son — 2019-08-24

CANON (Completely Autotrophic Nitrogen-removal Over Nitrite) is the process combined Partial Nitritation and Anammox in a single reactor to remove ammonium from wastewater. This study used a lab-scale SBR Sequencing Bach Reactor for CANON process (CANON-SBR) to treat ammonium from old municipal solid waste landfill leachate. The reactor was run at two phases: (i) In adaptation phase, the synthetic wastewater containing 139 9 mg/l as NH4 +-N was fed into the reactor, and (ii) In operation phase, the reactor was fed with leachate taken from the Go Cat municipal lanfill which was closed since 2007. The reactor was run at ammonium loading rate of 0.2 kgN/m3.day and HRT of 0.6 day in the adaptation phase. pH and DO values in the reactor were controled in the ranges of 7.4 – 7.6 and 0.1 – 0.2 mg/l, respectively. After 15 days of adaptation, total nitrogen removal of 72% was obtained. Then, the leachate containing 3,000 mg/l NH4 +-N and 100 mg/l TSS was fed into the SBR. DO and pH were the key operation parameters for CANON process control. CANON-SBR obtained stable treatment efficiciency at DO ranging from 0.05-0.2 mg/l and pH values of 7.5 – 7.6. The obtained TN and COD removals were above 93% and 40%, respectively, when SBR was run at nitrogen loading rate of 0,4 kgN/m3.day and HRT of 7.43 day. TN concentration of the final batch was 34 mg/l that is met with column B1 QCVN 25:2009/BTNMT (TN< 60 mg/l), while nitrite and nitrate were not detected in the supernatant. This shows that co-existence of denitrifiers which consume nitrate produced from Anammox was available in biomass of the reactor. Numerous Anammox granules in dark red color happened after 20 days of running with leachate. Size of Anammox granules ranged from 5 - 800 μm, among that 73% of granule with size of 20 - 200 μm. The average granule diameter was 97.57 μm.