Bui Xuan Thanh

Mangrove Mapping and Change Detection in Ca Mau Peninsula, Vietnam, Using Landsat Data and Object-Based Image Analysis

Mangrove forests provide important ecosystem goods and services for human society. Extensive coastal development in many developing countries has converted mangrove forests to other land uses without regard to their ecosystem service values; thus, the ecosystem state of mangrove forests is critical for officials to evaluate sustainable coastal management strategies. The objective of this study is to investigate the multidecadal change in mangrove forests in Ca Mau peninsula, South Vietnam, based on Landsat data from 1979 to 2013. The data were processed through four main steps: 1) data preprocessing; 2) image processing using the object-based image analysis (OBIA); 3) accuracy assessment; and 4) multitemporal change detection and spatial analysis of mangrove forests. The classification maps compared with the ground reference data showed the satisfactory agreement with the overall accuracy higher than 82%. From 1979 to 2013, the area of mangrove forests in the study region had decreased by 74%, mainly due to the boom of local aquaculture industry in the study region. Given that mangrove reforestation and afforestation only contributed about 13.2% during the last three decades, advanced mangrove management strategies are in an acute need for promoting environmental sustainability in the future.

Pilot study on the removal of TOC, THMs, and HAAs in drinking water using ozone/UV–BAC

AbstractThe contaminated water is a main source of many waterborne diseases such as cholera, typhoid, etc. causing many serious public health crises, especially in developing countries with the low hygiene condition. In Vietnam, previous studies have reported that industrial and domestic waste cause adverted pollution on Saigon River that supplies water for 30% of 10 million residents in Ho Chi Minh City. Annual monitoring water quality data during 2006–2011 showed that concentration of ammonia and organic matter has been significantly increased and over the allowable limit (COD > 10 mg/L). In order to reduce these pollutants in the finished water and for disinfection, a large dose of chlorine (about 3–6 mg/L) needs adding in the treatment process at Tan Hiep water treatment plant. A negative effect of using too much chlorine is the formation of disinfection by-products (DBPs) such as trihalo-methanes (THMs) and haloacetic acids (HAAs). The concentration of THMs in finished water of Tan Hiep plant ranged ...

Laboratory-scale membrane up-concentration and co-anaerobic digestion for energy recovery from sewage and kitchen waste.

This study assessed an alternative concept for co-treatment of sewage and organic kitchen waste in Vietnam. The goal was to apply direct membrane filtration for sewage treatment to generate a permeate that is suitable for discharge. The obtained chemical oxygen demand (COD) concentrations in the permeate of ultrafiltration tests were indeed under the limit value (50 mg/L) of the local municipal discharge standards. The COD of the concentrate was 5.4 times higher than that of the initial feed. These concentrated organics were then co-digested with organic kitchen wastes at an organic loading rate of 2.0 kg VS/m(3).d. The volumetric biogas production of the digester was 1.94 ± 0.34 m(3)/m(3).d. The recovered carbon, in terms of methane gas, accounted for 50% of the total carbon input of the integrated system. Consequently, an electrical production of 64 Wh/capita/d can be obtained when applying the proposed technology with the current wastes generated in Ho Chi Minh City. Thus, it is an approach with great potential in terms of energy recovery and waste treatment.

Low flux submerged membrane bioreactor treating high strength leachate from a solid waste transfer station

A submerged membrane bioreactor was employed to treat high strength leachate generating from a solid waste transfer station. The reactor was operated at low fluxes of 1.2; 2.4; 3.8 and 5.1 LMH. The organic loading rate (OLR) ranged from 2 to 10 kg COD/m(3)day. Results show that 97% removal efficiency of COD at flux of 2.4 LMH. The highest removal of ammonia nitrogen and total nitrogen was 92.0 ± 1.5% and 88.0 ± 2.0% respectively at flux of 3.8 LMH. Fouling rates were observed to be 0.075; 0.121; 3.186 and 6.374 kPa/day for the fluxes of 1.2; 2.4; 3.8 and 5.1 LMH, respectively. Membrane fouled very slowly at low flux operation. The sustainable flux was identified to be less than 2.4 LMH for treating high strength leachate. It reveals less fouling was able to achieve for high strength wastewater by reducing the membrane flux.

Fouling mitigation in a submerged membrane bioreactor treating dyeing and textile wastewater

Abstract The present study aims to assess the treatment efficiency and membrane fouling propensity of a submerged membrane bioreactor (MBR) treating dyeing and textile wastewater by introducing Powder-Activated Carbon (PAC) and Alum (called “fouling reducer”). The treatment performance and fouling behavior of MBR when adding PAC and Alum were compared to those of the control MBR. The components of dyeing and textile wastewater were fluctuated with Chemical oxygen demand (COD), color, and turbidity of 500–2,500 mg/L, 370–2,700 Pt-Co, and 50–370 NTU, respectively. The Mixed Liquor Suspended Solids (MLSS) concentration in an MBR fluctuated from 6,000 to 9,000 mg/L. The mixed liquor volatile suspended solids (MLVSS) to MLSS ratio was 0.76. The organic loading rate was operated in the range of 1.4–1.7 kg COD/m3 d. In the control MBR (without the addition of a fouling reducer into the bioreactor), the results showed that the MBR could only remove the color at a maximum efficiency of 50% and COD of 60–94% during...

Urban growth mapping from Landsat data using linear mixture model in Ho Chi Minh City, Vietnam

Rapid urbanization in Ho Chi Minh City (HCMC), Vietnam, is creating societal impacts on the environment attributed to the increasing population. Understanding spatio-temporal dimensions of land-use changes that shape the urbanization is thus critical to the process of urban planning. We explore the urban growth in HCMC through Landsat images for 1990, 2002, and 2010 using the linear mixture model (LMM). The data are processed through four steps: (1) data pre-processing, (2) image classification by LMM using endmembers extracted from the original image using minimum noise fraction, (3) accuracy assessment of the classification results using field verification data, and (4) urban growth analysis to understand the spatial changes of land cover. The results achieved by comparisons between the classification results and ground reference data indicate that the overall accuracy and Kappa coefficient obtained for 1990 were 87.1% and 0.83, respectively, while those for 2002 were 92.5% and 0.89, and those for 2010 were 89.6% and 0.86. The results of urban growth analysis indicate that high albedo class (i.e., built-up areas) expanded from 12.3% in 1990 to 27.2% in 2002 and to 31.1% in 2010. When investigating land-cover conversions to high albedo class from 1990 to 2002, the largest conversion is observed for soil class (9.2%), followed by vegetation class (7.2%), and low albedo class (2.2%). From 2002 to 2010, 4.5% area of soil class was converted to high albedo class, while conversions from vegetation and low albedo classes were 3.5% and 2.5%, respectively.

Performance of wetland roof with Melampodium paludosum treating septic tank effluent

AbstractWetland 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...

Nutrient removal by different plants in wetland roof systems treating domestic wastewater

AbstractThis 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...

Study on treatment performance of low cost membrane based septic tank at various fluxes

The objective of this study was to evaluate the performance and fouling behavior of membrane based septic tank (MBST).Woven Fiber Microfiltration (WFMF) introduced in the chamber of a septic tank as a submerged membrane for domestic wastewater treatment. Concentrations of black water stored in the third chamber were 125 ± 15 mg/L COD, 124 ± 28 mg/L SS and 59 ± 9 mg/L TKN. Results showed that COD removal was 54-78 % of which effluent achieved less than 50 mg/L. In addition, the withdrawal was mostly non-performed suspended solids. TMP level increased gradually, indicated low membrane fouling rate (dTMP/dt) of 0.4-1.0 kPa/day at flux as low as 2.5 LMH. While at the flux greater than 3.4 LMH the fouling rate increased rapidly with the fouling rate of 13 kPa/day

Performance of Ozonation Process as Advanced Treatment for Antibiotics Removal in Membrane Permeate

Abstract There was an investigation into the removal of 6 types of antibiotics from hospital wastewater through membrane bioreactor (MBR) treatment and ozonation processes. Six types of antibiotics, namely, Sulfamethoxazole (SMZ), Norfloxacin (NOR), Ciprofloxacin (CIP), Ofloxacin (OFL), Erythromycin (ERY), and Vancomycin (VAN) which had high detection frequencies in collected samples from hospital wastewater treatment plant (HWTPs). After MBR treatment, the removal efficiencies of SMZ, NOR, OFL, and ERY were 45%, 25%, 30%, and 16%, respectively. Among of them, almost no elimination was observed for CIP and VAN since their concentrations increased by 0.24 ± 0.18 (μg·l-1) and 0.83 ± 0.20 (μg·l-1), respectively. Then, residues of the antibiotics were removed from the MBR effluent by the ozonation process. The overall removal efficiencies of SMZ, NOR, CIP, OFL, ERY, and VAN were approximately 66 %, 88 %, 83 %, 80 %, 93 %, and 92 %, respectively. The reason might be depended on different ozone consumption of those antibiotics (ABS) in a range of 313 to 1681 μg ABS·gO--1. Consequently, the ozonation process performed better in the antibiotics removal (e.g. CIP and VAN) so ozonation could be considered as important support for the MBR treatment to reduce the risk of antibiotic residues.