Engineering Headway Vol. 40

Abstract: Antibiotic contamination in water environment remains a serious issue in Vietnam, primarily caused by untreated and/or ineffectively wastewater from hospitals, pharmaceutical factories, and antibiotic overuse in aquaculture and livestock. High levels of antibiotic residues, often in µg/L range, have been detected in major rivers, fostering the spread of antibiotic-resistant bacteria and genes. Despite the implementation of Vietnam’s National Action Plan on Antimicrobial Resistance (2020–2025), weak wastewater treatment infrastructure continues to limit effective control. The use of vermiculite (Ver) and TiO₂ carrier enhances the removal efficiency of norfloxacin (NOR) from water by improving adsorption capacity and photocatalytic activity. Ver provides a large surface area support for contaminant capture, while TiO₂ facilitates photocatalytic degradation of NOR under UV or visible light irradiation. In this study, Ver was acid modified using HNO₃, H₂SO₄ and HCl with concentration ranging from 1 to 3M. The soaking time ranged from 1 to 7 days. Modified Ver was used as a TiO₂ carrier by sol-gel method to enhance the efficiency of both photocatalytic and adsorption processes. The properties of the TiO₂/modified Ver material were evaluated using SEM, XRD, and Zeta potential analysis. With increasing soaking time, SEM images reveal that the modified Ver surface becomes more cracked and porous compared to the smooth surface of the original Ver. However, no significant difference was observed with changing soaking time. Additionally, the Ver surface modified with HNO₃ found more uniform porosity and cracks compared to the other used acids. The XRD spectra of TiO₂/modified Ver using HNO₃ 3M showed the strongest and clearest anatase TiO₂ peak compared to the other samples. The TiO₂/modified Ver (soaked for 1 day in HNO₃ 3.0M) also showed better adhesion and a more uniform TiO₂ coating. The Zeta potential of this modified material was the lowest and negative, indicating the strongest reduction in TiO₂ particles electrostatic interaction, resulting in the most stable dispersion and a more uniform surface. The removal efficiency of norfloxacin by Ver was only 20% whereas TiO₂/modified Ver material using H₂SO₄ 3M, HNO₃ 3M and HCl 3M achieved of 74, 60 and 45%, respectively, under fluorescent light with an initial norfloxacin concentration of 20 ppm and a material dose of 2.0g/L after 6.0 hours. The treatment efficiency reached the highest 99% with flow rate 1mL/min.

Abstract: This study assesses the potential for wastewater reuse from the dragon fruit (Hylocereus) concentrate production process, utilising an integrated membrane bioreactor (MBR) in conjunction with a UV/H₂O₂ advanced oxidation process (AOP). The MBR system effectively removed organic matter, nitrogen, suspended solids, and colour, with COD and total nitrogen (T-N) reduced to 92–226 mg/L and <0.2 mg/L, respectively. The removal efficiencies exceeded 91% and 98%, respectively. The MBR effluent met discharge standards and was suitable for further treatment. Subsequent AOP polishing significantly improved water quality, yielding BOD₅, total phosphorus (T-P), and total nitrogen (T-N) concentrations of 18.2 mg/L, 0.3 mg/L, and <0.2 mg/L, respectively, enabling reuse in fruit washing, equipment cleaning, and agricultural or aquacultural applications. A cost analysis revealed a sharp decrease in treatment cost, from $3.50/m³ at 50 L/min to $0.74/m³ at 1000 L/min, demonstrating economic viability at larger scales. Although AOP remains relatively costly, long-term cost-effectiveness can be improved through technological innovations, system integration, and operational optimisation. These findings offer a promising and sustainable approach to managing agro-industrial wastewater and conserving water resources.

Abstract: Previous studies have demonstrated the effectiveness of struvite (MgNH₄PO₄·6H₂O) precipitation for simultaneous recovery of phosphorus (P) and nitrogen (N) from wastewater as an alternative, sustainable option for recycling and removing nutrients. Magnesium plays an essential role in struvite formation, yet other divalent cations such as calcium (Ca²⁺) are also likely to be incorporated in the same precipitation reactions. In this study, construction wastes (CWs) were utilized as several rich calcium resources to recover nitrogen and phosphate in waste water through precipitation process. Ca in CW samples were leached by acidification process with (1%; 3% and 5%). At a concentration of 1% HCl, the calcium concentration was measured at 3200 mg Ca/L. This amount increased significantly to 7200 mg Ca/L and 7800mg/L when using 3% and 5% HCl, respectively. The resulting Ca-rich filtrate and phosphate was added to solution to recover high nitrogen concentration. The influence of pH and Ca:N:P molar ratio in the recovery of Ca,N, P was investigated. pH is 8.5, Ca:N:P molar ratio is 1.2:1:1 in 60 mins was optimal conditions for achieving N, P recovery efficiency. The results of the phase transition of the compounds were evaluated, when Calcium was utilized the recovery efficiency of phosphate was higher compared to nitrogen.

Abstract: Mg-impregnated biochar was created by pyrolyzing powder coffee waste in order to recover nitrogen and phosphorus from pig wastewater. The drawback of biochar is its low-nutrient while struvite production is its high chemical cost. The experiment examined the effects of Mg concentrations (1M, 1.5M, and 3M) on the of modified powder coffee waste. The influence of Mg/N/P molar; pH was studied. A maximum of 96.5% of PO₄ ^3- -P and 86.8% of NH₄ ⁺-N could be recovered by Mg-biochar at pH=9, Mg/P=1.2/1, and stirring in 30 minutes. Results of XRD and FT-IR showed that phosphate and nitrogen were recovered on Mg-PCW by covalent bonding, which promoted the production of struvite crystals. In terms of selectivity or specificity for struvite synthesis, Mg-biochar showed superior result to Mg chemical (non-biochar). N converted to struvite from the recovered or removed NH₄ ⁺ in waste water is 50% and 75% with Mg-non biochar and Mg-biochar, respectively. This approach emphasizes the cost-effective synthesis of struvite and the advantages of CO₂ sequestration in addition to waste recycling and pollution reduction.

Abstract: Adding green spaces to developed urban areas is crucial for enhancing ecosystem services and enhancing residents’ health, comfort, and urban resilience. This study presents an integrated GIS–AHP (Analytic Hierarchy Process) framework to evaluate spatial suitability for urban green space expansion in the historic core of Hue City, Vietnam. Nine spatial criteria, including slope, distance to water bodies, land use/land cover, population density, distance to major roads, housing density, proximity to heritage zones, distance to existing parks, and Land Surface Temperature, were analyzed using a multi-criteria decision-making model. The AHP was applied to assign weights based on expert judgment, and spatial datasets were integrated in a GIS environment to generate a composite suitability map. The results classified urban land into five suitability levels, with 0.5% categorized as highly suitable, 6.1% as moderately suitable, 52.9% as appropriate, 37.7% as marginally suitable, and 2.8% as unsuitable. Approximately 29.66% of the total area was identified as having spatial potential for urban green space development beyond existing green coverage. The findings provide planners with spatially explicit guidance on where green space expansion is both feasible and impactful, particularly in dense inner-city areas near transportation and hydrological networks. The study underscores the importance of context-sensitive, data-driven planning tools in addressing land-use challenges in compact, heritage-sensitive cities. The proposed GIS-AHP approach offers a replicable and adaptable framework for supporting sustainable green infrastructure planning in rapidly urbanizing environments.

Abstract: The mangrove forest in An Hoa lagoon, Quang Nam province, Central Vietnam is a vital natural ecosystem that provides significant economic and environmental services in coastal wetlands. However, this mangrove forest has been declining due to human activities. Despite its importance, there have been limited studies evaluating the temporal and spatial changes of the mangrove forest in An Hoa lagoon. This study utilized multi-temporal Landsat satellite imagery and GIS technologies to create mangrove change maps over the past two decades (2000–2020). The classification results demonstrated high accuracy (Ҡappa coefficient > 0.81, Overal accuracy reached 89.2%). The analysis revealed significant changes in the mangrove forest during the period 2000–2020. In 2000, the mangrove forest covered 108.7 hectares, but this area decreased to 78.5 hectares by 2010 due to deforestation for aquaculture expansion by local communities. Over the next decade, however, the mangroves forest area increased to approximately 73.8 hectares, reflecting the efforts of local authorities in mangrove restoration and improved management policies. This study contributes to evaluating the effectiveness of mangrove management and rehabilitation of projects and provides valuable insights for improving policies aimed at the sustainable development of mangrove ecosystems.

Abstract: Incense burning is a significant source of indoor air pollution. In Vietnam, this practice is deeply rooted in cultural and religious traditions and is commonly observed in most households. Assessing the pollution levels associated with incense burning is essential for providing timely health recommendations to the public. This study conducted indoor air quality monitoring in a room in a residential property in Vinh Yen City, Vinh Phuc Province. This room is designated for ancestor worship, with frequent practice of incense burning. PM_2.5, NO_2, and O₃ were monitored continuously using AQMesh sensors from December 22, 2021, to February 18, 2022. The mean and standard deviation of hourly indoor PM_2.5, NO₂ and O₃ concentration during whole monitoring period were 59 ± 50 µg/m³, 24 ± 13 µg/m³, 9 ± 5 µg/m³, respectively. Indoor to outdoor (I/O) ratios of the three parameters were lower than 1 for most of the study period, indicating that outdoor sources were generally dominant. The I/O ratio of PM_2.5 rose above 1 during incense burning periods and for some time afterward, indicating a dominant contribution from indoor sources. Six PM_2.5 pollution events were recorded during incense burning periods, with the average peak hourly concentration of indoor PM_2.5 reaching 571 µg/m³, while outdoor concentrations remained largely unchanged. These findings highlight the substantial impact of incense burning on indoor air quality and emphasize the need to raise public awareness about its potential health risks in residential environments.

Abstract: This study evaluated the occurrence of pharmaceuticals and personal care products (PPCPs) in the rivers and lakes in the North of Vietnam. Surface water samples from rivers and lakes were collected to determine PPCP concentrations. The analysis results showed that the total concentration of PPCPs in river water samples ranged from 23.6 to 772 ng/L, while in lake water samples, it ranged from 36.2 to 1004 ng/L. Caffeine was the most abundant compound, and antibiotics were the predominant therapeutic class, with sulfamethoxazole having the highest concentration, followed by lincomycin. Along the rivers, there was a trend of PPCP accumulation downstream. The level of PPCPs was affected by population density and proximity to discharge sources. The highest levels of PPCPs were observed after the river flowed through major cities like Hanoi and Thai Nguyen. PPCP levels were lower during the rainy season compared to the dry season. A semi-quantitative risk quotient (RQ) assessment indicated a high ecological risk to algae at in lakes and at the downstream sites of rivers.

Abstract: With the rapid growth and industrial expansion of the footwear sector in Vietnam over the past three decades, the issue of solid waste management (SWM) has become increasingly critical. Footwear production generates a amount of leather, rubber, and fabric waste. There is only 0.8% of SW final treatment reused or recycled through closed-loop systems, 88.8% is incinerated with energy recovery and 7.7% is downcycled into lower-value materials. This highlights the urgent need to implement circular economy (CE) strategies in the footwear sector. This article employs the DPSIR (Driving - Force - Pressure - State - Impact - Response) framework to evaluate the impact of CE strategies on SWM in footwear manufacturing. And this term integrates the 3Rs principles (Reduce, Reuse, Recycle) with material substitution, waste segregation, and closed-loop supply chain management. The module framework profiles how market dynamics, waste generation pressures, and regulatory gaps interact with environmental outcomes and policy responses. If applying this integrated approach, the sector could obtain significant benefits: a reduction of 756 tons of CO₂e emissions in 2024 and an estimated savings of over USD 1174,474 in external health and environmental costs. These consequences confirm that CE adoption not only enhances resource efficiency but also improves cost effectiveness for enterprises. Government support through policy enforcement and financial incentives are also critical to the sustainable production and effective waste management in the footwear industry.