Khoa Môi trường, Trường Đại học Khoa học Tự nhiên, Đại học Quốc gia Hà Nội

Irrigated rice cultivation plays an important role in affecting atmospheric greenhouse gas concentrations. In recent years, extrapolation and simulation of impact of farming management on GHGs fluxes from field studies to a regional scale by models approach has been implementing. In this study, the DeNitrification & DeComposition (DNDC) model was validated to enhance its capacity of predicting methane (CH4) emissions from typical irrigated rice-based system in Vu Gia-Thu Bồn River Basin with two water management practices: Continuous Flooding and Alternate Wetting-Drying.2 rice field experiments were conducted at delta lowland (Duy Xuyen district) and midland (Dai Loc district), considered as  typical regions along topography transect of study areas. The observed flux data in conjunction with the local climate, soil and management information were utilized to test a process based DNDC model, for its applicability for the rice-based system. The model was further refined to simulate emissions of CH4 under the conditions found in rice paddies of study area. The validated model was tested for its sensitivities to variations in natural conditions including weather and soil properties and management alternatives. The validation and sensitive test results indicated that (1) the modeled results of CH4 emissions showed a fair agreement with observations although minor discrepancies existed across the sites and treatments; (2) temperature factor changes had considerable impact on CH4 emissions; (3) soil properties affected significantly on CH4 emissions; (4) varying management practices could substantially affect CH4 flux from rice paddies. It was suggested that DNDC model is capable of capturing the seasonal patterns as well as the magnitudes of CH4 emissions from the experimental site in Vu Gia-Thu Bồn River Basin.Keywords:  DNDC model, validation, Methane (CH4), rice paddy, Vietnam.

The development of Industrial Zones in Vietnam will put pressure on water resources at local as well as national scale, due to the large amounts of water consumed and discharged to environment. This study, via water mass balance, provides analyses and assessments on water demand and wastewater generated in each trading groups (industrial sectors) of the Long Thanh Industrial Zone and the Nhon Trach III Industrial Zone phase 2, Dong Nai – the province with the most industrial zones in Vietnam. According to the water mass balance calculation results, the water demand of industrial sectors depends on their manufacturing characteristics. Of which, Textile and Garment are the sectors with the highest demand, as well as highest water loss rate and highest amount of wateswater dischared. Meanwhile, Electronic and Construction Materials cosume the least amount of water. Machinery sector has the lowest amount of water loss. The wastewater/supply water ratio of the Long Thanh Industrial Zone is always 1,1 (for Textile) to 1,5 (for Machinery) times higher than the Nhon Trach III Industrial Zone phase 2, while the wastewater/supply water ratio of the Nhon Trach III Industrial Zone phase 2 is always less than 80%.

In this paper, an electrocoagulation reactor was set up to investigate the ammoniumremoval in Nam Son landfill leachate. The research focused on studying several factors that affectto the ammonium removal namely current intensity, operating time, initial pH and electrodematerials. A mono-polar electrocoagulation reactor was set up in a batch system with ironelectrodes and 1.8 L leachate. The research indicated that current intensity and operating time aredirectly proportional with NH4+ treatment performance. When applied current increased from 1 to4A, the NH4+ removal percentage went up from 14.03 to 24.99% after a 1 hour treatment. Theeffect of initial pH in range of 5 to 10 has showed that the best NH4+ treatment efficiency inneutral and mild alkaline conditions. It is noticeable that iron electrodes had higher NH4+ removalthan aluminum one during nearly the first 40 min, however this trend has been reversed later withthe advantage belonging to aluminum anode. The optimum operating conditions found arealuminum electrodes, applied current of 3A, electrolysis time of 60 min, raw pH of 8, resulting inNH4+ treatment performance of approximately 24%. As a result, the electrocoagulation method isnot really effective in NH4+ removal and might be applied as a pre-treatment.Keywords Ammonium, electrocoagulation, landfill leachate, iron, aluminum, electrodes References [1] I. Linares-Hernández, C. Barrera-Díaz, G. Roa-Morales, B. Bilyeu, F. Ureña-Núñez, Influence of the anodic material on electrocoagulation performance, Chemistry of Engineer Journal, 148, 2009, 97-105.[2] C.B. Shivayogimath, W. Chandrakant, Landfill leachate treatment by electrocoagulation process using iron sacrificial electrodes, International Journal of Renewable Energy and Environmental Engineering, 02, 2014, 3.[3] M. Mollah, P. Morkovsky, J.A.G. Gomes, M. Kesmez, J. Parga, D.L. Cocke, Fundamentals, present and future perspectives of electrocoagulation, Journal of Hazardous Materials, B 114, 2004, 199–210.[4] N. Daneshvar, A. Oladegaragoze, N. Djafarzadeh, De-colorization of basic dye solutions by electrocoagulation: an investigation of the effect of operational parameters, Journal of Hazardous Materials B,129, 2006, 116–122.[5] M. Kobya, O.T. Can, M. Bayramoglu, Treatment of textile wastewaters by electrocoagulation using iron and aluminum electrodes, Journal of Hazardous Materials B, 100, 2003, 163–178.[6] Nguyen Manh Khai, Hoang Thi Quynh Trang, Chemical Precipitation of Ammonia and Phosphate from Nam Son Landfill Leachate, Hanoi, Iranica Journal of Energy and Environment, 3, 2012, 32-36.[7] Hoang Viet Yen, Doctor Thesis of Science: Optimization of partial nitrification and de-nitrification processes in landfill leachate treatment using sequencing batch reactor technique, Université de Liège, 2009.[8] Phan The Nhat, Ha Nhu Biec, Nguyen Thi Tuyet Mai, Bui Xuan Thanh, Nguyen Phuoc Dan, Application of a partial Nitritation and anammox system for the old landfill leachate treatment, International Bio-deterioration and Biodegradation 95, 2014, 144-150.[9] I. Fatih, K. Ugur, A. Omer, M. Talha Gonullu, Treatment of leachate by electrocoagulation using aluminum and iron electrodes, Journal of Hazardous Materials, 154, 2008, 381-389.[10] X. Chen, G. Chen, P.L. Yue. Separation of pollutants from restaurant wastewater by electrocoagulation, Separation Purification and Technology, 19, 2000, 65-76.[11] X. Li, J. Song, J. Guo, Z. Wang, Q. Feng, Landfill leachate treatment using electrocoagulation, Procedia Environmental Sciences, 10, 2011, 1159-1164.[12] E. Bazrafshan, Performance evaluation of electrocoagulation process for removal of chromium (VI) from synthetic chromium solutions using iron and aluminum electrodes, Turkish Journal of Engineering and Environmental Science, 32, 2008, 59–66.[13] X. M. Chen, G.H. Chen, P.L. Yue, Separation of pollutants from restaurant wastewater by electrocoagulation, Separation and Purification Technology,19, 2000, 65–76.[14] M. Kobya, H. Hiz, E. Senturk, C. Aydiner, E. Demirbas, Treatment of potato chips manufacturing wastewater by electrocoagulation, Desalination, 190, 2006, 201–211.

The water quality of Suoi Hai reservoir, the largest reservoir in Hanoi city, is being threatened by human activities of the surrounding area, as reported by the press. The trophic status of the reservoir is the result of both natural eutrophication and nutrient inputs from anthropogenic sources, particularly the leachate from a lakeside waste treatment plant. This study aims to identify the trophic status of the Suoi Hai reservoir and the changes of water trophic state over space and time. Data of chlorophyll-a concentration, total phosphorus, and Secchi disk depth from 51 sites during three field campaigns in October 2019, August 2020, and March 2021 was used to calculate Carlson’s trophic state index (CTSI). Resultant CTSI (ranged from 60 to 72) allows classifying Suoi Hai reservoir as highly eutrophic water. Its variations in space and time provided evidence for an influence of anthropogenic activities on the reservoir trophic state. Analysis of the trophic state index deviations suggested that total phosphorus is the key factor that influenced the reservoir trophic state. Therefore, managing the anthropogenic nutrient inputs load to the reservoir should be a critical task to control eutrophication in Suoi Hai Reservoir at present. 

In this work, the combination of two advanced oxidation processes, electro-Fenton (hydroxyl radical ●OH generated by reactions on cathode) and anodic oxidation (●OH produced directly on anode), in the same reactor was studied to evaluate the treatment of methylene blue (MB) dye in aqueous solutions. This electrochemical system was equipped with a commercial carbon felt cathode (9.5cm 12cm), lead dioxide-coated titanium anode (10 12cm), direct current (DC) and continuously aerated. The effects of operating parameters such as pH, applied current (I), catalyst concentration ([Fe2+]) and MB concentration (C0) on MB removal efficiency were investigated through monitoring MB concentration at different times by spectrophotometric method. An optimal process was achieved at the condition of [Fe2+] = 0.1 mM; pH 3.0; [Na2SO4] = 0.05 M; i = 2.5 mA.cm-2 and after 60 minutes of electrolysis, 92.19% of MB was removed which was far higher than the figure obtained by using individually electro-Fenton (73.77%) or anodic oxidation (58.04%). These experimental results have demonstrated that the combination of electro-Fenton and anodic oxidation using Ti/PbO2 electrode is a prospective method for destruction of persistent dyes.

In recent years, the demand for electric power in Vietnam has increased at annual growth rates of 10% to 12%, and the challenge is to promote renewable energy sector. One of these sustainable energy sources is to harness energy from the wind through wind turbines (WTs). In fact, more wind power plants in Vietnam are continuously to be built due to the rapidly growing demand of country's industrialization and modernization process. However, a significant hindrance preventing the widespread use of WTs in Vietnam is the noise they produce, which significantly contributes to the annoyance experienced by residents living near wind farms. The prediction of noise impacts for new wind farms is one of the many aspects of the environmental impact assessment process in Vietnam as well as in the world. In addition, the determination of the 45 dBA noise contour-line is very important because it is the basis for determining the scope of the project impact according to the IFC/WB performance standards and the number of households to be relocated from the project site. The article’s main focus is therefore on the estimation and simulation of the acoustical noise produced by 18 WTs during the operation phase of Nexif Energy Ben Tre wind power plant and the background noise levels at the project site have been performed by using a combination of specific study methods such as environmental modeling (iNoise Pro modeling software), mapping and geographic information systems. The obtained results show the importance of using modeling method in quantifying the noise levels generated from 18 wind turbines of the Nexif Energy Ben Tre wind power plant met IFC standard and Vietnamese regulation on noise during day-time, but did not meet IFC standard on noise during night-time. The level of background noise measured during night-time in the project area also did not meet IFC standard. Therefore, the overall cumulative noise level exceeds the IFC standard for residential area (45 dBA only). In addition, the appropriate solutions to reduce noise levels from WTs are also proposed.

Nước thải chứa thành phần Mononitrotoluene (MNT) có ảnh hưởng đến sức khỏe con người, sinh vật và môi trường xung quanh. Trong nghiên cứu này, hiệu quả xử lý MNT trong môi trường nước của quá trình Sono-Photo- Fenton-like kết hợp vật liệu nano sắt hóa trị 0 (nZVI) được nghiên cứu đánh giá. Trong đó, ảnh hưởng của các yếu tố pH, nồng độ H2O2, nồng độ nZVI, thời gian phản ứng đến hiệu quả xử lý được nghiên cứu đánh giá thông qua quy hoạch thực nghiệm bằng phương pháp bề mặt đáp ứng (RSM). Kết quả nghiên cứu cho thấy hiệu quả xử lý MNT bằng quá trình Sono- Photo-Fenton kết hợp nZVI đạt 100% tại điều kiện pH = 2, C0MNT = 100 mg/L, CnZVI = 0,5 mM; CH2O2 = 5 mM, thời gian phản ứng 30 phút.

Nghiên cứu này tập trung vào việc ứng dụng WebGIS trong thành lập bản đồ trực tuyến hiện trạng đốt rác thải ngoài trời trên địa bàn quận Hoàng Mai, thành phố Hà Nội. Từ kết quả điều tra và phân tích số liệu thực địa đã chỉ ra 65 điểm đốt rác thải trên địa bàn khu vực nghiên cứu với sự đa dạng về diện tích, khối lượng, và tần suất đốt rác tại các điểm này. Quá trình xây dựng dữ liệu GIS và bản đồ trực tuyến sử dụng phần mềm QGIS và nền tảng web Leaflet giúp nâng cao chính xác vị trí các điểm bãi rác và tạo ra một công cụ hiệu quả để truyền đạt thông tin cho cả cộng đồng và cơ quan quản lý. Bản đồ không chỉ cung cấp cái nhìn tổng quan về tình hình đốt rác mà còn kích thích nhận thức và ý thức cộng đồng về bảo vệ môi trường.

Kiểm soát tiếng ồn trong môi trường lao động là cần thiết cho sức khỏe con người và môi trường xung quanh. Mức độ tiếng ồn nguy hiểm, được coi là ngưỡng gây ra các vấn đề về tâm sinh lý cho người lao động. Mục đích của nghiên cứu này xây dựng bản đồ phân bố không gian mức độ tiếng ồn bằng số liệu đo được tính toán dựa trên mô hình tiếng ồn. Một khu công nghiệp sản xuất nhựa tại thành phố Hải Phòng đã được lựa chọn và mức áp suất âm thanh được đo tại 60 điểm riêng biệt tại khu công nghiệp. Các phép đo được tiến hành vào các khung giờ buổi Sáng (8h00 – 10h00) với mức độ tiếng ồn vào buổi sáng dao động từ 37,5 đến 95,2 dBA, buổi Trưa (11h30 – 13h30) dao động từ 17,0 đến 74,0 dBA và buổi Chiều (14h00 – 16h00) từ 38,7 đến 100 dBA. Dữ liệu mức tiếng ồn thu được của khu công nghiệp được lập bản đồ bằng mô hình mạng nơ-ron hàm cơ sở xuyên tâm (RBF). Kết quả chỉ ra rằng chất lượng môi trường lao động trong khu công nghiệp ở mức trung bình, có nghĩa là việc tiếp xúc với các mức độ này trong một thời gian dài có thể ảnh hưởng đến sức khỏe và chất lượng cuộc sống của người lao động. Đề xuất giải pháp khả thi để giảm mức độ tiếng ồn trong khu vực xuống các giá trị giới hạn cho phép nhằm nâng cao chất lượng môi trường lao động.

Constructed wetlands (CWs) have been applied to treat various wastewater types including domestic wastewater, livestock wastewater, industrial wastewater and acid mine drainage with the advantages of low cost, environmentally-friendly technology and high treatment efficiency. Mining wastewater with the high content of heavy metals often causes negative impacts on the ecosystems and human health. In this study, the capacity of using limestone, hydrolyzed rice husk as filter materials and the CWs planted with Caladium bicolor to treat iron and manganese in artifical wastewater treatment are evaluated. The wetland model has the size of length x width x height of 50 cm x 15 cm x 20 cm. 10 liters of the synthetic wastewater were used and initial Fe and Mn concentrations varied from 5, 10, 15, 20 and 25 mg/L. The results showed that limestone and hydrolyzed rice husk with the weight ratio of 5 : 2.5 (kg) had good ability to remove Fe and Mn with treatment efficiencies of approximately 99.8% after 144 hours. During a 24-hour retention time, the Fe and Mn concentrations ​​in the wastewater decreased rapidly in CWs and the initial Fe and Mn concentrations affected treatment performance. When the initial Fe and Mn concentrations were below 20 mg/L, treatment efficiencies of Fe and Mn reached about 99% after 144 hours in the CWs and Fe and Mn concentrations met the national regulation QCVN 40: 2011/BTNMT, column B. The study highlights the potential applications of C. bicolor in CWs with the use of natural limestone and hydrolyzed rice husk as substrates in treatment of iron and manganese-contaminated wastewater. Keywords: Constructed wetlands, Caladium bicolor, limestone, rice husk, iron, manganese.