National Technical Regulation Research Articles

Surveying causes of surface water pollution at Sao River, Binh Thuy district, Can Tho city, Vietnam

Surface water sources play an important role in human and biological activities and the socio-economic development of the region. Therefore, the assessment of water quality and determination of the causes of water pollution in Sao river is essential for good management of the surface water environment. The study was conducted from July to December 2020. Water samples were collected at the time of low tide to evaluate the water quality indicators of temperature, pH, conductivity (EC), dissolved oxygen (DO), biological oxygen demand (BOD), total suspended solids (TSS), ammonium (N-NH4+), orthophosphate (P-PO43-) and coliform. The source of pollution was determined by direct interviews with households living near Sao river. The results showed that surface water quality in Sao river had signs of organic pollution and microbiological pollution due to BOD, TSS, N-NH4+, P-PO43-, coliform exceeded the allowable limits of National Technical regulation on surface water quality (QCVN 08-MT:2015/BTNMT, column A1). The results of the interview revealed that 70% of respondents said that water was seriously polluted and the main sources of pollution were domestic solid waste and domestic wastewater. Therefore, to improve surface water quality in Sao river, solid waste and wastewater management is urgently required. It is necessary to promote the monitoring and management of water quality with the participation of local authorities and communities.

Characterizing Seasonal Variation in Landfill Leachate Using Leachate Pollution Index (LPI) at Nam Son Solid Waste Landfill in Hanoi, Vietnam

The improper treatment of landfill leachates is one of the major problems associated with waste landfilling and causes serious environmental pollution at waste landfill sites and their surroundings. To develop a suitable landfill leachate treatment system and to minimize the risk of environmental pollution, it is important to characterize seasonal and temporal variations of landfill leachates. This study investigated the leachate quality of the Nam Son waste landfill in Hanoi, Vietnam in 2017–2019 and characterized the potential risks of landfill leachate using a leachate pollution index (LPI). The results of this study showed that the seasonal and temporal variation of the overall LPI during the monitoring period was small and in the range of 20–25 (values 2.5 times higher than the maximum permissible limits of Vietnam National Technical Regulation on Industrial Wastewater). The LPI sub-indices attributed to organic and inorganic pollutants were major components of the LPI. Especially, the annually averaged values of LPI of inorganic pollutants were 7.7 times higher than the maximum permissible limits, suggesting that the treatment of inorganic pollutants, such as ammonium-nitrogen (NH4+–N) and total nitrogen (TN), is highly required at Nam Son landfill to prevent environmental pollution surrounding the landfill site.

Unbaked materials from mixtures of waste sludge of a water purification plant, fly ash, and water glass

In water purification plants, a large area of urban land is using to store waste sludge (WS). The waste sludge from water filtration plants is aluminosilicate, which can be form a geopolymer. However, the waste sludge has low alkaline activity, so it must be used in combination with fly ash (FA) to create geopolymer products. Fly ash is a solid waste containing amorphous silica so that has high alkaline activity, suitable for treatment by geopolymer method. The geopolymerization of waste sludge from water purification plants is a relatively new method. The geopolymer is a binder formed by the chemical reaction between aluminosilicate materials and alkaline activated solutions. The alkaline activated solution used in these experiments was water glass (WG). The water glass is solution of sodium silicate (Na2O.nSiO2) dissolved in water. The research results of geopolymer materials from the mixture of fly ash, the waste sludge of Thu Duc water purification plant, Ho Chi Minh City (Vietnam), and water glass (WG) were introduced in this study. The activated Al2O3 and SiO2 oxides in the fly ash and the waste sludge can be dissolved in the water glass and polymerized into a geopolymer material. The test samples had pressed at a high pressure of 225 MPa to form cylindrical ones weighing approximately 3 grams, height about 18 mm, and 10 mm in diameter. These samples were then cured at 110 ◦C for 24 hours and at room temperature (30 +/- 5 ◦C). The methods of Fourier infrared spectroscopy (FTIR) and scanning electron microscope (SEM) had used to detect the microscopic structure and geopolymer bond formation of the samples. The compressive strength of the tested samples at 28 days old was higher than 3.5 MPa, the pH was less than 12.5, meeting the Vietnamese National Standards for unbaked materials (TCVN 6477:2016) and National Technical Regulation on environmental impact (QCVN 50:2013 / BTNMT), respectively. The results show a new approach of solidifying the waste sludge for further applications such as the manufacture of geopolymer concretes or landfill materials.

ASSESSING SURFACE WATER QUALITY IN FRESHWATER RESERVOIRS IN AN GIANG PROVINCE, VIET NAM

Water quality is critical for a healthy ecosystem, this study was conducted to evaluate the surface water quality in lakes in An Giang Province from 2017 to 2019. Water quality was assessed using variables of temperature, pH, dissolved oxygen (DO), total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), nitrate (NO3- - N), phosphate (PO3 4- - P ), ammonia (NH+ 4 - N), and coliforms at nine locationsbelonging to seven reservoirs including O Tuk Sa, Thuy Liem, Soai So, Soai Chek, O Thum, O Ta Soc, and Bung Binh Thien. Water quality criteria were assessed according to the National Technical Regulation on Surface Water Quality (QCVN 08-MT: 2015/BTNMT). Cluster analysis (CA) and principal component analysis (PCA)were applied to group water quality to identify the main parameters affecting water quality in the reservoirs. The findings indicated that the water quality in the reservoirs were polluted by TSS, organic matters (DO was low, while COD and BOD were high), and microorganisms (coliforms). The PCA analysis showed that the watervariables including temperature, pH, DO, TSS, COD, BOD, NO3- - N, PO3 4- - P , NO3- - N, and coliforms significantly influenced the surface of the water in the reservoirs. It is necessary to investigate pollution sources to propose appropriate solutions to treat and maintain the water quality in the reservoirs of An Giang Province .

Spatiotemporal Analysis of Surface Water Quality in Dong Thap Province, Vietnam Using Water Quality Index and Statistical Approaches

The study was conducted to spatiotemporally analyze the quality, location and critical water variables influencing water quality using water monitoring data from the Department of Environment and Natural Resources, Dong Thap province in 2019. The water quality parameters including turbidity, pH, temperature, dissolved oxygen (DO), total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrite (N-NO2−), nitrate (N-NO3−), ammonium (N-NH4+), total nitrogen (TN), orthophosphate (P-PO43−), chloride (Cl−), oil and grease, sulfate (SO42−), coliforms, and Escherichia coli (E. coli) were collected at 58 locations with the frequency of four times per year (February, May, August, and November). These parameters were compared with national technical regulation on surface water quality—QCVN 08-MT: 2015/BTNMT. Water quality index (WQI) was calculated and spatially presented by geographical information system (GIS) tool. Pearson correlation analysis, cluster analysis (CA), and principal component analysis (PCA) were used to evaluate the correlation among water quality parameters, group and reduce the sampling sites, and identify key parameters and potential water pollution sources. The results showed that TSS, BOD, COD, N-NH4+, P-PO43−, coliforms, and E. coli were the significant concerns impairing the water quality. Water quality was assessed from poor to medium levels by WQI analysis. CA suggested that the current monitoring locations could be reduced from 58 sites to 43 sites which can be saved the total monitoring budget up to 25.85%. PCA showed that temperature, pH, TSS, DO, BOD, COD, N-NH4+, N-NO2−, TN, P-PO43−, coliforms, and E. coli were the key water parameters influencing water quality in Dong Thap province’s canals and rivers; thus, these parameters should be monitored annually. The water pollution sources were possibly hydrological conditions, water runoff, riverbank erosion, domestic and urban activities, and industrial and agricultural discharges. Significantly, the municipal and agricultural wastes could be decisive factors to the change of surface water quality in the study area. Further studies need to focus on identifying sources of water pollution for implementing appropriate water management strategies.

Dạng sống và yếu tố địa lý của thực vật hoang dại làm thực phẩm theo kinh nghiệm của dân tộc Thái ở Khu Bảo tồn thiên nhiên Mường La, tỉnh Sơn La

The paper presents dynamics of environmental quality of surface water of Suoi Hai lake, Ba Vi district, Hanoi city from June 2020 to February 2021. There are 11 studied environmental parameters, including transparency, temperature, conductivity, pH, dissolved oxygen concentration, BOD, COD, total nitrogen, total phosphate, hardness and chlorophyll a. The results of analyses show that the lake water is showing signs of pollution. Some parameters at the sampling points during the monitoring period exceeded the permitted limits of the Ministry of Natural Resources and Enviroment's national technical regulations on surface water quality (QCVN 08-MT: 2015/BTNMT). The results of this work also give assessments and comments on the dynamics over time, rainy and dry seasons of the studied environmental parameters. The results of present work provide reference material for regulatory bodies, as well as for follow-up studies on the environment and ecology.

Complex engineering object digital twins – power engineering smart transformation basic concept

The formation of information models and digital twins is a general element of the modern description of complex engineering objects. Their presence is already becoming a requirement of national and international technical regulation and contractual relations. The stage of forming separate digital twins within different stages of the life cycle has been passed and the approach has proven to be effective and in demand. The most striking example is BIM technologies. Now it is important to switch to complex end-to-end information models and digital twins for the full life cycle of complex engineering objects. This innovation becomes a universal tool for the interaction of all stakeholders in high-tech industries. Competence in technologies for working with complex information models and digital twins on the full life cycle of complex engineering objects is already a key competitive factor for high-tech engineering and operating companies in power production. This is a proactive trend in the formation of intellectual energy data space. It will lead to another cycle of improving the efficiency, safety, and economy of the industry and businesses.

Housing Refurbishment for Energy Efficiency and Comfort

The housing stock in Vietnam has boomed in the last few decades, especially in urbanised areas. However, the increasing number of housing units did not go along with housing quality, a healthy living environment or a sustainable building stock. Recent legislation only applies to public buildings but not the private housing sector, which accounts for the majority of the building stock. Therefore, this research aimed to contribute to a more sustainable building stock in Vietnam by improving the energy efficiency in new and renovated urban houses. This research started with examining the energy upgrade potential of the existing houses in Vietnam. Both passive and active refurbishment design measures were investigated for the Vietnamese context. Among the measures, a green facade has a large potential in energy saving. Effect of a green facade on thermal and energy performance was tested by conducting a physical experiment on a real tube house in Hanoi. Next, a stepped design strategy was introduced in a student design workshop in Vietnam. The participants were trained to apply sustainable and energy efficient design measures for Vietnamese tube houses. In addition, the vision for designing future tube houses was discussed on several sustainability aspects: urban densification, energy efficiency, circular economy and social interaction. This research is also expected to contribute to the establishing of a future national technical regulation for private housing in Vietnam.

Analysis of the influence of non-sinusoidal and unbalanced network modes on induction motors

The parameters of electrical network modes do not correspond the requirements GOST 32144-2013 of Russian and the National technical regulation of Vietnam. In real operating conditions in electrical networks in non-sinusoidal and unbalanced modes there are harmonic components of voltages and currents as well as voltages and currents of negative sequence. They cause additional losses of active power, which leads to additional heating and causes premature aging of the insulation, and as the result, the reduction in the service life of induction motors. Currently, we see that the process of formation of intelligent electrical power systems is underway. Systems for continuous monitoring of power quality indices and parameters of electrical systems modes are being developed. These systems can be supplemented with programs for calculating characteristics that issue the warning when the unfavorable influence of the parameters of non-sinusoidal and unbalanced modes is detected on various electrical equipment of both electrical power systems and consumers of electrical energy. The paper provides an overview of the characteristics used to analyze, assess and predict the influence of poor power quality associated with non-sinusoidal and unbalanced of currents and voltages on induction motors. A computer program was developed to calculate these characteristics. The program was used to study the influence of non-sinusoidal and unbalanced modes on the induction motors of the coal sorting plant of the Vietnamese company “Cua Ong-Vinacomin”.

An A2O-MBR system for simultaneous biological nitrogen and phosphorus removal from brewery wastewater at various nitrate recirculation ratios

Anaerobic/Anoxic/Oxic – Membrane BioReactor (A2O-MBR) system including A2O unit at short solids retention time (SRT) for accumulation of PO43--P and MBR at long SRT for nitrification of NH4+-N was used to enhance simultaneous removal of nitrogen and phosphorus from brewery wastewater. The model of A2O-MBR system made from polyacrylic with the capacity of 49.5 liters was operated with organic loading rate of 0.75 kgCOD/m3.day. Nitrate recycling ratio was increased from 100 to 300% while sludge recirculation ratio was maintained at 100%. The results showed that for the nitrate recycling ratios of 100, 200, 300%, average NH4+-N and total nitrogen (TN) removal efficiencies of the model were 95.7 and 72.4, 99.2 and 86.7, 99.3 and 89.6%, respectively. The removal efficiencies of chemical oxygen demand (COD) and total phosphorus (TP) were over 90 and 75%, respectively, regardless of nitrate recirculation ratio. The output values of COD, NH4+-N, TN and TP were within the limits of Vietnam National Technical Regulation on Industrial Wastewater (QCVN 40:2011/BTNMT), column A, throughout the experiments. The model with recommended system configuration and optimum operational conditions could treat not only nitrogen but also phosphorus well due to appropriate nitrate recycling ratios.

Housing Refurbishment for Energy Efficiency and Comfort

The housing stock in Vietnam has boomed in the last few decades, especially in urbanised areas. However, the increasing number of housing units did not go along with housing quality, a healthy living environment or a sustainable building stock. Recent legislation only applies to public buildings but not the private housing sector, which accounts for the majority of the building stock. Therefore, this research aimed to contribute to a more sustainable building stock in Vietnam by improving the energy efficiency in new and renovated urban houses. This research started with examining the energy upgrade potential of the existing houses in Vietnam. Both passive and active refurbishment design measures were investigated for the Vietnamese context. Among the measures, a green facade has a large potential in energy saving. Effect of a green facade on thermal and energy performance was tested by conducting a physical experiment on a real tube house in Hanoi. Next, a stepped design strategy was introduced in a student design workshop in Vietnam. The participants were trained to apply sustainable and energy efficient design measures for Vietnamese tube houses. In addition, the vision for designing future tube houses was discussed on several sustainability aspects: urban densification, energy efficiency, circular economy and social interaction. This research is also expected to contribute to the establishing of a future national technical regulation for private housing in Vietnam.

БЕЗПЕКА ПРОДУКЦІЇ. ПОКАЗНИКИ ЕКОЛОГІЧНОСТІ ВІДПРАЦЬОВАНИХ ГАЗІВ ТЕПЛОВОЗІВ, ЯКИМ ПОДОВЖЕНО СТРОК СЛУЖБИ ПІСЛЯ КАПІТАЛЬНО-ВІДНОВЛЮВАЛЬНОГО РЕМОНТУ АБО ПІСЛЯ МОДЕРНІЗАЦІЇ

This article is the first in a series of related publications urgent in the field of railway transport, namely absence of new traction rolling stock and the presence of existing in operation, the condition of which remains uncommented. The article is concerned with the requirements specified in normative documents for the environmental security indices of diesel locomotives operated on the railways of Ukraine, the volume and qualitative characteristics of environmental indices, which must be checked before the operation of the repaired or upgraded locomotive is given; the impact of overhaul reconditioning or modernization measures of locomotives on the environmental indices of exhaust gases was determined. In the context of the article, it is reasonable to consider the safety requirements of the main, even the only source of exhaust gases - internal combustion engines used on locomotives (general view of locomotives is shown in Fig. 1). Safety requirements for engines and methods of their control are usually set in the technical specifications, design and operating documentation for engines of certain types. Engines must also meet the requirements of national technical regulations and national standards for them, taking into account their operational functions for which they are intended. In this case, any danger to personnel, which may occur during the operation of the engine, as a necessary element of the overall system to create a moving force (e.g. locomotive engine), its moving parts, hot surfaces, should be minimal. During the design of engines their purpose, operating conditions, environmental conditions, as well as characteristics of used materials, in particular the brand of diesel fuel should be taken into account. Special attention should be paid to the structure safety of: fuel supply systems; lubrication and cooling systems; engine control systems. The physical factors of dangerous and harmful effect include: moving elements; hot surfaces; exhaust gases; increased noise level; increased vibration level; flame emissions; - excess pressure in the crankcase; electric current. The chemical factors of dangerous and harmful effect include: harmful components of exhaust gases; fuel and fuel vapor; lubrication and its vapour; coolant; non-metallic materials. According to the lists of physical and chemical factors of dangerous and harmful effects of engines, one of the most important is indices of exhaust gases of diesel engines.

High Efficiency of Waste Stabilization Ponds using Para Grass (Brachiaria Mutica) Vegetation for Treatment of Industrial Wastei Ho Chi Minh City, Vietnam

In recent years, wastewater treatment by using biological method has been concerned because it low cost, easy to operate and enviromentally friendly. In this study, stabilization pond – one of the biological wastewater treatment methods has been researched for treating industrial wastewater in Industrial park, District 2, Ho Chi Minh city, Viet Nam. In stabilization pond, Para grass planted on the surface of the pond with roots in the water. Important elements of the treatment process were surveyed to provide optimal operation conditions, include: flow rate of influent, grass cutting cycle, initial COD concentration, fraction of N and P, the height of Para grass after cutting, pH in influent. The results show that Para grass grows well in wastewater and treatment efficiency of stabilization is high when flow rate of influent at 0.12 m3/h and 0.18 m3/h (corresponding to retention time is 7.8 days and 5.3 days, respectively). Besides, Para grass need to be cut periodically for about 20-22 days and the height of grass after cutting from 0.2 - 0.4 m to ensure the best treatment efficiency. Effect of pollution parameters of influent has been also surveyed. The results showed that stabilization pond treats wastewater efficiently when the initial COD concentration is from 200 to 350 mg/l, the fraction of N/P is from 4 to 6 and pH= 7. Wastewater after treatment with stabilization pond meets standards QCVN 40:2011/BTNMT (National Technical Regulation on Industrial Wastewater) with parameters in effluent such as COD, TN, TP, BOD5, Coliform. Moreover, biomass of Para grass after treatment can be used as feed source for livestock and ensure safety according to QCVN 01-183:2016/BNNPTNT. These results show the applicability of stabilization pond using Para grass vegetation in concentrated industrial wastewater treatment with low cost, simple but efficiency, environmentally friendly and towards sustainable development.

Honeybee products as potential bioindicators of heavy metals contamination from Northern Vietnam

Contamination of heavy metals (As, Cd, Hg, Pb and Sn) in honeybee products (Apis cerana) from Northern Vietnam is determined. The study was carried out in two main harvesting seasons of beekeeper farms (April and October), over two years (2018-2019). A total of 72 samples from 24 honeybee hives from 8 provinces and one city were collected. The results showed that the quality of three products in nearly all research sites were met the standards in accordance with the national technical regulation on the limits of heavy metal contamination in food of the Vietnamese Health Ministry, except for the pollen and beeswax from HY2 site. The concentration of Pb was most notably value in this study, which was determined at fairly high levels in pollen (3,767 mg/kg) and beeswax (5,840 mg/kg) from HY2 site. This can be a warning for this metal significant contamination in the habitat. Specially, Hg was not detected in most samples or only recorded without significant. For the environmental types, the mean value of As and Sn in all honeybee’s product types in semi-rural area were higher than that in rural area. Thus, the detection of the heavy metals proves that honeybee’s products could be good indicators to detect the environmental contaminants and monitor the habitat quality of a particular area

Enhanced removal of heavy metals using sorbent and Phragmites australis

Water pollution by heavy metals has currently been an increasing worldwide concern. This study was conducted to assess the removal efficiency of a treatment system using sorbent and common reed (Phragmites australis). Approximately 1400 g of sorbent that was modified from Ban Cuon iron mine drainage sludge by adding 10% sodium silicate solution and heating at 400 °C was put in a column of 1.8l. The initial concentrations of As and Cd in inflow water were 1.0 mg/l, those of Pb, Mn, and Zn were 6.0 mg/l. During 30 days of the laboratory experiment, aqueous solution of constant flow rate (50 l/day) was pumped through the sorbent column before flowing into surface and horizontal subsurface constructed wetlands using P. australis. The results showed that the removal efficiency of As, Cd, Mn, Pb and Zn by sorbent – surface constructed wetland were 83.0 – 89.5, 89.3 – 93.3, 69.7 – 98.0, 94.8 – 95.4, and 69.2 – 92.3%, respectively; those by sorbent – subsurface constructed wetland were 85.3 – 89.1, 98.5 – 98.7, 92.8 – 98.7, 95.5 – 96.0, and 93.1 – 96.2%. The concentrations of heavy metals in the outlet water met the National Technical Regulation on Industrial Wastewater of Vietnam (QCVN 40:2011–BTNMT) with the exception of As, which indicates the effectiveness of combined sorbent and P. australis for simultaneous removal of these metals from contaminated water.

Using biochar from spent coffee grounds to treat pollution in livestock wastewater

Four types of biochar material synthesized from spent coffee grounds by slow pyrolysis process CF1 (500(C/0.5h); CF2 (500(C/1.5h); CF3 (500(C/3h); CF4 (500(C/6h) is studied to treat two pollution parameters (COD and TSS) in livestock wastewater. Material characteristics were determined by SEM, EDX and BET methods. The results showed that the 4 samples of biochar materials were structured fiber clearly, the interplanar spacing which corresponds to the lattice plane. The C content in the biochar sample is higher than the initial raw material sample; the highest value recorded reaches 90.61% C (CF2). 100 mL of the original livestock waster water is filtered through columns with 4g of biochar CF1-CF4 during reaction times varied from 0h, 1h, 4h and 8h, the COD treatment efficiency and adsorption content of CF4 sample is highest of 96.41% and 188 mg/g after 8h, and the lowest value is 76.67% and 149.5 mg/g after 1h recorded in CF3 sample, however the COD value after treatment is still higher from 1.2 to 1.46 times than Vietnamese standard 62: 2016/MONRE - national technical regulation on the effluent of livestock. The CF3 material samples have the highest TSS treatment efficiency and adsorption content of 95.19% and 6.425 mg/g after 8h and the lowest of 66.78% and 4.575 mg/g recorded in CF1 samples after 1h, response the requirements of QCVN 62: 2016/MONRE. The results showed that biochar is a potential sorbent to removed pollutants from waste water.

Heavy metals emissions from joss paper burning rituals and the air quality around a specific incinerator

Burning joss paper is a traditional and long-term historical custom in Oriental countries. However, joss paper contains a lot of toxic components [1], which can be released into the environment during the burning stage [2,3] and caused health risk [4]. The objective of this study is to assess the heavy metals in bottom ash and dust fume by using a burning chamber in the laboratory; thereby, it also assesses the ambient air from the incinerator – a case study at Thien Hau pagoda, District 5, HCM city. The initial result showed that there is a significant amount of heavy metals in the dust fume and bottom ash in order Al < Fe < Mn < Cu < Pb < Zn < Cd. The result of analyzing metal contents in ash samples from T1 to T4 showed that all is higher than Vietnam Standard (QCVN 03:2008/BTNMT – National technical regulation on the allowable limits of heavy metals in the soils [5]) with 236.21 ppm Cu, 4.93 ppm Cd, and 128 ppm Pb. Moreover, the results of assessing the ambient air quality at a pagoda indicated that the incinerator (S3) was the source with the highest of dust concentration and had a significant impact on air quality to the location around.

Use of Moringa oleifera seeds powder as bio-coagulants for the surface water treatment

The research aims to evaluate the effectiveness of surface water treatment by using Moringa oleifera seeds by-products as bio-coagulant to remove turbidity and natural organic matter. This approach brings more benefits as compared to others, particularly, no chemical use, low cost, easy to implement but equivalent efficiency and also safe for the health. The surface water samples were collected from three sites in the Dong Nai River, Vietnam, with the average concentrations of pH, turbidity, chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) ranging from 6.2 ± 0.3 to 6.7 ± 0.2, 25.2 ± 2.5 to 41.7 ± 7.9 NTU, 22.4 ± 6.4 to 41.1 ± 5.9 mg L−1 and 0.70 ± 0.20 to 1.08 ± 0.15 mg L−1, respectively. The study has found that the optimum bio-coagulant dosage was 0.15 ml L−1 for the water samples in both rainy and dry seasons. In the rainy season, the turbidity removal efficiencies in Tan Luong Ferry, Nguyen Van Tri Park and Hoi Son Ferry ranged from 87.8 ± 2.9 to 93.3 ± 1.0%, while the tendency for dry season was obtained from 85.7 ± 2.5 to 94.3 ± 1.1%, respectively. The treated turbidity concentration met the Vietnam’s National Technical Regulation on domestic water quality. Furthermore, the paired t tests used to compare the pre-treatment and post-treatment dataset for COD and turbidity removal efficiencies were significant (p < 0.05) in three studied sites. Results indicated that Moringa oleifera extract is a promising material which is environmental-friendly and low cost to treat the surface water.

Semi-continuous removal of nutrients and biomass production from domestic wastewater in raceway reactors using Chlorella variabilis TH03-bacteria consortia

Abstract Production of algae biomass from wastewaters have been considered as an economical strategy for feasible commercialization of microalgae industry. Technically, large scale cultivation of microalgae in wastewaters should be conducted in semi-continuous and/or continuous modes, in which stable health of algal cultures of previous generations for the use of later generations needs to be ensured. In this regards, this study has investigated stability of growth and pollutant removal capability of Chlorella variabilis TH03-bacteria consortia using domestic wastewater as the sole of nutrient source in raceway ponds. Experiments were performed in semi-continuous mode with the aim of recovering valuable nutrients including carbon, nitrogen and phosphorous from the waste stream to algal biomass. Data revealed that prior domestication of C. variabilis TH03 in unsterilized domestic wastewaters established seed cultures of C. variabilis TH03–bacteria consortia, which enabled to grow effectively in new wastewaters under highly variable conditions. Moreover, once nutrient levels dropped below those required by the national technical regulation on domestic wastewater QCVN 14 : 2008/BTNMT, the replacement of 80% volume of the algal–bacteria culture with new wastewater media was recommended to ensure both culture stability as well as high pollutant treatment capacity of the raceway systems. Under the optimal replacement, biomass concentration and areal biomass productivity of 1.67–1.85 g/L and 11.1–15.3 g/m2 day, respectively, were steadily achieved over 148 days of the outdoor cultivations. Removal efficiencies of nutrients in the form of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorous (TP) removed by the C. variabilis TH03-bacteria consortia in the reactor systems were determined as 64.7–90.7, 85.1–96.8 and 99.7%–100%, respectively. The obtained results are useful for further optimization including design and manage C. variabilis TH03-bacteria consortia based continuous processes in larger scales for the production of high volume and low price biomass, helping to obtain returns from treatment of the waste stream, which is currently considered as a major source of water pollution in Vietnam.

Spatial Variations of Surface Water Quality in Hau Giang Province, Vietnam Using Multivariate Statistical Techniques

This study assessed the surface water monitoring system in Hau Giang Province in 2019. The monitoring data for pH, temperature, total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonium (NH4+_N), nitrite (NO2-_N), nitrate (NO3-_N), orthophosphate (PO43-_P), coliforms, and iron (Fe) were collected from the Department of Natural Resources and Environment, Hau Giang Province, Vietnam. The results were compared with the national technical regulation on surface water quality (QCVN 08-MT: 2015/BTNMT). Then, these parameters were used to determine the locations and parameters for water quality monitoring using multivariate analyses including cluster analysis (CA) and principal component analysis (PCA). The results indicated that the main concerns for the quality of water in the canal of Hau Giang Province were organic matter (high BOD and COD), nutrients (NH4+_N, NO2-_N, PO43-_P), coliforms and iron. The CA results showed that 42 monitoring locations could be decreased to 26 locations, reducing monitoring costs by up to 32%. The PCA identified 12 sources of pollution, of which three main sources were PC1, PC2 and PC3 accounting for 75.6% of the variation in water quality. PCA findings showed that all the current water variables in the 2019 monitoring program were significant. The present study could help local environmental managers to reconsider the selected locations and parameters in the environmental monitoring program.