Treatment of acidic wastewater from thien ke tin processing factory by sulfate reducing bioreactor: a pilot scale study

A pilot-scale system of a total volume of 6 m3 using sulfate reducing (SR) bioreactor technology was established for the treatment of acidic wastewater from Thien Ke tin processing factory in Tuyen Quang province, Vietnam. In the system, the acidic wastewater with high metal content went first to a collecting tank filled with limestone gravels to increase pH to a value favorable for SRB growth, and at the second step to a SR bioreactor where sulfate reduction occurred to produce sulfide for metal precipitation. To activate the SR bioreactor, a laboratory SRB mixed culture dominated by Desufovibiro, Desulfobulbus and Desulfomicrobium species was added at a cell density of 106 cell/ml so that a full activation was achieved just after a week of incubation. Molasses was added to the SR bioreactor at 0.5 ml/L as substrate for the SRB growth during the operation. The performance of the system was studied under batch and continuous modes. The batch mode showed good results after three day-operation. The pH increased from 2.8 – 3.2 to 7 – 7.2, and a total of 750 mg/L sulfate was reduced to sulfide presumably by the SRB. The produced sulfide efficiently removed metals from the wastewater, such as iron from 143.1 mg/L to 0.3 mg/L, copper from 16.32 mg/L to 0.04 mg/L and manganese from 10.9 mg/L to 0.05 mg/L. The continuous mode with a hydraulic load of 100 l/h and an according retention time of three days showed constitutive contaminant removal. The effluent pH of the system was around 7 within six-day period. The sulfate reduction was active, keeping sulfate concentration in the final effluent as low as 150 mg/L. Accordingly, the three most metal contaminants (iron, copper and manganese) were found at concentrations below the regulated limits. The results showed the possibility of applying SR bioreactor technology for the treatment of AMD is feasible and the use of previously enriched mixed culture of SRB could be a good approach to shorten the activation period of the SR bioreactor

EFL STUDENT’S PROBLEMS WITH PARAGRAPH WRITING AT TAY DO UNIVERSITY, VIETNAM

This paper studied problems in EFL students’ paragraph writing. The research participants were first-year students of English in Tay Do University (TDU). To achieve the desired aims of the current study, the researcher combined both qualitative and quantitative methods, using questionnaires, interviews, and observations as the main instruments. The researcher used the package of social sciences (SPSS) for analysis. Research results showed that the freshmen at TDU often encountered problems in writing paragraphs. These accounted for grammatical structures, vocabulary, and coherence. Basing on the research results, students could recognize their difficulties when writing and find some new ways to overcome them. It is suggested that teachers should find and update some new teaching methods so as to develop students’ paragraph writing skills. Article visualizations

DISTRIBUTION OF USEFUL AND HARMFUL MICROORGANISMS IN SHRIMP AQUACULTURE WATER IN TIEN HAI COASTAL OF THAI BINH PROVINCE

Joint Research on Environmental Science and Technology for the Eart

Critical Assessment of Feed-In Tariffs and Solar Photovoltaic Development in Vietnam

Vietnam became the world’s third largest market for solar photovoltaic energy in 2020. Especially after the Vietnamese government issued feed-in tariffs for grid-connected solar photovoltaic systems, the installed capacity of solar photovoltaic applications exploded in 2019. From studies carried out in the relevant literature, it can be said that support policies are highly important for the initial development of the renewable energy industry in most countries. This is especially true in emerging countries such as Vietnam. This paper reviews the feed-in tariffs issued and deployed in different regions of Vietnam for grid-connected solar photovoltaic applications. Moreover, the paper takes a closer look at the costs of electricity production from these systems in relation to the feed-in tariffs issued in Vietnam. The results show that the gap between the levelized cost of electricity and the feed-in tariff for solar photovoltaic electricity is relatively high, particularly in regions with a lower irradiation potential

Study change of the performance of airfoil of small wind turbine under low wind speed by CFD simulation

Renewable energy has received strong attention and investment to replace fossil energy sources and reduce greenhouse gas emissions. Quite good and good wind speed areas have been invested in building large-capacity wind farms for many years. The low wind speed region occupies a very large on the world, which has been interested in the exploitation of wind energy in recent years. In this study, the original airfoil of S1010 operated at low wind speed was redesigned to increase the aerodynamic efficiency of the airfoil by using XFLR5 software. After, the new VAST-EPU-S1010 airfoil model was adjusted to the maximum thickness and the maximum thickness position. It was simulated in low wind speed conditions of 4-6 m/s by CFD simulation. The lift coefficient, drag coefficient and $C_{L}$/$C_{D}$ coefficient ratio were evaluated under the effect of the angle of attack and the maximum thickness by using the $k-\epsilon$ model. Simulation results show that the VAST-EPU-S1010 airfoil achieved the greatest aerodynamic efficiency at the angle of attack of 3\,^{\circ}, the maximum thickness of 8\% and the maximum thickness position of 20.32\%. The maximum value of $C_{L}$/$C_{D}$ of the new airfoil at 6 m/s is higher than at the 4 m/s by about 6.25\%.Comment: 19 pages, 21 figure

A Rare Colonic Metastasis Case from Hepatocellular Carcinoma

BACKGROUND: Hepatocellularcarcinoma (HCC) metastasis include intrahepatic and extrahepatic metastasis. Similar to intrahepatic metastasis, extrahepatic metastases are not unusual in cases with HCC. However, colonic metastasis is infrequent. CASE REPORT: We describe a clinical case, he was diagnosed with HCC a year ago, treated with TACE (transarterialchemoembolisation), re-examined with abdominal pain and defecation disorder. The tests such as CT scan, colorectal endoscopy, fine needle aspiration (FNA) revealed secondary metastatic lesion of HCC in sigmoid colon. This is the first gastrointestinal (GI) tract metastatic we have encountered. CONCLUSION: HCC metastases of the colon are rare, especially cases of hematogenous spread. The prognosis of these patients is often very critical. Indications for surgical removal of the lesion may be used if the general situation of patient is acceptable

Evaluation of Phacoemulsification Cataract Surgery Outcomes After Penetrating Keratoplasty

BACKGROUND: Cataract is one of the reasons which causes impaired visual acuity (VA) of the eyes after penetrating keratoplasy (PK), which can be treated by cataract surgery after PK or triple procedure. Cataract surgery after PK has advantages that parameters of the eyes such as axial length, anterior chamber depth (ACD) as well as corneal curvature are stabilized after removing all sutures postoperatively, and intraocular lens (IOL) power can be calculated correctly. Therefore, postoperative VA will be improved significantly. In Vietnam, there have not been any study about cataract surgery after PK, therefore we conduct this research. AIM: To evaluate the outcomes of phacoemulsification cataract surgery following primary PK. METHODS: Non-randomized controlled intervention study. Ninteen eyes (19 patients) that underwent phacoemulsification plus IOL insertion after initial PK in Cornea department, Vietnam National Institute of Ophthalmology, from December 2013 to September 2014. RESULTS: All patients presented with reduced VA, including 17 eyes (89.9%) with VA ≤ 20/200, mean astigmatism was 7.9 ± 1.0 D. Clear corneal grafts in 16 eyes while corneal opacity was seen in 3 eyes. All eyes with cataract were diagnosed from grade 2. After cataract surgery, improved VA > 20/200 was achieved in 72.22% of cases. There was a markable reduce of postoperative astigmatism with 1,8 ± 0.8 D (p < 0.05). However, the immunologic graft reaction was presented in one eye, and two edematous corneas also reported after cataract surgery. After treatment, there was one cornea achieved its clarity. CONCLUSION: Phacoemulsification cataract surgery following initial PK showed good outcomes with improved postoperative VA, reduced astigmatism, and the ultimate graft survival rate was high

Screening for actinomyces isolated from soil with the ability to inhibit Xanthomonas oryzae pv. oryzae causing rice bacterial blight disease in Vietnam

Bacterial blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the major diseases in rice culture of Northen Vietnam, as well as other rice-growing regions of the world. In this study, we isolated and screened for actinomycete strains from Vietnam with the ability to inhibit Xoo isolates from northern Vietnam. From 90 actinomycete strains taken from soil in northern Vietnam in 2010, we screened for their antagonistic activity against 10 races of Xoo causing rice bacterial blight disease. Three actinomycete strains were found to inhibit all 10 Xoo races. Among the three strains, a strain namely VN10-A-44 was shown not to have the ability to produce toxic compounds and was selected for further study. The strain was identified as Streptomyces virginiae by 16S ribosomal RNA gene sequencing. We replaced soybean meal with tofu waste in antibiotic producing medium to improve antagonistic activity of VN10-A-44 against the Xoo pathogen and to make use of tofu waste for large-scale fermentation of VN10-A-44. We found that replacing soybean meal with 20 and 30 g of tofu waste/litter in the antibiotic producing medium gave the largest inhibition zone against the Xoo pathogen.Key words: Xanthomonas oryzae pv. oryzae, rice bacterial blight disease, Streptomyces virginiae, Vietnam

Surveying of acid-tolerant thermophilic lignocellulolytic fungi in Vietnam reveals surprisingly high genetic diversity

Thermophilic fungi can represent a rich source of industrially relevant enzymes. Here, 105 fungal strains capable of growing at 50 degrees C and pH 2.0 were isolated from compost and decaying plant matter. Maximum growth temperatures of the strains were in the range 50 degrees C to 60 degrees C. Sequencing of the internal transcribed spacer (ITS) regions indicated that 78 fungi belonged to 12 species of Ascomycota and 3 species of Zygomycota, while no fungus of Basidiomycota was detected. The remaining 27 strains could not be reliably assigned to any known species. Phylogenetically, they belonged to the genus Thielavia, but they represented 23 highly divergent genetic groups different from each other and from the closest known species by 12 to 152 nucleotides in the ITS region. Fungal secretomes of all 105 strains produced during growth on untreated rice straw were studied for lignocellulolytic activity at different pH and temperatures. The endoglucanase and xylanase activities differed substantially between the different species and strains, but in general, the enzymes produced by the novel Thielavia spp. strains exhibited both higher thermal stability and tolerance to acidic conditions. The study highlights the vast potential of an untapped diversity of thermophilic fungi in the tropics