A research on the performance of down-flow hanging sponge (DHS) reactor treating domestic wastewater

The aim of this study was to evaluate the performance of a down-flow hanging sponge (DHS) system in treating domestic wastewater. A pilot-scale of DHS system with a capacity of 60 L was designed and fabricated from polyvinyl chloride (PVC). The dimensions of DHS system are 1.5 m in height and square surface with 0.2 m in width, consists of three identical segments connected vertically in series. Each segment was filled by polyurethane sphere containing sponge. The total area of sponge and polyurethane sphere was 3,300 m2 m-3, density at 150 kg m-3, void ratio at 90%. DHS system was operated at ambient temperature within 82 days and stepwise increased of organic f rate from 0.5 to 1 and 1.5 kg COD m-3 d-1. The results showed that, this system performed well throughout the operational period and achieve the maximum removal of COD, BOD5, NH4+-N, and TN as 80%, 83%, 65% and 60%. The effluent of wastewater from DHS system achieved the requirement for National technical regulation on domestic wastewater of Vietnam type B QCVN 14:2008/BTNMT. In conclusion, the performance of DHS system indicated a high potential for application in removing organic matter and converting nitrogen ammonia to nitrogen nitrate, however it did not perform well for the removal of total nitrogen, it is necessary to study further by providing an anoxic zone in the system to enhance the treatment of nutrient in wastewater

Chemical composition and antibacterial activities of essential oils from Homalomena pierreana (Araceae)

30-37Homalomena is a genus of the Araceae family which contains several remedies used extensively in traditional Vietnamese medicine. H. pierreana is a rare plant species of Homalomena genus and found only in Phu Quoc National Park, Phu Quoc Island, Kien Giang Province, Vietnam. Therefore, the number of studies about this species is limited and the bioactivity of this species is still unknown. In this study, the chemical composition of essential oils was investigated which was isolated from leaves and rhizomes of H. pierreana at the first time by GC-MS. Eight and twelve compounds were identified from the essential oils of rhizomes and leaves, respectively. The major component from both the rhizomes and the leaves was aromadendrene (44 and 48%, respectively). Furthermore, the antibacterial activity of essential oils collected from leaves and rhizomes of H. pierreana was investigated and it was observed that the essential oil of rhizomes could inhibit the growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, while the essential oil of leaves exhibited an inhibitory effect against Staphylococcus aureus and Escherichia coli.</em

The Cenozoic Song Hong and Beibuwan Basins, Vietnam

The Vietnamese offshore margin holds a substantially underexplored petroleum potential. The key to unravelling this potential lies in understanding the tectono-stratigraphic framework of the region including the Cenozoic mechanisms governing syn-rift and source rock deposition. This is essential for prediction of, for instance the presence and nature of source rocks in South-East Asia and possible reservoir intervals in the syn-rift packages. The Vietnamese part of the Song Hong and Beibuwan Basins (Fig. 1) differs from other basins along the western margin of the South China Sea in that the Palaeogene syn-rift succession is sporadically exposed due to uplift and inversion. These exposures provide a unique glimpse into the Cenozoic syn-rift succession of the basin

A new species of Typhonium (Araceae) from Vietnam

Typhonium obtusum is described as a new species endemic to Vietnam. It is unique in the genus in having an oblong-elliptic spathe limb with an obtuse apex and yellowish-greenish filiform staminodes with a down-curved acumen. The ecology, distribution and assessment of the conservation status of the new taxon, as well as a key to all known Typhonium species in Vietnam, are provided

Cost optimization of two-stage helical gearboxes with second stage double gear-sets

In practice, the cost of a gearbox plays a very important role in the trade. Therefore, reducing the cost of gearboxes is an important task not only when manufacturing the gearboxes but also when designing them. In order to reduce the cost of a gearbox, there are many solutions in which determining the optimal partial gear ratios of a gearbox is an effective measure. This is because it not only the size, the mass but also the cost of a gearbox depends greatly on the partial gear ratios. This work presents a method for calculating the cost function of two-stage helical gearboxes with second-stage double gear-sets based on the mass of the components that construct the gearbox. The cost objective function is minimized to achieve the optimal transmission ratios. Furthermore, screening experiments are carried out with nine important input parameters that have significant effects on the optimum transmission ratio of the second stage. These parameters are the total gearbox ratio, the coefficient of wheel face width of the first stage, coefficient of wheel face width of the second stage, the allowable contact stress of the first stage, the allowable contact stress of the second stage, the output torque, the cost of gearbox housing, the cost of gears, and the shaft cost. The experimental results of were analysed by using the Analysis of Variance (ANOVA) method with the help of Minitab 19 software. The results demonstrate that the effective weight of the input parameters and their interactions on the output response was investigated. Also, a regression model for computing the optimal transmission ratio of the second stage was proposed. This brings significance not only in the design process but also in manufacturing since the gearbox cost can decreas

Chemical profiles and antibacterial activity of acetone extract of two Curcuma species from Vietnam

Curcuma thorelii Gagnep. and Curcuma cotuana Luu, Škorni?k. &amp; H.?.Tr?n are the rare species only found in Southeast Asia. The present study was the first to explore the chemical compositions and antibacterial effects of the whole plant acetone extracts of these 2 species. Altogether 41 and 31 compounds have been identified in C. thorelii and C. cotuana extracts by gas chromatography/mass spectrometry. Accordingly, the C. thorelii extract contained (E)-labda-8(17),12-diene-15,16-dial (33.37%), vitamin E (12.33%), phytol (9.83%) as the major compounds while C. cotuana extract contained predominantly (E)-labda-8(17),12-diene-15,16-dial (14.58%), n-hexadecanoic acid (10.96%), 3,7,11,15-tetramethylhexadec-2-en-1-yl acetate (8.13%), ?-sitosterol (7.97%). In addition, results from disc diffusion assay have shown that C. thorelii acetone extract had inhibitory effects on 5 out of 10 pathogenic bacterial strains such as Bacillus cereus (ATCC 11778), Listeria monocytogenes (ATCC 19111), Staphylococcus aureus (ATCC 25923), S. aureus (ATCC 29213) and S. saprophyticus (BAA750) while C. cotuana acetone extract was found to be effective only against B. cereus. The obtained results showed that the acetone extracts of C. thorelii and C. cotuana possessed several valuable bioactive compounds as well as promising antibacterial activity, which place a good foundation for future pharmaceutical product development

Comparison of several secondary metabolite and elemental ion contents of leaves from Kandelia obovata and Sonneratia caseolaris forests located in the Red River Delta

The two mangrove species Kandelia obovata and Sonneratia caseolaris were widely planted in the Red River delta. Both K. obovata and S. caseolaris forests play an important role in the economic development and environmental protection of the delta. However, chemical responses of the common mangrove forests to different ecological conditions in the delta have not yet been described. In this study, we evaluated chemical responses of K. obovata and S. caseolaris through comparisons of the content of metabolites and element ions in leaves of mangrove plants located under different ecological conditions in the Red River delta. In the low salinity area (Thuy Truong), specific leaf areas of K. obovata and S. caseolaris were much lower while the succulent index was higher compared to those in the high salinity area (Kim Trung). In Kim Trung, both species had a lower ratio of chlorophyll a/chlorophyll b. K. obvata in lower light (under the S. caseolaris canopy) had lower levels of chlorophyll b, resulting in a higher Chla/chlb ratio. There was no difference in the Mg content of leaves between two areas. An increase in Na content in leaves of mangrove plants in the higher salinity area was evident. The high K/Na ratio in leaves were eveluated for both species in high salinity areas. Our results also showed better uptake of K in leaves of S. caseolaris growing in the low salinity conditions (Thuy Truong), i.e. Thuy Truong has more favourable ecological conditions for S. caseolaris. Carotenoid contents in leaves of both species growing in the higher salinity were lower.