Hymenachnegrass (Hymenachne acutigluma) was planted in wastewater from intensive catfish (Pangasianodon hypophthalmus) with five inorganic nitrogen concentrations of 5, 10, 20, 30 and 40 mg/L, corresponding to reviewed inorganic nitrogen in fish pond, in which control treatment was wastewater from fish pond without Hymenachne. The experiment was arranged in completely randomized design with three replications. Water quality was evaluated weekly for 6 consecutive weeks and biomass was evaluated at the beginning and at the end of the experiment. Hymenachnegrass reduced NH4-N, NO2-N, NO3-N and TKN in wastewater at 69.7-96.9; 96.6-97.3; 99.3-99.9; 48.5-73.5%, respectively. In addition, Hymenachnegrass showed ability in reducing TP and PO4-P with respective deduction percentage of 84.8-95.6 and 85.7-92.5% as compared to the initial level of phosphorus. Besides the potential to reduce nitrogen, phosphorus in wastewater, fresh and dry weight of Hymenachnegrass were higher in nitrogen 30-40 mg/L than in the other treatments. Results showed that the higher concentrations of nitrogen were the better reduced efficiencies and higher biomass was achieved. Results indicated that Hymenachnegrass had high potential use in constructed wetlands for wastewater from intensive catfish pond with inorganic nitrogen concentrations from 5-40 mg N/L.

The objective of this research is to assess changes of groundwater level and the factors influencing groundwater level in the Soc Trang city, Soc Trang province. The research was conducted using: (i) descriptive statistical approaches; and, (ii) correlative analysis. The research showed that groundwater level in the three aquifers middle – upper Pleistocen (qp2-3), lower Pleistocen (qp1), and upper Miocen (n13)  have had an average decreasing rate from 0.3 to 0.39 m/year, of which, aquifer of middle – upper Pleistocen had the greatest decreasing rate (0.39 m/year). In addition, groundwater exploitation activities had a strong relation with the decreasing level of groundwater in the research area. A number of households using groundwater and water consumption were highly correlated to the declined groundwater level while the natural factors such as rainfall and temperature had low correlation with the declined groundwater level.

This research was conducted to study effects of recirculating rates on water quality in intensive whiteleg shrimp (Litopenaeus vannamei) culture tanks integrated with constructed wetlands of Canna sp. planted. Water sampling was carried out for ten weeks with three recirculating rates of 50%, 100% and 200% which corresponded to 0,5 m3, 1 m3 and 2 m3 water to be pumped per day through the systems. The results showed that tank water quality in three recirculating rates were in the suitable range for normal shrimp growth. Higher recirculating rates were connected to higher time-dependent accumulation of NO3-N và PO4-P. Shrimp grew best at 100% recirculating rate compared to the others. In this study, 100% recirculating rate appeared to be the rate of choice in terms of securing water quality and normal growth of whiteleg shrimp.

This paper describes a method for estimating methane gas emission from municipal solid waste (MSW) at the Thu Dau Mot city, Binh Duong province by the First Order Decay model (FOD) proposed by IPCC (2006). The CH4 emission from MSW in the year 2014 was calculated with historical data of MSW generated from the year 2007. In order to estimate the loaded methane in the year 2020, two scenarios were considered: (1) to refer to the Solid waste's Management and Treatment Programming of the Binh Duong province up to 2030; and, (2) To remain the current efficiency of solid waste management and treatment of the study area. The obtained resuts show there is an annual increase of methane emission; in 2014, the value was expected to be at 17.384 tone/year (equal to 434.600 tone CO2/year). The model indicates that there would be about 270.048 tone ofCH4-emission reduction (equal to 6.752.200 tone of CO2) from year 2015 to 2020. The benefits of solid waste recycling were remarkable, including reduction of green house gases and ability to take part in the Certified ofEmission Reduction (CER) credit.

The study was conducted to reflect the actual state management on groundwater extraction in Soc Trang province. Institutional and document management system issue groundwater of VietNam studied recognize globally and specific to the Soc Trang province. Staffs of local departments and companies related to the groundwater-extraction activities in the study area were interviewed to evaluate the reasonableness of each legal document for groundwater management within the local context. The dissemination of state regulation on groundwater extraction and protection, especially application for granting right of new extraction, were not well-established to the society. The study helped identify the gaps and overlaps in groundwater management between different relevant units. The research results were consulted to relevant departments and companies and conveyed to provincial government departments for proper decision-making on enacting legal documents for better groundwater management.

The study on “Evaluation of treatment efficiency of domestic wastewater by aquatic plants” was processed on a lab-scale artificial wetland system. Three aquatic plant variaties were chosen for this study, including: water cabbage, water hyacinth, and umbrella papyrus. The results showed that all three plant variaties were of high treatment efficiency on domestic wastewater showing through different parameters values (pH, EC, DO, turbidity, COD, BOD5, TKN, TP and total Coliforms). Umbrella papyrus had the greatest ratio (22.15%) of air cells/sectioning roots while water hyacinth and Water cabbage were lower at 19.63% and 10.47%, respectively. The establishment and increasing the air cell area offered the most importance mechanism that helped aquatic plants adapt to domestic wastewater.

The study was conducted from 2011 to 2014 in Long My, Vi Thuy and Phung Hiep district, Hau Giang province with the objective to assess the current status of pesticide use in double- and triple-rice farming systems and management of used pesticde-packages. The results showed that the pesticide use frequency and dose were unchangedduring the study period but distinguished betweenthe double- and triple-rice farming systems. Numbers of active ingredients in the triple-rice farming system were greater than that in the double-rice farming sytems (i.e. 57 vs. 44 active ingredients, respectively). Among the active ingredients, Carbofuran and Methomyl were banned from using in Vietnam.The management of empty pesticde containers by local farmers considerably changed during the study period. In fact, from 2011 to 2012, 34,7% of surveyed farmers were in the habit of discarding containers in the fields, but that decreased gradually in the period of 2012-2013 and 2013-2014. In the later period, the containers were sold and unsafelyburnt. In this study, the triple-rice farming system exaggerated the use of pesticide. Training local farmers in using proper dose of pesticide is an actual need to protect agricultural environment.

The Mekong Delta, in general and the coastal provinces, in particular, will be strongly affected by climate change and these negative impacts will greatly affect livelihood of local residents and food security of the area and the country. The spatial distribution of flood inundation and salinity intrusion (simulated by the Institute of Water Resources Planning) for the whole Mekong Delta of Vietnam was developed based on the based-year of 2004 and sea level rise scenarios in 2030 and 2050. This study used GIS approaches to identify hot-spot areas of different rice crops according to different salinity and flooding scenarios. The results showed that the vulnerable areas influenced by both flooding and salinity intrusion were of Soc Trang, Ca Mau and Bac Lieu provinces, parts of Ben Tre, Tien Giang and Tra Vinh provinces with total areas 12,257 ha in 2050. Rice cultivation will be strongly affected with the greatest area accounted for the triple-rice crop while mono-rice crop and integrated system of rice and upland crop are of the least affected by both flooding and salinity intrusion factors according to climate change scenarios.

The objective of this study is to assess the current status of meteorological droughts, and to assess impacts of climate change on meterological drought in the Mekong Delta, Vietnam. Firstly, data of rainfall and temperature simulated by the SEA START (Scenarios A2 and B2) were validated and bias-corrected. Standardized Precipitation Index (SPI) was then calculated to determine the 1, 3, 6 and 12 - month droughts for the current period of 1980-2012 and future period of 2015-2047. The SDF (Severity – Duration – Frequency) curve was established. The results were mapped for the whole Mekong Delta of Vietnam, and thus potential drought areas were identified. The results showed that in the Mekong Delta of Vietnam, the historical biases of rainfall (1980-2012) and temperature (2002-2012) between simulation and observation were +11.9% and +2.2oC, respectively. In the year 2030s, temperature (2025-2035) and rainfall (2015-2047) were highly variable in both scenarios A2 and B2. Results of the SPI calculation for the period of 2015-2047 compared with those for the 1980-2012 period varied in space and timing frequency. It was also found that drought frequency would not increase, but drought severity levels (severe, moderate, mild) would change.

To minimize pollutants from wastewater fish pond before discharging into the environment and figure out appropriate treatment methods, the experiment was carried out with 4 treatments, including: (1) Waste water (control), (2) Waste water + Eichhornia crassipes, (3) Waste water + E. Crassipes and aeration, and (4) Waste water + E. Crassipes + aeration and bacteria; each treatment was done with four containers (size 63x43x50 cm) characterized by three time repeated with flow rate of 150L/day/system. Samples were collected to evaluate at the time of 32, 64 and 96 days in each container. The results showed that in all 4 containers of the control treatments and treatments no. 2, the N-NH4+, NO2- and CO2 concentrations were higher than that defined in the National Technical Regulation on Wastewate. The treatments no. 4 brings high-performance treatments; indicators N-NH4+, H2S and CO2, industry standards achieved in the first container, indicator NO2- targets achieved after industry standards through 2 container. It shows very clearly the functions Eichhornia crassipes in removing wastewater pollutants catfish ponds in the constructed wetlands surface flow. Fresh weight after 96 days of in the first container 2 and 4 treatments compared with the corresponding initial increase of 21.7; 31 and 26.4 times. E. Crassipes died in ascending order container 2, 3, 4 for the treatments has aeration. The 3 treatment has effective best handled in the first container.

The Mekong Delta of Vietnam has about 48,830 hectares of coastal sand dunes. It is the narrow land strips distributing parallelly to the coastlines and allocated mainly in the coastal provinces with river mouths running through such as Tien Giang, Ben Tre, Tra Vinh and Soc Trang. The sand dunes are often characterized by relatively high population density with quite high diversity of agriculture - forestry - fishery production. During the past decade, the coastal sand dunes were under a number of adverse effects due to abnormal climate patterns. This study is carried out through synthesis analysis based on the field-surveys and discussions with groups of different livelihoods via direct interviews and discussions with 160 local farmers, who are cultivating in the coastal sand dunes. It is found that, multi-upland crop model is mostly applied (85-95%), while aquaculture nursery is of little choice (0-10% farmers surveyed). This study has recognized and evaluated the adaptability of the agriculture, forestry and fishery cultivation models in local communities, from which local residents are reasonably copings with climate change impacts. Five common solutions are selected in priority order as follows: (i) layout reasonable cropping calender (88%); (ii) selection of fitting plants - domestic animals (78.75%); (iii) application of agricultural technical solutions (73.12%); (iv) salvage of by-products for increasing income (60%); and, (v) organization of cooperation in production (51.25%). Statistical errors in the above preferential options are less than 10%. The study also suggested policy improvements for creating incentives in the long-term sustainable development for the region.

Assessment of litter production is essential to ascertain the status of nutrient cycling and forest health. The Ong Trang hillock mangrove is a pristine forest with the presence of three dominant mangrove species, including: Rhizophora apiculata, Bruguirea parviflora and Avicennia alba. Research on litterfall productivity of these forests is scanty; therefore, litterfall production of three mangrove species in the Ong Trang hillock was studied using litter traps for one year (from February 2013 to January 2014). For the Rhizophora apiculata, the annual dry weight of litterfalls was estimated to be 12,36 tonns/ha, of which: leaves were the most abundant (67%) contributory component of litters, followed by twigs (17%), stipules (8%), propagules (5%) and flower parts (3%). For the Bruguirea parviflora, the total annual dry weight of litterfalls was estimated to be 9,84 tonns/ha; leaves represented more than 71% of the total litter fall, followed by stipules (13%), propagules (8%), twigs (7%), and flower parts (1%). For the Avicennia alba, the total annual dry weight of litterfalls was estimated to be 10,12 tonns/ha; leaves were the most abundant (65%) of the total litter fall, followed by fruits (17%), twigs (12%), and flower parts (6%). The total litterfall of R. apiculata and B. parviflora did not show any seasonal variations. Total litterfall of Avicennia alba was higher during the dry season than those of the rainy season.

The objective of this study was to determine the belowground carbon accumulation of three dominant mangrove species at three land surface elevation levels, including: Avicennia alba, Rhizophora apiculata Blume and Bruguiera parviflora at low, medium and high elevations, respectively on the Ong Trang sand bar. The findings provided basis data for the payment of environmental services and forest management and protection. The plotting method of Kauffman& Donato (2012) was applied and three circle plots were designed along the transect of each land surface elevation level. On each plot, diameter at breast height (DBH1,3) was measured and soil samples were collected to analyse carbon accumulation in roots and soil carbon. The result showed that the carbon accumulation in roots was significantly different given land surface elevation, in which the carbon accumulation in roots of the medium elevation area (Rhizophora apiculata Blume) was the highest 38.14 tons/ha, followed by carbon accumulation in roots of high elevation area (Bruguiera parviflora) with 30.21 tons/ha and carbon accumulation in roots of low elevation area (Avicennia alba) was the lowest is 21.17 tons/ha. In the same context, the soil carbon accumulation was not significantly different, in which soil carbon accumulation of low elevation area (Avicennia alba) was the highest 304.7 tons/ha, followed by soil carbon accumulation of high elevation (Bruguiera parviflora) 303.88 tons/ha and soil carbon accumulation of medium elevation area (Rhizophora apiculata Blume) was the lowest 292.55 tons/ha. The carbon accumulation of soil layers was of significant differences and increased with soil depths.

Salinity intrusion is one of the major physical problems currently faced in the downstream section of the Mekong River in the Vietnamese Mekong Delta. In the recent years, given impacts of the land use change (from rice to either intensive or semi-intensive shrimp farming systems) in the coastal area, ​​the salinity intrusion becomes more serious with a highly complex process. In this study, a one-dimensional hydraulic model (HEC-RAS) was used to understand the general hydrodynamics of surface water resources of the downstream segments of the Tien River (Mekong River) under impacts of the Ba Lai culverts and to predict salinity intrusion in the future due to sea level rise and upstream discharge changes. The results showed that the Ba Lai culverts changed the river flow dynamics along the Ba Lai and An Hoa rivers but did not affect the flow dynamics of the others within the study river network. In addition, in the Ham Luong river, the salinity concentration of 4g/l could be found even greater than that of the baseline scenario in 2010 of about 25 km (further upstream). The results of this study confirm the applicability of the applied hydrodynamics model to predict the flow dynamics to support the hydraulic construction management and to assess environmental quality of surface water in the Vietnamese Mekong Delta.

This investigation aims to determine different kinds of chemicals and drugs used in intensive striped catfish culture in ponds in the Dong Thap province, Vietnam. Information on the current use of chemicals and drugs was collected by interviewing 30 catfish-farmers in the Chau Thanh district, Dong Thap province using prepared questionnaire. In a culture cycle, there were 17 chemicals and probiotics for pond preparation, 19 fish disease prevention and treatment products and 18 nutrient and probiotic products. The obtained results reveal that Enrofloxacine - a prohibited antibiotic - was widely used (70% interviewed farms), and 10 other antibiotics in a restricted list based on the Circular No. 03/2012/BNNPTNT (such as: amoxicilin, trimethoprime, ciprofloxacin, oxytetracycline, florfenicol, and so on) were commonly used in the study area. The origin and dosage of chemicals were not strictly controlled and often applied higher than the instruction based on farmers’ own perception. That might lead to more fish disease and antibiotics resistances. In addition, the study reported that the cost for chemicals and pharmaceuticals in one crop was 3,46% of the total investment and most of the interviewed farmers (96,7%; n=30) had distinct zones to store chemicals, pharmaceuticals and fish feed. The study also indicated that farmers were lack of sufficient knowledge regarding to the use of chemicals, appropriate dose, method of application and indiscriminate use of chemicals.

The Ben Tre province has the largest planted coconut area of Vietnam; coconut trees play a special role on local ecosystem, cultivation and landscape. The research entitled “The estimation of carbon-dioxide (CO2) absorptive capacity of coconut tree through biomass in Giong Trom district, Ben Tre province” was carried out in order to estimate amounts of biomass of coconut trees, accumulative carbon and absorbed CO2 in each part of the tree and on the total planted area. The study also investigated on the statistical interrelation between the two factors of diameter at breast height and dried biomass of the tree. Samples were collected on four standard-square cells which related to two groups of short and high coconut trees at the ages of 4 and 10 years. The research show that in average the fresh biomass volumes of  four-year coconut trees are  280.25 kg/tree and 160.4 kg/tree for the two groups of short and high coconut trees. Besides, the fresh biomass volumes of ten-year coconut trees are 861.478 kg/tree and 731.13 kg/tree of the high and short trees group, accordingly. According to the result, each hectare of 4–year coconut trees could absorb about 24.518 ton and 20.458 ton of CO2 with the reference to the high and short coconut tree groups, respectively. When the tree is at the age of ten, the absorbed amounts of CO2 are of the greatest. In fact, the groups of high and short coconut trees will absorb 75.2436 ton CO2/ha and 69.9189 ton CO2/ha, respectively. The interrelation factor between the diameter at breast height and dried biomass is fairly high (0.696 < r2 < 0.960).

The study is to assess the current groundwater resources management in the coastal area of the Vietnamese Mekong Delta in the context of rising demands and climate change, with the case study of the Vinh Chau District, Soc Trang Province. Descriptive statistics and individual interview approaches are applied in order to evaluate the efficiency and transparency in terms of governing and using groundwater resources and to consider the possible interactions between different stakeholders. The obtained results showed that the groundwater resources have been degraded rapidly in terms of quality and quantity due to the over-exploitation and insufficient water use. Groundwater resources management in the study area has faced different limitations in terms of transparency and efficiency of legal documents system. The co-management between different agencies for groundwater resources has not been effective. In addition, participations in groundwater resources management generally have not been well-coordinated between local government, management agencies and users. Periodically processes of checking the exploitation and contacting to local residents have not been well-performed. Besides, awareness of users on possible impacts of exploitation on groundwater resources sustainability is still limited. The research provides a suitable base towards possible measures for more effective and comprehensive groundwater governance.

This study was performed based on anaerobic batch experiment in 60 days with biological pre-treatment water hyacinth methods such as (i) biogas digester effluent, (ii) dark anoxic sediment, (iii) ditch water, and (iv) tap water and 100% pig manure. The results indicated that pre-treated water hyacinth by dark anoxic sediment could speed up biogas process and have greater daily biogas production capacity than that of pre-treated with tap water, biogas digester effluent and ditch water. On the 30th day, the cumulative biogas production of water hyacinth pre-treated by dark anoxic sediment, biogas digester effluence was greater than other pre-treatment methods (p

The study “Using the effluents from biodigesters with loading material from pig manure and giant water fern (Pistia stratiotes) for cultivating chili peppers (Capsicum frutescens L)" was conducted to assess the growth and development of chili peppers tree (Capsicum frutescens L) between the treatments of biogas waste water and the chemical treatment. The experiments were arranged completely randomized with 5 treatments, (1) 100% biodigester effluent, (2) 75% biodigester effluent + 25% pond water, (3) 50% biodigester effluent + 50% pond water (4) 25% biodigester effluent + 75% pond water, and (5) chemical fertilizer (control treatment). The results showed that the tree height was 62.3 cm/tree, chili pepper fruit was 57.2 fruit/tree and fresh weight was 79.6 g/plant in the treatment of 75% biogas waste water loading pig manure which were not statistically different from those of the chemical fertilizer treatment. The treatment watered by effluent from biodigester with loading material from giant water fern had significantly lower fruit number and fresh fruit weight compared to those of chemical fertilizer treatment. In the framework of this study that it could be possible to use effluent from pig manure biodigester replacing chemical fertilizers for growing chili peppers (Capsicum frutescens L.).

Drought is one of the most considered issues for agriculture in the Vietnamese Mekong Delta during the annual dry seasons. Aiming to ensure water requirement for corn cultivation, a study on water storage during annual flooding seasons to irrigate the dry season in a semi-dyke area was carried out in the Chau Phu district, An Giang province. In this study, field experiments and a numerical model of water-balance (the AquaCrop model) were conducted to: (1) determine design-parameters of a water-storage pond by a water-balance equation; (2) propose a model suitable for storing water to irrigate the Spring-Winter corn season. Results showed that with the 0.24 m3/day average precipitation, 1.87 m3/day surface water evaporation and 4.12 m3/day seepage from pond, the daily water demand for the crop was about 8.30 m3.

This study implemented two lab-scale submerged biological aerated filters (SBAF) which were operated in co-current and counter-current of air and wastewater modes. The results showed that the SBAF is suitable to use for treating catfish processing wastewater, and the counter-current SBAF having higher pollutants removal efficiency than that of the co-current one. At the hydraulic retention time of 8 hours, organic loading rate of 0.0066 kgBOD/m2*day, counter-current SBAF owning the COD, BOD5, TKN and TP removal efficiency of 97.12%, 98.58%, 95.65%, and 78.43%, respectively. The concentrations of these pollutants in the effluent reach the Vietnamese limit standard for discharge wastewater into stream according to the QCVN 11:2008/BTNMT and QCVN 40:2011/BTNMT (column A).

Organic fertilizers of intensive shrimp farming pond were used in this study to grow two continuous crops of pak choy (Brassica integrifolia) in order to evaluate the effectiveness of such organic fertilizers on the growth rate, productivity and profits of the crop. The study aimed to assess the effect of compost from shrimp pond sediment on brassica interrifolia growing in Dam Doi. The results showed that the growth of pak choy was significantly different in the treatment of mixing of 1kg/m2 organic fertilizers and 0.014kg/m2 NPK (16-16-8) fertilizer from the control treatment including the height average of 21,53± 0,23 cm, length of leaf 13,47±0,37 cm and width of leaf 10,1±0,26 cm. The height, length and width of the control were 18,93±0,98 cm, 11,57±0,72 cm and 8,27±0,24 cm respectively after five weeks growing. The yield of pak choy was significantly higher in the treatment of organic fertilizers and NPK (16-16-8) fertilizers (2,68-2,86 kg/m2) than in the control treatment (1,72-1,85 kg/m2) and in the organic fertilizers treatment (1,79-1,88 kg/m2). The profit from pak choy was higher in the treatment of organic fertilizers with NPK (16-16-8) fertilizers (33.326 VND/m2/crop) than that in of control treatment (19.135 VND/m2/crop) and the organic fertilizers treatment (19.025 VND/m2/crop).

This study aims to assess the effectiveness of the current surface water resources management on agriculture and aquaculture in the coastal area in the Vietnamese Mekong Delta and thereby to determine appropriate solutions for better water resources management based on conflicts between uses of surface water resources in agriculture and aquaculture and perception of local residents on the conflicts. The obtained results showed that conflicts in water uses between local farmers were mainly caused by improper water management leading to wide-spread of water pollution and aquaculture diseases, and further seawater intrusion into fresh water based agriculture zones. In addition, the study also provided an overview on the strengths and weaknesses of local farmers at the time being and the expected opportunities and threats in the future in terms of agriculture and aquaculture development in the study area. Finally, suggestions were provided to minimize the conflicts, leading to better (surface) water management for agriculture and aquaculture in each agro-ecological zones of the study area.

The purpose of the study is to examine the biomass and above-ground carbon accumulation of mangrove ecosystems at the Ong Trang sand-bar in the Ngoc Hien District, Ca Mau Province. The research focused on determining the biomass and carbon accumulation of mangrove trees and wood debris on three different elevations (of the land surface) with three dominant plants species such as Avicennia alba, Rhizophora apiculata Blume and Bruguiera parviflora. Standard plots and actual survey measurement and analysis of laboratory methods were used in the study. The results showed that the biomass and carbon accumulation among three elevations with different species were significantly statistically different. The biomass and carbon accumulation of two species Avicennia alba and Bruguiera parviflora were not different, and Rhizophora apiculata Blume and Bruguiera parviflora were not either. However, there were significant differences between Rhizophora apiculata Blume and Avicennia alba. Biomass and carbon accumulation in Avicennia alba was the lowest, followed by Bruguiera parviflora and biomass and carbon accumulation of Rhizophora apiculata Blume was the greatest. The biomass and carbon accumulation of wood debris was the highest at the Bruguiera parviflora area, followed by Rhizophora apiculata, and the lowest was at the Avicennia alba area. In addition, statistical analysis showed that the biomass and carbon accumulation of wood debris was not different among the three topographies. In addition, the total biomass and above-ground carbon accumulation of mangrove ecosystems at study area was 555,98 tons/ha and 269,21 tons/ha, respectively.

Study of mixing ratio effect on the ability of biogas production from co-digestion of cow manure (PB) with corn stalks (Zea mays) (TB) and aquatic weed (Pistia stratiotes L) (TT) was evaluated in three mixing ratios of manure and plant, including: 100:0, 75:25 and 50:50. The 21 L anaerobic digesters were set up to implement experiments in laboratory conditions. After 60 days, total biogas volume of the treatment of 100%PB:0%TB, 70%PB:25%TB and 50%PB:50%TB was 69±8.65 L, 102 ±3.4 L and 180±6.4 L, respectively and biogas yield was 196.1±5.55 L Kg-1VS-1, 241±5.3 L Kg-1VS-1 and 560.2±11.1 L Kg-1VS-1, respectively. Similarly, total biogas volume of the treatment of 100%PB:0%TT, 70%PB:25%TT and 50%PB:50%TT was 69±8.65L, 96.45±0.55 L and 142.3±9.5 L, respectively and biogas yield was 196.1±5.55 L Kg-1VS-1, 226.7±11.6 L Kg-1VS-1 and 314.2±12.1 L Kg-1VS-1, respectively. The results indicated that co-digestion of cow manure and plants can increase biogas volume.

The experiments of rearing snakeskin gourami with industrial pellet, pig manure and biogas digester (BD) waste water were carried out simultaneously in 100 m2 ponds with the stock density of 10 ind./m2. In the 1st pond, the amount of industrial pellet (with nitrogen of concentration of 42%) was daily supplied at the rate of 5%, 35% and 30% of total fish weight during the 1st, 2nd and 3rd two-month period, respectively. The nitrogen of pig manure and BD waste water in the 2nd and 3rd pond was analyzed at the beginning of the experiment and supplied to fish with the same amount of that supplied in the 1st pond. It was found that 76 species of zooplankton including 4 groups in which Rotatoria was the most abundant. In the pond with BD waste water supply, the zooplankton biomass was the greatest with the density fluctuated from 163,520 – 1,504,800ind./m3. After 6 months rearing, the growth of fish in the pond fed by BD waste water was similar to the one fed by industrial pellet. All of fish in the experimental ponds were not contaminated by E. coli and Salmonella so it is safe for human consumption. The waste water from BD system can be used for rearing snakeskin gourami to increase the household’s income.

The research on species elements of vascular plants was implemented from 2013 to 2014 in the Can Tho city. The potential biodiversity map was created based on 8 types of land use (classified based on 31 land use types presented on the current land use map of the city). The area was divided into 4 classes of potential diversity (high, medium, low and very low). From the potential biodiversity map, collecting sample sites were identified and totally 28 square areas (1km x 1km = 1km2) for collecting samples were chosen. The results of the survey showed that there were 620 species elements in higher plant generation in total, in which flowering plants were the most popular with 581 species (293 species of Monocotyledons and 288 species of Magnoliopsida), followed by seed plants and fern species with 11 and 28 species identified, respecitvely. Hence, the map of the potential biodiversity of the city was built based on those survey results. The Phong Dien, O Mon, Thot Not and Thoi Lai districts were of the greatest number of species (from 249 to 439 species) where wide areas of orchards in Can Tho city and Au Island could be found. Among all habitats, wild garden and perennial plant garden were of the greatest diversity of elements of species (82 species) and the least was on vegetable land (with 9 species).

In this study, we conducted liquid fuel recovery from solid waste by pyrolysis. 3 solid wastes (HDPE, butyl rubber and polypropylene) were used as a feedstock for pyrolysis. The results showed that 86% of liquid products were obtained for pyrolysis of the HDPE solid waste with slow and fast heating. However, liquid products obtained in the fast heating rate were of wax state at the room temperature. When applying pyrolysis for solid waste tyres, the results showed that slow heating rate delivered 44% of the liquid product in comparison to 52% for fast heating rate. Additionally, the composition of liquid pyrolysis product yielded 30% of gasoline, 63% of FO and DO. For solid waste polypropylene, the amount of liquid products increased with the heating rate. Specifically, liquid product was of 85% for the slow heating rate while it was of 93% for the fast heating rate. Liquid pyrolysis product from pyrolysis of polypropylene contained more gasoline than that of pyrolysis of the PE solid wastes and butyl rubber. This study also showed that the catalyst affected the amount of liquid pyrolysis products, but insignificantly affected the composition of the pyrolysis products. The results of this initial study may contribute to the use of waste for energy recovery in the future.

The study of “The use of collected sewage sludge compost in growing white radish (Raphanus sativus L.,)” was carried out from July to December in 2014 with following objectives (i) To assess vegetables productivity growing on the sewage sludge compost- chemical fertilizer treatment and the sewage sludge compost  treatment, (ii) To assess the nitrate concentration in vegetables grown on the sewage sludge compost treatment in comparing with the national standard defined by the Ministry of Agriculture and Rural Development (99/2008/QĐ-BNN). The result showed that the productivity of white radish in the sewage sludge compost- chemical fertilizer treatment was significantly higher than that in the sewage sludge compost treatment, but was not significantly different from that in the chemical fertilizer treatment with the yields ranged from 3.60 to 4.18 kg.m-2. The concentration of nitrate in white radish (Raphanus sativus L.,) at the treatment of the sewage sludge compost- chemical fertilizer treatment was less than that in the chemical fertilizer treatment and was unexceeded the standard of the Ministry of Agriculture and Rural Development (99/2008/QĐ-BNN). It is also found that E.coli did not present at white radish (Raphanus sativus L.,) after harvesting.