Enhancing biogas production by anaerobic codigestion of water hyacinth and pig manure

The characteristics of anaerobic batch co-digestion of water hyacinth (WH) with pig manure (PM) under seven mixing ratio 100%WH; 80%WH : 20%PM; 60%WH : 40%PM; 50%WH : 50%PM; 40%WH : 60%PM; 20%WH : 80%PM and 100%PM were investigated, each treatment was conducted in five replications with daily loading rate at 1 gVS.L-1.day-1. During the anaerobic digestion process of 60 days, maximum biogas production occurred in two periods, the first stage from 12- 22 days and second stage from 30 - 35 days. The maximum daily biogas productions from each stage were 17.2 L.day-1 and 15.1 L.day-1, respectively. The cumulative biogas production varied between 60 L (100%PM) and 360 L (60%WH : 40%PM). The results showed that the biogas yields of co-digestion 40- 80%WH were higher from 34.6 to 56.1% in comparison with 100%PM and from 109 to 143% in comparison with 100%WH. When mixing with WH, treatments were received more methane and the methane contents were higher than 45% (v/v) that good for energy using purposes.Nghiên cứu được thực hiện nhằm khảo sát khả năng gia tăng lượng khí sinh học khi tiến hành đồng phân hủy yếm khí lục bình (WH) và phân heo (PM) ở các tỉ lệ phối trộn khác nhau gồm 100%WH; 80%WH : 20%PM; 60%WH : 40%PM; 50%WH : 50%PM; 40%WH : 60%PM; 20%WH : 80%PM và 100%PM. Các nghiệm thức được nạp lượng nguyên liệu là 1 gVS.L-1.ngày-1 và bố trí lặp lại 5 lần. Theo dõi quá trình phân hủy của các nghiệm thức trong 60 ngày ghi nhận có 2 khoảng thời gian lượng khí sản sinh nhiều nhất - giai đoạn 1 từ ngày 12 đến 22, giai đoạn 2 từ ngày 30 đến 35. Lượng khí sản sinh cao nhất tương ứng trong mỗi giai đoạn là 17.2 L.ngày-1 và 15.1 L.ngày-1. Lượng khí tích lũy trong suốt thời gian thí nghiệm ghi nhận thấp nhất ở nghiệm thức 100%PM đạt 60 L, và cao nhất ở nghiệm thức 60%WH : 40%PM đạt 360 L. Năng suất khí sinh ra của các nghiệm thức phối trộn lục bình từ 40 đến 80% cao hơn từ 34,6 đến 56,1% so với nghiệm thức 100%PM và cao hơn từ 109% đến 143% so với nghiệm thức 100%WH. Hàm lượng mê-tan sinh ra từ các nghiệm thức có phối trộn lục bình ổn định trong khoảng > 45% đảm bảo nhiệt lượng cho nhu cầu sử dụng năng lượng

Sources of sedimentary PAHs in tropical Asian waters: differentiation between pyrogenic and petrogenic sources by alkyl homolog abundance

We collected surface sediment samples from 174 locations in India, Indonesia, Malaysia, Thailand, Vietnam, Cambodia, Laos, and the Philippines and analyzed them for polycyclic aromatic hydrocarbons (PAHs) and hopanes. PAHs were widely distributed in the sediments, with comparatively higher concentrations in urban areas (∑PAHs: ∼1000 to ∼100 000 ng/g-dry) than in rural areas (∼10 to ∼100 g-dry), indicating large sources of PAHs in urban areas. To distinguish petrogenic and pyrogenic sources of PAHs, we calculated the ratios of alkyl PAHs to parent PAHs: methylphenanthrenes to phenanthrene (MP/P), methylpyrenes + methylfluoranthenes to pyrene + fluoranthene (MPy/Py), and methylchrysenes + methylbenz[a]anthracenes to chrysene + benz[a]anthracene (MC/C). Analysis of source materials (crude oil, automobile exhaust, and coal and wood combustion products) gave thresholds of MP/P = 0.4, MPy/Py = 0.5, and MC/C = 1.0 for exclusive combustion origin. All the combustion product samples had the ratios of alkyl PAHs to parent PAHs below these threshold values. Contributions of petrogenic and pyrogenic sources to the sedimentary PAHs were uneven among the homologs: the phenanthrene series had a greater petrogenic contribution, whereas the chrysene series had a greater pyrogenic contribution. All the Indian sediments showed a strong pyrogenic signature with MP/P ≈ 0.5, MPy/Py ≈ 0.1, and MC/C ≈ 0.2, together with depletion of hopanes indicating intensive inputs of combustion products of coal and/or wood, probably due to the heavy dependence on these fuels as sources of energy. In contrast, sedimentary PAHs from all other tropical Asian cities were abundant in alkylated PAHs with MP/P ≈ 1–4, MPy/Py ≈ 0.3–1, and MC/C ≈ 0.2–1.0, suggesting a ubiquitous input of petrogenic PAHs. Petrogenic contributions to PAH homologs varied among the countries: largest in Malaysia whereas inferior in Laos. The higher abundance of alkylated PAHs together with constant hopane profiles suggests widespread inputs of automobile-derived petrogenic PAHs to Asian waters

Ubiquitous occurrence of sulfonamides in tropical Asian waters.

Seven sulfonamides, trimethoprim, five macrolides, lincomycin and three tetracyclines were measured in 150 water samples of sewage, livestock and aquaculture wastewater, and river and coastal waters, in five tropical Asian countries. The sum of the concentrations of the target antibiotics in sewage and heavily sewage-impacted waters were at sub- to low-ppb levels. The most abundant antibiotic was sulfamethoxazole (SMX), followed by lincomycin and sulfathiazole. The average concentration of SMX in sewage or heavily sewage-impacted waters was 1720 ng/L in Vietnam (Hanoi, Ho Chi Minh, Can Tho; n = 15), 802 ng/L in the Philippines (Manila; n = 4), 538 ng/L in India (Kolkata; n = 4), 282 ng/L in Indonesia (Jakarta; n = 10), and 76 ng/L in Malaysia (Kuala Lumpur; n = 6). These concentrations were higher than those in Japan, China, Europe, the US and Canada. A predominance of sulfonamides, especially SMX, is notable in these tropical countries. The higher average concentrations, and the predominance of SMX, can be ascribed to the lower cost of the antibiotics. Both the concentration and composition of antibiotics in livestock and aquaculture wastewater varied widely. In many cases, sulfamethazine (SMT), oxytetracycline (OTC), lincomycin, and SMX were predominant in livestock and aquaculture wastewater. Both human and animal antibiotics were widely distributed in the respective receiving waters (i.e., the Mekong River and Manila Bay). SMT/SMX ratios indicate a significant contribution from livestock wastewater to the Mekong River and nearby canals, with an estimated ~ 10% of river water SMX derived from such wastewater. Mass flow calculations estimate that 12 tons of SMX is discharged annually from the Mekong River into the South China Sea. Riverine inputs of antibiotics may significantly increase the concentration of such antibiotics in the coastal waters

Former and Present Cropping Patterns in the Mekong Delta

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。In a previous paper, I proposed five landform units and several subunits for the Mekong delta (see Fig. 1). This paper aims to describe the former and present cropping patterns in relation to the landform, particularly the interconnected features of microlandform, water conditions, soils and the traditional methods of rice culture. The first part of the paper describes the methods of rice growing which were predominant in the delta before the 1960s-1970s. These methods were severely affected by the uncontrolled water conditions, which differed markedly in different landform units of the untamed delta, and may be summarized in three groups, which are characterized most distinctively by three planting methods, i. e., broadcasting, double transplanting, and single transplanting. The second part of the paper describes the present changes in the cropping pattern and the development of various rice growing methods. The most remarkable change is observed in the tide-affected floodplain (middle reach of the delta). Conventional double transplanting has been completely replaced by new methods like direct-seeding sa chai, and single cropping has been replaced by the year-round cultivation. Floating rice in the high floodplain (the upper reach of the delta) has also been reduced by expansion of high-yielding rice varieties. The coastal complex and the broad depression, which are affected by saltwater and sulfate acidity respectively, retain the traditional rice culture. The remarkable change in rice culture and land use has achieved as the result of close observation of soil, microlandform and water conditions by the farmers, and through their selective adaptation to natural environments and proper technologies

Geo-Pedological Study of the Mekong Delta

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。The Mekong delta is divided into five landform units, namely, the floodplain, the coastal complex, the broad depression, the old alluvial terrace, and the hills-mountains, and some of them are further subdivided (Fig. 2). These landform units are discernible from LANDSAT imageries, topography, properties of sediment and agroecology. Except for the old alluvial soil, which was formed during the Tertiary to late Pleistocene period, the landforms were shaped by transgression and regression in the Holocene period. Stratigraphic properties of sediments were examined in terms of chemical characteristics and pollen content, and seven depositional environments were ascertained : fan wash-out into littoral, transitional, marine, lagoonal, tidal flat, intertidal, and riverine

Anaerobic co-digestion cow dung and corn stalk - effect of corn stalk pre-treated timing

The study was aimed to investigate the effect of corn stalk pre-treatment duration on biogas production when cow dung and corn stalk was co-digested in an anaerobic digestion. Corn stalks were pre-treated in different durations: 2-days, 5-days, and 8-days before being added to cow dung into anaerobic co-digesters. The experiments were set up randomly by using triplicate batch anaerobic apparatus in 21 L containers that run in 60-days. The mixing ratio between a corn stalk and cow dung was 50%: 50% (based on the volatile solid value of each material), but corn stalk was cut into small pieces with around 10 cm length, while the cow dung was air dried. The results of the study indicated that all operation parameters such as temperature, pH, and alkalinity in the anaerobic batch were suitable for biogas production. The results showed that there was a significant improvement in total gas produced in the pre-treated 5-days treatment (206.4±8.4 L) compared to 2-days (153.4±9.6 L), and 8-days ones (174±11.1 L). The biogas yield of the pretreated 2-days, 5-days, and 8-days treatments were 392.7±9.8 L/kg VSfermented, 469.8±10.1 L/kg VSfermented and 497.1±13.3 L/kg VSfermented, respectively, that was not significantly different (5%). In all treatments, low concentration of methane in the beginning phase had been observed but increased and reached the optimum value for energy use after 10 days. The result of the study showed that it is preferable to have 5-days pre-treatment of corn stalk before the corn stalk is loaded to an anaerobic digester in combination with cow dung.Nghiên cứu này nhằm đánh giá ảnh hưởng của thời gian xử lý thân cây bắp lên năng suất sinh khí khi ủ phối trộn phân bò và thân cây bắp trong điều kiện yếm khí. Ba mức thời gian xử lý thân cây bắp được chọn là 2 ngày, 5 ngày, và 8 ngày. Các thí nghiệm được bố trí ngẫu nhiên trong các bình ủ yếm khí theo mẻ 21 L, vận hành trong 60 ngày liên tiếp và có 3 lần lặp lại. Nguyên liệu ủ được phối trộn theo tỷ lệ 50% phân bò và 50% thân bắp, trong đó thân bắp được cắt nhỏ cỡ 10 cm. Kết quả thí nghiệm cho thấy tất cả các thông số pH, nhiệt độ, độ kiềm của mẻ ủ đều phù hợp để vận hành. Lượng khí sinh ra của các nghiệm thức xử lý ở 2 ngày, 5 ngày, 8 ngày được ghi nhận là 153,4±9,6 L, 206,4±8,4 L và 174±11,1 L; năng suất sinh khí của các nghiệm thức không khác biệt và đạt giá trị 392,7±9,8 L/kg VSphânhủy, 469,8±10,1 L/kg VSphânhủy và 497,1±13,3 L/kg VSphânhủy. Tất cả các nghiệm thức đều sản sinh lượng CH4 thấp ở giai đoạn đầu nhưng tăng dần theo thời gian ủ và đạt hiệu quả sử dụng sau 10 ngày ủ. Kết quả cho thấy có thể chọn mốc thời gian 5 ngày để xử lý thân cây bắp trước khi đưa vào hầm ủ biogas

SỰ HẤP PHỤ NITRATE CỦA THAN SINH HỌC SẢN XUẤT TỪ TRẤU (O. sativa L., OM5451)

This study assesses the influence of solution pH, biochar dose, reaction time, and initial nitrate concentration on the nitrate adsorption in aqueous solutions by biochar prepared from rice husks (O. sativa L., OM5451). The biochar was prepared with the pyrolysis method at 700 °C. The pHpzc of the biochar is 9.51. The optimal conditions for the adsorption process include biochar 0.5 g, pH = 4, time 120 minutes, and initial concentration of  50 . Under the optimal conditions, the nitrate removal efficiency is 69.7%. The adsorption equilibrium data are more consistent with the Langmuir isothermal model ( = 0.993) than the Freundlich isothermal model ( = 0.965), and the maximal nitrate adsorption capacity of the biochar, calculated from the Langmuir equation, is 12.843 mg·g–1. The adsorption of the biochar fits well with both the pseudo-first-order kinetic model ( = 0.964) and the pseudo-second-order kinetic model ( = 0.963).Nghiên cứu này đánh giá ảnh hưởng của pH dung dịch, khối lượng than, thời gian và nồng độ ban đầu lên quá trình hấp phụ nitrate trong dung dịch của than sinh học sản xuất từ trấu (O. sativa L., OM5451). Than sinh học được sản xuất bằng phương pháp nhiệt phân trấu ở 700 °C. pHpzc của than là 9,51. Điều kiện tối ưu cho quá trình hấp phụ bao gồm khối lượng than 0,5 g, pH  4, thời gian 120 phút và nồng độ đầu 50 . Tại điều kiện tối ưu, hiệu suất loại  là 69,7%. Dữ liệu cân bằng phù hợp với mô hình đẳng nhiệt Langmuir ( = 0,993) hơn mô hình Freundlich ( = 0,965). Dung lượng hấp phụ nitrate cực đại tính theo phương trình Langmuir là 12,843 mg·g–1. Sự hấp phụ  của than sinh học phù hợp với cả hai mô hình động học biểu kiến bậc 1 ( = 0,964) và bậc 2 ( = 0,963)

Indigenous Knowledge of Peanut Cultivation of the Ethnic Khmer Resident in the Mountainous Area in An Giang Province, Vietnam

Indigenous knowledge (IK) can provide useful information on local people's activities within environmental contexts. For countries vulnerable to climate change as Vietnam, research on IK might assist in revealing information about local people's responses to environmental stresses and potentially support decision-making. To enrich the study context in this field, this study aims at determining the IK of peanut cultivation of the Khmer ethnic groups. The study site is in the mountainous area in An Giang province, Vietnam, where the Khmer people are located. The methods of documentary collection, focus group discussion, semi-structured interviews, and experiments were applied in this study. The investigation results showed the innovation of local people in the cultivation. For instance, applying cow manure to a sandy soil can reduce chemical fertilizers and improve peanut yield. The IK reported that the application of the broadcasting method could achieve the cultivation economic profit approximately 2.5 times higher than the dibbling method. The former method is mostly preferred due to its time/labor saving and the growing aged population in the study location. The experimental results indicated that the combination of indigenous and scientific knowledge in peanut cultivation, such as chemical fertilizer application, crop calendar, crop rotation, and varieties, could bring high economic efficiency, improve soil nutrients, and ability to adapt to climate change. The research approaches in this study comprehensively revealed the IK, which can be potentially applicable to similar studies

ĐA DẠNG THỰC VẬT NỔI Ở TRONG VÀ NGOÀI ĐÊ BAO KHÉP KÍN CỦA XÃ VĨNH THẠNH TRUNG, HUYỆN CHÂU PHÚ, TỈNH AN GIANG

Phytoplankton samples were collected in the dry season (April) and flood season (October). Thirty sampling sites were selected for each season. In the dry season, 94 species were identified in the FD system and 92 in the SD system. Whereas, in the flood season, the numbers were 109 and 117. The Euglenophyta and Chlorophyta were dominant in the two systems. The density of phytoplankton in the FD system is higher than in the SD system in the dry season. In the flood season, the value is the opposite. The water in the FD system is qualified as slightly to heavily polluted in the flood season and moderately to heavily polluted in the dry season. In the SD system, the water is qualified as slightly to moderately polluted in the dry season and moderately to heavily polluted in the flood season. In general, the FD system affects the phytoplankton species and their composition.Nghiên cứu được thực hiện nhằm đánh giá sự đa dạng của thực vật nổi trong và ngoài đê bao khép kín của xã Vĩnh Thạnh Trung, huyện Châu Phú, tỉnh An Giang. Mẫu thực vật nổi được thu vào thời điểm mùa khô (tháng Tư) và mùa lũ (tháng Mười) với tổng cộng 30 vị trí/đợt. Nghiên cứu đã xác định được tổng số loài thực vật nổi trong đê (94 loài) cao hơn so với ngoài đê (92 loài), nhưng vào mùa lũ thì tổng số loài thực vật nổi trong đê (109 loài) thấp hơn ngoài đê (117 loài). Ngành tảo mắt và tảo lục chiếm ưu thế ở hai khu vực nghiên cứu. Mật độ thực vật nổi trong đê cao hơn ngoài đê vào mùa khô, nhưng vào mùa lũ thì mật độ thực vật nổi trong đê thấp hơn ngoài đê. Chất lượng nước trong đê nằm trong khoảng từ ô nhiễm nhẹ đến ô nhiễm nặng (mùa lũ) và từ trung bình đến ô nhiễm nặng (mùa khô), khu vực ngoài đê thì từ ô nhiễm nhẹ đến trung bình (mùa khô) và từ trung bình đến ô nhiễm nặng (mùa lũ). Nhìn chung, số loài và thành phần thực vật nổi chịu ảnh hưởng của hệ thống đê bao khép kín