Biogas effluent (BE) is a potential source of fertilizer for rice. Alternate wetting and drying (AWD) irrigation based on surface water level can increase rice grain yield (GY), but its effect under BE application is still unclear. To test whether AWD can increase GY under BE application, we conducted a mesocosm experiment under screen-house conditions in Can Tho, Vietnam. We measured rice growth and yield under three nitrogen (N) treatments-zero-N (Z), synthetic fertilizer (SF), and BE-and two irrigation regimes-continuous flooding (CF) and AWD with a re-irrigation threshold of 15 cm below the soil surface. Chlorophyll content (SPAD) and leaf color chart (LCC) values were higher in SF than in BE, but plant height was comparable. Although GY was not significantly different between CF and AWD, AWD increased it by 12% in BE relative to CF. All N use efficiency (NUE) indices (apparent N recovery, agronomic NUE, and internal NUE) were comparable between AWD and CF in BE and SF. The results indicate that AWD irrigation is feasible under the application of cattle BE and the combination can improve rice GY.

This study applied one chemical coagulant, PAC, and three biological coagulant aids include Moringa seed gum, Cassia seed gums and polymer. The results indicated that the best dose of PAC be used as coagulants was 480 mg/L. Using polymer as aids with PAC could remove 66.70 % of COD, 66.86 % of SS, 39.01 % of color from studied wastewater. Using Moringa seed gums as aids with PAC could remove 69.34 % of COD and, 69.61 % of SS, 36.25 % of color from studied wastewater. Similarly, using Cassia seed gums as aids with PAC could remove 70.54 % of COD, 68.34 % of SS and 35.94 % of color from fish blood. These results, showed natural products such as Moringa seed gums or Cassia seed gums would be efficient workable substitutes for synthetic chemical polymer.

The purpose of this study assessed the effect of solid waste treatment practices, especially municipal solid waste towards sustainable development in the Mekong Delta region, southern Vietnam. This study also proposes to use the Life Cycle Assessment method with waste material flow, which will provide a calculation and estimation method based on the database of the assessment factors and normalization references for aspects, such as greenhouse gas emission/reduction, energy generation/consumption, economic benefit, investment and operating cost, and land use burden. The results shown that, composting is apparently a preferable option for promoting waste reduction and recycling from biodegradable waste in the Mekong Delta region.

The study aimed to diversify the treatment technology of catfish processing wastewater. The experiments were implemented on lab-scale package cage rotating biological contactors with the first stage in anaerobic condition and the second stage in the aerobic condition, using PVC flexible conduit medium. The selected hydraulic retention time of anaerobic stage was 12 hours, and that of aerobic rotating package cage biological contactor was 4 hour 12 minutes. The results showed that almost monitoring parameters (pH, SS, DO, COD, BOD5, TKN, Ptotal) met the national standards of QCVN 11-MT:2015/BTNMT (column A), except +NH4 only reached the QCVN 11-MT:2015/BTNMT (column B). The results confirmed that combining both anaerobic and aerobic package cage rotating biological contactors with PVC flexible conduict medium could apply to treat catfish processing wastewater.