Water hyacinth (WH) biomass is one of the popular materials in the Vietnamese Mekong Delta, a potential substrate for biogas production. The effectiveness of utilizing WH for producing biogas under anaerobic digestion was demonstrated in the previous studies, but the research was focused on the loading rate of about 1.0% volatile solid (VS). Therefore, in the present study, a semi-continuous anaerobic digestion experiment was conducted with the five levels of VS, including 1.0%VS, 1.5%VS, 2.0%VS, 2.5%VS, and 3.0%VS, to examine how loaded VS can affect biogas production. Each treatment was designed with three replications over 60 days. The measured parameters included pH, temperature (Temp; °C), redox potential (Eh; mV), daily produced biogas volume (L), cumulative biogas volume (L), and methane (CH 4 ) concentration (%) during the 60 days of the experiment. The obtained results showed that pH, tempt, and Eh parameters did not negatively affect biogas production. However, the volume of daily biogas in the treatment of 3.0%VS was higher than in other treatments. In addition, the cumulative biogas volume in the treatment of 3.0%VS was the highest and significantly different between all reactors (p<0.05). Meanwhile, the treatment of 1.0%VS was known with the lowest values. The study explored that the volume of biogas could be increased when the organic loading rate VS is increased.

Mangrove forest protection is an essential solution for mitigating the impacts of natural disasters in coastal zones and climate change. Integrated mangrove-shrimp farming (IMSF) system has been promoted as a sustainable livelihood that can provide income for farmers and protect mangrove forests. However, the productivity of shrimp is limited. Therefore, to enhance the revenue for farmers, improving the value of shrimp products is a good option. Organic shrimp farming practices following the EU aquaculture organic standards have been previously applied in some areas of the Mekong delta. This study was conducted to compare technical, financial characteristics and environmental parameters between the applied (i.e., organic farms) and non-applied (i.e., non-organic farms) standards of Naturland, aiming to support the development of ecological shrimp farming and contribute towards green development. The study was carried out in Nhung Mien mangrove forest, Ngoc Hien district, Ca Mau province, Vietnam. Fifty organic farms and 50 non-organic farms were directly interviewed using structured questionnaires. And then, three farms in each system were selected for monitoring water quality. Results showed that the average mangrove coverage was 54.1% in the organic IMSF system and significantly different from the non-organic IMSF system (p<0.05). Total shrimp yield, total income and total profits tended to increase in organic IMSF system and the selling shrimp price increased by 10% compared to the conventional price. The study showed that following organic farming methods could provide higher income for farmers and a better chance to mitigate natural disasters and climate change impacts.

The present study aimed to assess the physicochemical characteristics of surface water in the full-dyke (FD) and semi-dyke (SD) systems of the An Giang province. Water samples were collected in both seasons in 2019 (1) the first monitoring phase in the dry season (April) and (2) the second monitoring phase in the rainy season (October). At each season, the surface water samples were collected at 15 sites in the FD system and 15 sites in the SD system to analyze the water quality parameters. The results showed that the concentrations of DO, COD, BOD, TSS, NO 3 -, NH 4 + , TKN, PO 4 3and TP parameters in the FD system were higher than in the SD system and there was a significant difference (p<0.05), except the value of pH and DO in the dry season. The DO, COD, BOD 5 and TSS concentrations in the FD system tended to exceed the Vietnamese standard threshold (QCVN 08:2015/ BTNMT, column B1), but in the SD system, these values were within the allowable limits of Vietnamese Standard. Other parameters, such as NO 3 -, NH 4 + , TKN, PO 4 3and TP exceeded the threshold of the Vietnamese standard in both systems. The results of this study provide the scientific information on water pollution inside the FD system. Therefore, it was expected that the local government of the An Giang province should have long-term strategies to manage the FD system to improve the water quality inside the FD system.

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