Nitrogen source recovery efficiency in the catfish farming zero emission integrated system in Mekong delta, Viet Nam

The purpose of this study is to optimize the nitrogen recovery efficiency in the catfish farming agro-based zero emission integrated system (AZEIS) in Mekong delta, Vietnam with special focuses on limiting the nitrogen loss into the environment, as well as on saving cost for other agriculture activities. Nitrogen source was recovered from catfish wastewater, sediment and dead fish bodies. Optimal nitrogen recovery system was estimated based on the amount of waste and nitrogen concentration in the treatment processes within the integrated system. In this study, LINGO software was used to estimate nitrogen recovery efficiency, and the construction area for the system. In addition, Material Flow Analysis (MFA) technique was used to monitor the transportation and accumulation ratio of nitrogen circulating within the integrated zero emission system. This study results indicate that a high nitrogen recovery efficiency was obtained in the study system which helps to reduce nitrogen discharging rate into the environment. The total nitrogen quantity of 12,049.9 KgN was recovered for the total designed farming area of 120,062 m2, and the optimal area ratio between fish ponds and other treatment components (composting area, grass garden, water hyacinth pond, cow breeding cage etc) in the integrated system was also obtained. This designed system has been successfully applied to a local catfish farm with an area of 10,000 m2 which produced valuable by-products such as organic fertilizer (with 1.7% total Nitrogen), hydrolyzed protein solution (with 3.08% total Nitrogen). Moreover, the nitrogen recovery efficiency from catfishpond wastewater for further supply to corn cultivation and water hyacinth were 47.9% and 79.5%, respectively.