Waste Treatment And Soil Cultivation In A Zero Emission Integrated System For Catfish Farming In Mekong Delta, Vietnam

The purpose of this study is to investigate the process of waste treatment (wastewater and solid waste) within an intensive catfish farming agro-based zero emission integrated system (AZEIS) in which the fish farming, livestock and cultivation are combined in the same area, as well as the role of this process for soil cultivation of the garden in the same integrated system. The material flow analysis (MFA) technique was used throughout the study for calculating efficiency of waste treatment processes and also for conversion/accumulation of materials with purpose to improve the soil quality for cultivation purpose in the garden. The experimental results showed that the garden in the system plays an important role in receiving, conversion, uptake and accumulation of the nutrients from waste flows, and by that way, in effective removal the pollutants from waste flows as well.In this system, the wastewater from catfish ponds was treated by using water morning glory, a local aquatic plant, before to be reused for watering the cultivation plants in the garden, and the removal percentage of Total Organic Carbon, Nitrogen, Phosphorus and Kallium in wastewater were 33.3, 21.7, 59,5 and 37,5%, respectively. All the solid wastes (sludge from catfish ponds, cow manure from livestock, and absorbed biochar material) were reused as organic fertilizer (compost), and served as sources of additional nutrients for cultivation of Pennisennon purpurecums-schumach grass and maize plants in the garden. Biochar material, which was produced from dried leaves in the garden, was used for treatment of biogas effluent before using later for watering the garden. Total wastewater after being treated and reused for maize plants was 9575 m(3)/ha, in which absorbed water by maize plant was 48.02 m(3)/ha, and 9527 m(3)/ha was evaporated and accumulated in soil. The Nitrogen absorbed by maize plant was 4.12 g/m(2), and the soil organic carbon stock in the AZEIS system was 0.19 mg/ha/crop. (C) 2020 Elsevier Ltd. All rights reserved.