Research on evaluating the efficiency of recovery nutrients (N, P) in an integrated ecology system for catfish farming

Abstract

The purpose of this is to evaluate the ability to recover nutrients (N, P) emitted from catfish farming by using an integrated ecological system towards zero emissions. An integrated system has been designed and implemented for a catfish pond with a water surface area of 10,300 m2. Wastewater is treated with water hyacinth, sludge is used for organic fertilizer production, and dead fish carcasses are used as raw material for liquid fertilizer production. The SFA (substance flow analysis) method was applied to evaluate the efficiency of nutrient source recovery in the system. The results show that the nutrient supply to fish ponds is mainly from fish food (about 30,450 kgN/ha/crop and 3,675 kgP/ha/crop). Harvested fish in the adult stage accumulate N and P content in fish biomass of 12,480 kgN ha/crop and 540 kgP/ha/crop respectively. Wastewater from fish ponds sent through aquatic ditches has an amount of 11,509 kgN/ha/crop and 2,978 kgP/ha/crop. The treatment efficiency of the aquatic pond reached 70%, and the amount of nutrients emitted into the environment through wastewater was 3,453 kgN/ha/crop and 893 kgP/ha/crop respectively. The efficiency of retaining nutrients after composting is about 70 - 80%, the product of this process is organic fertilizer containing N and P contents of 0.26% and 0.12% respectively.