Abstract
Development of modern aquaculture involves increasing the share of production in closed systems with water recirculation. In such facilities, waste with a considerable content of the solid fraction and a high concentration of biogenic elements is generated in the process of water treatment. According to present legislation, such waste cannot be used as fertilizers, which is contradictory to the idea of sustainability and rationalization of the use of environmental resources. The aim of this paper was to assess the chemical composition of African catfish farming waste in the context of the possibility of using it for fertilization purposes. The assumed goal was achieved by studying the waste generated at a water treatment facility that uses the method of active microscreens in an African catfish farm. 10 samples of waste (which, in raw form, is transported to the local wastewater treatment plant) were collected for the research. The content of dry matter, macroelements, microelements and heavy metals was determined in the studied waste. Dry matter content was determined by weight method, nitrogen and carbon content – by elemental analysis method, whereas the content of the other macroelements and trace elements was determined using the ICP-OES method. Results of the conducted research point to high concentrations of nitrogen and phosphorus. These are the main elements which decide on the fertilizing value of the studied material. Nitrogen content was approximately 5.354%, whereas phosphorus content – 3.436% calculated on dry matter. The content of other macroelements and trace elements was at a level observed in natural fertilizers. Heavy metals content did not disqualify the studied material from being used for fertilization purposes. Results of the conducted research indicate unambiguously that the studied material should be used for fertilization. Directing this waste to wastewater treatment plants is not well-founded from the economic and environmental point of view. The issue of proper management of waste generated in aquacultures with water recirculation should be regulated at the legislative level to reduce the amount of biogens dispersed in the environment and to improve the efficiency of production of aquaculture animals.
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