Waste and its characterization in closed recirculating aquaculture systems – a review

Abstract

Just like every economic activity, aquaculture has a particular effect on environment, which manifests itself due to waste through declining quality of subterranean water and eutrophication of surrounding surface water. Less than half of the feed in aquaculture is digested and assimilated, the rest ending up as waste either solid or dissolved and the nutrients phosphorus (P) and nitrogen (N) that are derived from fish excretion, faeces, and uneaten feed. The advantage of recirculating aquaculture systems (RAS) is that their wastewater discharges are 10–100 times lower and pollutant concen-tration respectively 10–100 times higher and can reach the level of pollution of household waste. This makes the pollution much easier to control. Additionally, striving to ensure and improve the stability and longevity of RAS, additional technological solutions, warranting the reduction of the amount of used water, waste concentration increase and their sec-ondary utilization as bio stock are added. This article presents the research information from the engineering perspective, summarizing RAS design sensitive data concerning aquacultural waste components excreted in RAS.