Waste and Its Characterization in Closed Recirculating Aquaculture Systems – A Review

Abstract

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 concentration 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 secondary 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.

Nitrogen and Phosphorus budget for Nile tilapia hatchery

“…In freshwater bodies, phosphorus is the main limiting factor for development of flora. Unused feed phosphorus in aquaculture, make its way to environment and encourages eutrophication (Mongirdas et al, 2017). In the present study results showed that fish retained at least 2.74 ± 0.37 % of the feed phosphorus content.…”

“…Our results are also similar to those reported by Summerfelt et al, (2001) who calculated that every kilogram of fed feed emits 0.43 kg of suspended solids, additional 9% suspended solids of feed emerge from activity of heterotrophic organisms and another 0.09% due to activity of nitrification bacteria. Mongirdas et al, (2017) reported that it is unreal to expect less than 200 g of sediment in real growing conditions, and values higher than 450 g does not appear as well, because that would suggest uneconomical use of feed and would extremely increase the first cost of fish production.…”

“…Similarly, Cripps and Bergheim (2000) reported that particulate wastes commonly contain 7-32% of the total nitrogen (TN) and the remainder is in the dissolved fraction in wastewater. Mongirdas et al, (2017) reported that nitrogen from protein, used up during fish vital processes is emitted through gill -60-90 %as ammonia and 9-27 % as urea. However, dissolved organic nitrogen (DON) in the present study was higher than dissolved inorganic nitrogen (DIN) and that can be attributed for two reasons: organic form of nitrogen as well as phosphorus needs time (i.e.…”

Recirculation Aquaculture Systems: Components, Advantages, and Drawbacks

“…So in this system, it is necessary to treat the water continuously to remove the waste products excreted by the fish and also add oxygen so that the fish will be provided with enough oxygen to be alive and well (Bregnballe, 2015). In the RAS to ensure the optimal condition of various water quality, many physical and chemical parameters need to be controlled including ammonia, nitrites, nitrates, carbon dioxide, biological oxygen demand (BOD), alkalinity, pH, and others (Mongirdas et al, 2017). Biofilters and solids removal are the most important to optimize the water quality for healthy fish and good system performance (Badiola et al, 2012).…”

Improving the Efficiency of Lambari Production and Diet Assimilation Using Integrated Aquaculture with Benthic Species

“…Diet is the major operating cost in fed monoculture systems [4]. Moreover, it is the primary waste source in fish and shrimp monocultures [5][6][7]. This situation is because a single species is not able to assimilate most diet nutrients and energy.…”