Solids management in freshwater-recirculating aquaculture systems: Effectivity of inorganic and organic coagulants and the impact of operating parameters.

Autor: Heiderscheidt E; Water Energy and Environmental Engineering Research Unit, Faculty of Technology, 90014 University of Oulu, Finland. Electronic address: Elisangela.heiderscheidt@oulu.fi., Tesfamariam A; Water Energy and Environmental Engineering Research Unit, Faculty of Technology, 90014 University of Oulu, Finland., Pulkkinen J; Natural Resources Institute Finland, Survontie 9A, 40500 Jyväskylä, Finland., Vielma J; Natural Resources Institute Finland, Survontie 9A, 40500 Jyväskylä, Finland., Ronkanen AK; Water Energy and Environmental Engineering Research Unit, Faculty of Technology, 90014 University of Oulu, Finland.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2020 Nov 10; Vol. 742, pp. 140398. Date of Electronic Publication: 2020 Jun 20.
DOI: 10.1016/j.scitotenv.2020.140398
Abstrakt: Coagulants are widely used for solids (uneaten food, faeces, etc.) management in recirculating aquaculture systems (RAS), but no recent research has been performed on the effectiveness of different coagulants in treatment of aquaculture sludge. This study examined the effectivity of selected inorganic (polyaluminium chloride, PAC) and organic products (polyamine- and starch-based) as coagulant agents for solids management in RAS. Reductions in residual concentrations of total phosphorus (tot-P), phosphate‑phosphorus (PO 4 -P), suspended solids (SS) total nitrogen (tot-N), nitrate‑nitrogen (NO 3 -N), ammonium‑nitrogen (NH 4 -N), aluminium (Al) and chemical oxygen demand (COD) in reject water were determined. The effect of process parameters (coagulant type, dose, mixing and sedimentation time) on sludge treatment was also evaluated. The PAC products tested were most effective at concentrating pollutants (Tot-P, PO 4 -P, SS, COD) in RAS sludge into the solid phase. The organic products tested, especially a high-molecular-weight polyamine product (pAmine1), achieved good performance and can be considered a valid alternative to inorganic salts. At optimum dose, PAC (dose 32 mg/L) and pAmine1 (dose 15 mg/L) removed, respectively, 99.4% and 82.8% of turbidity, 98.2% and 65.4% of PO 4 -P and 97.7% and 73.6% of SS. The mixing time applied in flocculation and the time allowed for sedimentation had significant effects on coagulant performance, with the organic coagulants being most affected. Flocculation times of 5-15 min and sedimentation times of 15-60 min showed good results and can be used as a starting point in process optimisation with both inorganic and organic coagulants. The use of coagulants for treatment of RAS sludge enhances flock formation and improves particle settling characteristics, substantially decreasing nutrient, organics and solids concentration in reject water.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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