title: Lamella dissolved air flotation treatment of fish farming effluents as a part of an integrated farming and effluent treatment concept.
abstract: Nutrient emissions from fish farming can be reduced by a bag pen, i.e., a floating circular basin which serves simultaneously both as a fish cultivation tank and a swirl separation tank. Solid matter (excreta and uneaten feed) is collected at the bottom of the bag pen and pumped as an underflow to a dissolved air flotation (DAF) unit for nutrient removal. DAF equipped with lamella elements was studied in real conditions. Altogether 3000 rainbow trout females (2.0 kg each) were cultivated. Solid-water mixture was pumped from the bottom of the bag pen to an equalizing basin using a sequence of 2-min pumping followed by a 4-min pause. In some tests the influent was pumped directly and continuously from the bag pen to DAF. The influent quality changed substantially: average suspended solids (SS) and phosphorus (P) concentrations were 290 mg l⁻¹ ± 110 mg l⁻¹ and 3.2 mg l⁻¹ ± 1.2 mg l⁻¹, respectively. When the influent was fresh and P strongly associated with SS, DAF without precipitation chemicals produced up to 86% SS and 83% P removals. The influence of chemical doses was studied using 6.4-29.2 mg Fe l⁻¹ with hydraulic loadings (HLs) of 11.0-11.7 m h⁻¹. SS and P removal did not change substantially and the effluent concentration levelled at 30 mg SS l⁻¹ and 0.20-0.30 mg P l⁻¹, respectively. The lamella DAF, coupled with ferric precipitation, produced up to 90% P and 80% nitrogen reductions. HLs, excluding recycle water flow and lamella projection, up to 21 m h⁻¹ could be used.
authors.affiliation: a Department of Chemistry and Bioengineering , Tampere University of Technology , P.O. Box 541, FIN-33101 Tampere , Finland.
authors.forename: Petri
authors.initials: P
authors.lastname: Jokela
authors.forename: Raghida
authors.initials: R
authors.lastname: Lepistö
mesh_terms: D000388:Air; D000818:Animals; D017756:Aquaculture / Q000295:instrumentation / Q000379:methods*; D005260:Female; D009584:Nitrogen / Q000032:analysis; D017686:Oncorhynchus mykiss; D010758:Phosphorus / Q000032:analysis; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen
keywords: bag pen; dissolved air flotation; fish farming; lamella; nutrient removal