Seminar on Smolt Production March 1st 2000 - Campbell River, BC Why use recirculation Recirculation vs. single pass flow through systems In-tank BIOFISH type of recirculation History of BIOFISH development - Testing BIOFISH for the production of: Rainbow trout Atlantic salmon smolt (1st and 3rd generation of BIOFISH) Arctic char Brown trout for restocking (Turbot and halibut in sea water) Effluent discharge from smolt production in BIOFISH Conclusions BIOFISH: Use feed with a low dust content Avoid overfeeding Research Director B. Eikebrokk, SINTEF/NTNU

Traditional recirculation systems Fish tanks Particle removal Biofiltra- tion Aeration/ Oxygen Particle rem Heating Water treatment volume 50 -100 % of fish tank volume Complex, high risk of disease transfer from tank to tank

Traditional flow through systems Fish tanks Particle removal Water flow: 0.5-1 liters per minute per kg of fish Frequent tank flushing

Tank - Internal Recirculation systems Particle removal Discharge Water consumption and discharge 0.02-0.05 L/min/kg Water treatment volume 5 -10 % of fish tank volume Less complex, less risk of disease transfer from tank to tank

Background - BIOFISH development: The need for a simple and production-effective fish farming technology with low water consumption rates (compared to flow through) low discharge rates advanced effluent treatment (optional) to meet the strict regulations regarding discharge to fresh water recipients in Norway Development of: simplified water reuse technology (BIOFISH) dual outlet with efficient particle removal from effluent disinfection of effluent water (not described here)

The BIOFISH recirculation system (“2nd generation” ) From Eikebrokk et al (1995) Aq. Res 26: 589-599

The BIOFISH recirculation system (“3rd generation” )

The KMT moving bed biofilter Material: poly ethylene Sp. Density: 0,96 Sp. Biofilm Growth Area: 500m2/m3

The dual outlet with particle removal Whirl separator Treated effluent Tower screen pipe Fish tank bottom Particle effluent to whirl separator Bottom screen Recirculated water to bioreactor Uneaten feed can be observed feeding control!

Water Sampling - Smolt experiments Make up water S Screened effluent(40 µm) S S S Particle effluent 12 L/min Recirculated water 250 L/min

Biomass and feeding Species : Atlantic salmon (Salmo salar) Average fish weight : 190 g Stocking density : 62 kg/m3 Spec water consumption : 0,025 L/min*kg Temperature : 13,6 oC Oxygen conc. : 9 mg/L Feed type : Tess Edel 2,5 mm pellets Feed supply : 5,27 kg /d Total dry matter (DM) : 94,7 % COD : 1162 g/kg Tot-P : 9,9 mg/kg Tot-N : 96,2 mg/kg

Analyses Water samples : SS COD tot-P tot-N Sludge : TDS (total dry solids) Ash

Mass balance calculation from sampling and feeding data Mass flow Feed supply Effluent Mass balance calculation from sampling and feeding data FISH AND BIOFILTER WIRL SEPARATOR SLUDGE SCREEN EFFLUENT FEED (100%)

SS in mixed samples (4hrs)

Suspended solids (SS) Feed supply Effluent Sludge 100 82 16 0,6 1,2

Organic matter (COD) Feed supply Effluent Sludge 100 86 9 0,6 4,2

Phosphorous (tot-P) Feed supply Effluent Sludge 100 33 55 2 9,5

Nitrogen (tot-N) Feed supply Effluent Sludge 100 49 9 0,5 42

Calculated mass flows (whirl separation only)

Calculated mass flows (whirl separation + screening 40 µm)

Calculated removal efficiencies by particle removal from effluent water (%)

Calculated total discharges (g/kg feed supplied)

Characterization of sludge from whirl separator Sludge production: 1.59 L /kg feed supplied

Screening combined with sludge thickening (Bergheim et al, 1993) *) UNIK rotary screen ( 150/60 µm ) Effluent from flow through tanks (sea wtr.) Step 1 RECIPIENT 60 µm Step 2 RECIPIENT 0.2 m/h Step 3 RECIPIENT Sludge *) Aq. Eng. 12 (1993) 97 - 109

This study BIOFISH recirculation tank 16,5 m/h Sludge RECIPIENT Step 1

Comparing total removal efficiencies

Conclusions A simplified full scale recirculation system (BIOFISH) with dual outlet and whirl separation was applied successfully for salmon smolt production Sampling and mass balance calculations showed low effluent discharge rates (17, 55 and 1.2 g/kg feed of SS, COD and tot-P respectively) High removal efficiencies were obtained by whirl separation (SS: 90 % ,COD: 66 % , and tot-P: 82 % ) Nitrogen compounds are mostly dissolved and can not be removed as particles Visual observation of uneaten feed contributes to an effective feeding control, low fcr and low discharge rates The whirl separator produces a concentrated sludge ( > 9 % TDS ), well suited for further treatment and disposal

History of BIOFISH development Idea/Predesign (1982-83) Calculations on tank hydraulics, aeration and nitrification capacities Building of first prototype tank (1986) Experimental testing/verification of idea Rainbow trout (data on production, water quality, capacities) Modified tank design/testing (1st generation, 1988) Atlantic salmon smolt (data on production, water quality, capacities) Arctic char (data on production, water quality, capacities) Modified design/testing (2nd generation, 1990) Brown trout for restocking (production, water quality, capacity data) Modified design and testing (3rd generation, 1995) Atlantic salmon smolt (production, incl. effluent discharge data) Turbot and halibut (saline water - not presented here)