3rd NordicRAS workshop on recirculating aquaculture systems, molde, norway, 30 september 1 october 2015 book of abstracts

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3rd NordicRAS Workshop on Recirculating Aquaculture Systems, Molde, Norway, 30
September - 1 October 2015
Book of Abstracts
Dalsgaard, Anne Johanne Tang

Publication date:
2015
Document Version
Publisher's PDF, also known as Version of record
Link back to DTU Orbit

Citation (APA):
Dalsgaard, A. J. T. (Ed.) (2015). 3rd NordicRAS Workshop on Recirculating Aquaculture Systems, Molde,
Norway, 30 September - 1 October 2015: Book of Abstracts. Charlottenlund: National Institute of Aquatic
Resources, Technical University of Denmark. (DTU Aqua Report; No. 301-15).

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3rd NordicRAS Workshop on Recirculating Aquaculture Systems
Molde, Norway, 30 September - 1 October 2015
Book of Abstracts

DTU Aqua report no. 301-2015
By Anne Johanne T. Dalsgaard (ed.)


The workshop is organized by the Nordic Network on Recirculating Aquaculture
Systems (NordicRAS) in cooperation with the Technical University of Denmark
(DTU Aqua) and Nofima
The workshop is supported by:
Nordic Council of Ministers
The Research Council of Norway
VRI Møre og Romsdal
Main sponsor:
BioMar A/S
Other sponsors:
Grundfos DK A/S
SalmoBreed AS

The granted support is hereby acknowledged

rd

Title:

3 NordicRAS Workshop on Recirculating Aquaculture Systems
Molde, Norway, 30 September - 1 October 2015
Book of Abstracts

Author:

Edited by Anne Johanne T. Dalsgaard

DTU Aqua report no.:

301-2015

Year:

September 2015

Reference:

Reference: Dalsgaard, A. J. T. (ed.), 2015. 3rd NordicRAS Workshop on
Recirculating Aquaculture Systems. Molde, Norway, 30 September - 1 October
2015. Book of Abstracts. DTU Aqua Report No. 301-15. National Institute of
Aquatic Resources, Technical University of Denmark, 56 pp.

Cover photos:

Peter Lauesen and Martin Dam Kristensen.

Published by:

Technical University of Denmark, National Institute of Aquatic Resources
Jægersborg Allé 1, 2920 Charlottenlund, Denmark
Ph. + 45 35 88 33 00
E-mail:
Web: www.aqua.dtu.dk

Download:

www.aqua.dtu.dk/publikationer

ISSN:

1395-8216

ISBN:

978-87-7481-215-9 (print)
978-87-7481-214-2 (web)


3rd NordicRAS Workshop on
Recirculating Aquaculture Systems
Book of Abstracts
Molde, Norway 30 September - 1 October 2015

DTU Aqua report no. 301-2015


Committee Members
NordicRAS Network Steering Committee Members
Asbjørn Bergheim

International Research Institute of Stavanger (IRIS), Norway

Helgi Thorarensen

Holar University College, Iceland

Jouni Vielma

Natural Resources Institute Finland, Finland

Per Bovbjerg Pedersen

Technical University of Denmark, DTU Aqua, Denmark

Torsten E.I. Wik

Chalmers University of Technology, Sweden

Scientific Planning Committee for the Workshop
Anne Johanne T. Dalsgaard

Technical University of Denmark, DTU Aqua, Denmark

Alexander Brinker

Fisheries Research Station of Baden-Württemberg, Germany

Asbjørn Bergheim

International Research Institute of Stavanger (IRIS), Norway

Bendik Fyhn Terjesen

Nofima, Norway

Per Bovbjerg Pedersen

Technical University of Denmark, DTU Aqua, Denmark

Organizing Committee Members for the Workshop
Anne Johanne T. Dalsgaard

Technical University of Denmark, DTU Aqua, Denmark

Jelena Kolarevic

Nofima, Norway

Grete Solveig Byg

Technical University of Denmark, DTU Aqua, Denmark

Astrid Buran Holan

Nofima, Norway

Bendik Fyhn Terjesen

Nofima, Norway

Per Bovbjerg Pedersen

Technical University of Denmark, DTU Aqua, Denmark

Correspondence:

Anne Johanne T. Dalsgaard


2


Preface
Welcome to the 3rd workshop on recirculating aquaculture systems by the NordicRAS Network
(NordicRAS). This time the workshop is held in scenic Molde at the western coast of Norway. It
is organized by NordicRAS in collaboration with the Technical University of Denmark (DTU
Aqua) supported by Nofima as local organizer.
The aim of this biennial workshop is to bring together engineers, scientists, farmers, managers,
equipment and systems manufacturers, consultants and other professionals with an interest in
RAS to share ideas, present new findings, promote collaboration across sectors, and further
promote the industry.
Recirculation components, technologies, system operation and farming practices have been
optimized for years, and increasingly larger commercial systems are being built in the Nordic
countries especially for production of salmonids, but also sturgeon and pike perch systems are
seeing the light of day. Recirculating systems are, however, still complex to operate and new
challenges arise as the intensity of recirculation increases and as new species are introduced.
One of these challenges are particles that may accumulate in the systems, and the first day of
the workshop will focus on how particles are generated, how they are measured, how they are
removed, and how they interact with bacteria. This will be succeeded by as session on microbial
water quality given the growing realization that it is possible to affect microbial dynamics in
RAS, and that this may be of paramount importance for the well-being of the fish.
As the intensity of recirculation increases in the systems so does the concentrations of particles,
nutrients and other components that are not fully removed by mechanical, biological, ozone, UV
or other types of in-line treatment devises but solely balanced via make-up water. The effects of
this on water quality and on fish performance and welfare are touched upon on the second day
of the workshop. The workshop will finalize with a session on integrated system approaches.

The prospective of establishing complete systems that can also handle intake -and especially
discharge water and sludge is gaining more and more attention as system size increases while
discharge legislation, at best, remains the same.
The program will be tight as “always”, including 36 interesting presentations in the 1½ days the
workshop lasts. In addition to the presentations, there will be a few posters introducing new
research systems and potential, cross-country collaboration opportunities. The posters will be
located in the exhibition area at the Scandic Seilet hotel lobby where also some companies
have the opportunity to present themselves to the workshop audience.
BioMar is again main commercial sponsor of the workshop for which we are very grateful, as we
similarly are for the commercial sponsorships from Grundfos and SalmoBreed. In addition to
this, we thank Norden, the Norwegian Research Council, and VRI Møre og Romsdal for their
financial support without which the workshop would never have taken place.
At the time of writing, there were 212 registered participants from 28 countries around the world!
This is very overwhelming and way beyond what we had ever dreamt of when starting
NordicRAS, and we hope and believe that your days in Molde will be worthwhile. Have a great
workshop.
On behalf of NordicRAS,
Anne Johanne T. Dalsgaard, DTU Aqua

3


4


Table of Contents
Preface ............................................................................................................................................... 3
Table of Contents .............................................................................................................................. 5
rd

Program for the 3 NordicRAS workshop .................................................................................... 11
Abstracts of oral presentations ..................................................................................................... 17
Recirculation feed for Atlantic salmon
K.S. Ekmann, M.D. Jensen ....................................................................................................... 18
When the shit hits the fan: diet composition, indigestible binders and fecal stability
B.-S. Sæther, A. Brinker, J. Holm, K. T. Carlsen ...................................................................... 19
First experiences of floating faeces and its rapid removal in RAS
M. Schumann, A. Brinker .......................................................................................................... 20
Feed composition affects sludge as a resource for denitrification
C.O. Letelier-Gordo, B.K. Larsen, J. Dalsgaard, P.B. Pedersen .............................................. 21
Biofilter effects on micro particle dynamics
P.M. Fernandes, L.-F. Pedersen, P.B. Pedersen ..................................................................... 22
Evaluation of membrane treatment effect on water quality in recirculating aquaculture
systems (RAS) for Atlantic salmon post-smolts (Salmo salar)
A.B. Holan, J. Kolarevic, R. Fossmark, I. Bakke, O. Vadstein, B.F. Terjesen .......................... 23
Monitoring RAS organic matter by fluorescence EEM spectroscopy
A.C. Hambly, E. Arvin, L-F. Pedersen, P.B. Pedersen, C.A. Stedmon ..................................... 25
Humic substances in recirculating aquaculture systems and their effect on fish health
G. Yamin, J. van Rijn................................................................................................................. 26
First findings on the effects of suspended solids in recirculating trout aquaculture on
selected health parameters
C. Becke, M. Schumann, A. Brinker .......................................................................................... 27
Room for all? - particulate surface area and bacterial activity in RAS
P.B. Pedersen, M. von Ahnen, P. Fernandes, C. Naas, L.-F. Pedersen, J. Dalsgaard ............ 28
Beneficial fish-microbe interactions: the fourth dimension of RAS
O. Vadstein, K.J.K. Attramadal, I. Bakke, Y. Olsen .................................................................. 29

5

A novel real-time bacteria sensor for monitoring water in recirculating aquaculture
systems
B. Seredyńska-Sobecka M. Dahlqvist ....................................................................................... 30
Microbial community dynamics in three RAS with different salinities for production of
Atlantic postsmolt
I. Bakke, A.L. Åm, J. Kolarevic, T. Ytrestøyl, O. Vadstein, K.J.K. Attramadal, B.F. Terjesen ... 32
Microbial influence in different rearing systems: flow through, microbially matured and
recirculating aquaculture systems
K. Attramadal, O. Vadstein, Y. Olsen ........................................................................................ 34
Microbiota in recirculating and semi-closed aquaculture systems for post-smolt
production
I. Rud, M.R. Jensen, J. Kolarevic, B.F. Terjesen ...................................................................... 35
Microbial water quality dynamics in RAS during system start-up
P.A.R. Tirado, P.B. Pedersen, L.-F. Pedersen .......................................................................... 36
Crossbred fish will lower the risk of disease outbreaks and increase the eyed-egg supply
for RAS-facilities
B. Hillestad................................................................................................................................. 37
Practical experiences with smolt system startup and operation
P. Lauesen................................................................................................................................. 38
Atlantic salmon post-smolts in RAS: effects of salinity, exercise and timing of seawater
transfer on performance, physiology and welfare
T. Ytrestøyl, H. Takle, J. Kolarevic, S. Calabrese, G. Timmerhaus, T.O. Nilsen, S.O.
Handeland, S.O. Stefansson, L.O.E. Ebbesson, B.F. Terjesen ................................................ 39
Comparing the effects of high versus low nitrate on post-smolt Atlantic salmon
performance and physiology in RAS
J. Davidson, C. Good, C. Russell, S. Summerfelt ..................................................................... 40
The influence of nitrate nitrogen on post-smolt Atlantic salmon (Salmo salar)
reproductive physiology in replicated RAS
C. Good, J. Davidson, G. Weber, J. Birkett, L. Iwanowicz, M. Meyer, D. Kolpin, C. Russell,
S. Summerfelt ............................................................................................................................ 41

Performance improvements with stable pH values in RAS
C. Frisk, A.F. Andreasen, K.S. Ekmann .................................................................................... 42
Monitoring water parameters, fish health and welfare in production scale RAS – a follow
up study
A.M. Eriksson-Kallio, K. Pelkola, P. Koski , T. Kiuru ................................................................. 43

6


The automatization of the water quality monitoring in recirculation aquaculture systems
(RAS)
J. Kolarevic, D. Bundgaard, B.K.M. Reiten, K.S. Nerdal, B.S. Saether .................................... 44
A sustainability evaluation, based on environmental indicators, of Recirculating
Aquaculture Systems (RAS) applied to all countries and all species
M. Badiola, B. Albaum, D. Mendiola ......................................................................................... 45
Co-culture of Japanese short-neck clam (Ruditapes philippinarum) and sea cucumber
(Apostichopus Japonicus) by feeding Pyropia spheroplasts based diets in Recirculating
Aquaculture System (RAS) - a preliminary report
M.N.D. Khan, A.M. Shahabuddin, D. Saha, N. Arisman, E. Ayna, K. Wonkwon, T. Araki, T.
Yoshimatsu.. ............................................................................................................................. 46
Salmon farming -an integrated research project on land-based aquaculture systems in
Norway
T. Bennich ................................................................................................................................. 47
Ponds, Raceways, RAS - benchmarking trout grow-out economics
T. Lasner, A. Brinker, R. Nielsen, F. Rad, S. Simons ............................................................... 48
Woodchip denitrification bioreactor nitrate and solids removal from RAS wastewater
L. Christianson, C. Lepine, S. Summerfelt ................................................................................ 49
End-of-pipe removal of nitrogen using woodchip beds
M. von Ahnen, P.B. Pedersen, J. Dalsgaard............................................................................. 50
Comparison of Atlantic salmon postsmolt (Salmo salar) produced in recirculating

aquaculture systems (RAS) and a traditional sea cage
V. Hilstad, K. Steen, J. Kolarevic, L. Verstraeten, B.K.M. Reiten, A.B. Holan .......................... 51

7


Scaling of culture tanks and unit processes, relevant for Atlantic salmon post-smolt
production in land-based systems
B.F. Terjesen, W. Abbink, E. Blom, A. Kamstra, Å. Espmark, J. Kolarevic, T.O. Nilsen, L.
Ebbesson, S. Handeland, L. Sveen, H. Takle ........................................................................... 52
Poster abstracts .............................................................................................................................. 53
Carbon dioxide as limiting factor in partial reuse RAS
A. Bergheim, T. Øvrebotten, S. Fivelstad, Y. Ulgenes .............................................................. 54
A new experimental fresh water RAS-system with emphasis on online water quality
monitoring
J. Vielma, T. Kiuru, J. Koskela................................................................................................... 55
The IFREMER Palavas research platform for marine temperate and tropical aquaculture
S. Triplet, J.P. Blancheton, E. Rezzouk, B. Chatain ................................................................. 56

8


9


10


Program for the 3rd NordicRAS workshop
Day 1, Wednesday 30 September 2015

00

09 -10

00

Page
-

Registration

Opening session

-

10 -10

00

10

Opening and welcome by Nordic RAS
J. Dalsgaard, DTU Aqua, Denmark

-

10 -10

10

20

Welcome address by Nofima
H. Toften, Nofima, Norway

-

20

45

Opening keynote
K. Steen, Lerøy Midt AS, Norway

-

10 -10

Session 1: Particles, diets and diet-related waste characteristics in RAS
Chair: B.F. Terjesen, Nofima, Norway

-

10 -11

45

15

Keynote

T.O. Leiknes, King Abdullah University of Sci. and Technol., Saudi Arabia

11 -11

15

30

Recirculation feed for Atlantic salmon
K.S. Ekmann and M.D. Jensen

18

11 -11

30

45

When the shit hits the fan: diet composition, indigestible binders
and fecal stability
B.-S. Sæther et al.

19

11 -12

45

00

First experiences of floating faeces and its rapid removal in RAS
M. Schumann and A. Brinker

20

00

00

Lunch

12 -13

Session 1 - continued
Chair: A. Brinker, Fisheries Research Station, Langenargen, Germany

-

-

13 -13

00

15

Feed composition affects sludge as a resource for denitrification
C.O. Letelier et al.

21

13 -13

15

30

Biofilter effects on micro particle dynamics
P.M. Fernandes et al.

22

13 -13

30

45

Evaluation of membrane treatment effect on water quality in
recirculating aquaculture systems (RAS) for Atlantic salmon postsmolts (Salmo salar)
A.B. Holan et al.

23

45

00

Monitoring RAS organic matter by fluorescence EEM spectroscopy

A.C. Hambley et al.

25

13 -14

11


Day 1, Wednesday 30 September 2015

Page

14 -14

00

15

Humic substances in recirculating aquaculture systems and their
effect on fish health
G. Yamin and J. van Rijn

26

14 -14

15

30

First findings on the effects of suspended solids in recirculating
trout aquaculture on selected health parameters
C. Becke et al.

27

30

00

Coffee break

14 -15

-

Session 2: Microbial water quality in RAS
Chair: J. van Rijn, The Hebrew University of Jerusalem, Israel

-

15 -15

00

30

Keynote
H.-J. Albrechtsen, Technical University of Denmark, Denmark

15 -15

30

45

Room for all? - particle surface area and bacteria activity in RAS
P.B. Pedersen et al.

28

15 -16

45

00

Beneficial fish-microbe interactions: the fourth dimension of RAS
O. Vadstein et al.

29

16 -16

00

15

A novel real-time bacteria sensor for monitoring water in

recirculating aquaculture systems
B. Seredyńska-Sobecka and M. Dahlqvist

30

16 -16

15

30

Microbial community dynamics in three RAS with different salinities
for production of Atlantic postsmolt
I. Bakke et al.

32

30

00

Coffee + sandwich break

16 -17

-

-

Session 2 - continued

Chair: C. Good, The Conservation Fund’s Freshwater Institute, USA

-

17 -17

00

15

Microbial influence in different rearing systems: flow through,
microbially matured and recirculating aquaculture systems
K. Attramadal et al.

34

17 -17

15

30

Microbiota in recirculating and semi-closed aquaculture systems for
post-smolt production
I. Rud et al.

35

17 -17

30

45

Microbial water quality dynamics in RAS during system start-up
P.A. Tirado et al.

36

45

00

Crossbred fish will lower the risk of disease outbreaks and increase
the eyed-egg supply for RAS-facilities
B. Hillestad

17 -18

12

37


Day 1, Wednesday 30 September 2015

18 -20

00

00

Posters and exhibition area

00

00

Workshop dinner at Hotel Scandic Seilet

20 -24

Page

54-56

Gideonveien 2
6429 Molde
Tel: +47 71 11 40 00
Mail:
Web: www.scandichotels.no/Hotels/Norge/molde/seilet#.Vf5SHt-qqkr

13


Day 2, Thursday 1 October 2015
45

08 -08

55

Page
nd

Good morning and welcome to the 2
J. Dalsgaard, DTU Aqua, Denmark

workshop day

Session 3: Water quality in RAS
Chair: L.-F. Pedersen, DTU Aqua, Denmark

-

-

08 -09

55

15

Invited speaker: Start-up and operation of RAS for smolts
P. Lauesen, Billund Aquakulturservice A/S, Denmark

38

09 -09

15

30

Atlantic salmon post-smolts in RAS: effects of salinity, exercise and
timing of seawater transfer on performance, physiology and welfare
T. Ytrestøyl et al.

39

09 -09

30

45

Comparing the effects of high versus low nitrate on post-smolt
Atlantic salmon performance and physiology in RAS
J. Davidson et al.

40

09 -10

45

00

The influence of nitrate nitrogen on post-smolt Atlantic salmon
(Salmo salar) reproductive physiology in replicated RAS

C. Good et al.

41

10 -10

00

15

Performance improvements with stable pH values in RAS
C. Frisk et al.

42

10 -10

15

30

Monitoring water parameters, fish health and welfare in production
scale RAS – a follow up study
A.M. Eriksson-Kallio et al.

43

10 -10

30

45

The automatization of the water quality monitoring in recirculation
aquaculture systems (RAS)
J. Kolarevic et al.

44

45

15

Coffee break

10 -11

-

Session 4: Integrated system approach
Chair: E. Eding, Wageningen University, the Netherlands
11 -11

15

45

11 -12

45

00

00

15

12 -12

Keynote
S. Summerfelt, The Conservation Fund’s Freshwater Institute, USA

-

-

A sustainability evaluation, based on environmental indicators, of
Recirculating Aquaculture Systems (RAS) applied to all countries
and all species
M. Badiola et al.

45

Co-culture of Japanese short-neck clam (Ruditapes philippinarum)
and sea cucumber (Apostichopus Japonicus) by feeding Pyropia
spheroplasts based diets in Recirculating Aquaculture System
(RAS) - a preliminary report
M.N.D. Khan et al.

46

14


Day 2, Thursday 1 October 2015
12 -12

15

30

30

30

12 -13

Page

Salmon farming -an integrated research project on land-based
aquaculture systems in Norway
T. Bennich
Lunch

47

-

Session 4 - continued
Chair: J. Vielma, Natural Resources Institute Finland, Finland

-

13 -13

30

45

Ponds, Raceways, RAS - benchmarking trout grow-out economics
T. Lasner et al.

48

13 -14

45

00

Woodchip denitrification bioreactor nitrate and solids removal from
RAS wastewater
L. Christianson et al.

49

14 -14

00

15

End-of-pipe removal of nitrogen using woodchip beds
M. von Ahnen et al.

50

14 -14

15

30

Comparison of Atlantic salmon postsmolt (Salmo salar) produced in
recirculating aquaculture systems (RAS) and a traditional sea cage
V. Hilstad et al.

51

14 -14

30

45

Scaling of culture tanks and unit processes, relevant for Atlantic
salmon post-smolt production in land-based systems
B.F. Terjesen et al.

52

45

00

Goodbye and see you next time, by Nordic RAS
J. Dalsgaard, DTU Aqua, Denmark

14 -15

15

-


16


Abstracts of oral presentations
Presented at the
3rd NordicRAS Workshop on
Recirculating Aquaculture Systems

Molde, Norway
30 September - 1 October 2015

17


Recirculation feed for Atlantic salmon

1

1

Kim S. Ekmann *, Mikkel D. Jensen
1

BioMar A/S, Mylius Erichsensvej 35, DK-7330 Brande, Denmark

ABSTRACT
The RAS production of salmon smolts in both Norway and Chile has been steeply increasing for
more than a decade. This has been caused partly by an increase in number of salmon smolts
produced, but also by a trend of growing smolts bigger (up to 400 grams or more) prior to sea
cage stocking. As a consequence there is a demand for developing bespoke salmon smolt
feeds for RAS with focus on:
• Superior growth performance (SGR)
• Improved feed conversion ratio (FCR)
• High nutrient digestibility and retention
• Stabilizing faecal matter
-in order to safely maintain high stocking densities and fast production cycles and reduce
discharge of both organic and nitrogenous waste to a minimum without jeopardizing overall feed
performance. Stabilization of fecal matter will not be treated in this presentation.
From a number of preceding trials, one experimental RAS diet was chosen to be trialled against
two commercially available diets for Atlantic salmon smolt (Salmo salar) in a growth trial using
3
triplicate 1m tanks. Both commercial diets were known to have been previously used for
salmon smolt culture in RAS. The three diets were fed to salmon smolt growing from 20 – 175
grams over two time periods with a combined duration of 118 days. Fish were fed ad libitum for
24 hours per day at a temperature of 14°C. Light regime was 24L:0D throughout the trial.
Fish fed the experimental RAS diet showed significantly lower FCR values (0.75) compared to

the commercial diets (both 0.78), while no significant differences were found in SGRs between
-1
dietary treatments (2.06 – 2.11% d ). Protein and lipid digestibilities of the two commercial diets
(88.7-90.3% and 95.9-97.2%, respectively) were significantly lower than observed in the
experimental RAS diet (91.7% and 98.0%, respectively). Similarly, fish fed the experimental
RAS diet displayed an improved retention of digested protein (55.2%) compared to fish fed the
two commercial diets (51.9 – 52.5%).
Collectively, these dietary measures allowed a reduction of nitrogen excreted via faeces and
gills/urine of 20.5-33.6% and 10.6-13.1% per kg produced fish, respectively, and a reduction of
dry matter feces excretion between 1.9-6.1% when using the proposed recirculation diet.
*

18


When the shit hits the fan: diet composition, indigestible binders and fecal
stability
1

2

3

3

Bjørn-Steinar Sæther *, Alexander Brinker , Jørgen Holm , Kristian T. Carlsen
1

Nofima AS, Tromsø, Norway
Fischereiforschungstelle des Landes Baden-Württemberg, Germany

3
Biomar AS, Norway
2

ABSTRACT
The dietary requirements of Atlantic salmon are well known, and feeds may incorporate a
variety of raw materials to achieve optimal nutrient composition. Considerations of availability
and price have driven a trend in which marine ingredients are increasingly substituted with raw
material of vegetable origin. The introduction of RAS to salmon smolt production presents new
challenges for feed technology, as these systems have limited capacity for handling organic
waste. Initial mechanical treatment of waste is relatively uncomplicated, with low investment and
running costs. The following biological treatment, by comparison, is costly, labour-intensive and
much more challenging when it comes to controlling key water quality parameters. The
efficiency of biological treatment depends on organic load, and thus improved mechanical
filtration that reduces the amount of organic matter in the water is highly desirable. Feed
designed for RAS should meet the nutritional requirements of the fish but also support particle
removal by maximizing the mechanical stability of fecal waste.
A range of experimental salmon feeds with varying compositions were developed using raw
ingredients including soya protein concentrate (SPC), corn concentrate, pea protein
concentrate, wheat gluten and two types of indigestible binders in varying quantities. Twenty
one diets were screened in salmon parr growth trials. Feed intake was measured at tank level,
and at the end of the trial values for growth rate, feed conversion, digestibility and nutrient
retention were calculated and intestinal histology of the fish was examined. At the final
sampling, rheological properties of fecal material were measured for all treatment groups.
The results from the trials give a wide range of parameters on which the diets can be evaluated,
and no single diet excelled on all counts. The different combinations of raw materials indicate
some positive effects of SPC on rheological properties of the feces at high inclusion rates, but
this outcome has to be treated carefully because of the potential detrimental emulsifying
properties of SPC. The most consistent improvements were achieved by one of the binders
tested, suggesting that recipes using a variety of raw ingredients easily can be adapted to RAS

requirements simply by adding a binder. However, the possibility that mechanically stabilization
of chyme may damage fish intestinal tissues must also be considered. Our results revealed that
binder inclusion did affect the mucus layers in the mid gut of salmon smolts, but only one trial
diet, a commercially available control supplemented with guar gum, yielded any significant
negative effect on fish intestines.
*

19


First experiences of floating faeces and its rapid removal in RAS
1

Mark Schumann *, Alexander Brinker

1

1

Fisheries Research Station, Argenweg 50/1, 88085 Langenargen, Germany

ABSTRACT
Previous extensive laboratory experiments and a commercial-scale trial in a semi-recirculating
aquaculture system (RAS) have tested a novel approach to controlling fish waste, using cork as
a functional feed additive for the production of floating faecal casts. The results suggest the
approach has great potential, not least in terms of efficiency.
The present study transferred the trial to a low water exchange RAS. A commercial diet
3
producing feces in the upper recorded density range (1,034 ± 0,0042 g/cm ) was used as a
control. The addition of 2.5% cork to the control diet resulted in stable and consistently floating

3
faecal casts with a mean density of 0.993 ± 0.003 g/cm .
The experiment was carried out in duplicate RAS, each stocked with 500 rainbow trout
(Oncorhynchus mykiss). Fish were fed six days a week until apparent satiation over a period of
3
120 days. Stocking density increased from 10 kg/m at the beginning of the experiment to a final
3
density of 75 kg/m . Mean final fish weight was 567 g and did not differ statistically between
systems.
Solid waste from the control system was collected in a pit before being transported to a drum
filter. The tanks of the system in which the experimental cork diet was fed were additionally
equipped with simple outlet pipes at the water surface, which transported the floating feces
directly to the drum filter.
The effectiveness of solid removal for floating and normal (control) feces and the consequences
for water quality parameters and waste treatment performance in the system were examined.
Mechanical removal efficiency of cork-treated wastes was more than four times greater than
that achieved in the control (89% vs. 20%). Total ammonia nitrogen (TAN) and nitrite nitrogen
levels were comparable during the first weeks of the experiment. However, when the biofilters
reached their capacity, TAN and nitrite removal was more efficient for the cork-treated system
than the control. Physiological assays indicated no pathologic tissue alterations associated with
the experimental diet and growth, survival and feed conversion were unaffected.
In conclusion, by simultaneously addressing environmental, welfare and economic concerns, a
minimal feed-mediated density modification of fish faeces improves nearly all aspects of water
quality investigated, with important implications for the future of modern closed fish farming.
*

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Feed composition affects sludge as a resource for denitrification

1

1

1

Carlos O. Letelier-Gordo *, Bodil K. Larsen , Johanne Dalsgaard , Per Bovbjerg Pedersen

1

1

Technical University of Denmark, DTU Aqua, The North Sea Research Centre, DK-9850
Hirtshals, Denmark
ABSTRACT

Organic waste produced by fish (i.e., sludge) can be used as a carbon source (C) for
denitrification, reducing the potential need for external carbon sources in on-farm nitrogen
removal. By using sludge for denitrification, the discharge of organic matter and nitrate may be
reduced, there may be no need to buy external carbon sources, energy for transport of waste is
avoided and moreover, the waste is treated at the end of the process chain rather than being
displaced to another environment (end-of-pipe concept). The capacity for denitrification
depends on the presence of readily available carbon sources e.g., in the form of volatile fatty
acids (VFAs) and alcohols, and on the C:N ratio. Volatile fatty acids and alcohols can be
generated from sludge via hydrolysis and fermentation.
Undigested feed is by far the main source of organic waste in RAS, and knowing the digestibility
of the feed makes it possible to predict the nutrient composition and consequently the organic
matter content of the produced sludge. The purpose of the current study was to examine the
effects of fish feed composition on the types and dynamics of readily available carbon sources
obtained from concomitant hydrolysis/fermentation of sludge from rainbow trout fed diets with

different protein:energy (P:E) content.
Rainbow trout faeces from fish fed 5 diets with different dietary P:E ratios were used to evaluate
the net production (quantity and quality) of VFAs and ethanol. The faeces were hydrolyzed and
fermented for 7 days in 1L batch reactors under anaerobic conditions. Samples for VFA and
ethanol analysis were obtained daily and measured by HPLC and test kits. Values were
converted to COD units, corresponding to the amount of readily available carbon sources.
Four to five days of hydrolysis/fermentation was required to achieve the maximum yield of VFAs
and ethanol. The composition and quantities of readily available carbon sources changed
according to diet composition and duration of the hydrolysis/fermentation process. The total
yields obtained did not show statistical differences between dietary treatments, but diets with
low P:E ratios produced more butyric acid and ethanol whereas diets with high P:E ratios
produced more acetic and valeric acid.
Different P:E ratios in the diets affected the types of readily available carbon sources produced
and the conditions of incomplete anaerobic digestion (e.g. pH). The results verified that it is
possible to influence and optimize the quantity and quality of readily available carbon sources
produced from sludge by manipulating the composition of fish feed, enabling an accumulation of
intermediate organic acids (propionic, butyric and valeric acids) as well as more reduced end
products (acetic acid and ethanol). Based on the obtained results an industrial scale side
stream hydrolysis/fermentation reactor was built for evaluating the capacity of performing singlesludge denitrification at a commercial farm.
Acknowledgements: This research was funded by The Ministry of Food, Agriculture and
Fisheries of Denmark and by the European Union through The European Fisheries Fund (EFF).
*

21


Biofilter effects on micro particle dynamics
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1

Paulo Mira Fernandes *, Lars-Flemming Pedersen , Per Bovbjerg Pedersen

1

1

DTU Aqua, Technical University of Denmark, The North Sea Research Centre, DK-9850
Hirtshals, Denmark
ABSTRACT
Accumulation of fine particulate organic matter in recirculating aquaculture systems (RAS) is a
balance between system input (from feed to waste), internal transformation, removal and
dilution. The mechanisms leading to fine particle accumulation in RAS are not fully understood,
and neither is the potential influence of biofilters in this respect.
This study describes the effect of fixed bed biofilters (FBB) and moving bed biofilters (MBB), on
3
particle size distribution and organic matter. It was assessed in an 8.7 m RAS with four equal
biofilters (two FFB and two MBB) stocked with rainbow trout (Oncorhynchus mykiss), and
3
operated under constant feed loading conditions (1 kg feed/m of make-up water) for more than
3 months. Carrier media was similar in shape and specific surface area for both reactor types,
differing only in specific density.
Particle concentration was reduced by ca. 200 particles/mL in FBBs, and increased by ca. 250
particles/mL in MBBs. In FBBs, a 10 % reduction in particle concentration also represented a 10
% reduction in total particle surface area and particle volume. In MBBs, a 10 % increase in
particle concentration also represented a 10 % increase in total particle surface area, but had
no effect on total particle volume. A volumetric reduction of particles > 100 µm, and an
equivalent volumetric increase of particles < 40 µm showed that MBBs produced fine particles
by disintegration of larger particles. A constant volumetric removal of particulate matter by FBB
in all size classes demonstrates their function as secondary particle removal units.

Net removal of organic matter occurred at the same rates in both modes of operation. However,
FBB removed a higher amount of dissolved BOD5 than MBB, while MBB removed a higher
amount of particulate BOD5 than FBB. All filters performed with stable nitrification rates when
operated together or separately, with net removal of ammonia and nitrite being larger in FBB
than in MBB.
Differences in biofilm formation, development, and maintenance, coupled to reactor flow
characteristics are discussed in relation to the fate of micro particles and organic matter when
operating FBBs or MBBs.
*

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