Aquaculture Europe 2014

October 14-17, 2014

Donostia–San Sebastián, Spain

PERFORMANCE OF THE MULTI-SENSOR AUTOMATED PLATFORM  FOR CONTINUOUS MONITORING OF THE WATER QUALITY IN RECIRCULATION AQUACULTURE SYSTEMS (RAS)

J. Kolarevic*1, D. Bundgaard1, B.K.M. Reiten1, K.S. Nerdal1, K. Bink2, P. Bouma2 M. Frederiksen3, P. Petersen4, J. Linga5, C. Abbott5 and B.S. Saether6
 
1Nofima AS, NO-6600 Sunndalsøra, Norway; 2Philips Research, Eindhoven, The Netherlands,  3Eurofish, Copenhagen, Denmark, 4Oxyguard, Farum, Denmark, 5The UK Intelligent Systems Research Institute, Melton Mowbray, United Kingdom, 6Nofima, Postboks 6122, NO-9291 Tromsø, Norway; E-mail: jelena.kolarevic@nofima.no

Introduction
The use of recirculating aquaculture system (RAS) is increasing in Europe. The need for more rational use of available water sources, better control of the rearing environment and an increase in production are some of the reasons for increased interest in water reuse systems for fish production (Kolarevic et al., 2014). On the other hand, substantial investment and operating costs, the need for higher skilled personal and the complexity of the daily management of RAS are some of the challenges that European aquaculture industry is facing today. Further expansion of the land based close containment production will largely depend on the continuous improvements of the system design and optimization of both build and operating costs in order to increase the profitability of RAS.
Water quality monitoring is an integral part of the daily RAS management. It is both time consuming and often requires skilled personal with knowledge in water chemistry. The measurement of nitrite and ammonia is especially challenging. The automatization of the water quality monitoring is thus one of the key issues that would lead to more effective operation of the RAS. Currently number of on-line probes for continuous measurement of water quality are available on the market, however they are not custom made for use in aquaculture systems and are often unreliable. The aim of the EU FP7 project AQUAlity is to lower costs for European fish farmers by developing a multi-sensor platform for continuous monitoring of water quality in RAS that will also contain built-in knowledge of best practice conditions for the farmed species in close-containment systems. A customized miniaturized automated colorimetric analyzer (MACA) for the measurement of total ammonia nitrogen (TAN) and nitrite-nitrogen (NO2-N) in aquaculture is developed within the project as an integrative part of the platform and has been tested together with the other parts of the platform in this study.
 
Methods
The performance of the AQUAlity platform was tested in the Nofima Centre for Recirculation in Aquaculture (NCRA; described in Terjesen et al., 2013) between May and August 2014. Atlantic salmon parr (n=10520, 11 g ind-1) were stocked in four octagonal 3.2m3 tanks supplied with recirculating freshwater. Salmon smolts were produced during 90 days following established commercial production. The RAS loop consisted of culture tanks, followed by mechanical (Salsnes, Norway) and biological (Kaldnes MBBR with Biofilm Chip P, KrügerKaldnes, Sandefjord, Norway) water treatment and degassing (AquaOptima). Finally water was oxygenated and returned to the culture tanks. Recirculating water was ozonized prior to the mechanical treatment in period between June and August in order to monitor the effects of this treatment on the RAS water quality. The RAS was operating at the 99.4% of recirculation degree of the total flow that was on average 492 ± 9 L min -1 (± SD). The amount of new water added to the system was 3 ± 3 L min -1 and the daily system volume exchange rate was 12.7%. An AQUAlity platform consisting of the Pacific control unit (Oxyguard, Farum, Denmark) and five on-line probes (salinity, oxygen (O2), pH, total gas pressure (TGP), carbon dioxide (CO2)) was installed in the degassing sump for continuous measurements of the water quality within RAS. Data logging, monitoring and trending was further on facilitated via AQUAlity software and SQL server 2012. By the end of June 2014 MACA was not integrated into AQUAlity platform and TAN and NO2-N measurements were done in the lab using the water collected from the RAS. Regular daily, weekly (three times a week) and monthly water quality measurements were done using standard lab and commercially used instruments in order to establish accuracy, response time and maintenance requirements of the AQUAlity platform. Atlantic salmon performance (growth and mortality) were measured throughout the study and the number of external welfare parameters were evaluated according to Kolarevic et al. (2013) at the start and at the end of the study.
 
 
Results and discussion
The results of the AQUAlity platform testing indicate the importance of the proper maintenance of the on-line probes. The formation of the biofilm on the surface of the pH, CO2 and O2 probe affected significantly the accuracy of the continuous measurements. Cleaning of the pH probe caused an immediate increase in measured pH of between 0.1 and 0.3. This indicates that, in systems with high biological loading as in the test, a daily cleaning routine is necessary.  Alternatively the use of probe cleaning systems commonly used in waste-water treatment plants could be used (Kolarevic et al., 2011). In addition, an offset of 5 mg L-1 CO2 was recorded after on-line probe was operated for ten days without maintenance. Initial results indicate that MACA can reproduce stable nitrite nitrogen measurement in the range between 0.05 and 2.5 mg L-1 of NO2-N. The accuracy and the reproducibility of the TAN measurements in the area between 0.1 and 10 mg L-1 are currently being tested and the results will be presented.
 
Acknowledgements
The research leading to these results has received funding from the European Union's Seventh Framework Programme managed by REA Research Executive Agency (http://ec.europa.eu/research/rea) (FP7/2007-2013) under grant agreement number [286995] in a research for the benefits of SME associations, project AQUAlity: "Multi-sensor automated water quality monitoring and control system for continuous use in recirculation aquaculture systems".
 
References
Kolarevic, J., Ciric, M., Zühlke, A., Terjesen, B.F., 2011. On-Line pH Measurements in Recirculating Aquaculture systems (RAS), Aquaculture Europe 2011. European Aquaculture Society, Greece, Rhodos, pp. 570-571.
 
Kolarevic, J., Selset, R., Felip, O., Good, C., Snekvik, K., Takle, H., Ytteborg, E., Bæverfjord, G.,
Åsgård, T., Terjesen, B.F., 2013. Influence of long term ammonia exposure on Atlantic
salmon (Salmo salar L.) parr growth and welfare. Aquaculture Research 44, 1649-1664.
 
Kolarevic J., Bæverfjord G., Takle H., Ytteborg E., Megård Reiten B.K., Nergård S., Terjesen B.F., 2014. Performance and welfare of Atlantic salmon smolt reared in recirculating or flow through aquaculture systems. Aquaculture 432, 15-25.
 
Terjesen, B.F., Summerfelt, S.T., Nerland, S., Ulgenes, Y., Fjæra, S.O., Megård Reiten, B.K., Selset, R., Kolarevic, J., Brunsvik, P., Bæverfjord, G., Takle, H., Kittelsen, A., Åsgård, T., 2013. Design, dimensioning, and performance of a research facility for studies on the requirements of fish in RAS environments. Aquacultural Engineering. 54, 49-63.