EVALUATION OF MEMBRANE TREATMENT EFFECT ON WATER QUALITY IN RECIRCULATING AQUACULTURE SYSTEMS (RAS) FOR ATLANTIC SALMON POST-SMOLTS (Salmo Salar)
Introduction
Accumulation of solids is a challenge in recirculating aquaculture systems (RAS) and this could affect the water quality and fish health. Typical particle removal systems only manage to remove particles larger than 40-60µm (Cripps & Bergheim, 2000) leaving the fine solids. There is clearly a need for advanced particle removal system. By integrating a membrane unit removing particles <1µm, accumulation of microfines can be avoided. This study evaluated effects on water quality.
Materials and Methods
This study was done at Nofima Centre for Recirculation in Aquaculture (Terjesen et al., 2013). A membrane modified RAS (mRAS) was compared to a conventional RAS (cRAS) for production of Atlantic salmon post-smolts. A membrane (AQUAFLEX 64®, Pentair/X-flow) with nominal pore size of 20 nm and total area of 60m2 was connected to the outlet of the biofilter, and clean permeate water was returned back into the system. This setup filtered 5% of the total system flow for 10 h d-1, corresponding to 50% of the total system volume. Fish weight and tank density were 250 g and 50 kg/m3, respectively.
Physiochemical water quality parameters, total suspended solids (TSS), particle size distribution (PSD), turbidity, total ammonia nitrogen (TAN), and total organic carbon (TOC) were measured.
Results
The membrane improved the water clarity and had a significant effect on several water quality parameters. Turbidity, TSS and TOC were lower in mRAS compared to cRAS (p=0.05) (Fig. 1, A - C, respectively). Furthermore, the treatment had a positive effect on the TAN removal during the whole experiment (Fig. 1, D).
Acknowledgements
Funded by Research Council of Norway strategic institute program, pr. 194050/F40 "Development of future controlled-environment aquaculture". The membrane was supplied by Pentair.
References
Cripps, S. J., & Bergheim, A. (2000). Solids management and removal for intensive land-based aquaculture production systems. Aquacultural Engineering, 22(1-2), 33-56. doi:10.1016/s0144-8609(00)00031-5
Cripps, S. J., & Bergheim, A. (2000). Solids management and removal for intensive land-based aquaculture production systems. Aquacultural Engineering, 22(1-2), 33-56. doi:10.1016/s0144-8609(00)00031-5
Terjesen, B. F., Summerfelt, S. T., Nerland, S., Ulgenes, Y., Fjæra, S. O., Megård Reiten, B. K., . . . Åsgård, T. (2013). Design, dimensioning, and performance of a research facility for studies on the requirements of fish in RAS environments. Aquacultural Engineering, 54(0), 49-63. doi:http://dx.doi.org/10.1016/j.aquaeng.2012.11.002