World Aquaculture Magazine - June 2021

52 JUNE 2021 • WORLD AQUACULTURE • WWW.WA S .ORG Protocol for Biofloc Production in the Photobioreactor Nitrogen sources are mainly nitrate and ammonia obtained from culture water and carbon source used are CO 2 , HCO 3 - or organic carbon sources like acetate or glucose. Air stripping technique is applied to remove total nitrogen and total phosphorus from the aquaculture effluents before inoculating into the photobioreactor. After the purification of pollutants, pure culture of biofloc is inoculated along with growth medium. A gas mixture is supplied to the photobioreactor using sparger and air flow rate and CO 2 flow rate is adjusted to control media pH. The culture is circulated through the tubes by an airlift pump or other suitable low-shear mechanism. The maximum flow rate is limited by the tolerance of the algae to hydrodynamic stress. The flow velocity is usually 30-50 cm/sec. Temperature, DO, pH and ORP are monitored throughout the culture process. Biomass measurements are recorded every 12 hours and a volumetric pipette can be used to withdraw a 100-mL sample from the growing media. Then the average biomass on a daily basis can be calculated. Biofloc biomass can then be separated using vacuum filtration equipment and the concentrated biomass collected using Whatman filter paper (number 4) with a diameter of 40 mm and a pore size of 20-25 µ m. Biomass collected on filter paper can be weighed and dried in a hot-air oven at 70 to 80 C for ten hours. Oven-dried biomass can be then be used as an ingredient for fish or shrimp feed. Summary A comparison of the advantages and disadvantages of raceways and photobioreactor is provided in Table 1. Use of photobioreactor and raceway for the production of biofloc is a considerably new approach in aquaculture. The importance of this approach lies in replacement of conventional ingredients in fish feed as well as for upkeep of the environment. The designs discussed for the ex-situ biofloc production can serve as a model that brings out the advantage of using biofloc meal in fish and shrimp feeds. The operational experience with the raceway and photobioreactor will allow continuous progress in the knowledge of design criteria and parameters to be used in ex-situ biofloc production. Notes S. Felix, Past-president, WAS-APC, felixfisheries@gmail.com M. Menaga, Assistant Professor, Tamil Nadu Fisheries University, mena.fishcos@gmail.com References Burford, M.A., Thompson, P.J., McIntosh, R.P., Bauman, R.H., Pearson, D.C., 2004. The contribution of flocculated material to shrimp ( Litopenaeus vannamei ) nutrition in a high-intensity, zero- exchange system. Aquaculture 232:525-537. Collazos-Lasso, L.F. and J.A. Arias-Castellanos. 2015. Fundamentos de la tecnología biofloc (BFT). Una alternativa para la piscicultura en Colombia. Revisión Orinoquia 19:77-86. Crab, R., T. Defoirdt, P. Bossier andW. Verstraete. 2012. Biofloc technology in aquaculture: Beneficial effects and future challenges. Aquaculture 356-357:351-356. Kumar, S., P.S.S. Anand, D. De, J.K. Sundaray, R.A. Raja, G. Biswas, A.G. Ponniah, T.K. Ghoshal, A.D. Deo, A. Panigrahi and M. Muralidhar. 2014. Effects of carbohydrate supplementation on water quality, microbial dynamics and growth performance of giant tiger prawn ( Penaeus monodon ). Aquaculture International 22:901-912. Kuhn, D.D., G.D. Boardman, S.R. Craig, G.J. Flick and E. Mclean. 2008. Use of microbial flocs generated from tilapia effluent as a nutritional supplement for shrimp, Litopenaeus vannamei , in recirculating aquaculture systems. Journal of the World Aquaculture Society 39:72-82. Kim, S.K., Z. Pang, H.-C. Seo, Y.R. Cho, T. Samocha and I.K. Jang. 2014. Effect of bioflocs on growth and immune activity of Pacific white shrimp, Litopenaeus vannamei post larvae. Aquaculture Research 45:362-371. Tacon, A., J.J. Cody, L.D. Conquest, S. Divakaran, I.P. Forster and O.E. Decamp. 2002. Effect of culture system on the nutrition and growth performance of Pacific white shrimp, Litopenaeus vannamei (Boone) fed different diets. Aquaculture Nutrition 8:121-137. Wasielesky, W., H. Atwood, A. Stokes and C.L. Browdy. 2006. Effect of natural production in a zero exchange suspended microbial floc based super-intensive culture system for white shrimp Litopenaeus vannamei . Aquaculture 258:396-403. Xu, W.J. and L.Q. Pan. 2013. Enhancement of immune response and antioxidant status of Litopenaeus vannamei juvenile in biofloc- based culture tanks manipulating high C/N ratio of feed input. Aquaculture 412:117-124. TABLE 1. Advantages and disadvantages of raceways and photobioreactor for ex-situ biofloc production. Factor Raceways Photobioreactor Capital cost Smaller Greater Difficulty in terminating nitrification Greater Smaller Operational costs Smaller Greater Operational problems Smaller Greater Process control equipment Smaller Greater Sludge production Smaller Greater Susceptibility to changes in BOD load Greater Smaller Susceptibility to changes in toxic load Greater Smaller