Abstract
This study researched the use of six microalgae species (N. gaditana, P. lutheri, I. galbana, T. chuii, P. tricornutum and C. gracilis) and a bloom to treat effluent from a marine fish farm and produce quality biomass. More specifically, simulated water from a recirculating aquaculture system (RAS) was used. Microalgae culture was carried out under controlled conditions using 18 L bubble column photoreactors under batch and semi-continuous operation. The main parameters analysed were micronutritional requirements, biomass productivity, nutrient removal rate (nitrogen and phosphorus), biomass composition, and quality. Also, based on the results obtained, a quantitative classification of the microalgae was carried out. The results showed that all microalgae required at least trace metals. In certain species, the addition of vitamins was also required for viable cultivation. In the case of biomass productivity under batch operation, values were between 67 mg L−1 d−1 and 7 mg L−1 d−1 using T. chuii and C. gracilis, respectively, and between 71 mg L−1 d−1 and 9 mg L−1 d−1 using T. chuii and N. gaditana under semi-continuous operation. In the case of total dissolved phosphorus removal, no differences were found between species, reaching in all cases final concentrations <0.01 mg L−1. Total dissolved nitrogen removal rate varied between species and operating conditions, being the highest obtained using T. chuii under semi-continuous operation (12.6 mg L−1 d−1) and the lowest with C. gracilis batch operation (0.15 mg L−1 d−1). Biomass composition in terms of protein and lipids varied between species and operating conditions, but quality in terms of amino acids and fatty acids profile remained homogeneous in all cases. Finally, according to the developed score methodology, I. galbana was the microalgae with the highest biomass production score, while T. chuii was for wastewater treatment.
Highlights
Aquaculture is an essential food industry, providing a source of an imal protein for more frequent consumption and lower production costs [1]
The main environmental issues facing aquaculture are the dependence on the wild fish meal (FM) and fish oil (FO) for feed production and the environmental degradation resulting from aquaculture activity [2]
This study aims to select the optimal species for cultivating micro algae using marine recirculating aquaculture system (RAS) stream through a multi-criteria decision system including the following parameters: biomass productivity, nutrient removal kinetic, nutritional requirements, harvestability and biomass composition
Summary
Aquaculture is an essential food industry, providing a source of an imal protein for more frequent consumption and lower production costs [1]. The annual consumption of fish as an animal source of protein per capita has increased by 1.5%, reaching 20.5 kg in 2018 [2]. According to the Food and Agriculture Organization of the United Nations (FAO) [2], world fish production reached 179 million tons in 2018, of which 46% came from aquaculture, this is equivalent to a value of USD 250 billion. The main environmental issues facing aquaculture are the dependence on the wild fish meal (FM) and fish oil (FO) for feed production and the environmental degradation resulting from aquaculture activity [2]. The latest data for overall aquaculture was 0.22 in 2015
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