Abstract
This study aimed to evaluate the growth of Arthrospira (Spirulina) platensis cultivated in Zarrouk culture medium and effluent from Nile tilapia (Oreochromis niloticus) reared in biofloc system. Four treatments were used: Control (100% Zarrouk), E50 (50% Zarrouk + 50% Tilapia effluent), E75 (25% Zarrouk + 75% Tilapia effluent), and E100 (100% Tilapia effluent), and the experiment lasted 10 days. Growth parameters such as maximum cell density (MCD), doubling time (DT), and growth rate (K) were daily evaluated, as well as pH and water temperature. In addition, the concentrations of total ammonia nitrogen (TAN), nitrite-N (NO2-N), and nitrate-N (NO3-N) were analyzed in order to compare nitrogen absorption. Among treatments, E50 and E75 obtained higher maximum cell densities and presented an exponential growth rate similar to the control treatment. Regarding the concentrations of nitrogen compounds, a significant reduction was observed in all treatments, with an NO3-N uptake of 99%, followed by 80% of TAN and 90% of NO2-N. Thus, giving the results obtained, besides being able to grow in wastewater, A. platensis can also be used in bioremediation processes, confirming the potential of this species.
Highlights
As few studies have investigated the potential use of aquaculture wastewater, which in addition to containing the basic nutrients necessary for the growth of microalgae, still reduce production costs (AbdelRaouf, Al-Homaidan, & Ibraheem, 2012), the aim of this study was to evaluate the growth and nitrogen uptake by A. platensis cultured in Nile tilapia biofloc wastewater
The curves corresponded to the proposed model and the coefficients showed a correlation above 0.90. As it is shown in the control curve (100% Zarrouk), A. platensis entered the exponential phase of growth on the second day, and remained in that phase until the fourth day, showing faster growth from the first day onwards
Differently from the results presented above, the data obtained in this study showed higher concentrations of biomass, as well as higher growth rates, when A. platensis was being grown under autotrophic conditions
Summary
Aquaculture activities generate significant quantities of nutrient-rich effluents containing organic and inorganic compounds such as nitrogen, phosphorus, and carbon, which may cause eutrophication of surrounding water bodies. These effluents can increase the occurrence of pathogenic microorganisms and the introduction of invasive species (Crab, Defoirdt, Bossier, & Verstraete, 2012). New aquaculture systems, such as biofloc (BFT), have been developed to enhance water quality by balancing nitrogen and carbon in the system (Crab et al, 2012). Fungi, nematodes, rotifers, copepods, feed leftovers, and feces are present in this kind of system (Crab et al, 2012)
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