Biosorption and bioaccumulation of geosmin from recirculating aquaculture system : fate of geosmin in aquaculture water
Baral, Asmit (2023)
Diplomityö
2023
School of Engineering Science, Kemiantekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe20231213153748
https://urn.fi/URN:NBN:fi-fe20231213153748
Tiivistelmä
Geosmin (GSM) is one of the most common off-flavor compounds found in aquaculture wastewater which is responsible for the odor-related problems in fish. The microalgae assisted water treatment unit is used in Recirculating aquaculture system (RAS) due to its natural capacity of removing nutrients. In addition, the biomass derived from microalgae is a potential source of feed for fish in the aquaculture industry. It is meaningful to investigate the interaction between Geosmin on dead or live microalgal cells to determine the fate of GSM in RAS.
Tetraselmis Suecica (T. suecica) and Nannochloropsis Oculata (N. oculata) were selected to investigate the relationship between GSM and algae (both living and dead). The initial adsorbate concentration of 2 mg/L and the adsorbent concentration of 1 g/L in the preliminary adsorption study indicate that the biomasses of N. oculata and T. suecica removed 53.56% and 25.06% of GSM over the course of a 24-hour period. GSM being semivolatile, 1.2 % was volatilized in the respective time. N. oculata was selected as an adsorbent for kinetic and isotherm studies based on its superior removal performance. Isotherm models (Langmuir, Freundlich, and Henry’s law) was used to study adsorption process. The result showed that the adsorption between microalgae and GSM could be best described by Henry’s law and pseudo-second order model. The analysis of GSM was performed using Solid-phase microextraction accompanied by Gas chromatography-mass spectrometer (SPME/GC-MS).
To examine bioaccumulation similar strains of live microalgal cells were used and removal of GSM (initial concentration = 2 mg/L) was observed to be 53.98 % and 42.15 % by N. oculata and T. Suecica within the span of 24 h (initial cell concentration 2.21·10⁸ and 4.4 ·10⁶ cells/ml respectively). N. oculata was further used to study the impact of GSM on microalgal growth. The experiment was conducted in RAS and f/2 media (initial cell concentration = 3.72 · 10⁶ cells/ml) for three days. In day 1, the removal of GSM was observed 7.78 % and 7.52 % in RAS (9.34% volatilization) and f/2 (7.97% volatilization) respectively. The removal of GSM was decreased to 3.97 % (RAS) and 1.19 % (f/2 media) on day 3. The volatilization of GSM from borosilicate bottle was increased to 10.18 % and 16.24 % in RAS and f/2 media respectively on day 3. There was formation of Extracellular polysaccharides (EPSs) in RAS media spiked with GSM on day 3. The cell concentration of microalgae has decreased in the medium spiked with GSM which is possibly due to cell death (GSM being in high concentration). However, the cell concentration has increased slightly in both RAS and f/2 medium in absence of GSM. These findings highlight the potential of microalgal biomasses as an mighty adsorbent for the removal of GSM rather than feed in RAS process water. Nonetheless, there is lack of research on the fate of GSM in RAS process water therefore, extra research is needed to clarify the applicability of microalgal biomasses as a direct feed and fate of GSM in RAS process water.
Tetraselmis Suecica (T. suecica) and Nannochloropsis Oculata (N. oculata) were selected to investigate the relationship between GSM and algae (both living and dead). The initial adsorbate concentration of 2 mg/L and the adsorbent concentration of 1 g/L in the preliminary adsorption study indicate that the biomasses of N. oculata and T. suecica removed 53.56% and 25.06% of GSM over the course of a 24-hour period. GSM being semivolatile, 1.2 % was volatilized in the respective time. N. oculata was selected as an adsorbent for kinetic and isotherm studies based on its superior removal performance. Isotherm models (Langmuir, Freundlich, and Henry’s law) was used to study adsorption process. The result showed that the adsorption between microalgae and GSM could be best described by Henry’s law and pseudo-second order model. The analysis of GSM was performed using Solid-phase microextraction accompanied by Gas chromatography-mass spectrometer (SPME/GC-MS).
To examine bioaccumulation similar strains of live microalgal cells were used and removal of GSM (initial concentration = 2 mg/L) was observed to be 53.98 % and 42.15 % by N. oculata and T. Suecica within the span of 24 h (initial cell concentration 2.21·10⁸ and 4.4 ·10⁶ cells/ml respectively). N. oculata was further used to study the impact of GSM on microalgal growth. The experiment was conducted in RAS and f/2 media (initial cell concentration = 3.72 · 10⁶ cells/ml) for three days. In day 1, the removal of GSM was observed 7.78 % and 7.52 % in RAS (9.34% volatilization) and f/2 (7.97% volatilization) respectively. The removal of GSM was decreased to 3.97 % (RAS) and 1.19 % (f/2 media) on day 3. The volatilization of GSM from borosilicate bottle was increased to 10.18 % and 16.24 % in RAS and f/2 media respectively on day 3. There was formation of Extracellular polysaccharides (EPSs) in RAS media spiked with GSM on day 3. The cell concentration of microalgae has decreased in the medium spiked with GSM which is possibly due to cell death (GSM being in high concentration). However, the cell concentration has increased slightly in both RAS and f/2 medium in absence of GSM. These findings highlight the potential of microalgal biomasses as an mighty adsorbent for the removal of GSM rather than feed in RAS process water. Nonetheless, there is lack of research on the fate of GSM in RAS process water therefore, extra research is needed to clarify the applicability of microalgal biomasses as a direct feed and fate of GSM in RAS process water.