The use of wastewater will reduce the need for additional sources of nitrogen and phosphorus by about 55% (Yang et al., 2011). Integrated aquaculture systems are considered a promising technology, but recent efforts have focused primarily on microalgae (Troell et al., 2003). Nutrients (nitrogen, phosphorus) are usually concentrated in the wastewater discharged from intensive aquaculture, mainly from fish excreta and feed residues (Crab et al., 2007).
Microalgae have been widely used to treat wastewater because they remove nitrogen, phosphorus, BOD and COD very efficiently (Wang et al., 2010). Ammonia nitrogen and phosphates in wastewater serve as a complete medium equivalent to chemical media from a kinetic point of view (Li et al., 2011). In fact, several studies have demonstrated the use of microalgae for the production of valuable products in combination with environmental applications (Bilanovicet al., 2009).
Microalgal cultures provide an effective solution for tertiary and quaternary wastewater treatments due to the ability of microalgae to use inorganic nitrogen and phosphorus for their growth (Kumar et al., 2010). The prokaryotic microorganism consists of cyanobacteria (Cyanophyceae), and green algae (Chlorophyta) or diatoms (Bacillariophyta) are eukaryotic microalgae (Li et al., 2008). Microalgae play an important role in providing energy and essential nutrients for the proper growth of aquatic species in open water (Habib et al., 2003).
They are also the main live food for rotifers, cladocera, zooplankton and fish and shrimp larvae (Gallardo et al., 1995).
Salinity
Microalgae Growth Phases
In this phase, water quality deteriorates and nutrient depletion reaches levels that are no longer able to sustain growth. The cell density decreases rapidly and the culture collapses.
Proximate composition
Protein
Lipid
Carbohydrate
Wastewater was collected at Niribili Shrimp Hatchery, Cox's Bazar from the shrimp (Penaeus monodon) breeding tank. Four sources of aquaculture wastewater were selected for the screening. The results showed that the siphon wastewater had the highest increase in microalgae productivity due to the difference in wastewater composition with collection time, making it the main candidate as a wastewater medium for microalgae aquaculture. . Siphon operation is a practical cleaning process carried out by farmers to renovate pond water by taking out the old water and discharging it together with shrimp feces, exoskeleton and other waste material into the lower layer of the pond. Wastewater was collected per container in a batch container with a capacity of 20L.
Media Preparation
Preparation of Conway Medium (Tompkins et al., 1995)
Nutrient Analysis of Wastewater
Total ammonium nitrogen (TAN)
Nitrite (NO 2 -N)
Determination of Phosphate phosphorus (PO 4 -P)
Microalgae Sample Collection
Lipid Analysis
Based on Marsh & Weinstein (1966), lipid analysis was performed by the sulfuric acid carbonization method, carbonization method using tripalmitin as a standard after lipid extraction by the method of Bligh & Dyer (1959). Samples were extracted from 4.5 mL of chloroform:methanol (concentration 1:2) and then centrifuged at 10,000 rpm for 10 min. After separating the supernatant from the biomass, 1.5 mL of chloroform and 1.5 mL of distilled water were added and the sample was centrifuged again to facilitate the separation of the two phases.
Then, 3 portions of 200 μL each were taken from this solution and transferred to test tubes and the solvent was evaporated again. The carbonization process was carried out at 200 °C for 15 min, then the tubes were cooled and 3 ml of water was added to each tube. The samples were analyzed by adding 1 mL of 5% phenolic solution and 5 mL of concentrated sulfuric acid.
Statistical Analysis
RESULTS
Physicochemical Parameters of Aquaculture Wastewater
Growth Parameter Analysis
- Growth of Chlorella vulgaris in Wastewater and Conway media
Proximate Composition
- Protein content of Chlorella vulgaris cultured in Wastewater and Conway Media
- Lipid content of Chlorella vulgaris cultured in Wastewater and Conway Media
- Carbohydrate content of Chlorella vulgariscultured in Wastewater and Conway Media
There was a significant difference (p > 0.05) in the carbohydrate content grown at different concentrations of ww.
DISCUSSION
Laven and Sorgeloss (1996) also provide a simplified set of conditions for growing microalgae where all physical properties were within the scope of this study (Table 4.1). The wastewater medium provided nitrogen in the form of nitrates, nitrites, and ammonium salts, which were readily available in inorganic form (Thompson et al., 1989). The sum of nitrate nitrogen (NO3-N), nitrite nitrogen (NO2-N), ammonium nitrogen (NH3-N) and organically bound nitrogen is total nitrogen (TN). Many of these nitrogen sources have been used to process microalgae (Becker, 1994).
The source of phosphorus was found naturally in wastewater in the form of inorganic phosphate. Inorganic phosphate is a type of phosphate that is commonly added to culture media and is favorable for the growth of microalgae (Probert and Klaas, 1999). For the best growth of microalgae, a constant supply of nitrogen and phosphorus plays a major role. In the metabolism of microalgal cells, nitrogen is essential, and nitrogen uptake is directly related to photosynthesis.
Moreover, the Conway media contained all the recommended balanced nutrients, which also ensured proper growth of experimental algal strain. Based on Figure 4.2.1, there were no significant differences (p > 0.05) in terms of cell density and optical density in C. According to Barsanti and Gualtieri (2006), microalgae need a certain period of time to physiologically adjust and adapt to the new environment even if the cells were viable as they were not yet able to undergo division.
But 50% ww treatment had no significant difference in % protein content with commercial Conway's medium. In addition, there was a significant difference (p > 0.05) regarding the lipid content of C. Some species of algae (N. oculata and T. . chuii) are interesting and important microorganisms in the field of biotechnology due to their high lipid content, more protein and essential fatty acids (Ghezelbash et al., 2008).
According to the results of this study (Figure 4.3.3) there was significant difference (p > 0.05) in terms of carbohydrate content in C. The highest carbohydrate content was found in 50% ww followed by Conway medium and the lowest in 75% ww . However, all the values of carbohydrate content in five different treatments were within the recommended range demonstrated in previous studies.
CONCLUSION
PROSPECTS AND RECOMMENDATION
Biomass production and variation in the 88 biochemical (total protein, carbohydrates, RNA, lipids and fatty acids) of seven species of marine microalgae. Culture and nutritional value of Moinamicrura fed on Chlorella vulgaris grown in digested palm oil mill effluent. Molecular phylogenetics and biogeography of the eastern Asian eastern North American disjunct Mitchella and its close relative Damnacanthus (Rubiaceae, Mitchelleae).
Effects of environmental factors and nutrient availability on the biochemical composition of algae for biofuel production: a review. Isolation of novel nanoplanktonic diatom strains and their evaluation as a diet for the juvenile Pacific oyster (Crassostrea gigas). Microalgae carbohydrates: an overview of the factors influencing carbohydrate production and the main bioconversion technologies for biofuel production.
Effects of iron limitation on photosynthesis and carbohydrate metabolism in the Antarctic diatom Chaetocerosbrevis (Bacillariophyceae). Crude composition and fatty acid composition of 18 species of tropical Australian microalgae for potential use in mariculture. Effect of salt concentration on the intracellular accumulation of lipids and triacylglycerides in cells of the marine microalga Dunaliella.
Effect of different light regimes on the content of docosahexaenoic acid (DHA) in Isochrysisgalbana (cloneT-ISO). Regeneration and maturation of daughter cell walls in the autospore-forming green alga Chlorella vulgaris (Chlorophyta, Trebouxiophyceae). Effect of nitrogen, salt and iron content of the growth medium and light intensity on lipid production by microalgae isolated from freshwater sources in Thailand.
Appendix A: One-way ANOVA of protein content of Chlorella vulgaris grown in wastewater and Conway medium. Appendix B: One-way ANOVA of lipid content of Chlorella vulgaris cultured in wastewater and Conway media. Appendix C: One-Way ANOVA of Carbohydrate Content of Chlorella Vulgarized in Wastewater and Conway Media.
