Pengaruh Kadar Fosfor dalam Media Limbah Cair Sintetik terhadap Laju Pertumbuhan Spesifik Sel, Produktivitas Biomassa dan Produksi Minyak dari Konsorsium Mikroalga

Abstract

Indonesia is famous as a rich country in natural resources, particularly which are found in the waters, one of them is microalgae. In nature, microalgae are usually found in microalgal consortium form which is a mixture of various types of microalgae and their contaminations (other microorganisms). Microalgae have an ability to synthesize food reserves such as carbohydrates, proteins and fats. Organic wastewater is generated from agriculture and domestic sources which contain organic matters, nitrogen and phosphorus in high concentrations. Agroindustrial wastewater is one of the organic wastewater and generally rich in nutrients N (nitrogen), P (phosphorus), C (carbon), and S (sulfur) which are the nutrients for microalgal cells growth. Microalgal growth will be optimum if the nutrients are in a certain concentration and a certain ratio. The aims of this research were to know the characteristric of microalgal consortium growth in the organic wastewater media, to know the effect of various phosphorus concentrations of synthetic wastewater media on cell specific growth rate, biomass productivity and oil content of microalgal consortium and also to determine the best phosphorus concentration for microalgal consortium growth. Before the main research, conducted the preliminary research with microalgal consortium cultivation in 4 litres cultures scale. The preliminary research was began by the characreizations of organic wastewater (slaughter house, livestock and sugar factory wastewater). These were showed that the nutrients and COD were relatively high (the highest nutrient content in 1,490 mg/L and the highest COD content in 32,000 mg/L) which might inhibit microalgal consortium growth, so before cultivated microalgal consortium, wastewater media were diluted before so that the highest nutrient concentrations were only in the range of hundreds and the highest COD concentrations were only in the range of thousands. For this preliminary research, the first was prepared the topless and then wastewater and microalgal consortium suspensions entered into the topless. The growth of microalgal consortium was observed until the cultures entered the death phase. Before organic wastewater cultivation stage 1, conducted the characterizations of microalgal consortium before. The composition of organic wastewater media stage 1 were 75% wastewater and 25% inoculums of microalgal consortium with the form of receptacles in fiberglass tanks, the cultures volume were in 180 litres and the cultures height were in 30 cm. Before proceed to organic wastewater cultivation stage 2, conducted the characterizations of organic wastewater 2 (slaughter house and livestock wastewater). In this organic media cultivation stage 2 had composition 75% organic wastewater and 25% inoculums of microalgal consortium with the receptacles in the form of aquariums, the cultures volume were in 20 litres and the cultures height were in around 16.7 cm. After organic wastewater cultivation stage 2, then cultivated in synthetic media with the characterization of fertilizers and synthetic media made before. The synthetic media were made by various phosphorus concentrations, i.e. 11 mg/L, 16.5 mg/L and 22 mg/L. In this synthetic media cultivations, the compositions were 75% synthetic wastewater and 25% inoculums of microalgal consortium with the receptacles of aquarium, the cultures volume in 28 litres and the cultures height in 23.3 cm. The results of the first and second organic wastewater characterizations showed that the livestock wastewater had the highest nutrient concentration in the overall characterizations. The characteriation results of microalgal consortium had cells density in 2.25 x 106 cells/ml and were dominated by groups of Chlorophyceae and Cyanophyceae. The cultures of microalgal consortium in organic wastewater media stage 1 had cultivation periods in 20 days. The complete life cycle phases curve of microlgal growth (from the lag phase up to the death phase) only on the growth curve of slaughter house wastewater culture while the growth curve of livestock and sugar factory wastewater were incleaned toward stationary.