Judul: Pengaruh Kadar Fosfor dalam Media Limbah Cair Sintetik terhadap Laju Pertumbuhan Spesifik Sel, Produktivitas Biomassa dan Produksi Minyak dari Konsorsium Mikroalga
Abstrak: 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
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Judul: Kultivasi Konsorsium Alamiah Mikroalga dengan Memanfaatkan Nutrien pada Berbagai Limbah Cair Agroindustri
Abstrak: During the last two decades, Indonesian economic growth focused on industrial development especially agroindustrial sector (Suardana, 2008). As a result, agroindustrial wastewater pollution became serious problem. Organic wastewater with high nutrient content can stimulate uncontrolled microalgae growth (Pustekkom, 2005), whereas discipline control can be very profitable. According to Pirt (1986), microalgae is low level vegetation (5 – 30 2m) with high productivity and efficiency in biofuel producing through photosynthesis. Its productivity in producing triglycerides reached 100 000 L/ha, while oil palm reached only 5 950 L/ha (Kabinawa, 2008). Specific cultivation of microalgae raised feasibility problem particularly in Indonesia. Cultivation of natural microalgae consortium in many agroindustrial wastewater, will be delivered to produce dominant, natural selected microalgae with good ability to survive in such extreme condition. This research was performed to determine the effect of several agroindustrial wastewater as nutrient in microalgae natural consortium cultivation. In addition, application of coagulation/flocculation and centrifugation method for separating/harvesting microalgae was also investigated. In the early stage, preparation was performed to create cultivation vessel based on raceway design, characterization of agroindustrial wastewater (slaughterhouse wastewater/L1, livestock wastewater/L2, and sugar mill wastewater/L3), characterization of microalgae natural consortium from LSI Lake- IPB, and also making of trial cultivation. Next stage, primary cultivation was launched in wastewater medium with circulation, wastewater medium without circulation, and synthetic wastewater medium (in many concentrations of NPK fertilizer, without circulation). In the last stage, separation of consortium after cultivation was carried out with centrifugation, and also coagulation/flocculation with alum and polyaluminium chloride (PAC). Characterization of wastewater showed that L2 contain the highest nitrogen (1 490 mg/L) and potassium (304.70 mg/L) concentration, but orthophosphate concentration (8.0 mg/L) lower than L1 (14.8 mg/L). Meanwhile L3 had nitrogen (0 mg/L), orthophosphate (0.6 mg/L), and potassium (107.70 mg/L) concentration at the lowest. Microalgae consortium cell density attained 2 250 000 cell/ml, and its prevalence showed that there are three species of chlorophyceae in large amount, Selenastrum sp., Ankistrodesmus sp., and Dictyosphaerium sp.. Uncounted species in consortium assumed to be in very small amount. Cultivation in wastewater medium with circulation showed that complete microalgae growth phase occurred in 20 – 30 days. During the phase, nutrients such as N, NO3 -, PO4 3-, and K decreased, however, fluctuation occurred (especially NO3 - and PO4 3-) by the perpetual conversion activity which related to food chain between microalgae and the other contaminant microorganisms. Its pH value ranging in proper microalgae growth pH from 7 to 9 but tend to be 8. Drastic color change according to chlorophyceae growth was not appeared due to effect of circulation on the chlorophyll amount. Next cultivation was carried out without circulation in wastewater medium. During 16 days cultivation, complete growth phase was well-detected. NO3 -, PO4 3-, and K concentration also showed decreasing trend, while pH value ranging from 6 to 9 but also tend to be 8. Cultivation in synthetic wastewater medium, consist of 9 serial concentrations of NPK fertilizer (Sy1 – Sy9), was run to prove that nutrient concentration affect the growth rate of microalgae. As a result, the growth peak of Sy3
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf