Judul: Kajian proses degradasi bahan organik limbah cair pada kondisi anaerobik dengan konsentrasi garam tinggi
Abstrak: Waste with high level of salinity is usually difficult for microorganism to degrade because the high level of saliity concentration in the environment or waste can hamper microorganism to reduce organic materials in it. High level of salinity can hamper the function of bacteria metanogen in reducing organic material and asetat acid to become gas or metan. Reduction of sulfate and metabolism H2 may also be hampered in high level of salinity concentration. In ecosystem, anaerobic fermentation can produce CO2, C& and H2S. However, this is hard to do in waste with high level of saliity where there is an acummulation of VFA and H2. Generally, ecosystem with high level of salidity can hamper and limit the growth of bacteria and microorganism. The optimum limit of salinity concentration for vertebrate (Tilapia spp.) is around 10 percent. Above this level, only invertabrate species such as brine shrimp (Artemia salina) or brine tlies, alga genus (Dunaliella salina), bacteria (wich belong to Halobacteriaceae and Haloanaerobiaceae, methanogen, etc.), and cyanobacteria (Oscillatoria spp.) which have been identified. This research was aimed at studying degradation process of organic materials in anaerobic condition with high level of salinity concentration and determining kinetic parameter value for liquid waste with high level of salinity concentration. The main research was conducted with three operation conditions with inoculum as much as 15 % out of total sample volume in which a number treatments in terms of adding salt fiom 0 mgkg (reactor l), 32 mgkg (reactor 2), to 52 mgkg (reactor 3). This research was used some synthetic liquid waste (molases) with inoculum came fiom salt made location. The initial COD content in molases which has been made into liquid is averagely out of two test was 400000 mg/l. The COD content required for this reserach was 4000 mg/l. The analyses conducted were those of COD, MLSS, MLVSS, and gas production. It also analysed caused of addition of trace element and the calculation of kinetic parameter.
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Judul: Konversi sampah organik pasar dengan sistem fermentasi media padat menjadi biogas dan pupuk organik.
Abstrak: In 2010 Indonesia produced 200 thousand tons of waste everyday. It causes problems for the society and for environment. The purposes of this research are to design and get an optimal process condition for solid medium fermentation to convert organic waste from traditional market into bioenergy and organic fertilizer, to characterize biogas, digestate, and leachate. The experiments were conducted with 1.5 L and 10 L reactors . Composition of organic waste from traditonal market that gave higest volume of biogas are banana leaf 7.5%, cornhusk 24.2%, bitter melon 14.8%, cabbage 19.9%, chicory 6.2%, water spinach 8.0%, mustard 8.0%, carrots 11.5% (w/w). It produced 4500 ml biogas/kg biomass and the maximum production was reached within 17 days. This equal to biogas production of 37.63 ml biogas/gram VS. Fermentation process in 10 liter reactor with adition of 75% feed, 50% of feed, and 100% feed produced 12378 ml, 10908 ml, and 16707 ml biogas, respectively leachate consists nitrogen 473-4500 ppm, phosphat 47-150 ppm, and COD 8333-12500 mg/l, while the digestate consists of carbon 28-49%, nitrogen 0.7-1.7%, phosphat 0.2-0.4%, and COD 16000-18000 mg/kg. Concentration of methane in biogas is still low and hence futher experiments needed to increase methane concentration. Keywords : organic waste, biogas, digestate, leachate, solid state fermentation
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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