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"There are many researches to solve the effects of global warming caused by great amount of CO2 in the air. One of the effective alternatives to reduce this gas in atmosphere is by using micro alga Spirulina platensis due to its ability of CO2 fixation and the very useful biomass that it produced. Spirulina platensis contains high protein and can cure diseases such as cancer and cholesterol reduction. In considering of these benefits, this research focused on increasing the biomass production of Spirulina platensis by alteration of light illumination during microbial growth. The cultivation holds in a series of photo-bioreactors at 29"C and I atm where each of photo-bioreactor has volume of 500 ml., using Conwy medium as nutrition. 3% CO2 is the carbon source for the cultivation with superficial velocity 1.2 m/h. Phillips Halogen lamp 20W/12V/50Hz is the source for illumination. The cultivation using constant intensity of light illumination was also be done as a control. Cultivation of Spirulina platensis with alteration illumination method successfully increased the biomass production 55.1 % higher than constant intensity of light illumination. The energy of producing biomass in alteration of light illumination method lower than continuous intensity illumination which was only 21.6 % than constant intensity of light illumination. Kinetic studies of this microbial growth at alteration of light illumination also concluded that specific growth rate and bicarbonate concentration as essential compound followed Ierusalemsky kinetic model equation."

"Penggunaan listrik di dunia semakin meningkat seiring dengan meningkatnya kebutuhan dan populasi manusia sehingga dibutuhkan energi berkelanjutan dan ramah lingkungan untuk menghasilkan listrik, salah satunya pemanfaatan Biological Photovoltaic Cell (BPV). Sel BPV memanfaatkan sifat fotosintetik mikroalga untuk memproduksi arus listrik. Sistem BPV akan mengambil elektron yang terbentuk pada mikroalga yang sedang berfotosintesis.Penerapan reaktor BPV tanpa membran dan tanpa biofilm pada bioanoda meskipun memiliki laju transfer elektron yang relatif kecil dapat tetap dilakukan dan produksi listrik masih dapat ditingkatkan, diantaranya dengan meningkatkan densitas sel dan mengatur intensitas cahaya pada reaktor BPV. Oleh karena itu, pada penelitian kali ini telah dilakukan variasi intensitas cahaya dan densitas sel mikroalga pada BPV tanpa mediator. Mikroalga yang akan digunakan adalah Spirulina platensis.Pada penelitian ini, Open Circuit Voltage terbesar yang dihasilkan adalah 320 mV pada saat kondisi Optical Density sel S. platensis bernilai 0,9 dengan intensitas cahaya 1700 lux. Densitas daya yang dihasilkan 1,5 mW/m2 masih relatif kecil dibandingkan penelitian-penelitian yang dilakukan sebelumnya.Dari penelitian ini dapat disimpulkan bahwa peningkatan densitas sel dan pengaturan konfigurasi intensitas cahaya dapat meningkatkan listrik yang dihasilkan dan perlu dilakukan hal-hal lain untuk meningkatkan produksi listrik seperti menambah permukaan elektroda dan membuat biofilm mikroalga agar BPV nantinya dapat digunakan digunakan secara komersial sebagai sumber energi listrik terbarukan yang ekonomis dan ramah lingkungan.

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Electricity consumption in the world is increasing along with the increasing needs and the human population, then we need sustainable and environmentally friendly energy to produce electricity, one of the application is Biological Photovoltaic Cell (BPV). BPV cells utilizing the properties of photosynthetic microalgae to produce electric current. BPV system will take the electrons that produced by photosynthetic microalgae.

The application of BPV reactor without membrane and without biofilm on bioanoda yielding a low rate of electron transfer, but still can be done and electricity production can be improved, such as by increasing the cell density and adjust the light intensity at the reactor BPV. Therefore, the present study has been done variations of light intensity and density of microalgae cells in BPV without mediators. Microalgae to be used is Spirulina platensis.

In this study, the Open Circuit Voltage generated the largest is 320 mV when the condition Optical Density S. platensis cells is about 0.9 with 1700 lux light intensity. The resulting power density of 1.5 mW/m2 is still relatively small compared to studies conducted earlier.

From this study it can be concluded that the increase in cell density and configuration settings light intensity can improve the electricity is generated and the other things needs to be done to increase electricity production, such as increasing the electrode surface and makes biofilm microalgae so that BPV later can be used in commercial use as a source of electrical renewable energy that economically and environmentally friendly."

"Cultivation of chlorella vulgaris buitenzorg with alteration of light illumination using a maximum carbon dioxide trnasfer rate (CTR) base curve syccessfully enhanced the CTR value up to 1.74 times compared to alteration of light illumination with a growth base curve...."

"This paper presents the efficiency improvement in aerobic wastewater treatment technology through the application of a microbubble generator (MBG) for aeration. Aeration using an MBG is accomplished through water circulation and does not need air compressors, making it more energy efficient than conventional aerators. The MBG aerobic system with the variations on liquid flow rate (Q1) and airflow rate (Qg) combination was tested using artificial wastewater with a typical composition of organic waste. Experimental data were evaluated by means of a simplified mathematical model to systematically compare different MBG schemes. The study confirmed that the soluble chemical oxygen demand (SCOD) removal efficiency was significantly affected by the Qg values. Lower Qg values were preferable because they tended to have higher soluble chemical oxygen demand (SCOD) removal efficiency. However, the microbubbles were less stable at lower Qg due to the high incidence of bubble collisions. The study concluded that for applications in an actual aerobic waste treatment pond, the positioning of the MBG in the pond had to be carefully designed to minimize the collision tendency."

"Penelitian mengenai optimasi multiobjektif terhadap pertumbuhan populasi Synechococcus HS-9 telah dilakukan. Pada penelitian digunakan Synechococcus HS-9 yang merupakan koleksi dari Laboratorium Taksonomi Tumbuhan Departemen Biologi FMIPA UI, Depok. Penelitian bertujuan untuk mengetahui hasil simulasi hidrodinamika Synechococcus HS-9 pada program Computational Fluid Dynamics (CFD) dan mengetahui kondisi hidrodinamika yang optimum untuk pertumbuhan Synechococcus HS-9. Penelitian dilakukan dengan mensimulasikan photobioreactor dengan menggunakan program CFD. Penelitian juga melakukan optimasi untuk mengetahui kondisi optimum untuk pertumbuhan Synechococcus HS-9 menggunakan Artificial Neural Network (ANN). Hasil penelitian menunjukkan kondisi optimum untuk pertumbuhan Synechococcus HS-9 dicapai dengan kondisi, yaitu suhu (T) sebesar 30,30C; derajat keasaman (pH) sebesar 9,4; Dissolved oxygen (DO) sebesar 1,4 mg/l, oxidation reduction potential (ORP) sebesar 34,7 mV; intensitas cahaya (I) sebesar 291,2 µmol m-2s-1; turbulance eddy dissipasion (TED) sebesar 0,00135 m2s-2; dan turbulance kinetic energy (TKE) sebesar 0,000238 m2s-2.

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Research on the Multiobjective Optimization of Synechococcus HS-9 Population Growth using Artificial Neural Network has been carried out. Research using Synechococcus HS-9, which is the collection of the Plant Taxonomy Laboratory, FMIPA UI, Depok. This research purposes are to find out the results of the hydrodynamic simulation of Synechococcus HS-9 in the Computational Fluid Dynamics (CFD) and to find out the optimum hydrodynamic conditions for the growth of Synechococcus HS-9. The research was conducted by simulating a photobioreactor using CFD program. The study also carried out optimization to determine the optimum conditions for the growth of Synechococcus HS-9 using Artificial Neural Network (ANN). The results showed that the optimum conditions for the growth of Synechococcus HS-9 were achived with the following conditions, i.e. Temperature (T) of 30.3 0C, acidity (pH) 9.4, dissolved oxygen (DO) 1.4 mg/l, oxidation reduction potential (ORP) sebesar 34.7 mV, intensity (I) 291.2 µmol m-2s-1, turbulance eddy dissipasion (TED) 0.00135 m2s-2 and turbulance kinetic energy (TKE) 0.00023872 m2s-2."

"ABSTRACTOur present investigation aimed to examine the natural convection boundary layer flow of nanofluids over a vertical flat plate embedded in a saturated Darcy porous medium containing gyrotactic microorganisms. For carrying out the numerical solution, two steps are performed. The governing partial differential equations are firstly simplified into a set of highly coupled nonlinear ordinary differential equations by suitable similarity variables, and then numerically solved by applying the cubic spline collocation technique. The obtained similarity solution depends on non-dimensional parameters, i.e., the bioconvection Lewis number, bioconvection Rayleigh number, bioconvection Peclet number, Brownian motion parameter, the Buoyancy ratio, the thermophoresis parameter, the power-law variation index, and the Lewis number. A comprehensive numerical computation is carried out for various values of the parameters that describe the flow characteristics. Rescaled velocity and temperature distributions are found to be depending strongly on the bioconvection Rayleigh number and power-law variation index parameter. For making the result more reliable a comparison has been shown in the present work with existing results for some special values of governing parameters and the results are found to be in excellent accuracy."

"Mikroalga telah dikenal memiliki kemampuan untuk melakukan fiksasi CO2 melalui proses fotosintesis dan mengubah CO2 secara langsung menjadi senyawa karbon atau biomassa seperti polisakarida, protein, atau lipid yang bernilai cukup ekonomis. Penelitian mengenai proses fiksasi CO2 dengan memanfaatkan kemampuan fotosintesis mikroalga Spirulina platensis merupakan salah satu aternatif yang diusulkan untuk mengatasi permasalahan gas rumah kaca, yang telah menjadi permasalahan yang serius akhir-akhir ini. Proses fiksasi CO2 dan produksi biomassa menggunakan Spirulina platensis ini dilakukan dengan menggunakan medium Conwy dalam sebuah fotobioreaktor dengan perlakuan alterasi pencahayaan dan pencahayaan konstan. Fotobioreaktor yang digunakan tersusun secara seri dan tunggal dengan volume masing-masing 500 ml dan 1.500 ml. Proses tersebut berlangsung pada kondisi : suhu 29_C, kecepatan superfisial gas sebesar 1,2 m/jam, kandungan CO2 3% volume dalam aliran udara dan intensitas cahaya berkisar antara 1,48 Watt/m2 ?5,76 Watt/m2. Secara umum hasil yang diperoleh dalam penelitian ini adalah dengan semakin banyak konfigurasi reaktor dan semakin tingginya intensitas cahaya yang diterima oleh sel dalam medium, peningkatan jumlah sel yang terjadi juga semakin tinggi. Besarnya peningkatan jumlah sel ini berbanding terbalik dengan kemampuan fiksasi CO2. Laju fiksasi CO2 dan laju pertumbuhan sel yang tertinggi dicapai dengan menggunakan reaktor susun seri melalui perlakuan alterasi pencahayaan. Peningkatan fiksasi CO2 ditandai dengan meningkatnya nilai rata CTR dan qCO2 hingga mencapai 5,53 g/dm3 h-1 dan 41,77 h-1. Model pendekatan secara empiris terhadap laju fiksasi CO2 mengikuti persamaan Haldane dan persamaan Ierusalemsky.

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Microalgae has known for its ability to fix CO2 with photosynthesize and convert into biomass product such as polysacharide, protein, or lipid. The research of CO2 fixation using Spirulina platensis has become a promising alternative to reduce green house effect. CO2 fixation process and biomass production with Spirulina platensis was cultivated in photobioreactor with fixed and alteration of light illumination with Conwy as a medium. Two configuration of photobioreactors are arranged in single and three stages serial photobioreactor with reactor volume of photobioreactors are 1.500 mL and 500 mL/reactor, orderly. The fixation experiment were carried out in : Temperatur 29_C , gas supervicial velocity 1,2 m/hour, CO2 concentration : 3 % volume and range of light intensity 1,48 Watt/m2 ? 5,76 Watt/m2. The experimental findings for this system show that the increasing of reactor number and accepted light intensity in medium will be rise the number of cell in reactor. The rate of cell growth was oppposite to CO2 fixation rate. The highest of CO2 fixation and cell growth rate was reached in three stages serial photobioreactor with alteration light of illumination. The highest mean value of CTR and qCO2 could reach 5,53 g/dm3 h-1 dan 41,77 h-1. The empirical equation models of CO2 fixation rate follow Haldane and Ierusalemsky equation."