Judul: The Effect of Variation on  Hydraulic Loading Rate in Performace of Rotating Biological Contactor  Modification Processing of Palm Oil Mill Effluent
Abstrak: Limbah Cair Kelapa Sawit (LCKS) memiliki kandungan bahan organik yang sangat tinggi dan berbahaya bagi lingkungan. Oleh karena itu, penelitian ini bertujuan menganalisis efisiensi pengolahan unit modifikasi RBC terhadap LCKSberdasarkan variasi laju pembebanan hidraulis (HLR) dan mengestimasi jumlah biomassa berdasarkan nilai parameter biokinetika terpilih. Penelitian diawali dengan tahap persiapan reaktor, aklimatisasi, konfigurasi reaktor, dan pengoperasian reaktor. Persen penyisihan terbaik dicapai saat pengoperasian reaktor dengan variasi HLR 0,15 m3/m2∙hari, yaitu sebesar 90% untuk parameter COD. Efisiensi pengolahan sangat dipengaruhi oleh ketersediaan biomasa di dalam reaktor, sehingga estimasi nilai konsentrasi biomassa (Xa”) dapat dijadikan acuan dalam pembuatan model. Berdasarkan hasil permodelan yang dilakukan dapat diketahui nilai parameter biokinetika terpilih berupa µmax-a, µmax-s Ys, Ya, Ks-a, Ko, dan Ks-s secara berturut-turut sebesar 6; 5,54/hari; 2,21; 0,33 mgMLVSS/mgCOD; 262; 0,56; dan 30 mg/L. Parameter biokinetika dengan pengaruh terbesar terhadap estimasi nilai Xa”, yaitu Ys dan µmax-s yang menandakan peranan mikroorganisme tersuspensi di dalam unit modifikasi RBC., Palm Oil Mill Effluent (POME) contains a high concentration of organic matter that is hazardous to the environment. Therefore, this study aims to analyze the efficiency of the modified Rotating Biological Contactor (RBC) unit in treating POME based on variations in hydraulic loading rate (HLR) and estimate the biomass quantity based on selected biokinetic parameter values. The study began with reactor preparation, acclimatization, reactor configuration, and reactor operation stages. The highest removal percentage was achieved during reactor operation at HLR variation of 0.15 m3/m2·day, that reaching 90% for the COD parameter. The treatment efficiency is significantly influenced by the availability of biomass within the reactor, thus the estimated value of biomass concentration (Xa'') can serve as a reference in model development. Based on the modeling results, the selected biokinetic parameter values for µmax-a, µmax-s Ys, Ya, Ks-a,Ko, dan Ks-s, are 6; 5.54/day; 2.21; 0.33 mgMLVSS/mgCOD; 262; 0.56; and 30 mg/L. Among these parameters Ys and µmax-s have the greatest influence on estimating the value of Xa", indicating the role of suspended microorganisms in reactor.
Keyword: bioball, biokinetic, HLR, LCKS, RBC

Judul: Performance of Modification Hybrid Attached Growth Biofilm on Suspended Media on Anaerobic-Aerobic Unit in Treating Palm Oil Mill Effluent
Abstrak: Produksi minyak sawit mentah (CPO) di Indonesia hingga tahun 2022 telah mencapai 48,3 juta ton dari total produksi dunia sebanyak 75,45 juta ton dan tingginya produksi CPO menyebabkan peningkatan Limbah Cair Kelapa Sawit (LCKS) atau Palm Oil Mill Effluent (POME). Penelitian ini bertujuan untuk efektifitas pengolahan LCKS dengan variasi waktu detensi (HRT) yang berbeda pada Reaktor Anaerobic Contact-Stabilization (ACSt). Penelitian ini juga berfokus pada kajian mengenai parameter biokinetika pada unit Integrated Fixed-Film Contact Stabikization (IFCS) untuk estimasi nilai substrat di efluen. Penelitian terdiri atas tahap persiapan reaktor, aklimasasi, konfigurasi reaktor, dan pengoperasian reaktor, dan analisis data. Berdasarkan penelitian diketahui bahwa perubahan variabel operasional HRT berpengaruh terhadap persen penyisihan substrat sCOD pada pegolahan menggunakan Reaktor ACSt (Variasi 1 = 99,41%, Variasi 2 = 99,17%, Variasi 3 = 99,65%, Variasi 4 = 98,633% dan Variasi 5 = 96,47%). Selain itu, perhitungan parameter biokinetika untuk pengolahan LCKS menggunakan Reaktor ACSt pada unit IFCS memperoleh hasil nilai Kec, Kea, Yc, Ya, μmax-c, μmax-a, Ks-c, Ks-a dengan nilai berturut-turut sebesar 0,04 hari-1, 0,0018 hari-1, 3,51 mgMLVSS/mgCOD, 1,95 mgMLVSS/mgCOD, 2,33 hari-1, 2,09 hari-1, 75,55 mg/L, dan 49,57 mg/L, Production of crude palm oil (CPO) in Indonesia until 2022 has reached 48.3 million tons of the world's total production of 75.45 million tons and the high production of CPO can increase Palm Oil Mill Effluent (POME). This study aims to determine the effectiveness of POME processing with various detention time (HRT) in Anaerobic Contact-Stabilization (ACSt) Reactor. This research also focuses on the study of biokinetic parameters in the Integrated Fixed-Film Contact Stabikization (IFCS) unit to predict the value of the substrate concentration in the effluent. This research starts with reactor preparation, acclimation, reactor configuration, reactor operation, and data analysis. Based on the research, it is known that changes in HRT operational variables affect the percentage of sCOD substrate removal in processing using the ACSt Reactor (Variation 1 = 99.41%, Variation 2 = 99.17%, Variation 3 = 99.65%, Variation 4 = 98.633% and Variation 5 = 96.47%). In addition, the calculation of biokinetic parameters for LCKS processing using the ACSt Reactor in the IFCS unit yielded the values of Kec, Kea, Yc, Ya, μmax-c, μmax-a, K_s-c, K_s-a with consecutive values of 0.04 day-1, 0.0018 day-1, 3.51 mgMLVSS/mgCOD, 1.95 mgMLVSS/mgCOD, 2,33 day-1, 2.09 day-1, 75.55 mg/L, and 49.57 mg/L.
Keyword: Anaerobic Contact Stabilization, bioball, biokinetic, Hydraulic Retention Time, Palm Oil Mill Effluent

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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