Judul: The Effect of Modified Rotating Biological Contactor's Rotational Speed Variation on the Treatment Model of Palm Oil Mill Efluent
Abstrak: Proses pemanfaatan tandan buah segar kelapa sawit menghasilkan limbah cair kelapa sawit (LCKS) yang harus diolah terlebih dahulu sebelum dibuang ke lingkungan. Untuk mengurangi konsentasi polutan pada LCKS, proses pengolahan limbah cair secara Rotating Biological Contactor (RBC) digunakan. Penelitian bertujuan untuk mengidentifikasi pengaruh kecepatan rotasi terhadap kinerja RBC dalam pengolahan LCKS. Variasi kecepatan rotasi yang diteliti yaitu 3, 5 dan 8 rpm. Prosedur penelitian dilakukan dalam tiga tahap, yaitu rancang bangun reaktor RBC, seeding dan aklimatisasi, serta uji dan analisis kinerja RBC. Hasil pengoperasian RBC dengan kecepatan rotasi 3 rpm mendapat persen penyisihan terbesar, yaitu 67,4% SCOD; 92,4% TSS; 73% NH3. Melalui pengembangan pemodelan biokinetika, nilai μmxa, μmxs, Ya, Ys, Ku, Ks, K1, Kc’, Ko, O* diperoleh berurutan sebesar 0,0368 hari-1; 0,0255 hari-1; 0,4012 mgMLSS/mgSCOD; 0,3021 mgMLSS/mgSCOD; 10 mg/L; 30 mg/L; 2; 0,03 m/hari; 0,001 mg/L; 2 mg/L. Validasi kelaikan dan uji statistik diperoleh hasil bahwa model biokinetika memiliki kemampuan yang presisi dalam memprediksi proses pengolahan LCKS berdasarkan data pengukuran., The utilization process of fresh oil palm fruit bunches yields palm oil mill effluent (POME), which requires pre-treatment before being discharged into the environment. To mitigate the concentration of pollutants in POME, the Rotating Biological Contactor process is employed for wastewater treatment. The aim of this research was to investigate the influence of rotational speed on the performance of RBC in treating POME. The rotational speeds studied were 3, 5, and 8 rpm. The research was conducted in three stages: RBC reactor design and construction, seeding and acclimatization, and RBC performance testing. The results showed that the RBC operated at a rotational speed of 3 rpm achieved the highest removal percentages, 67.4% for SCOD, 92.4% for TSS, and 73% for NH3. Through the development of biokinetic modeling, the values of μmxa, μmxs, Ya, Ys, Ku, Ks, K1, Kc’, Ko, O* were determined as follows: 0,0368 day-1; 0,0255 day-1; 0,4012 mgMLSS/mgSCOD; 0,3021 mgMLSS/mgSCOD; 10 mg/L; 30 mg/L; 2; 0,03 m/day; 0,001 mg/L; and 2 mg/L, respectively. Through fitness validation and statistical analysis, it was found that the biokinetic model exhibited a high level of accuracy in predicting the POME treatment process based on the measurement.
Keyword: Kecepatan rotasi, Limbah cair kelapa sawit, Rotating biological contactor, Transfer oksigen

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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