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: 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: 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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