Judul: Effect of Inhibitor on Biokinetic Estimation of Anaerobic Process in Anaerobic Contact Stabilization Reactor Treating Palm Oil Mill Effluent
Abstrak: Indonesia and Malaysia have become the largest palm oil contributors in the world. Palm oil production in Indonesia and Malaysia covers 80% of global palm oil demand. One of the palm oil industry’s secondary products negatively impacting the environment is palm oil mill effluent (POME). The concentrations of COD, BOD, oil and grease, TSS, and TN in POME are 50,000-150,000 mg/L, 25,000-75,000 mg/L, 4000 mg/L, 40,000 mg/L, and 750 mg/L, respectively. The concentration of organic compounds in POME has exceeded the quality standard established by the Indonesian governors. POME potentially pollutes the environment due to the direct discharge of POME into the environment without appropriate wastewater treatment. Therefore, the Anaerobic-Contact Stabilization (ACSt) reactor was utilized as the biological treatment for POME. In order to satisfy the requirements in the field, biokinetic modeling was conducted. The research was conducted from November 2022 until July 2023. Several procedures conducted in this research were designing the reactor, inoculum preparation, laboratory examination, and biokinetic modeling. The COD percent removal in each variation was around 96.60%-99.47%, while the TSS percent removal in each variation was around 98.63%-99.86%. The COD and TSS percent removal in v.1 and v.2 satisfied the desired value. The biokinetic parameters were estimated using the Monod and Hinshelwood model. The accuracy of the model was evaluated using the student’s t test and MAPE. The data obtained from model and experiment was concluded similar and the MAPE of each modeling was below 50%. Therefore, the models were classified as reasonable forecasting ability.
Keyword: anaerobic, biokinetic, inhibitor, POME, UASB

Judul: Influence of Ammonia Accumulation  and Environmental Factors on the Efficiency of Anaerobic Contact Stabilization  Treatment for Palm Oil Mill Effluent
Abstrak: Limbah cair kelapa sawit (LCKS) mengandung konsentrasi BOD dan COD berada diatas baku mutu berturut - turut sebesar 25.000 mg/L dan 50.000 mg/L. Penanganan yang telah dilakukan yaitu dengan pengolahan biologis menggunakan sistem kolam. Namun, sistem kolam ini memiliki kelemahan dalam menangani fluktuasi debit air dan memerlukan area lahan yang besar. Oleh sebab itu, dilakukan pengembangan dengan anaerobic contact stabilization (A-CSt). Penelitian ini bertujuan menganalisis kinerja A-CSt, mengestimasi nilai biokinetika unit stabilisasi rangkaian A-CSt, melakukan uji sensitivitas, mengestimasi konsentrasi substrat efluen berdasarkan parameter biokinetika, dan menguji kelayakan model. Prosedur penelitian skala laboratorium dilakukan dalam empat tahap, antara lain tahap persiapan, tahap pengambilan sampel, tahap pengujian reaktor pada kondisi tidak tunak, dan tahap analisis laboratorium. Parameter biokinetika yang dicari diantaranya Ke, Y, μmax, Ks. Persamaan umum biokinetika yang digunakan antara lain Monod dan Hinshelwood dengan melibatkan konsentrasi produk, pH, dan temperatur. Berdasarkan hasil perhitungan, niai parameter biokinetika Ke, Y, μmax, dan Ksmodel Monod tanpa dipengaruhi faktor pH dan temperatur diperoleh berturut - turut sebesar 0,34 hari-1 , 70,89 mgMLSS/mgCOD, 1,63 hari-1 , dan 20,00 mg/L sedangkan model Monod dengan dipengaruhi pH dan temperatur diperoleh berturut - turut sebesar 1,04 hari-1 , 27,96 mgMLSS/mgCOD, 1,26 hari-1 , 20 mg/L. Di sisi lain, model Hinshelwood menghasilkan niai parameter biokinetika Ke, Y, μmax, dan Ks berturut - turut sebesar 0,10 hari-1 , 132,41 mgMLSS/mgCOD, 3,20 hari-1 , dan 20,00 mg/L tanpa pengaruh faktor pH dan temperatur. Sementara itu, model Hinshelwood dipengaruhi faktor pH dan temperatur menghasilkan nilai Ke, Y, μmax, dan Ks berturut - turut sebesar 0,21 hari-1 , 27,79 mgMLSS/mgCOD, 1,25 hari-1 , dan 20,00 mg/L. Setelah nilai parameter biokinetika diperoleh, uji performa dengan menggunakan R 2 dilakukan. Hasil R 2 menunjukkan kedekatan antara variabel independen terhadap variabel dependen dengan nilai mendekati satu.
Keyword: anaerobic contact stabilization (A-CSt), biokinetic, Palm Oil Mill Effluent (POME)

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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