Judul: Treatment of Leather Tannery Sludge Waste at the Leather Factory X
Abstrak: Pabrik penyamakan kulit merupakan industri yang menghasilkan berbagai jenis limbah. Sludge sebagai salah satu jenis limbah yang berasal dari Instalasi Pengolahan Air Limbah penyamakan kulit. Proyek desain utama agroindustri ini bertujuan mengidentifikasi sumber dan jumlah limbah yang terbentuk, menganalisis formulasi pengomposan dan mutu kompos, peningkatan skala pengomposan, serta analisis biaya. Pengomposan dilakukan dengan metode in vessel composting menggunakan aerasi alami dengan variasi konsentrasi EM4 0%; 0,1%; dan 0,2%. Hasil analisis mutu terbaik terdapat pada kompos dengan konsentrasi EM4 0,1%. Dimensi reaktor pengomposan skala laboratorium diperbesar untuk skala pilot plant dan skala industri kecil dengan jumlah reaktor yang diperlukan masing-masing sebanyak 3 dan 9 buah dengan dimensi yang sama. Analisis biaya pengomposan menggunakan harga pokok produksi pada skala laboratorium sejumlah Rp2.039,46/kg; skala pilot plant sejumlah Rp249,38/kg; dan skala industri kecil sejumlah Rp567,9/kg. Kompos dengan konsentrasi aktivator EM4 0,1% memenuhi baku mutu SNI untuk parameter kadar air, suhu, pH, dan nisbah C/N sedangkan kadar logam krom masih belum memenuhi baku mutu SNI. Hasil mutu kompos yang dihasilkan direkomendasikan pengaplikasiannya untuk tanaman berbatang tinggi atau tanaman hias. Pengkajian terkait pengomposan lebih lanjut untuk menurunkan kadar krom yang masih relatif tinggi dapat direkomendasikan menggunakan metode pengomposan lainnya salah satunya vermicomposting., Leather tanning factory is an industry that produces various types of waste. Sludge as a type of waste originating from the tannery wastewater treatment plant. The main design project for this agro-industry aims to identify the source and amount of waste generated, analyze compost formulation and compost quality, increase the scale of composting, and analyze costs. Composting was carried out using the in-vessel composting method using natural aeration with a variation of 0%; 0.1%; and 0.2% EM4 concentration. The best quality analysis results were found in compost with 0.1% EM4 concentration. The dimensions of the laboratory scale composting reactor were enlarged for pilot plant scale and small industrial scale with the required number of reactors being 3 and 9 respectively with the same dimensions. Composting cost analysis uses the cost of production on a laboratory scale in the amount of IDR 2,039.46/kg; pilot plant scale of IDR 249.38/kg; and small industrial scale in the amount of IDR 567.9/kg. Compost with an EM4 activator concentration of 0.1% complies with SNI quality standards for parameters of water content, temperature, pH, and C/N ratio, while chromium metal content still does not meet SNI quality standards. The quality of the resulting compost is recommended for its application for tall-stemmed plants or ornamental plants. Studies related to further composting to reduce chromium levels which are still relatively high can be recommended using other composting methods, one of which is vermicomposting.
Keyword: in-vessel composting, compost, chromium, scale up, sludge

Judul: Perancangan Reaktor Elektrokoagulasi terhadap Air Limbah Pabrik Kulit "X"
Abstrak: Idealnya setiap kegiatan industri penyamakan kulit harus mengolah air limbah yang dihasilkan agar mampu memenuhi standar baku mutu yang ditetapkan. Pabrik Kulit “X” merupakan satu diantara banyak industri yang masih belum mampu mengurangi kadar polutan yang ada pada air limbah sehingga air limbah yang dihasilkan memberikan dampak negatif terhadap lingkungan. Biaya operasional yang tergolong tidak sedikit juga menjadikan faktor utama dalam pengelolaan air limbah yang dihasilkan sehingga menjadikan penelitian ini difokuskan dalam mendesain unit instalasi pengolahan air limbah yang efektif dan efisien. Tujuan penelitian ini adalah merancang unit instalasi pengolahan air limbah yang efektif dan efisien dalam menurunkan kadar polutan yang ada dengan menggunakan biaya operasional yang rendah. Hasil perancangan yang didapatkan adalah desain unit elektrokoagulasi dalam bentuk Detail Engineering Design (DED) dan rencana anggaran biaya operasional dari unit elektrokoagulasi. Hasil perancangan dari unit elektrokoagulasi didapatkan dimensi reaktor (P x L x T) (70 cm x 20 cm x 30 cm) dengan tegangan 63,26 volt, arus 76,16 ampere dan biaya operasional sekitar Rp 1.583 / m3., Ideally every activity in the leather tanning industry must treat the wastewater produced in order to be able to meet the set quality standards. The Leather Factory “X” is one of the many industries that has not been able to reduce the levels of pollutants in wastewater so that the resulting wastewater has a negative impact on the environement. Operational costs which are relatively expensive are also a major factor in the management of the wastewater produced so that this research is focused on designing effective and efficient wastewater treatment plant units. The purpose of this research is to design a wastewater treatment plant unit that is effective and efficient in reducing exsisting pollutant levels by using low operating costs. The design results obtained are the design of the electrocoagulation unit in the form Detail Engineering Design (DED) and the operational cost budget plan of the electrocoagulation unit. Design results of electrocoagulation unit obtained the dimensions of the reactor (L x W x H) (70 cm x 20 cm x 30 cm) with a voltage of 63.26 volts, a current of 76.16 amperes and an operational cost of Rp 1,583/m3.
Keyword: operational cost, detail engineering design, electrocoagulation

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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