Judul: IPB (Bogor Agricultural University)
Abstrak: pencemaran lingkungan akibat kegiatan industri. Pada penelitian ini telah diamati pola penanganan limbah cair kegiatan penyamakan kulit (tannery) serta penerapan teknik perolehan kembali krom (chromium recovery) sebagai upaya Q' engurangi pembuangan krom pada kegiatan penyamakan kulit di Kabupaten Bogor. Perolehan kembali krom dilakukan dengan mengendapkan krom yang terdapat pada limbah cair proses penyamakan (lanning) dengan cara menambahkan larutan NaOH d , 5 M pada limbah tersebut sehingga dicapai pH 8 atau 9. Pemilihan pH bertujuan h t u k mendapatkan konsentrasi krom pada filtrat sebesar 20 ppm, yaitu batas P) $onsentrasi pengendapan krom yang masih efisien. Selanjutnya, krom yang masih gersisa pada filtrat dijerapkan pada zeolit menggunakan dua cara. Cara pertama pengalirkan filtrat ke dalam unggun zeolit (fzxed-bed method); dan cara kedua Qnengocok filtrat dengan zeolit (batch method). Zeolit yang digunakan berasal dari h qenambangan di daerah Cikalong, Lampung dan Cikembar. Pengukuran kemampuan &enjerapan zeolit terhadap larutan horn simulasi telah juga dilakukan sebagai 5pembanding.
Keyword: Kimia kalogen, Zeolit, Adsorpsi

Judul: IPB (Bogor Agricultural University)
Abstrak: Air Sungai Cikijing yang tercemar buangan industri tekstil mengandung natrium dan logam berat. Air sungai tersebut digunakan sebagai irigasi bagi tanah sawah setempat. Penelitian ini bertujuan untuk menghasilkan cara rehabilitasi tanah sawah tercemar air irigasi aliran Sungai Cikijing melalui pencucian, penggunaan vegetasi, bahan organik dan bakteri. Percobaan vegetasi dilakukan di rumah kaca dengan menggunakan rancangan acak lengkap. Vegetasi yang digunakan adalah enceng gondok (Eichornia crassipes), mendong (Fimbristylis globulosa), akar wangi (Vertiveria zizanioid) dan haramay (Boehmeria nivea Gaud). Sedang untuk penggunaan bahan organik dan bakteri dilakukan di rumah kaca dan lapang dengan menggunakan rancangan petak terpisah (split plot). Petak utama merupakan jenis air irigasi yaitu air irigasi saring dan air sumur dalam, dan anak petak adalah bahan organik dan bakteri. Bahan organik yang digunakan adalah kotoran ayam, sapi, kambing dan kompos tanaman. Bakteri yang digunakan adalah Desulfotomaculum orientis ICBB 1204 dan ICBB 1220 dengan tanaman indikator padi. Hasil percobaan di rumah kaca menunjukkan bahwa penggunaan vegetasi, bahan organik dan bakteri secara nyata (pada taraf 5 %) mampu menurunkan kandungan logam berat Pb, Cd dan Cr tersedia dalam tanah dibandingkan dengan tanpa penggunaan vegetasi, bahan organik dan bakteri. Sementara hasil percobaan di lapang menunjukkan bahwa penggunaan berbagai macam bahan organik dan bakteri mampu menurunkan kandungan logam berat tersedia dalam tanah akan tetapi penurunannya tidak berbeda nyata. Pencucian dengan menggunakan air sumur dalam dan air irigasi mampu menurunkan kandungan natrium dalam tanah.
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Judul: The Effects of Variance of Interest rate to Variance of Annuity Future Values
Abstrak: Time value of money is a concept that refers to the difference of the value of money due to time difference. The value of money for present time would not be the same as the value of money in the future. The value of money for present time is called as Present Value (PV) of the money and the value of money for future time is called Future Value (FV) of the money. Determination the value of money, for present and future time, depends on the time and rate of return. The value of money is determined by several factors such as inflation, fluctuation of interest rates, and government policy in securities and taxation. Due to fluctuation of the value of money we need a FV formulation, it is useful for knowing whether an investment can be profitable or not, and this information is useful also in budget analysis. Annuity is defined as a series of payments made for a specific period. The payment, fixed or varied, can be made at the beginning or at the end of the period. Annuity paid at the beginning of the period is called annuity-due and annuity paid at the end of the period is called immediate annuity-certain. The accumulated value of the annuity after few years later is called as a final value or a future value. Burnecki et al. (2003) have discussed about the FV of a fixed-rate annuity in which payments are made according to the arithmetic or geometric series. They have also examined FV for annuities in which payments are made according to arithmetic or geometric series with random rates of interest. This paper examines FV for annuity-due in which payments are made according to arithmetic or geometric series with interest rates as a random variable, which is normal distribution ,  . Future value formula is expressed in recursive form. FV for annuity-due which payments are made according to the arithmetic or geometric series with random rates of interest is calculated by theoretical way and simulation way. The random rates of interest is denoted as k k i  i  , where k i an independent random variable; i is a constant and k  is a random variable which has normal distribution ,  . By using the determined parameters, a sequence of random rates of interest are generated for theoretical calculation. Meanwhile for the simulation, the random rates of interest is generated 1000 times for the simulation. The generated data give mean value, variance, and standard deviation. Moreover, error of mean value, variance, and standard deviation from the theoretical and simulation results are calculated. Error calculation uses Symmetric Mean Absolute Percentage Error (SMAPE). The smaller the value of SMAPE is the more accurate the simulation. The interest rate variances are varied from 0.000036 to 0.0001 to study the relationship between variance of rates of interest and variance of future value. The theoretical and simulation results show that when the variance of random rates of interest increases, then the variance of FV increases linearly. FV of the annuity-due in
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