Abstract. Elimination of ammonium concentration from urea fertilizer plant wastewater through struvite crystal (NH 4 MgPO 4 .6H 2 O) formation by adding MgCl 2 , KH 2 PO 4 , and KOH were studied. This method of elimination has two benefits, namely, reducing ammonium nitrogen content in the wastewater, as well as production of a valuable material (struvite crystal). Struvite is known as a slow-release fertilizer and less soluble. This report presents the ammonium removal efficiencies during struvite formation. The growth of struvite production under different molar ratios of Mg 3-of 1.2:1:1, 1:1:1.2, and 1:1:1 were evaluated. Each of the molar ratios was treated at the solution pH of 8, 9, and 10. It was found that, the highest ammonium removal efficiency was 94.7% at the molar ratio of 1.2:1:1 and pH of 9. Primarily, the growth rate of struvite formation complied with a first-order kinetic model. The rate constants (k 1 ) were calculated to be 2.6, 4.3, and 5.0 h -1 for solution pH of 8, 9, and 10, respectively. The findings of the study provide suggestion for an alternative sustainable recovery of ammonium nitrogen content in a urea fertilizer plant effluent.

Elimination Residence time distribution (RTD) analysis is necessary to explain the hydrodynamic behavior of a continuous stirred tank reactor. In this study, RTD was applied in a laboratory scale struvite crystallization reactor to estimate the degree on non-ideality and its effect on the reactor performance i.e. effective volume, actual hydraulic residence time (HRT), and material dispersion. An impulse-response tracer (NaCl saturated solution) approach and a conductivity meter to detect of the NaCl at the effluent of the reactor were applied. To evaluate effects on the reactor performance, variation of impeller locations, impeller speeds, and flowrates were conducted. The main findings from this study showed that the difference between actual and theoretical HRT was found around as around 10%-34% and 30%-37% for condition of the impeller location at the upper and lower part, respectively. These percentages were corresponding to the reactor’s effective volume, lower percentage means higher effective volume. This finding correlated to the value of dispersion number. It was found to be about 1.612 and 0.49 for the impeller location at the upper and lower part, respectively. Finally, it was observed that the tracer was being almost 100% recovered in the reactor due to a good flow pattern and its impeller location affects the reactor’s performance.

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Bioplastik merupakan plastik yang dibuat dari bahan-bahan alami yang akan hancur terurai oleh aktivitas mikroorganisme setelah habis terpakai. Tujuan dari penelitian ini adalah untuk mengkaji pengaruh variasi konsentrasi pati dan volume gliserol terhadap sifat fisik dan mekanik bioplastik. Metode penelitian ini menggunakan proses ekstraksi pati dan pembuatan larutan bioplastik dengan mencampurkan pati, gliserol dan kitosan sampai homogen yang dipanaskan sampai 70°C dengan waktu pengadukan 15 menit. Film yang dihasilkan dicetak dan diperoleh bioplastik dengan berbagai variabel. Kondisi optimum pada bioplastik diperoleh dengan formulasi pati 20%, dan gliserol 3 mL dengan nilai daya serap air 39,063%, terdegradasi dalam tanah sebanyak 82,232% dalam waktu 20 hari, nilai kuat tarik sebesar 2,864 MPa, nilai elongasi sebesar 120,47% dan nilai modulus elastisitas sebesar 2,377 MPa.