PENGARUH AERASI DAN RESIDENCE TIME PADA KRISTALISASI STRUVITE DALAM FLUIDIZED BED REACTOR
SUSMARDI MASTI C, Chandra Wahyu Purnomo, S.T., M.E., M.Eng., D.Eng. ; Muslikhin Hidayat, S.T., M.T., Ph.D.
2018 | Tesis | MAGISTER TEKNIK KIMIATingginya tingkat konsumsi fosfat berbanding terbalik dengan ketersediannya di alam. Di Indonesia yang merupakan negara agraris, konsumsi pupuk berbahan dasar fosfat juga jauh di atas tingkat produksinya. Sehingga Indonesia harus melakukan impor untuk memenuhi kebutuhan tersebut. Sementara itu banyak dari kegiatan manusia yang menghasilkan banyak limbah yang mengandung fosfat dan menyebabkan terjadinya eutrofikasi. Kristalisasi struvite menggunakan fluidized bed reactor yang dilengkapi dengan aerasi merupakan salah satu metode yang dapat meningkatkan fungsi dari fosfat. Struvite merupakan slow release fertilizer yang diperoleh dari perbandingan jumlah molar yang sama antara Mg2+, NH_4^+dan PO_4^(3-). Pada penelitian ini, campuran larutan air limbah sintesis dan MgCl2 telah dilakukan di dalam reaktor fluidized bed yang dilengkapi dengan aerasi untuk menghasilkan struvite. Kemudian, akan dilakukan investigasi terhadap perubahan aerasi dan kecepatan influent air limbah (yang menggambarkan residence time) untuk mengetahui dampaknya terhadap kinerja reaktor, P removal efficiency dan amonia removal efficiency serta ukuran kristal struvite yang dihasilkan. Penelitian dilakukan selama 240 menit dengan variasi laju aerasi 0,5 L/menit, 1 L/menit dan 1,5 L/menit ; variasi kecepatan influent air limbah 150 ml/menit, 250 ml/menit dan 350 ml/menit (residence time 55,32 menit, 26,88 menit dan 17,61 menit) dengan kecepatan yang tetap dari larutan MgCl2 sebesar 50 ml/menit. Campuran larutan di dalam reaktor dikondisikan pada pH 9 menggunakan larutan NaOH 2 M. Percobaan dilakukan secara kontiniu. Konsentrasi NH_4^+dan PO_4^(3-)pada aliran masuk dan keluar reaktor diukur setiap 60 menit untuk mengetahui NH_4^+dan PO_4^(3-) efficiency removal. Untuk mengetahui konsentrasi NH_4^+dan PO_4^(3-)digunakan spektrofotometer. Sedangkan untuk mengetahui ukuran rata-rata kristal struvite dilakukan analisis dengan menggunakan particle size distribution. Hasil percobaan menunjukkan bahwa reaktor bekerja sesuai dengan yang diharapkan. Peningkatan laju aerasi dan residence time sejalan dengan peningkatan P removal efficiency, amonia removal efficiency dan yield of MAP. P removal efficiency dan amonia removal efficiency tertinggi dicapai pada laju aerasi 1,5 L/menit dengan residence time 55,32 menit yaitu sebesar 82,76% dan 56,67%. Sementara itu, peningkatan laju aerasi dan penurunan residence time diikuti dengan peningkatan ukuran kristal struvite. Namun berbagai variasi penelitian dan hasil analisis yang dilakukan diperoleh ukuran kristal yang sama yaitu sebesar 58 µm yang terjadi pada laju aearsi 1,5 L/menit dan residence time 17,61 menit. Hal ini menunjukkan bahwa kristal juga membutuhkan waktu yang cukup untuk terus tumbuh sesuai dengan yang diharapkan.
The high level of phosphate consumption is inversely proportional to its availability in nature. In Indonesia, which is an agrarian country, the consumption of phosphate-based fertilizers is also far above the level of production. Consequently, Indonesia has to import phosphate to fulfil those needs. Whereas, many of the human activities produce much waste which contains phosphate and causes eutrophication. Struvite crystallization using a fluidized bed reactor equipped with aeration is one method which able to improve the function of phosphate. Struvite is a slow release fertilizer obtained from the same molar ratio of Mg2+, NH_4^+ and PO_4^(3-). In this study, a mixture of synthetic wastewater and MgCl2 solutions were treated in a fluidized bed reactor equipped with aeration to produce struvite. Subsequently, the changes of aeration rate and wastewater influent rate (which reflects residence time) were investigated to determine its impact on reactor performance, P removal efficiency, ammonia removal efficiency as well as the size of struvite crystals. The study was carried out for 240 minutes with variations in aeration rate of 0.5 L / minute, 1 L / minute and 1.5 L / minute; the variation of influent rates of wastewater are 150 ml/minute, 250 ml/minute and 350 ml/minute (residence time 55.32 minutes, 26.88 minutes and 17.61 minutes) with a constant speed of MgCl2 solution of 50 ml/minute. The experiment used Ph 9 solution mixture which treated in the reactor using 2 M NaOH solution and carried out continuously. the concentration of NH_4^+ dan PO_4^(3-) at inflow and outflow in the reactor were measured every 60 minutes to find out NH_4^+dan PO_4^(3-)efficiency removal. a spectrophotometer was used to determine the concentration of NH_4^+ dan PO_4^(3-). Whereas the analysis using the distribution of pratical size were used to find out the average size of struvite crystals. The reactor works as expected. The experimental results show the increasing aeration and residence time rates are in line with the increasing of P removal efficiency, ammonia removal efficiency and yield of MAP. The highest removal efficiency and ammonia removal efficiency were achieved at an aeration rate of 1.5 L / min with a residence time of 55.32 minutes which was 82.76% and 56.67%. Meanwhile, an increase in aeration rate and decreased residence time was followed by an increase in the size of struvite crystals. However, the various variations of the research and the results of the analysis obtained the same crystal size of 58 μm which occurred at an aeration rate of 1.5 L / min and residence time of 17.61 minutes. It indicates that the crystals need sufficient time to continue to grow as expected.
Kata Kunci : fluidized bed reactor, struvite, limbah sintesis, aerasi, residence time / fluidized bed reactor, struvite, synthetic wastewater, aeration, residence time
