Transfer Oksigen Fisik Berdasarkan Kekasaran Permukaan Dan Komponen Kecepatan Kontaktor Di Rotating Biological Contactor

Hendrasarie, Novirina (2017) Transfer Oksigen Fisik Berdasarkan Kekasaran Permukaan Dan Komponen Kecepatan Kontaktor Di Rotating Biological Contactor. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Transfer oksigen di reaktor pengolah limbah Rotating Biological Contactor (RBC) merupakan faktor penting, karena berpengaruh terhadap efisiensi RBC. Tetapi dalam aplikasinya untuk mengolah limbah, sering mengalami defisit oksigen saat operasional. Beberapa literatur mengkaji upaya meningkatkan transfer oksigen dengan memperbesar geometri reaktor, meningkatkan jumlah disk dan stage, meningkatkan kecepatan putaran disk. Dalam penelitian ini, upaya untuk meningkatkan transfer oksigen, dengan memasukkan faktor kekasaran permukaan disk (Kvg). Sehingga dapat meningkatkan transfer oksigen tanpa memperbesar geometri reaktor dan tanpa meningkatkan kecepatan putaran disk. Tujuan khusus dalam penelitian ini, membuat model empirik untuk memprediksi transfer oksigen di RBC dan mempelajari mekanismenya. Penelitian yang dikerjakan terdiri dari dua pekerjaan utama, yaitu: kajian eksperimental dan model. Model empirik dengan metoda analisis dimensi dan visualisasi aliran menggunakan perangkat lunak Computational Fluid Dynamic (CFD). Pada kajian eksperimental, air baku yang digunakan air bersih, tanpa biofilm. Variabel peubah yang digunakan kekasaran permukaan (Kvg) dan komponen kecepatan disk. Kvg yang dianalisa, meliputi ukuran mikrometer (Kv) dan makrometer (Kg). Komponen kecepatan disk, meliputi kecepatan di sisi tepi disk (R) dan kecepatan karena kedalaman disk (H) Hasil penelitian, didapatkan dengan memasukkan faktor kekasaran permukaan (Kvg), mampu meningkatkan transfer oksigen fisik di RBC. Selanjutnya dikembangkan model untuk mengestimasi transfer oksigen fisik, berdasarkan analisis dimensi. Model estimasi transfer oksigen fisik (KLa) di RBC dipengaruhi oleh tiga kelompok utama, yaitu : (1) gaya-gaya yang bekerja (dapat dilihat dari bilangan Sherwood); (2) parameter desain dan operasi, yang meliputi : kecepatan putaran, kekasaran permukaan, diameter, luas disk, luas permukaan bulk rector, luas basah disk, ketebalan liquid film, working volume; (3) kedalaman area disk ( dihitung dengan menggunakan jari-jari disk dan jarak poros disk terhadap permukaan air di bulk reactor). Ketiga kelompok tersebut telah terintegrasi pada persamaan model transfer oksigen fisik yang dihasilkan. Selanjutnya, penelitian ini juga mempelajari mekanisme transfer oksigen fisik di RBC. Pada mekanisme transfer oksigen fisik pada rangkaian disk permukaan datar (KLa)f, didapatkan dua kondisi mekanisme berdasarkan kekasaran permukaan. Pada mekanisme yang pertama, di kekasaran permukaan kurang dari 10 nm, maka transfer oksigen fisik melalui turbulensi (KLat). Mekanisme yang kedua, di kekasaran permukaan lebih dari 50 nm, transfer oksigen melalui turbulensi (KLat) dan liquid film (KLad). Sedangkan mekanisme transfer oksigen fisik pada rangkaian disk permukaan berkontur (KLa)g, konsepnya sama dengan di disk permukaan datar, tetapi perbedaannya di parameter kekasaran permukaan secara makroskopik (Kg) dan specific interfacial (Si). Dengan menambahkan nilai Kg saja, tidak bisa menggambarkan perubahan pola kontur permukaan disk yang variatif. Maka dalam penelitian ini, diperkenalkan, variabel baru, yaitu NITS (The number of roughness and contoured surface, in rotating vertically flow). Dengan adanya KITS ini, diharapkan akan mempermudah aplikasi di lapangan untuk pemilihan jenis material disk dan pola konturnya. =============================================================================================== Oxygen transfer of a Rotating Biological Contactor (RBC) reactor is an important factor, since it affect the RBC efficiency. Insufficient level of oxygen is a common condition during its operation in waste water processing. Thus, researchers attempted to increase the oxygen transfer capability by either enlarging the reactor geometry, increasing the number of discs and stages or increasing the velocity of the discs rotation. In this work, the attemp to increase the RBC oxygene transfer capability was done by solely including a variety of surface roughness factor of the disc (Kvg) without enlarging the reactor geometry and without increasing the rotational velocity of the discs. The work was also aiming to develope an empirical model to predict the RBC oxygen transfer capability and its mechanism. The experiment was performed by making use of an RBC with vertical rotating discs partially immersed in an open basin. Ability of the method to increase the oxygen transfer capability was determined using experimental work, empirical model based on dimensional analysis and flow visualization based on computational fluid dynamic (CFD). The raw water used during the experiment was only using an amount of clean water without any biofilm. Some variables used in this research were surface roughness (Kvg) and component of disc velocity. Kvg which is affected by the micrometer (Kv) and macrometer (Kg) measurement. Component of disc velocity consists of peripheral velocity(R) and velocity due to the depth of the disc (H) It was justified in this work that the incorporation of the surface roughness factor (Kvg) was able to increase the capability of oxygen transfer in RBC. A model was developed using dimension anaysis method to estimate the physical oxygene transfer (KLa). Such transfer in RBC is affected by three primary situation of: (1) affecting forces during the process (represented from the Reynolds number and the Froud number); (2) Desain and operation parameter of rotational velocity, disc surface roughness, bulk reactor surface area, disc wetted area, liquid film thickness, and working volume; (3) immersed disk area (calculated by using the disk radius and its shaft distance to the water surface inside the bulk reactor). Thus, all the above mentioned three primary situation were included in the model. Further, the work was also studying the mechanism of physical oxygene transfer under a series of flat discs (KLa)f, there were two kind mechanism of oxygen transfer due to the roughness of the disc surfaces. The first mechanism viii was occured on the surface having a roughness level of lower than 10 nm that only turbulence mechanism (KLat) was observed while the second one with a roughness level of higher than 50 nm, both the turbulence mechanism (KLat) and the liquid film mechanism (KLad) were observed. The work also utilised a series of contoured discs denoted as (KLa)g which was determined by its macroscopic surface roughness (Kg) and its specific interfacial factor (Si). A new variable of roughness number and contoured surface in rotating vertically flow (NITS) was introduced to adapt the application of the method due to the discs material and surface contour pattern. Such a new variable was introduced to resolve the problem that the utilition of Kg was insufficient to represent a wide variaty of disc surface contours and patterns.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Transfer oksigen; Liquid film; Kekasaran permukaan; Kecepatan putaran; Rotating Biological Contactor
Subjects: T Technology > TD Environmental technology. Sanitary engineering > TD646 Sewage--Purification
T Technology > TD Environmental technology. Sanitary engineering > TD789 Refuse and refuse disposal
Divisions: Faculty of Civil Engineering and Planning > Environment Engineering > (S3) PhD Theses
Depositing User: Sarie Novirina Hendra
Date Deposited: 15 Jan 2018 08:05
Last Modified: 05 Mar 2019 03:22
URI: http://repository.its.ac.id/id/eprint/48640

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