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.
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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
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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 > 25001-(S3) PhD Thesis |
| 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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