Pelarutan, Pemisahan, dan Recovery Alum dari Lumpur Pengolahan Air Minum

Barakwan, Rizkiy Amaliyah (2021) Pelarutan, Pemisahan, dan Recovery Alum dari Lumpur Pengolahan Air Minum. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kadar aluminium yang tinggi pada lumpur pengolahan air minum diakibatkan oleh
penggunaan aluminium sulfat atau alum sebagai koagulan. Lumpur alum berpotensi
menyebabkan pencemaran lingkungan. Konsentrasi aluminium yang tinggi di lumpur alum
berpotensi untuk di-recovery sebagai koagulan alum. Pada recovery koagulan, langkah
pertama yang harus dilakukan adalah pelarutan aluminium dari lumpur yang dapat
dilakukan secara kimia dan biologis. Pengolahan secara kimia termasuk asidifikasi yaitu
dengan menambahkan asam sulfat, sedangkan bioleaching menggunakan mikroorganisme
untuk melarutkan aluminium dari lumpur. Namun, asidifikasi secara kimia dan bioleaching
adalah proses nonselektif karena terlarutnya logam-logam lain dan zat organik. Oleh karena
itu, proses lebih lanjut diperlukan untuk memisahkan aluminium terlarut dari kontaminan
lain. Proses ini dapat dilanjutkan dengan metode elektrolisis menggunakan membran
penukar ion semipermeable untuk meningkatkan kemurnian material hasil recovery.
Tujuan dari penelitian ini adalah mengkaji karakteristik fisik dan kimia serta toksisitas
lumpur pengolahan air minum sebagai dasar penentuan metode pengolahannya yang tepat,
membandingkan efisiensi pelarutan aluminium dari lumpur pengolahan air minum secara
kimia dan biologis, mengkaji efektifitas metode elektrokimia untuk pemisahan alum hasil
recovery dari pengotor, dan mengkaji efektifitas metode elektrokimia optimum pada skala
pilot untuk pemisahan alum hasil recovery dari pengotor.
Sampel lumpur alum diambil dari unit clearator di Instalasi Pengolahan Air
Minum (IPAM) 1 Jawa Timur, Indonesia. Karakterisasi lumpur meliputi karakteristik fisik
dan kimia serta toksisitas terhadap organisme Daphnia magna dan mikroorganisme.
Asidifikasi secara kimia dilakukan dengan menambahkan asam sulfat sampai pH 2 dengan
pengadukan selama 2 jam menggunakan magnetic stirrer. Selanjutnya, sentrifugasi
dilakukan selama 20 menit pada 3.000 rpm untuk memisahkan fase cairan dari padatan
lumpur. Bioleaching tahap 1 dilakukan dalam reaktor batch dengan pengadukan 150 rpm
selama 15 hari. Jenis mikroorganisme yang digunakan adalah fungi (Aspergillus niger,
Penicillium simplicissimum) dan bakteri (Pseudomonasfluorescens, dan Acidithiobacillus
ferrooxidans). Komposisi media (M) dan lumpur alum (L) adalah 50/50, 25/75, 12,5/87,5,
dan 0/100 (v/v). Bioleaching tahap 1 dilakukan menggunakan lumpur alum steril. Hasil
optimumnya diikuti dengan penentuan adanya pengaruh mikroorganisme indigenous
lumpur alum pada bioleaching aluminium. Parameter yang diukur adalah konsentrasi
aluminium dan pH setiap 3 hari sekali. Konsentrasi logam lain (besi, mangan, zink, timbal,
kromium, dan tembaga), COD, N-total, dan P-total diukur pada awal dan akhir percobaan.
Recovery alum dilakukan dengan metode elektrolisis pada skala laboratorium. Volume sel
elektrolisis dan luas permukaan elektroda masing-masing adalah 200 mL dan 24 cm2
. Uji
voltametri siklik dilakukan untuk mendapatkan jenis material anoda dan katoda yang
optimum untuk elektrolisis dengan elektrolit dari hasil asidifikasi lumpur alum. Jenis anoda
dan katoda adalah karbon (C)/ perak (Ag), platina (Pt)/ platina (Pt), dan platina (Pt)/
stainless steel A304 (SS A304). Kuat arus listrik diperoleh dari hasil uji polarisasi pada masing-masing jenis elektroda. Larutan elektrolit yang digunakan adalah supernatan hasil
asidifikasi pada pH 3. Konfigurasi reaktor elektrolisis yang digunakan adalah elektrolisis
tanpa membran dan elektrolisis dengan membran. Membran penukar ion semipermeable
yang digunakan adalah cation exchange membrane (CEM) dan anion exchange membrane
(AEM). Elektrolisis skala pilot dirancang dengan menyamakan nilai rasio luas penampang
elektroda dan sel elektrolisis (Ae/Ac) serta perbandingan luas penampang elektroda dan
volume reaktor (Ae/V) berdasarkan kondisi optimum elektrolisis skala laboratorium.
Volume sel elektrolisis dan luas permukaan elektroda masing-masing diperbesar menjadi
400 mL dan 48 cm2
. Volume feedtank diperbesar dari 1 L (skala laboratorium) menjadi 5
L pada skala pilot dengan waktu elektrolisis diperpanjang menjadi 10 jam. Elektrolisis
dilakukan pada kuat arus 400 mA, 600 mA, dan 800 mA untuk mendapatkan densitas arus
seperti pada skala laboratorium. Total dissolved solids dan nilai pH pada elektrolisis skala
laboratorium dan pilot diukur setiap jam. Konsentrasi aluminium, mangan, besi, zink,
timbal, kromium, dan tembaga diukur menggunakan ICP Agilent Technologies 700 Series
ICP-OES pada awal dan akhir elektrolisis. Endapan-endapan yang terbentuk ditimbang dan
diukur pada akhir proses.
Hasil penelitian menunjukkan bahwa lumpur alum mengandung konsentrasi
aluminium (1.194-6.736,3 mg/L), besi (1.077,09-3.800 mg/L), mangan (1.041 mg/L), dan
COD (2.166,67-4.914 mg/L) yang tinggi. Konsentrasi polutan lebih tinggi pada musim
hujan dibandingkan kemarau. Toksisitas lumpur alum pada D. magna terjadi pada
konsentrasi 10,12%. Metode pelarutan aluminium dari lumpur alum yang paling sesuai
adalah metode kimia dengan asidifikasi menggunakan asam sulfat. Hal ini karena
asidifikasi membutuhkan waktu yang lebih cepat dibandingkan bioleaching. Jenis
elektroda yang sesuai untuk elektrooksidasi pada proses recovery alum berdasarkan hasil
uji voltametri siklik adalah platina sebagai anoda dan SS A304 sebagai katoda. Proses
elektrolisis yang optimum pada recovery alum adalah 67,56% dengan komposisi
kandungan aluminium (90,94%), mangan (5,78%), besi (3,10%), zink (0,17%), dan
tembaga (0,0087%). Alum hasil recovery bebas dari kontaminan organik karena
penggunaan CEM pada elektrolisis. Densitas arus optimum pada elektrolisis skala pilot
adalah 12,5 mA/cm2 dengan efisiensi recovery alum sebesar 68,06% dan nilai SEC 53,47
kWh/kg. Komposisi kandungan aluminium pada alum hasil recovery dibandingkan dengan
logam lainnya adalah 91,23% dengan peningkatan konsentrasi aluminium dalam
kompartemen katoda mencapai 61,77%. Elektrolisis skala laboratorium dan pilot memiliki
efektifitas yang tidak jauh berbeda pada densitas arus yang sama. Aplikasi teknologi ini
sangat bermanfaat bagi lingkungan, namun teknologi ini juga dinilai tidak layak secara
ekonomi dengan nilai NPV negatif dan BCR<1.
=================================================================================================
The high level of aluminum in drinking water treatment sludge (DWTS) or alum
sludge is due to the use of aluminum sulfate or alum, as a coagulant. The alum sludge is
potential to cause environmental pollution. The high aluminum concentration in the alum
sludge is potential to be recovered as alum coagulant. First step in coagulant recovery is
the dissolution of aluminum from the sludge which can be carried out by chemical or
biological methods. The chemical process includes acidification using sulfuric acid, while
bioleaching uses microorganisms for separating aluminum from the sludge. However,
chemical acidification and bioleaching are non-selective processes due to the dissolution
of other metals and organic matter. Therefore, further process isrequired to separate the
dissolved aluminum from contaminants. These processes can be followed by electrolysis
using a semipermeable ion exchange membrane to increase the purity of the recovered
material. Aims of this study are to examine the physical and chemical characteristics and
toxicity of the DWTS as a basis for determining the appropriate treatment method, to
compare the efficiency of aluminum dissolution from DWTS using chemical and biological
methods, to examine the effectiveness of electrochemical methods for separating the
recovered alum from impurities, and to examine the effectiveness of optimum
electrochemical method in the pilot scale for separating the recovered alum from
impurities.
Alum sludge samples were collected from clearator unit in drinking water
treatment plant (DWTP) 1 East Java, Indonesia. Alum sludge characterization included
physical and chemical characteristics and toxicity to Daphnia magna and microorganisms.
Chemical acidification was carried out by adding sulfuric acid to pH 2 and stirring for 2
hours using magnetic stirrer. Then, centrifugation was carried out for 20 minutes at 3,000
rpm to separate the liquid phase from the sludge solid. Bioleaching in first stage was
carried out in a batch reactor and stirred at 150 rpm for 15 days. The types of
microorganisms used were fungi (Aspergillus. niger, Penicillium simplicissimum) and
bacteria (Pseudomonas fluorescens, and Acidithiobacillus ferrooxidans). The composition
of the medium (M) and alum sludge (L) were 50/50, 25/75, 12.5/87.5, and 0/100 (v/v). First
stage of the bioleaching was carried out using sterile alum sludge. The optimum results
was followed by determination of the effect of indigenous microorganisms to the sludge.
Parameters measured were aluminum concentrations and pH every 3 days. Other metal
concentrations (iron, manganese, zinc, lead, chromium, and copper), COD, N-total, and
P-total were measured at the initial and end of the experiment. Alum recovery was carried
out using electrolysis methods in a laboratory scale. The electrolysis cell volume and the
electrodes cross-sectional area were 200 mL and 24 cm2
, respectively. Cyclic voltammetry
test was carried out to obtain the optimum type of anode and cathode materials for
electrolysis with electrolyte from acidified alum sludge solution. Types of anode and
cathode were carbon (C)/silver (Ag), platinum (Pt)/platinum (Pt), and platinum
(Pt)/stainless steel A304 (SS A304). Electrical current was obtained from polarization test results on each type of electrode. The electrolyte solution was the supernatant from the
acidification at pH 3. Configuration of the electrolysis reactors were electrolysis without
membrane and electrolysis with membranes. The membranes were semipermeable ion
exchange membrane, namely cation exchange membrane (CEM) and anion exchange
membrane (AEM). The pilot-scale electrolysis cell was designed by using similar ratio of
the electrodes and cell cross-sectional areas (Ae/Ac) and the ratio of electrodes cross�sectional area and reactor volume (Ae/V) of earlier the optimum condition of laboratory�scale experiment. The electrolysis cell volume and the electrodes cross-sectional area were
enlarged to 400 mL and 48 cm2
, respectively. The feedtank volume was enlarged from 1 L
(in laboratory-scale) to 5 L in pilot-scale with the electrolysis time extended to 10 h. The
electrolysis was performed at electrical currents of 400, 600, and 800 mA to get similar
current density variation as those in the laboratory-scale. Total dissolved solids and pH in
laboratory and pilot scale reactors were measured every hour. The concentrations of
aluminum, manganese, iron, zinc, lead, chromium, and copper were measured using ICP
Agilent Technologies 700 Series ICP-OES at the initial and end electrolysis. Those of the
deposits were measured at the end of experiment.
The results showed that the alum sludge had high concentrations of aluminum
(1,194 to 6,736.3 mg/L), iron (1,077.09 to 3,800 mg/L), manganese (1,041 mg L), and COD
(2,166.67 to 4,914 mg/L). Pollutant concentrations in the alum sludge was higher in the
rainy season than in the dry season. The toxicity of alum sludge to D. magna occurred at
a concentration of 10.12%. The most suitable method of aluminum separation from alum
sludge was chemical method with acidification using sulfuric acid. It was caused the
acidification required a shortertime than the bioleaching process. The suitable electrodes
types for electrooxidation according to the cyclic voltammetry test were platinum as anode
and SS A304 as cathode. Optimum electrolysis efficiency in alum recovery was 67.56%
with composition of aluminum (90,94%), manganese (5,78%), iron (3,10%), zinc (0,17%),
and copper (0,0087%). The recovered alum was free from organic impurities due to the
used of CEM during electrolysis. The optimum current density in the pilot-scale electrolysis
was 12.5 mA/cm2 with alum recovery of 68.06% and SEC value of 53.47 kWh/kg. The
aluminum content in the recovered alum compared to other metals was 91.23% with an
increase of the aluminum concentration in the cathode compartment reaching 61.77%.
Laboratory and pilot-scales electrolysis had the similar effectiveness at the same current
density. Application of this technology is very beneficial for the environment, howeverthis
technology was also considered economically inadequate with a negative NPV and
BCR<1.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Asidifikasi, bioleaching, elektrolisis, lumpur alum, recovery alum. ================================================================================== Acidification, alum recovery, alum sludge, bioleaching, electrolysis.
Subjects: T Technology > TD Environmental technology. Sanitary engineering > TD420 Water pollution
T Technology > TD Environmental technology. Sanitary engineering > TD433 Water treatment plants
T Technology > TD Environmental technology. Sanitary engineering > TD455 Chemical precipitation. Coagulation. Flocculation. Water--Purification--Flocculation.
T Technology > TD Environmental technology. Sanitary engineering > TD480.5 Electrodialysis
T Technology > TP Chemical technology > TP159.M4 Membranes (Technology)
T Technology > TP Chemical technology > TP248.25.M45 Membrane reactors
T Technology > TP Chemical technology > TP255 Electrochemistry, Industrial.
Divisions: Faculty of Civil Engineering and Planning > Environment Engineering > 25001-(S3) PhD Thesis
Depositing User: Rizkiy Amaliyah Barakwan
Date Deposited: 22 Aug 2021 12:45
Last Modified: 22 Aug 2021 12:45
URI: http://repository.its.ac.id/id/eprint/88447

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