Transcript 2). DO-BOD-COD - WordPress.com

DO – BOD – COD
Sigid Hariyadi
Dept. Manajemen Sumberdaya Perairan - IPB
Dissolved Oxygen (DO)
TINGKAT JENUH (SATURASI) OKSIGEN TERLARUT:
http://www.bbc.co.uk/schools/gcsebitesize/science/im
ages/50_composition_of_the_earth.gif
http://eesc.columbia.edu/courses/ees/slides/climate/gas_comp.gif
FAKTOR KELARUTAN / TINGKAT SATURASI OKSIGEN:
 Efek ketinggian (altitude) :
ketinggian bertambah,  tekanan parsial gas menurun,  kelarutan
gas berkurang
ketinggian
tingkat berkurangnya kelarutan

0 - 600 m
4 % per 300 m
 600 - 1500 m
3 % per 300 m
 1500 - 3000 m
2,5 % per 300 m
 Efek temperatur : temperatur meningkat -- kelarutan berkurang
 Efek salinitas : adanya berbagai mineral terlarut -- menurunkan
kelarutan gas.
 tk. kejenuhan gas dalam air laut, 18 - 20 % lebih rendah daripada dalam akuades.
TINGKAT SATURASI O2
DI PERAIRAN LAUT
Kandungan chloride (Cl) dihitung
berdasarkan nilai salinitas :
S %o = 0,030 + 1,805 Cl (%o)
atau
S (ppm) = 30 + 1,805 Cl (ppm)
Dissolved Oxygen (DO)
• Oksigen adalah gas terlarut dalam air
• bila sampel terekspose ke udara  DO bisa berkurang
atau bertambah dari seharusnya
• pengambilan sampel utk titrasi  perlu alat khusus
DISTRIBUSI VERTIKAL O2
 input fotosintesis
 penggunaan oleh biota &
proses-proses kimia
Bottle train sampler
Sigid Hariyadi – 2005/2008
dipengaruhi oleh:  kondisi kelarutan
 hidrodinamika -- pergerakan air

endapan coklat
• bila tidak ada Oksigen:
endapan putih

penambahan asam
proporsional dg jumlah O2 yang ada

biru
indikator
tak berwarna
Sigid Hariyadi – 2005/2008
Prinsip penentuan DO (metode Winkler/Iodometri):
Modifikasi metode Winkler/Iodometri:
 Flokulasi alum : 10% K2SO4Al2(SO4)3 & 35% NaOH
 bila air keruh
 Sulfamic acid : NH2SO2OH  bila kadar nitrit tinggi
 azide alsterberg : NaN3  bila kadar nitrit & bhn organik tinggi
dan NaOH (10N) sbg pengganti NaOH + KI
 bila kadar oksigen lewat jenuh (over saturated)
Sigid Hariyadi – 2005/2008
 Pomeroy – Kirscman – Alsterberg : penggunaan NaI (6 N)
Pengukuran dgn DO-meter:
1.
2.
3.
4.
Warming up (on & biarkan bbrp menit)
Kalibrasi alat pada angka nol (zero adjustment)
Kalibrasi alat pada “red line” (red line adjusment)
Kalibrasi alat thd kadar O2 udara pada temperatur
dan tekanan udara (atau ketinggian tempat)
 Standardisasi dgn metode Winkler pd sampel yg sama (scr periodik)
Tekanan O2
dlm air
Sensor/
membran
arus
Jarum penunjuk skala
/ digital
Sigid Hariyadi – 2005/2008
Prinsip Pengukuran:
Sigid Hariyadi – 2005/2008
Botol BOD
probe DO-meter
(Biological)
BOD (Biochemical Oxygen Demand):
( DOi - DO5 ) mg/L
 Inkubasi sampel dlm botol BOD pada 20oC selama 5 hari
 shg O2 terlarut pd hari ke-5 masih ada & terukur
Sigid Hariyadi – 2005/2007
 Perlu pengenceran yg cermat & aerasi
DOi
Botol gelap
Inkubasi 20oC
5 hari
DO5
 Senyawa pengganggu:
Bahan beracun: Hg, Cr6+, Cl2
Kurangnya nutrien
Kurangnya mikroorganisme/bakteri
pH < 6½ atau pH > 8½
Sigid Hariyadi – 2005/2007




Sigid Hariyadi – 2005/2008
BOD decomposition rates vary widely
Municipal,
industrial
BOD loads
DO
Consumed
(mg/l)
Black water
organic matter
Time
5 days
Sigid Hariyadi – 2005/2008
BOD5
Decaying phytoplanton
biomass
BOD decomposition rates vary widely
Black water
organic matter
DO
Consumed
(mg/l)
Decaying phytoplanton
biomass
5 days
Time
50 days
Sigid Hariyadi – 2005/2008
Municipal,
industrial
BOD loads
Sigid Hariyadi – 2005/2008
Sigid Hariyadi – 2005/2008
Pre – treatment:
Penambahan
Nutrien
&
Pengenceran
BOD (Biochemical Oxygen Demand):
BOD3  inkubasi pada 30 oC selama 3 hari (Tropik)
Nilai BOD :
 Jenis dan jumlah bahan organik terlarut & tersuspensi (koloid)
 Jenis dan jumlah (komposisi) mikroorganisme pengurai
 kecukupan oksigen
 upayakan nilai DO5(end) sekitar 1 mg/L
Pengenceran:
 mengubah pH, seluruh aktivitas ionik
 mengubah aktivitas organik
 mengubah salinitas
lingkungan fisik-kimiabiologi air sampel
Sigid Hariyadi – 2005/2007
 sebaiknya selisih DO berkisar 5 – 7 mg/L
From: DHV Consultants BV & DELFT HYDRAULICS, 1999. Training module # WQ - 15
Understanding biochemical oxygen demand test. Hydrology Project Technical Assistance. New Delhi
COD (Chemical Oxygen Demand):
Sigid Hariyadi – 2005/2008
potassium dichromate
 Bhn organik  dioksidasi dg K2Cr2O7 pada kondisi asam & panas
 Kelebihan K2Cr2O7  dititrasi dg FAS (back titration) dg indikator
feroin
Ferrous Ammonium Sulfate
 perlu larutan blanko
 senyawa pengganggu: Cl (air laut), NO2-
sulfamic acid
+ HgSO4 (200 mg/L per 1000 mg/L chloride)
S %o = 0,030 + 1,805 Cl (%o)
Contoh :
atau
S (ppm) = 30 + 1,805 Cl (ppm)
S= 30 %o = 30 000 ppm  Cl = 16603,88 ppm  3,321 g HgSO4 per
liter sampel
Sigid Hariyadi – 2005/2008
Reflux,
untuk penentuan COD
Wastewater type
BOD5 (mg/L)
COD (mg/L)
Tomato processing
Corn processing
Cherry processing
Poultry plant processing
Milk plant processing
450 - 1,600
1,600 - 4,700
660 - 1,900
150 - 2,400
940 - 4,790
650 - 2,300
3,400 -10,100
1,200 - 3,800
200 - 3,200
1,240 - 7,800
Becker, 2000. University of Maryland
Perairan-peruntukan
COD (mg/L)
Air tawar – Kelas I
2
10
→ air baku minum
Air tawar – Kelas II
3
25
→ rekreasi air
Air tawar – Kelas III
6
50
→ budidaya ikan, ternak
Air tawar – Kelas IV
12
100
→ irigasi pertanian
Air laut - Biota
20
-
Air laut - Wisata
10
-
-
-
Air laut - Pelabuhan
25
Sigid Hariyadi
BOD (mg/L)
Berdasarkan prinsip analisisnya, maka dapat dikatakan
bahwa:
 COD menggambarkan jumlah bahan organik total, baik
yang mudah urai maupun yang sulit urai
 BOD menggambarkan bahan organik mudah urai
 Nilai permanganat (TOM-total organic matter) TIDAK
pernah lebih besar daripada nilai COD, karena oksidator
yang digunakan pada analisis COD lebih kuat
 Parameter bahan organik lainnya adalah TOC (total
organic carbon)
26
Sigid Hariyadi
 TVS (total volatile solids) juga menggambarkan bahan
organik berdasarkan prinsip analisis pembakaran residu
organik sampel pada suhu tinggi (550oC) dan gravimetri
BOD/COD
rasio antara bahan organik mudah urai dgn
bahan organik total/sulit urai
COD ≥ BOD
COD ≥ TOM
Total Organic Matter
oxidator: KMnO4
TOC
Total Volatile Solid
Total Organic Carbon
 bahan organik dibakar
 tidak mengukur Oksigen ekuivalensi
 dapat dihubungkan dgn BOD
COD
TOM
BOD
27
Sigid Hariyadi
TVS
TOC:
Total Carbon (TC) – all the carbon in the sample, including both inorganic and organic carbon
Total Inorganic Carbon (TIC) – often referred to as inorganic carbon (IC), carbonate, bicarbonate, and dissolved carbon dioxide (CO2); a
material derived from non-living sources.
Total Organic Carbon (TOC) – material derived from decaying vegetation, bacterial growth, and metabolic activities of living organisms or
chemicals.
Non-Purgeable Organic Carbon (NPOC) – commonly referred to as TOC; organic carbon remaining in an acidified sample after purging
the sample with gas.
Purgeable (volatile) Organic Carbon (POC) – organic carbon that has been removed from a neutral , or acidified sample by purging with an
inert gas. These are the same compounds referred to as Volatile Organic Compounds (VOC) and usually determined by Purge and Trap Gas
Chromatography.
Dissolved Organic Carbon (DOC) – organic carbon remaining in a sample after filtering the sample, typically using a 0.45 micrometer
filter.
Suspended Organic Carbon – also called particulate organic carbon (PtOC); the carbon in particulate form that is too large to pass through a
filter.
TOC:
Analysis of
1.
2.
3.
TOC:
Acidification
Oxidation
Detection and Quantification
Acidification :
The removal and venting of IC and POC gases from the liquid sample by acidification and sparging occurs in the following manner.
Oxidation :
The second stage is the oxidation of the carbon in the remaining sample in the form of carbon dioxide (CO2) and other gases.
Modern TOC analyzers perform this oxidation step by several processes:
1. High Temperature Combustion
2. High temperature catalytic (HTCO) oxidation
3. Photo-oxidation alone
4. Thermo-chemical oxidation
5. Photo-chemical oxidation
6. Electrolytic Oxidation
High temperature combustion:
Prepared samples are combusted at 1,350o C in an oxygen-rich atmosphere. All carbon present converts to carbon dioxide,
flows through scrubber tubes to remove interferences such as chlorine gas, and water vapor, and the carbon dioxide is
measured either by absorption into a strong base then weighed, or using an Infrared Detector.[3] Most modern analyzers use
non-dispersive infrared (NDIR) for detection of the carbon dioxide.
Detection and quantification:
Accurate detection and quantification are the most vital components of the TOC analysis process. Conductivity and non-dispersive
infrared (NDIR) are the two common detection methods used in modern TOC analyzers.