Sigid Hariyadi

DO – BOD – CODDO – BOD – COD

Dept. Manajemen Sumberdaya Perairan - IPB

TINGKAT JENUH (SATURASI) OKSIGEN TERLARUT:

Dissolved Oxygen (DO)

http://eesc.columbia.edu/courses/ees/slides/climate/gas_comp.gif

http://www.bbc.co.uk/schools/gcsebitesize/science/images/50_composition_of_the_earth.gif

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.

FAKTOR KELARUTAN / TINGKAT SATURASI OKSIGEN:

S %o = 0,030 + 1,805 Cl (%o)

S (ppm) = 30 + 1,805 Cl (ppm)

atau

Kandungan chloride (Cl) dihitung berdasarkan nilai salinitas :

TINGKAT SATURASI TINGKAT SATURASI O O22 DI PERAIRAN DI PERAIRAN LAUTLAUT

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 ODISTRIBUSI VERTIKAL O2 2 DISTRIBUSI VERTIKAL ODISTRIBUSI VERTIKAL O2 2

dipengaruhi oleh: kondisi kelarutan hidrodinamika -- pergerakan air input fotosintesis penggunaan oleh biota &

proses-proses kimia

Bottle train sampler

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Prinsip penentuan DO (metode Winkler/Iodometri):

endapan coklat

• bila tidak ada Oksigen:

endapan putih

proporsional dg jumlah O2 yang ada

penambahan asam

indikatorbiru

tak berwarna

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Modifikasi metode Winkler/Iodometri:

Flokulasi alum : 10% K2SO4Al2(SO4)3 &

35% NaOH

bila air keruhSulfamic acid : NH2SO2OH bila kadar nitrit

tinggiazide alsterberg : NaN3 bila kadar nitrit & bhn

organik tinggi

Pomeroy – Kirscman – Alsterberg : penggunaan NaI

(6 N)

dan NaOH (10N) sbg pengganti

NaOH + KI

bila kadar oksigen lewat jenuh (over

saturated)

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Pengukuran dgn DO-meter:

1. Warming up (on & biarkan bbrp menit)

2. Kalibrasi alat pada angka nol (zero adjustment)

3. Kalibrasi alat pada “red line” (red line adjusment)

4. Kalibrasi alat thd kadar O2 udara pada temperatur

dan tekanan udara (atau ketinggian tempat)

Standardisasi dgn metode Winkler pd sampel yg sama (scr periodik)

Prinsip Pengukuran:

Tekanan O2

dlm airSensor/

membranarus

Jarum penunjuk skala/ digital

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Botol BOD

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probe DO-meter

BOD (Biochemical Oxygen Demand):(Biological)

( DOi - DO5 ) mg/L

Inkubasi sampel dlm botol BOD pada 20oC selama 5 hari

shg O2 terlarut pd hari ke-5 masih ada & terukur

Perlu pengenceran yg cermat & aerasi

Botol gelapInkubasi 20oC5 hari

DO5

DOi

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Bahan beracun: Hg, Cr6+, Cl2 Kurangnya nutrien Kurangnya mikroorganisme/bakteri pH < 6½ atau pH > 8½

Senyawa pengganggu:

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BOD decomposition rates vary widely

DO Consumed(mg/l)

Decaying phytoplanton biomass

Black water organic matter

Municipal, industrial BOD loads

Time 5 days

BOD5

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BOD decomposition rates vary widely

Time 50 days5 days

Black water organic matter

Municipal, industrial BOD loads

DO Consumed(mg/l)

Decaying phytoplanton biomass

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Pre – treatment:PenambahanNutrien &Pengenceran

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BOD (Biochemical Oxygen Demand):

BOD3 inkubasi pada 30 oC selama 3 hari

Jenis dan jumlah bahan organik terlarut & tersuspensi (koloid) Jenis dan jumlah (komposisi) mikroorganisme pengurai kecukupan oksigen

Nilai BOD : Nilai BOD :

upayakan nilai DO5(end) sekitar 1 mg/L sebaiknya selisih DO berkisar 5 – 7 mg/L mengubah pH, seluruh aktivitas ionik mengubah aktivitas organik mengubah salinitas

lingkungan fisik-kimia- biologi air sampel

Pengenceran:Pengenceran:

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(Tropik)

From: DHV Consultants BV & DELFT HYDRAULICS, 1999. Training module # WQ - 15Understanding biochemical oxygen demand test. Hydrology Project Technical Assistance. New Delhi

CODCOD (Chemical Oxygen Demand): (Chemical Oxygen Demand):

Bhn organik dioksidasi dg K2Cr2O7 pada kondisi asam & panas

Kelebihan K2Cr2O7 dititrasi dg FAS (back titration) dg indikator feroin

potassium dichromate

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)

S (ppm) = 30 + 1,805 Cl (ppm)atau

S= 30 %o = 30 000 ppm Cl = 16603,88 ppm 3,321 g HgSO4 perliter sampel

Contoh :

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Reflux,untuk penentuan COD

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Wastewater type BOD5 (mg/L) COD (mg/L)

Tomato processing 450 - 1,600 650 - 2,300Corn processing 1,600 - 4,700 3,400 -10,100Cherry processing 660 - 1,900 1,200 - 3,800Poultry plant processing 150 - 2,400 200 - 3,200Milk plant processing 940 - 4,790 1,240 - 7,800

Becker, 2000. University of Maryland

Perairan-peruntukan BOD (mg/L) COD (mg/L)

Air tawar – Kelas I 2 10

Air tawar – Kelas II 3 25

Air tawar – Kelas III 6 50

Air tawar – Kelas IV 12 100

Air laut - Biota 20 -

Air laut - Wisata 10 -

Air laut - Pelabuhan - -

→ rekreasi air

→ budidaya ikan, ternak

→ air baku minum

→ irigasi pertanian

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COD menggambarkan jumlah bahan organik total, baik yang mudah urai maupun yang sulit urai

Berdasarkan prinsip analisisnya, maka dapat dikatakan bahwa:

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

TVS (total volatile solids) juga menggambarkan bahan organik berdasarkan prinsip analisis pembakaran residu organik sampel pada suhu tinggi (550oC) dan gravimetri

Parameter bahan organik lainnya adalah TOC (total organic carbon)

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BOD COD/ rasio antara bahan organik mudah urai dgnbahan organik total/sulit urai

COD ≥ BOD

COD ≥ TOM

Total Organic Matteroxidator: KMnO4

TVS Total Volatile Solid

TOC Total Organic Carbon bahan organik dibakar tidak mengukur Oksigen ekuivalensi dapat dihubungkan dgn BOD

COD

BOD

TOM

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Total Carbon (TC) – all the carbon in the sample, including both inorganic and organic carbonTotal 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:

1. Acidification2. Oxidation3. Detection and Quantification

Analysis of TOC:

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 Combustion2.High temperature catalytic (HTCO) oxidation3.Photo-oxidation alone4.Thermo-chemical oxidation5.Photo-chemical oxidation6.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.

TOC: