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/images/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 dipengaruhi oleh: kondisi kelarutan hidrodinamika -- pergerakan air input fotosintesis penggunaan oleh biota & proses-proses kimia Sigid Hariyadi – 2005/2008 Bottle train sampler

Prinsip penentuan DO (metode Winkler/Iodometri): Sigid Hariyadi – 2005/2008  endapan coklat bila tidak ada Oksigen: endapan putih  proporsional dg jumlah O2 yang ada penambahan asam  biru indikator tak berwarna

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   Pomeroy – Kirscman – Alsterberg : penggunaan NaI (6 N) dan NaOH (10N) sbg pengganti NaOH + KI  bila kadar oksigen lewat jenuh (over saturated) Sigid Hariyadi – 2005/2008

Pengukuran dgn DO-meter: 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) Prinsip Pengukuran: Jarum penunjuk skala / digital Tekanan O2 dlm air Sensor/ membran arus Sigid Hariyadi – 2005/2008

Botol BOD Sigid Hariyadi – 2005/2008

probe DO-meter

( DOi - DO5 ) mg/L BOD (Biochemical Oxygen Demand): (Biological) DOi 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 gelap Inkubasi 20oC 5 hari DOi Sigid Hariyadi – 2005/2007 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 Decaying phytoplanton biomass BOD5 Municipal, industrial BOD loads DO Consumed (mg/l) Black water organic matter Sigid Hariyadi – 2005/2008 Time 5 days

BOD decomposition rates vary widely Black water organic matter Municipal, industrial BOD loads DO Consumed (mg/l) Decaying phytoplanton biomass Sigid Hariyadi – 2005/2008 Time 5 days 50 days

Sigid Hariyadi – 2005/2008

Pre – treatment: Penambahan Nutrien & Pengenceran Sigid Hariyadi – 2005/2008

BOD (Biochemical Oxygen Demand): BOD3  inkubasi pada 30 oC selama 3 hari (Tropik) Jenis dan jumlah bahan organik terlarut & tersuspensi (koloid) Jenis dan jumlah (komposisi) mikroorganisme pengurai kecukupan oksigen Nilai BOD : upayakan nilai DO5(end) sekitar 1 mg/L sebaiknya selisih DO berkisar 5 – 7 mg/L Pengenceran: mengubah pH, seluruh aktivitas ionik mengubah aktivitas organik mengubah salinitas lingkungan fisik-kimia- biologi air sampel Sigid Hariyadi – 2005/2007

From: DHV Consultants BV & DELFT HYDRAULICS, 1999 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): potassium dichromate Bhn organik  dioksidasi dg K2Cr2O7 pada kondisi asam & panas Kelebihan K2Cr2O7  dititrasi dg FAS (back titration) dg indikator feroin Sigid Hariyadi – 2005/2008 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) atau S (ppm) = 30 + 1,805 Cl (ppm) Contoh : S= 30 %o = 30 000 ppm  Cl = 16603,88 ppm  3,321 g HgSO4 per liter sampel

Reflux, untuk penentuan COD Sigid Hariyadi – 2005/2008

Wastewater type BOD5 (mg/L) COD (mg/L) Tomato processing 450 - 1,600 650 - 2,300 Corn processing 1,600 - 4,700 3,400 -10,100 Cherry processing 660 - 1,900 1,200 - 3,800 Poultry plant processing 150 - 2,400 200 - 3,200 Milk plant processing 940 - 4,790 1,240 - 7,800 Becker, 2000. University of Maryland

Baku mutu di perairan: 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 Air laut - Pelabuhan → air baku minum → rekreasi air → budidaya ikan, ternak → irigasi pertanian Sigid Hariyadi

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 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) Sigid Hariyadi

/ Total Volatile Solid BOD COD COD ≥ BOD COD ≥ TOM rasio antara bahan organik mudah urai dgn bahan organik total/sulit urai COD ≥ BOD COD ≥ TOM Total Organic Matter oxidator: KMnO4 TVS Total Volatile Solid COD TOM TOC Total Organic Carbon bahan organik dibakar tidak mengukur Oksigen ekuivalensi dapat dihubungkan dgn BOD BOD Sigid Hariyadi

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 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: High Temperature Combustion High temperature catalytic (HTCO) oxidation Photo-oxidation alone Thermo-chemical oxidation Photo-chemical oxidation 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.

Thanks Danke

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