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.