bod (biochemical oxygen demand) analysis

8/13/2019 BOD (Biochemical Oxygen Demand) ANALYSIS

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BOD (Biochemical Oxygen

Demand) ANALYSIS


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BOD

adalah prosedur kimia untuk menentukan jumlahoksigen terlarut yang dibutuhkan oleh organismebiologis aerobik dalam badan air untuk memecah

bahan organik yang ada dalam sampel air padasuhu tertentu selama periode waktu tertentu.

Ini bukan tes kuantitatif yang tepat, meskipunbanyak digunakan sebagai indikasi kualitas

organik air. paling sering disajikan dalam miligram oksigen

yang dikonsumsi per liter sampel selama 5 hariinkubasi pada 20 C


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The organic material broken down bymicroorganism/bacteria :

HaObCnNc+ B+ (n+a/4 - b/2 c) O2

nCO2+ (a/2 3/2 c) H2O + cNH3

B:bacteria


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BOD Test Procedure

Untuk memastikan bahwa semua kondisi lain

adalah sama, jumlah yang sangat kecil dari

benih mikro-organisme ditambahkan ke setiap

sampel yang diuji. Benih ini biasanya dihasilkan dengan

mengencerkan lumpur aktif dengan aquades.


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The BOD test is carried out by : mengencerkan sampel dengan aquades jenuh

oksigen

menyuntik dengan sejumlah tetap benih,

mengukur oksigen terlarut (DO) dan kemudianmenyegel sampel untuk mencegah oksigenlarut dalam air lebih lanjut.

Sampel disimpan pada 20 C dalam gelap

untuk mencegah fotosintesis (danpenambahan oksigen) selama 5 hari, danoksigen terlarut diukur lagi.

Hal ini disebut sebagai BOD520


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DO

The difference between the final DO and initial DO isthe BOD.

BOD can be calculated by: Undiluted BOD = Initial DO Final DO

Diluted BOD =

((Initial DO Final DO) BOD of seed) x dilution factor

BOD is equal to oxygen dissolved

The high BOD :DO consumed by bacteria for organic material breakingdown is also high that make other biotas can not life oran anaerobic condition is formed


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BOD test condition

The rate of biological reaction is determined by : A number of bacteria

The number of bacteria has to be adequate

as neededneeds to be added from soil.

Nutrients

N, P, and trace elements have to be available

adequately

Temperature. Temperature has to be kept constant at 20oC

during the test, that similar to nature condition


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Nitrification and oxidation of the nitrite

Caused by heterotro ph ic bacter ia when theincubat ion m ore than 5 days

2 NH3+ 3O22NO2- + 2 H+ + 2H2O

2NO2-+ 2 H+ + O22NO3

- + 2 H+

Oxidation inhibitor : 2-chloro-6 (trichloro

methyl)pyridine (TCMP)


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Some chemicals in the water are toxic for thebacteria, including :

Phenol

Cr(VI) ion

Time (d)

BOD

(mg/L)

+ 6 mg/L Cr(VI) ion

+ 1 mg/LCr(VI) ion

+ 0 mg/LCr(VI) ion

Time (d)

BOD(mg/L)

5 5

+ 0 mg/L phenol

+ 5 mg/L phenol

+ 50 mg/L phenol


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Measurement of DO

Volumetric with Winkler method Electrometric using DO meter


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BOD versus COD BOD is similar in function to chemical oxygen

demand(COD), in that both measure the

amount of organic compoundsin water.

However, COD is less specific, since itmeasures everything that can be chemically

oxidized, rather than just levels of biologically

active organic matter.
http://en.wikipedia.org/wiki/Chemical_oxygen_demandhttp://en.wikipedia.org/wiki/Chemical_oxygen_demandhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Chemical_oxygen_demandhttp://en.wikipedia.org/wiki/Chemical_oxygen_demand

bod (biochemical oxygen demand) analysis

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