The calculated seed BOD represents the BOD exerted by 300 mL of undiluted seed material. The ratio of the seed BOD to 300 mL will be used to calculate the seed correction for seeded samples.
What is the dilution factor for BOD?
Only dilutions with DO depletions of at least 2 mg/L, and DO 5 of at least 1 mg/L may be used to calculate the sample’s BOD.
How do you prepare dilution water for BOD?
Add 1 mL each of PO4 buffer; MgSO 4 , CaCl 2 , and FeCl 3 per Liter or the contents of one buffer pillow (buy the right size!). Before use bring dilution water temperature to 20 ± 1°C. Saturate with DO: shake or aerate with organic-free filtered air.
How do you calculate BOD in water?
For example: 1.0 mL of a full strength wastewater sample added to 9.0 mL of DI water results in a 0.1 dilution of the wastewater. The DO concentration (mg/L) reduction must then be multiplied by 10 to determine the final BOD concentration.
What is the need for using seeded dilution water in the BOD test?
When determining BOD, it is necessary to have a population of microorganisms that can oxidize (or consume) the biodegradable organic matter present in the sample . If there is too little seed present in the sample, complete consumption of biodegradable matter may not occur, resulting in inaccurate results.
How does dilution affect BOD?
The dilution of water samples for BOD determination was linked to changes in the environment for microbial growth such as nutrition . ... BOD(5) increased with the specific amount of inorganic nutrient per microbial mass when the natural water was diluted.
How is dilution factor calculated?
Dilution factor is defined as: total volume of solution per aliquot volume . Where total volume of solution is: 10.0 + 240.0 = 250.0 mL (volumetric flask.) Note: For multiple dilutions the dilution factor is the product of the dilution factors for each individual dilution.
What is BOD formula?
BOD = biochemical oxygen demand, mg/L . When seed is added, seed control tests must be done to determine the amount of oxygen depleted by the seed. Calculation of BOD includes a correction factor for seed as expressed by Equation 2.
Why is BOD test done for 5 days?
The standard oxidation (or incubation) test period for BOD is 5 days at 20 degrees Celsius (°C) (BOD5). The BOD5 value has been used and reported for many applications, most commonly to indicate the effects of sewage and other organic wastes on dissolved oxygen in surface waters (see TECHNICAL NOTE).
Why is it usually necessary to dilute the sample?
Dilutions can be important when dealing with an unknown substance. ... By performing a dilution on a sample it may reduce the interfering substance to a point where it no longer interferes with the test . When performing a dilution there is a equation that can be used to determine the final concentration.
What is BOD COD ratio?
COD is a measure of total organic molecules dissolved in waste water, Where as The concept of BOD came after cities started dumping their waste water into the water bodies and this led to depletion of oxygen and then death of water bodies.BOD/COD ratio is a measure of food value .
What is COD and BOD in water?
The biochemical oxygen demand (BOD) represents the amount of dissolved oxygen (DO) consumed by biological organisms when they decompose organic matter in water. The chemical oxygen demand (COD) is the amount of oxygen consumed when the water sample is chemically oxidised .
Why is COD higher than BOD?
COD stands for ‘Chemical Oxygen Demand’ where BOD stands for Biochemical Oxygen Demand. ... COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised .
What is BOD 3day?
The BOD is an emperical test , to estimate the relative oxygen requirement of the waters . Microorganisms, as their source of carbon , utilise the oxygen dissolved in water for bio-chemical oxidation of organic matter. ... BOD measurement is done at 20 ? in 5 days which is 70 -80 % of ultimate BOD for domestic waste water.
What are the main sources of error during BOD test?
Dilution water demand (DWD) can cause a positive error when the dilution biochemical oxygen demand (BOD) method is used. Dilution water demand may be attributed to oxidation of organic impurities in the dilution water and nitrification of ammonia added as a nutrient .
What is a dilution factor of 1?
Dilution factor refers to the ratio of the volume of the initial (concentrated) solution to the volume of the final (dilute) solution 1 , that is, the ratio of V 1 to V 2 .
