Why is the test run in the dark (or in a black bottle)? Why is K usually necessa

Question

Why is the test run in the dark (or in a black bottle)? Why is K usually necessary to dilute the sample? Why is it sometimes necessary to seed the sample? Why isn't ultimate BOD measured? Incoming wastewater, with BOD3 equal to about 200 mg/l, h ondary treatment plant that removes 90 percent of the BOD, BOD test with a standard 300-ml bottle, using a mixture of the water (no seed ). Assume the initial DO is 92 mg/L Roughly what maximum volume of treated wastewater you want to have at least 2.0 mg/l of DO at the end of the bottle with water)? If you make the mixture half treated waste water expected DO of the after five days determined be 1.0 mg/L what is BODs?

Explanation / Answer

mL sample added to BOD bottle = (minimum allowable depletion, mg/L x Volume of BOD bottle, mL)/estimated BOD, mg/L Example: minimum mL sample = [(8 mg/L 6 mg/L) x 300 mL]/400 mg/L minimum mL sample = (2 x 300)/400 = 600/400 = 1.5 mL B. mL sample added to BOD bottle = (maximum allowable depletion, mg/L x Volume of BOD bottle, mL)/estimated BOD, mg/L Example: maximum mL sample = [(8 mg/L 1 mg/L) x 300 mL]/400 mg/L maximum mL sample = (7 x 300)/400 = 2100/400 = 5.25 mL

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