Water Quality

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Water Quality Lecture 13: Introduction to Environmental Engineering

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Measures of Water Quality What is perfect water? Is D.C's. drinking water clean? What are a few parameters that decide water quality? Broken down oxygen – oxygen test and oxygen meter Biochemical Oxygen Demand Solids Nitrogen – smelling salts Bacteriological quality

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Biochemical Oxygen Demand BOD Measurement of the rate at which microorganisms debasing natural matter utilize oxygen One can compute the hypothetical oxygen request If you know the substance recipe – for instance 1.67 x 10 - 3 M glucose C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O 6 x 1.67moles/L x 32 g/mole x 1000 mg/g = 321 mg/L BOD is utilized on the grounds that wastewater would one say one isn't natural particle

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Biochemical Oxygen Demand Standard BOD Test Run without light (green growth) @ 20 C for 5 days, characterized as BOD 5 Standard 300 mL volume BOD bottle BOD extreme, L, BOD more prominent than 20 days BOD = I –F I = beginning DO, mg/L F = last DO, mg/L

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Biochemical Oxygen Demand What if the F is =0? Weakening of the example is required when F = 0. On the off chance that F = 0 we don't know the amount DO would have been utilized. Body = (I – F)D D = weakening

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Biochemical Oxygen Demand Dilution by what amount? The best possible weakening sum is infrequently known before the test. An appropriate BOD test requires a change of DO of 2 mg/L And more than 2 mg/L staying toward the end of the test The weakening required is ascertained as:

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Biochemical Oxygen Demand Seeding The expansion of dynamic microorganisms that take up oxygen May be required in tests that don't have their own particular If seeding is vital, any BOD that is contributed by the seed must be subtracted

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Biochemical Oxygen Demand BOD with weakening and seed BODt = BOD at time t, mg/L I, F = introductory and last DO of test and seed, mg/L I', F' = starting and last DO of seed water, mg/L X = seeded weakening water in test bottle, mL Y = seeded weakening in jug with just seed weakening water mL D = weakening of test

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Biochemical Oxygen Demand Example Standard BOD test with a 1:30 weakening with seeded weakening water is run. Both jugs start at immersion, 9.2 mg/L. Following five days, the jug with waste has a DO of 2 mg/L, while the DO of the seed = 8 mg/L. Discover the BOD 5 .

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Biochemical Oxygen Demand Typical BOD values Wastewater BOD 5  250 mg/L Effluent BOD 5 from wastewater < 30 mg/L Industrial wastewater = 30,000 mg/L US Engineers regularly talk as far as lbs BOD 5/day Mass rate heap of a plant to the accepting stream

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Biochemical Oxygen Demand The BOD test happens in a container, Thus the mass adjust is Rate of DO accum. = rate of DO devoured dz/dt = - r z = broke down oxygen, mg/L Assume that it is a first-arrange response

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Biochemical Oxygen Demand As O 2 is utilized, the sum still to be utilized is z, the sum effectively utilized is y L = y + z L= extreme request

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Biochemical Oxygen Demand Variables y = BOD whenever t L = extreme BOD k 1 = deoxygenation consistent Example Find the BOD5 for a waste with an extreme BOD = 282 mg/L and a k 1 = 0.348/day

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Nitrogenous Oxygen Demand Nitrogenous BOD Organic matter + O 2  microscopic organisms + NH 3 + CO 2 + et.al. 2NH 3 + 3O 2  2NO 2 - + 2H + 2H 2 O 2NO 2 - + O 2  2 NO 3 - Two moles of O 2 for each mole of NH 3 BOD ult = a (BOD 5 ) + b(KN) KN = Kjeldahl nitrogen (measure of natural nitrogen and alkali) an and b are constants, a = 1.2 & b = 4.0 for instance

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Homework Chapter 8 Problems: 3, 7, 16, 22