Science of Water : Concepts and Applications

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Environmental Biomonitoring, Sampling, and Testing 259 Some experimentation is needed to determine the appropriate dilution factor for a particular sampling site. The result is the difference in DO between the fi rst measurement and the second, after multiplying the second result by the dilution factor. Standard Methods prescribes all phases of procedures and calculations for BOD determination. A BOD test is not required for monitoring water supplies. BOD Sampling, Analysis, and Testing The approved BOD sampling and analysis procedure measures the DO depletion (biological oxidation of organic matter in the sample) over a 5-day period under controlled conditions (20°C in the dark). The test is performed using a specifi ed incubation time and temperature. Test results are used to determine plant loadings, plant effi ciency, and compliance with NPDES effl uent limitations. The duration of the test (5 days) makes it diffi cult to use the data effectively for process control. The standard BOD test does not differentiate between oxygen used to oxidize organic matter and that used to oxidize organic and ammonia nitrogen to more stable forms. Because many biological treatment plants now control treatment processes to achieve oxidation of the nitrogen compounds, there is a possibility that BOD test results for plant effl uent and some process samples may produce BOD test results based on both carbon and nitrogen oxidation. To avoid this situation, a nitrifi cation inhibitor can be added. When this is done, the test results are known as carbonaceous BOD (CBOD). A second uninhibited BOD should also be run whenever CBOD is determined. When taking a BOD sample, no special sampling container is required. Either a grab or composite sample can be used. BOD 5 samples can be preserved by refrigeration at or below 4°C (not frozen)—composite samples must be refrigerated during collection. Maximum holding time for preserved samples is 48 h. Using the incubation approved test method, a sample is mixed in several different concentrations (dilutions) with dilution water. The dilution water contains nutrients and materials to provide optimum environment. Chemicals used include dissolved oxygen, ferric chloride, magnesium sulfate, calcium chloride, phosphate buffer, and ammonium chloride. √ Note: Remember, all chemicals can be dangerous if not used properly and in accordance with the recommended procedures. Review appropriate sections of the individual chemical materials safety data sheet (MSDS) to determine proper methods for handling and for safety precautions that should be taken. Sometimes it is necessary to add (seed) healthy organisms to the sample. The DO of the dilution and the dilution water is determined. If seed material is used, a series of dilutions of seed material must also be prepared. The dilutions and dilution blanks are incubated in the dark for 5 days at 20°C ± 1°C. At the end of 5 days, the DO of each dilution and the dilution blanks are determined. For the test results to be valid, certain criteria must be achieved. These test criteria are listed as follows: 1. Dilution water blank DO change must be ≤0.2 mg/L. 2. Initial DO must be >7.0 mg/L but ≤9.0 mg/L (or saturation at 20°C and test elevation). 3. Sample dilution DO depletion must be ≥2.0 mg/L. 4. Sample dilution residual DO must be ≥1.0 mg/L. 5. Sample dilution initial DO must be ≥7.0 mg/L. 6. Seed correction should be ≥0.6 but ≤1.0 mg/L. The BOD 5 test procedure consists of 10 steps (for unchlorinated water) as shown in Table 8.8. √ Note: BOD 5 is calculated individually for all sample dilutions that meet the criteria. Reported result is the average of the BOD 5 of each valid sample dilution.
260 The Science of Water: Concepts and Applications BOD 5 Calculation (Unseeded) Unlike the direct reading instrument used in the DO analysis, BOD results require calculation. There are several criteria used in selecting which BOD 5 dilutions should be used for calculating test results. Consult a laboratory testing reference manual (such as Standard Methods) for this information. At present, there are two basic calculations for BOD 5 . The fi rst is used for samples that have not been seeded. The second must be used whenever BOD 5 samples are seeded. In this section, we illustrate the calculation procedure for unseeded samples. Example 8.2 BOD (Unseeded) 5 (DO start, mg/LDO final, mg/L) 300 mL Sample Volume, mL Problem: The BOD5 test is completed. Bottle 1 of the test had a DO of 7.1 mg/L at the start of the test. After 5 days, bottle 1 had a DO of 2.9 mg/L. Bottle 1 contained 120 mg/L of sample. Solution: TABLE 8.8 BOD 5 Test Procedure 1. Fill two bottles with BOD dilution water; insert stoppers. 2. Place sample in two BOD bottles; fi ll with dilution water; insert stoppers. 3. Test for DO. 4. Incubate for 5 days. 5. Test for DO. 6. Add 1 mL of MnSO 4 below surface. 7. Add 1 mL of alkaline KI below surface. 8. Add 1 mL of H 2 SO 4 . 9. Transfer 203 mL to a fl ask. 10. Titrate with PAO or thiosulfate. BOD (Unseeded) 5 (7.1 mg/L2.9 mg/L) 300 mL 10.5 mg/L 120 mL BOD 5 Calculation (Seeded) If the BOD 5 sample has been exposed to conditions that could reduce the number of healthy, active organisms, the sample must be seeded with organisms. Seeding requires the use of a correction factor to remove the BOD 5 contribution of the seed material. Seed Material BOD5Seed in Dilution, mL Seed Correction 300 mL [(DO start, mg/LDO final, mg/L) Seed Corr.] 300 BOD 5 (Seeded) Sample Volume, mL (8.2) (8.3) (8.4)
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Second Edition THE SCIENCE OF WATER
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Cover Image: Falling Spring at Fall
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Contents Preface ..................
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Contents ix Velocity Head .........
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Contents xi Specifi c Conductance .
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Contents xiii (5) Beetles (Order: C
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Contents xv Chlorine Residual Testi
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Contents xvii Water Filtration Calc
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To the Reader In reading this text,
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1 Introduction When color photograp
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Introduction 3 On second look, we s
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Introduction 5 As mentioned earlier
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Introduction 7 This scream of lost
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Introduction 9 Metcalf & Eddy, Inc.
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12 The Science of Water: Concepts a
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3 Water Hydraulics Anyone who has t
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Water Hydraulics 47 Another relatio
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Water Hydraulics 49 • • 1 ft 3
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Water Hydraulics 51 √ Important P
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Water Hydraulics 53 FIGURE 3.4 Thru
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Water Hydraulics 55 Example 3.8 Pro
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Water Hydraulics 57 FIGURE 3.6 Lami
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Water Hydraulics 59 With regard to
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Water Hydraulics 61 or hydraulic gr
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Water Hydraulics 63 E 1 smaller fl
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Water Hydraulics 65 √ Note: In de
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Water Hydraulics 67 • Cone of dep
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Water Hydraulics 69 • • • •
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Water Hydraulics 71 The Darcy-Weisb
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Water Hydraulics 73 Of course, pipe
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Water Hydraulics 75 In this section
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Water Hydraulics 77 Slope (S) The s
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Water Hydraulics 79 and important c
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Water Hydraulics 81 and the depth o
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Water Hydraulics 83 TYPES OF DIFFER
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Water Hydraulics 85 √ Important P
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Water Hydraulics 87 Meter backpress
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Water Hydraulics 89 VELOCITY FLOWME
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Water Hydraulics 91 The positive-di
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Water Hydraulics 93 Solution: 1200g
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Water Hydraulics 95 Water and Waste
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6 Water Ecology The subject of man
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Water Ecology 157 The environment i
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Water Ecology 159 FIGURE 6.2 Notone
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Water Ecology 161 H 2 O O 2 FIGURE
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Water Ecology 163 FeS FIGURE 6.6 Th
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Water Ecology 165 Algae FIGURE 6.8
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Water Ecology 167 2. Likewise, biom
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Water Ecology 169 Population densit
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Water Ecology 171 succession can be
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Water Ecology 173 dark winter month
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Water Ecology 175 In rain events wh
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Water Ecology 177 long profi le, cr
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Water Ecology 179 THE FLOODPLAIN A
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Water Ecology 181 It is important t
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Water Ecology 183 Specifi c Adaptat
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Water Ecology 185 serve to indicate
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Water Ecology 187 UNITS OF ORGANIZA
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Water Ecology 189 FIGURE 6.20 Stone
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Water Ecology 191 FIGURE 6.22 Midge
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Water Ecology 193 FIGURE 6.25 Riffl
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Water Ecology 195 They push their m
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Water Ecology 197 FIGURE 6.32 Damse
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Water Ecology 199 Darwin, C., 1998.
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10 Water Treatment Calculations Gup
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