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L1592_Frame_C31 Page 286 Tuesday, December 18, 2001 2:50 PM
Exercises
31.1 BOD/COD Correlation. The table gives n = 24 paired measurements of effluent BOD 5 and
COD. Interpret the data using graphs and correlation.
COD (mg/L) 4.5 4.7 4.2 9.7 5.8 6.3 8.8 5.7 6.3 9.7 15.4 12.0
BOD (mg/L) 5.0 4.1 6.7 5.0 5.0 3.8 6.1 4.1 4.2 4.3 4.0 3.7
COD (mg/L) 8.0 11.1 7.6 8.1 7.3 8.5 8.6 7.8 7.2 7.9 6.4 5.7
BOD (mg/L) 5.7 5.4 4.4 5.9 4.9 4.9 5.5 3.5 4.3 5.4 4.2 3.9
32.2 Heavy Metals. The data below are 21 observations on influent and effluent lead (Pb), nickel
(Ni), and zinc (Zn) at a wastewater treatment plant. Examine the data for correlations.
Inf. Pb Eff. Pb Inf. Ni Eff. Ni Inf. Zn Eff. Zn
18 3 33 25 194 96
3 1 47 41 291 81
4 1 26 8 234 63
24 21 33 27 225 65
35 34 23 10 160 31
31 2 28 16 223 41
32 4 36 19 206 40
14 6 41 43 135 47
40 6 47 18 329 72
27 9 42 16 221 72
8 6 13 14 235 68
14 7 21 3 241 54
7 20 13 13 207 41
19 9 24 15 464 67
17 10 24 27 393 49
19 4 24 25 238 53
24 7 49 13 181 54
28 5 42 17 389 54
25 4 48 25 267 91
23 8 69 21 215 83
30 6 32 63 239 61
31.3 Influent Loadings. The data below are monthly average influent loadings (lb/day) for the
Madison, WI, wastewater treatment plant in the years 1999 and 2000. Evaluate the correlation
between BOD and total suspended solids (TSS).
1999 BOD TSS 2000 BOD TSS
Jan 68341 70506 Jan 74237 77018
Feb 74079 72140 Feb 79884 83716
Mar 70185 67380 Mar 75395 77861
Apr 76514 78533 Apr 74362 76132
May 71019 68696 May 74906 81796
Jun 70342 73006 Jun 71035 84288
Jul 69160 73271 Jul 76591 82738
Aug 72799 73684 Aug 78417 85008
Sep 69912 71629 Sep 76859 74226
Oct 71734 66930 Oct 78826 83275
Nov 73614 70222 Nov 73718 73783
Dec 75573 76709 Dec 73825 78242
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