Environmental Engineering Reference
In-Depth Information
Table 4 Summary of pollutant concentrations in A25 highway runoff
Range of values
No.
samples
Parameter
Min.
Max.
Average
Median
St. Dev.
72
113.0
970.0
388.3
405.5
230.2
Conductivity (mS/cm)
Salinity (mg/L)
72
60
520
205
216
120
Turbidity (FNU)
72
5.8
118.0
43.6
30.4
28.4
TSS (mg/L)
72
<5.0
250.0
67.7
45.0
60.1
Total hardness (mg
CaCO 3 /L)
72
36.0
208.0
85.3
78.0
44.8
Chlorides (mg/L)
72
15.8
370.9
108.2
81.4
92.6
TKN (mg/L)
24
<0.2
6.2
1.9
1.0
2.2
Total P (mg/L)
72
<0.05
7.38
1.14
0.38
1.78
COD (mg/L)
72
25.0
375.0
109.1
105.5
56.9
COT (mg/L)
72
6
91
31
27
17
Oil and grease (mg/L)
32
<0.184
7.260
1.359
0.810
1.789
BOD 5 (mg/L)
72
<2
90
14
6
16
Table 5 Salt deposition rate at A25 site using a wet candle device
Period of determination
Feb 19 until Apr 1, 2008
Apr 2 until May 26, 2008
Salt deposition rate (mg/m 2 day)
59
84
In terms of general climacteric conditions that may influence the salinity/organic
matter levels, the two monitoring periods took place during the autumn and the
winter seasons. May the higher values of organic matter be correlated with the high
values of salinity? At this stage of the research, it is not possible to answer the ques-
tion, although the facts indicate that such relation is possible.
The BOD 5 concentration is independent from the salt deposition, and although
showing a higher maximum value in 2008 (90 mg/L), average and median (14 and
6 mg/L) values are lower compared to the 2003/04 study (25 and 12 mg/L).
The 2008 monitoring study includes the COT determination, a parameter
directly associated with the organic matter. Comparing the COT results obtained at
A25 with the values found in the literature [9-11] , they indicate that highway run-
off from A25 has high levels of COT, meaning higher levels of organic matter.
The A25 oil and grease values showed a very high standard deviation (7,260
mg/L) and a minimum concentration below 0.184 mg/L. The average and median
are of 1.359 and 0.810 mg/L, respectively. The oil and grease are not commonly
measured in Portugal. Concentrations obtained in other studies were summarized
in Table 6 . As can be observed, the levels of concentrations are much below the
measurements at A25. Future sampling at this site, and other G-Terra case studies,
may help to understand the sources of oil and grease and their processes within the
road environment.
All the oil and grease samples concentrations are below the Portuguese law for
wastewater point discharges levels. However, concerning the SST, COD and BOD 5
 
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