Environmental Engineering Reference
In-Depth Information
Table 1
Characteristics of the three storm events at the Järnbrott pond, 2004
Rain depth
(mm)
Antecedent dry
period (days)
Stormwater
volumes (m
3
)
Date
10 October
11
3
15,000
18 November
9
2
12,000
24 November
12
1
16,000
events are given in Table
1
, including rain depths, dry periods (number of days
antecedent the rain event) and stormwater volumes.
Laboratory Analyses
Event mean concentrations (EMC) for the contaminants studied were determined
by analyses of samples pooled to one composite sample prior to the analysis.
Samples were analyzed for total suspended solids (TSS), volatile suspended solids
(VSS) and heavy metals (zinc, copper, lead, cadmium, nickel and cobalt). Nitrogen
analysis included measurements on total nitrogen (total-N), nitrite (NO
2
-N), nitrate
(NO
3
-N) and ammonium (NH
4
-N), and the phosphorous analyses included total
phosphorus (total-P) and phosphate phosphorus (PO
4
-P). The organic contaminants of
PAH, including the 16 specific US EPA-PAH
[12]
, were also analyzed. Concentrations
of these contaminants were given as µg/L.
Microbial analyses included total coliforms,
E. coli
and sulphite-reducing
clostridia (SRC) (during three events) as well as intestinal enterococci (IE) and
bacteriophages (during two of the events). Total coliforms and
E. coli
were ana-
lyzed with the membrane filtration method
[13]
, which also was used in the analy-
sis for intestinal enterococci
[14]
. Sulphite-reducing clostridia were analyzed
according to the standard
[15]
except for the preheating to exclude vegetative cells.
Bacteriophages analysed included somatic coliphages (SC) and F-specific RNA
coliphages, and samples were sterile-filtrated (45 mm high-flow filter) to remove
debris and bacteria prior to the standard analyses
[16]
. Microbial concentrations
given as colony forming units (CFU/100 mL, bacteria) and plack-forming units
(PFU/100 mL, bacteriophages) were presented on a logarithmic scale (log
10
) and
for comparison reasons also the chemical and physical contaminants are presented
on a logarithmic scale (log
10
).
Data Processing
The contaminant loads, based on a mass balance for the inflow and outflow of the
pond, were determined for the three events. A mass balance approach was applied
to determine the contaminant load (M
i
) calculated as the stormwater volume (V
i
),
