Environmental Engineering Reference
In-Depth Information
Table 11.3. Results of the test for significant
difference of mean water quality concentrations and
ranking.
Parameter
Site 1
Site 2
Site 3
Site 4
T (ºC)
A
A
A
A
EC (micro S/cm)
B
A
C
A
pH
A
A
B
A
Turbidity (NTU)
D
B
A
C
TSS (mg/l)
B
A
A
B
DO (mg/l)
AB
A
C
B
BOD
5
(mg/l)
C
BC
A
B
Nitrate (mg/l)
D
B
A
C
Ammonia (mg/l)
C
C
A
B
Ortho-P (mg/l)
D
B
A
C
TC (number/100 ml)
B
B
A
B
FC (number/100 ml)
B
B
A
B
Chlorides (mg/l)
B
A
A
B
Sulfates (mg/l)
C
A
B
C
Nutrients variations (Fig.11.9b) follow the trend with the highest concentrations of the
three observed parameters at site 3. The significantly increased concentrations of
nutrients at site 2 could be associated with informal discharges from blocked sewer
systems. It is also possible that some of the industries are contributing as well. The
highest concentration, observed at site 3, has an alarming value and is attributed to the
malfunctioning of the treatment plant. The observed nitrate concentrations are very high,
compared to other similar cases, presented in previous chapters. It could be expected that
with prevailing anaerobic conditions at the treatment plant, nitrification processes would
be suppressed, leading to lower nitrate concentrations. It is possible that the generally
high DO concentrations due to the steep slop, could help in boosting this process.
Additional investigations should be performed to determine the source of the nitrates
observed during this study.
A very high bacteriological contamination has been observed at site 3 (Fig.11.9c), the
major source being the treatment plant. At site 2, the presence of TC and FC could be
associated with the solid wastes, spread along the riverbanks, and informal discharges
from sewers and industries. At the control point, the TC and FC counts were negligible,
and at site 4, the TC and FC counts were less than 10 numbers/100 ml.
In general, a significant increase in the water quality concentrations between the
control point and sites 2 and 3 was found with respect to almost all measured parameters,
showing the presence of diffuse pollution from urban runoff and from waste material
