Rapid and sensitive molecular methods (mostly PCR based) introduced in the
1990s to detect pathogens in water [49] are still facing issues related to sampling
DNA preparation, standardising protocols, and assessing only viable. Consequently,
the use of indicators is still necessary for the assessment of both water quality and
Table 1 Heavy metal concentrations of wastewater irrigated-soils detected in several field studies,
considering the irrigation length period (short and long term), type of wastewater (source), and the
effects on soil and plant
Metal
Soil guidelines
(mg kg
À1
)
Case study (mg kg
À1
) Source
Period
Effect on
EUs
a
IR
b
Soil Plant
Cd
3.0
3.0
c
d
0.2 [41]
PTE effluent L-T
+
3.8 [42]
UE
L-T
+#
5–13 [39]
TE
S-T
+
d
0.037 [40]
STE
S-T
À
Cr
150
100
c
112.8 [42]
UE
L-T
+#
936.5 [43]
UE
L-T
+
À
Cu
140
100
c
d
35.0 [41]
PTE
L-T
+
75.0 [42]
UE
L-T
+#
8–16 [39]
TE
S-T
+
d
1.25 [40]
STE
S-T
À
d
94.4 [43]
UE
L-T
+
+"
Ni
75
50
c
d
5.76 [41]
PTE
L-T
+
703.2 [42]
UE
L-T
+#
d
0.80 [40]
STE
S-T
+
55.6 [43]
UE
L-T
+
+"
Pb
300
100
c
d
12.8 [41]
PTE
L-T
+
135.6 [42]
UE
L-T
+#
126 [39]
TE
S-T
À
d
2.0 [40]
STE
S-T
+
94 [43]
UE
L-T
+
+"
Zn
300
300
c
78.2 [42]
UE
L-T
+#
70–80 [39]
TE
S-T
À
d
1.25 [40]
STE
S-T
À
285.37 [43]
UE
L-T
+
+"
Mn
2,000
e
d
5.0 [40]
STE
S-T
+
77.5 [43]
UE
L-T
+
+"
PTE primary treated effluent, UE untreated effluent, TE treated wastewater, STE secondary treated
effluent, L-T long-time trial, S-T short-time trial
+, the concentration increases compared to control; +#, the concentration increase than control,
below guideline thresholds [96]; +", the concentration increase than control, above guideline
thresholds [96]; 2, the concentration does not increase compared to control
a EUs European union standards (EU 2002) [93]
b
IR international references [94, 95]
c [95]
d
Extractable content (DTPA method)
e [94]
86
G. Gatta et al.