On the contrary, other authors [13] found concentrations of Ni, Pb, Cd, and Cr in
the edible portions of okra vegetable crop grown on a soil irrigated with treated
wastewater well above the safe limit and a Health Risk Index (HRI) higher than
1, indicating a potential health risk. Similarly, heavy metal concentrations (Zn, Pb
and Cd) several times higher than the WHO prescribed permissible limits were
observed by Uddin et al. [91] in edible portions of red amaranth (Amaranthus
cruentus L.) and tomato irrigated with industrial wastewater.
The results of several research activities on wastewaters (untreated and treated)
clearly highlight that these irrigation sources are a rich source of nutrients and most
crops give higher than hypothesized yields with the adoption of a wastewater
irrigation system, diminishing the requirement for synthetic fertilizers and bringing
about reduction of investment cost to farmers. Nevertheless, if the estimated nitrogen
provided for harvesting by the wastewater system exceeds the required dosage for
the ideal yields, it may reinforce vegetative development, but it may delay growth
and cause adverse effect on crop yield [92]. The presence of toxic elements in
wastewater must be also considered since they are hazardous and might be poisonous to plants in high amounts and to human health. Therefore, evaluating the impacts
of wastewater irrigation sources on characteristics of crop yield in the different
agronomic situations is fundamental in a perspective of wastewater irrigation system
development, under the best agronomic and water management practices.
5 Final Considerations
In this chapter, the possibility of recovery of wastewater for irrigation purposes was
illustrated and discussed, highlighting the advantages, disadvantages, and possible
risks of the practice. Interest in wastewater reuse is continuously developing and
derives from the growing worldwide demand for water resources, particularly for
food crop irrigation, and not restricted to countries characterised by water scarcity.
The primary results of past and recent research on irrigation reuse of treated
wastewater, both of municipal and agro-industrial origin, can be summarised as
follows:
• The reuse of treated municipal and agro-industrial wastewater in agriculture can
mitigate the increasing scarcity of conventional water resources for a particularly
water-demanding sector such as agriculture; agricultural wastewater use could
improve the chemical fertility of the irrigated soils; treated wastewater could
represent a resource of strategic importance in terms of nutrient availability
(e.g. N, P, and K) for the irrigated plants. However, this benefit must be assessed
with particular attention because can cause plant nutritional imbalance and
phytotoxicity.
• The use of treated wastewater in agriculture (with particular reference to industrial or agro-industrial wastewaters) can lead to heavy metal accumulation in the
soil following long periods of application. Therefore, the monitoring of heavy
96
G. Gatta et al.
the edible portions of okra vegetable crop grown on a soil irrigated with treated
wastewater well above the safe limit and a Health Risk Index (HRI) higher than
1, indicating a potential health risk. Similarly, heavy metal concentrations (Zn, Pb
and Cd) several times higher than the WHO prescribed permissible limits were
observed by Uddin et al. [91] in edible portions of red amaranth (Amaranthus
cruentus L.) and tomato irrigated with industrial wastewater.
The results of several research activities on wastewaters (untreated and treated)
clearly highlight that these irrigation sources are a rich source of nutrients and most
crops give higher than hypothesized yields with the adoption of a wastewater
irrigation system, diminishing the requirement for synthetic fertilizers and bringing
about reduction of investment cost to farmers. Nevertheless, if the estimated nitrogen
provided for harvesting by the wastewater system exceeds the required dosage for
the ideal yields, it may reinforce vegetative development, but it may delay growth
and cause adverse effect on crop yield [92]. The presence of toxic elements in
wastewater must be also considered since they are hazardous and might be poisonous to plants in high amounts and to human health. Therefore, evaluating the impacts
of wastewater irrigation sources on characteristics of crop yield in the different
agronomic situations is fundamental in a perspective of wastewater irrigation system
development, under the best agronomic and water management practices.
5 Final Considerations
In this chapter, the possibility of recovery of wastewater for irrigation purposes was
illustrated and discussed, highlighting the advantages, disadvantages, and possible
risks of the practice. Interest in wastewater reuse is continuously developing and
derives from the growing worldwide demand for water resources, particularly for
food crop irrigation, and not restricted to countries characterised by water scarcity.
The primary results of past and recent research on irrigation reuse of treated
wastewater, both of municipal and agro-industrial origin, can be summarised as
follows:
• The reuse of treated municipal and agro-industrial wastewater in agriculture can
mitigate the increasing scarcity of conventional water resources for a particularly
water-demanding sector such as agriculture; agricultural wastewater use could
improve the chemical fertility of the irrigated soils; treated wastewater could
represent a resource of strategic importance in terms of nutrient availability
(e.g. N, P, and K) for the irrigated plants. However, this benefit must be assessed
with particular attention because can cause plant nutritional imbalance and
phytotoxicity.
• The use of treated wastewater in agriculture (with particular reference to industrial or agro-industrial wastewaters) can lead to heavy metal accumulation in the
soil following long periods of application. Therefore, the monitoring of heavy
96
G. Gatta et al.