efficiencies of 90–95% and allowing up to 30–40% water saving as compared to
sprinkler and surface irrigation systems. Localised irrigation systems save water
through mitigation of water loss through evaporation from the soil.
Drip irrigation systems are characterised by more frequent applications of smaller
water volumes, thus ensuring a low and nearly constant soil water tension in the root
zone (about À0.1/À0.2 MPa). These aspects mitigate the problems of salt concentration in the root zone due to possible salt addition from wastewater application.
Finally, drip irrigation is considered the more suitable irrigation method to use
with treated wastewater because it minimises toxicity hazards for plants, reduces the
contamination risk for edible crop products, and mitigates hazards to human health
by minimising direct contact with the wastewater. These latter advantages can also
be achieved by adopting the sub-irrigation method, with the concurrent benefits of
lower water loss to evaporation (15–30%), maximum irrigation efficiency, and lower
visual/environmental impact of wastewater distribution.
Experimental trials comparing wastewater application by drip and subsurface
irrigation methods did not show significant differences in the irrigated crop yields or
for the microbiological contamination levels of the soil and the marketable crop
[3, 19, 60].
Drip irrigation methods for crop irrigation with wastewater present a suitable and
useful technical solution applicable to all types of soil and crops. However, wastewater containing high total dissolved solids (TDS) can cause nozzle clogging in drip
irrigation systems and require the adoption of appropriate filtering systems and
treatment of the irrigation water with acid and/or chlorine [61].
Table 4 details the factors influencing the choice of irrigation method, the safety
measures that farmers must adopt for treated wastewater, and recommendations for
use relative to crop type.
4 Effects of Wastewater on Soil-Plant System
4.1 Effects on Physical and Chemical Characteristics
of the Soil
Many studies have been carried out to determine the effects of wastewater use on
various soil characteristics. Particular emphasis has been placed by some authors on
long-term variations in soil physical and chemical properties [62, 63].
The physical and mechanical properties of the soil (such as porosity, stability of
aggregates, water retention, infiltration, and permeability) are very sensitive to
organic matter and exchangeable ion types present in the irrigation water [64, 65].
The organic materials added by wastewater irrigation can accumulate in the soil
fraction where intense microbial degradation and transformation of these substances
occur, leading to the formation of humic compounds and the release of mineral
elements. The mineral elements released in the soil following organic substance
90
G. Gatta et al.
sprinkler and surface irrigation systems. Localised irrigation systems save water
through mitigation of water loss through evaporation from the soil.
Drip irrigation systems are characterised by more frequent applications of smaller
water volumes, thus ensuring a low and nearly constant soil water tension in the root
zone (about À0.1/À0.2 MPa). These aspects mitigate the problems of salt concentration in the root zone due to possible salt addition from wastewater application.
Finally, drip irrigation is considered the more suitable irrigation method to use
with treated wastewater because it minimises toxicity hazards for plants, reduces the
contamination risk for edible crop products, and mitigates hazards to human health
by minimising direct contact with the wastewater. These latter advantages can also
be achieved by adopting the sub-irrigation method, with the concurrent benefits of
lower water loss to evaporation (15–30%), maximum irrigation efficiency, and lower
visual/environmental impact of wastewater distribution.
Experimental trials comparing wastewater application by drip and subsurface
irrigation methods did not show significant differences in the irrigated crop yields or
for the microbiological contamination levels of the soil and the marketable crop
[3, 19, 60].
Drip irrigation methods for crop irrigation with wastewater present a suitable and
useful technical solution applicable to all types of soil and crops. However, wastewater containing high total dissolved solids (TDS) can cause nozzle clogging in drip
irrigation systems and require the adoption of appropriate filtering systems and
treatment of the irrigation water with acid and/or chlorine [61].
Table 4 details the factors influencing the choice of irrigation method, the safety
measures that farmers must adopt for treated wastewater, and recommendations for
use relative to crop type.
4 Effects of Wastewater on Soil-Plant System
4.1 Effects on Physical and Chemical Characteristics
of the Soil
Many studies have been carried out to determine the effects of wastewater use on
various soil characteristics. Particular emphasis has been placed by some authors on
long-term variations in soil physical and chemical properties [62, 63].
The physical and mechanical properties of the soil (such as porosity, stability of
aggregates, water retention, infiltration, and permeability) are very sensitive to
organic matter and exchangeable ion types present in the irrigation water [64, 65].
The organic materials added by wastewater irrigation can accumulate in the soil
fraction where intense microbial degradation and transformation of these substances
occur, leading to the formation of humic compounds and the release of mineral
elements. The mineral elements released in the soil following organic substance
90
G. Gatta et al.