In addition to the efficacy of the water treatment prior to reuse, it must be
considered that the survival rate of potential pathogenic microorganisms in the
treated water is highly variable, depending on the type of microorganism, water
stocking and distribution system, environmental conditions, and other variables.
Moreover, irrigation water is only one of the potential sources of contamination
for cultivated crops, and the safe reuse of wastewater alone is not sufficient to
eliminate risks related to other sources of potential contamination [57]. Therefore,
an integrative approach aiming to assess and evaluate risks through microbiological
laboratory tests, epidemiological studies, and quantitative microbiological risk
assessment (QMRA) is necessary to elaborate novel safety rules for wastewater
reuse in agriculture [2]. A balance must be struck between excessive restrictions that
hamper the reuse of wastewater reuse and a lack of safety procedures that could lead
to foodborne outbreaks; balanced legislation should therefore be a priority on the
agenda of national and international regulation agencies. For example, a scientific
study aiming at modelling the impact of recent FDA rules on the microbial safety of
lettuce production illustrated how less stringent microbial parameters could maintain
safety levels suitable for consumption [58].
3 Agronomic Practices Related to Treated Wastewater
Reuse: The Role of Irrigation Methods
The use of treated wastewater for crop irrigation requires proper management of
these resources at the farm and at the district level. The irrigation strategies for crops
should consider the characteristics of the available water sources. Irrigation variables
such as irrigation interval, irrigation volume, and seasonal irrigation volume should
be established according to the adopted irrigation method and regime (full irrigation
or deficit irrigation), temporal availability of the water source, climatic trends, and
crop phenological stage.
In the use of treated municipal and agro-industrial wastewater, the definition of
irrigation variables is based on the same principles and criteria used for conventional
water [59]. For this reason, the irrigation scheduling strategies adopted for conventional water use are also considered valid for wastewater irrigation reuse. Regardless,
the selection of adequate irrigation techniques for wastewater use plays an important
role in the qualitative and quantitative increase of yields, water resource preservation, and environment protection.
The choice of irrigation system is related to factors including the socio-economic
condition and the orographic characteristics of the agricultural area, the adopted crop
system, the level of agricultural mechanisation of the farm, and the availability and
qualitative properties of the irrigation water resource.
For irrigation with treated wastewater, the most suitable methods are drip and
subsurface irrigation systems. These methods offer several advantages. First, the
irrigation water efficiency of drip irrigation systems is very high, achieving
Wastewater Reuse in Agriculture: Effects on Soil-Plant System Properties
89
considered that the survival rate of potential pathogenic microorganisms in the
treated water is highly variable, depending on the type of microorganism, water
stocking and distribution system, environmental conditions, and other variables.
Moreover, irrigation water is only one of the potential sources of contamination
for cultivated crops, and the safe reuse of wastewater alone is not sufficient to
eliminate risks related to other sources of potential contamination [57]. Therefore,
an integrative approach aiming to assess and evaluate risks through microbiological
laboratory tests, epidemiological studies, and quantitative microbiological risk
assessment (QMRA) is necessary to elaborate novel safety rules for wastewater
reuse in agriculture [2]. A balance must be struck between excessive restrictions that
hamper the reuse of wastewater reuse and a lack of safety procedures that could lead
to foodborne outbreaks; balanced legislation should therefore be a priority on the
agenda of national and international regulation agencies. For example, a scientific
study aiming at modelling the impact of recent FDA rules on the microbial safety of
lettuce production illustrated how less stringent microbial parameters could maintain
safety levels suitable for consumption [58].
3 Agronomic Practices Related to Treated Wastewater
Reuse: The Role of Irrigation Methods
The use of treated wastewater for crop irrigation requires proper management of
these resources at the farm and at the district level. The irrigation strategies for crops
should consider the characteristics of the available water sources. Irrigation variables
such as irrigation interval, irrigation volume, and seasonal irrigation volume should
be established according to the adopted irrigation method and regime (full irrigation
or deficit irrigation), temporal availability of the water source, climatic trends, and
crop phenological stage.
In the use of treated municipal and agro-industrial wastewater, the definition of
irrigation variables is based on the same principles and criteria used for conventional
water [59]. For this reason, the irrigation scheduling strategies adopted for conventional water use are also considered valid for wastewater irrigation reuse. Regardless,
the selection of adequate irrigation techniques for wastewater use plays an important
role in the qualitative and quantitative increase of yields, water resource preservation, and environment protection.
The choice of irrigation system is related to factors including the socio-economic
condition and the orographic characteristics of the agricultural area, the adopted crop
system, the level of agricultural mechanisation of the farm, and the availability and
qualitative properties of the irrigation water resource.
For irrigation with treated wastewater, the most suitable methods are drip and
subsurface irrigation systems. These methods offer several advantages. First, the
irrigation water efficiency of drip irrigation systems is very high, achieving
Wastewater Reuse in Agriculture: Effects on Soil-Plant System Properties
89