2 Main Advantages and Risks of Treated Wastewater
Reuse in Agriculture
2.1 Supply of Mineral Nutrients for Crop Growth
The quantity of crop nutrients supplied to the soil by wastewater (municipal or agroindustrial) in irrigation must be carefully considered. The concentrations of the
primary mineral nutrients necessary for plant growth (such as N, P and K) in
municipal and agro-industrial wastewater vary significantly according to the quality
of the wastewater. Generally, nitrogen concentrations vary from 20 to 35 mg L
À1 ,
phosphorus concentrations from 3 to 10 mg L
À1 [10, 16–19], and potassium
concentrations from 10 to 25 mg L
À1 [18, 20].
Wastewater effluents can also contain high levels of micro-nutrients (e.g., boron,
iron, copper, zinc, manganese, and molybdenum), which are essential for the growth
and development of crops. The effects of macro- and micronutrients supplied with
wastewaters can change in relation to the crop cycle (i.e., vegetable annual crop vs
tree crops) and to different intake rate of nutrients.
As for vegetable crops, in a study carried out on a succession of processing
tomato (Lycopersicon esculentum Mill.) and broccoli (Brassica oleracea L. var.
italica) crops, secondary and tertiary treated agro-industrial wastewaters were compared with groundwater irrigation. The findings indicated that treated agro-industrial
effluents supplied greater amounts of mineral nutrients (N-NH 4 , N-NO 3 , and K
+ ) to
the crops [20]. The authors suggested that the use of treated agro-industrial effluents
as irrigation water could reduce the need for supplementary mineral compounds
through chemical fertilisation.
Other research has shown that treated wastewater irrigation of vegetable crops
(lettuce) could successfully increase the availability of irrigation water and increase
the concentration of some soil nutrients (K, Ca, H, Al, and S) [21].
In a study of the effects of secondary and tertiary treated wastewater irrigation on
globe artichoke crop performance, Gatta et al. [19] reported that the total inorganic
nitrogen (i.e. N-NH 4 , N-NO 3 ) supplied to the crops through treated irrigation water
was on average 95 kg ha
À1 and 66 kg ha
À1 for the secondary and tertiary wastewaters, respectively, representing approximately 25% to 17% of the nitrogen requirements of the artichoke crop.
As for tree crops, Vivaldi et al. [22] reported the effects of irrigation by treated
wastewater and the deficit irrigation strategy on almond trees (Prunus dulcis L.). The
results of this study showed that the nutritional contribution of treated wastewater to
irrigated soil was 35.8 kg ha
À1 of NO 3
À , 4.41 kg ha
À1 of PO 4
3À , and 149.9 kg ha
À1
of K
+ . Other similar studies on tree crops irrigated by reclaimed water have reported
that high concentrations of macro- and meso-nutrients supplied to soil through
wastewater could facilitate a significant reduction in fertiliser application [23–25].
The supply of mineral nutrients by wastewater application to cultivated species
represents a significant agronomic value of this water resource. However, this benefit
must be assessed with particular attention to the possibility of plant nutritional
Wastewater Reuse in Agriculture: Effects on Soil-Plant System Properties
83
Reuse in Agriculture
2.1 Supply of Mineral Nutrients for Crop Growth
The quantity of crop nutrients supplied to the soil by wastewater (municipal or agroindustrial) in irrigation must be carefully considered. The concentrations of the
primary mineral nutrients necessary for plant growth (such as N, P and K) in
municipal and agro-industrial wastewater vary significantly according to the quality
of the wastewater. Generally, nitrogen concentrations vary from 20 to 35 mg L
À1 ,
phosphorus concentrations from 3 to 10 mg L
À1 [10, 16–19], and potassium
concentrations from 10 to 25 mg L
À1 [18, 20].
Wastewater effluents can also contain high levels of micro-nutrients (e.g., boron,
iron, copper, zinc, manganese, and molybdenum), which are essential for the growth
and development of crops. The effects of macro- and micronutrients supplied with
wastewaters can change in relation to the crop cycle (i.e., vegetable annual crop vs
tree crops) and to different intake rate of nutrients.
As for vegetable crops, in a study carried out on a succession of processing
tomato (Lycopersicon esculentum Mill.) and broccoli (Brassica oleracea L. var.
italica) crops, secondary and tertiary treated agro-industrial wastewaters were compared with groundwater irrigation. The findings indicated that treated agro-industrial
effluents supplied greater amounts of mineral nutrients (N-NH 4 , N-NO 3 , and K
+ ) to
the crops [20]. The authors suggested that the use of treated agro-industrial effluents
as irrigation water could reduce the need for supplementary mineral compounds
through chemical fertilisation.
Other research has shown that treated wastewater irrigation of vegetable crops
(lettuce) could successfully increase the availability of irrigation water and increase
the concentration of some soil nutrients (K, Ca, H, Al, and S) [21].
In a study of the effects of secondary and tertiary treated wastewater irrigation on
globe artichoke crop performance, Gatta et al. [19] reported that the total inorganic
nitrogen (i.e. N-NH 4 , N-NO 3 ) supplied to the crops through treated irrigation water
was on average 95 kg ha
À1 and 66 kg ha
À1 for the secondary and tertiary wastewaters, respectively, representing approximately 25% to 17% of the nitrogen requirements of the artichoke crop.
As for tree crops, Vivaldi et al. [22] reported the effects of irrigation by treated
wastewater and the deficit irrigation strategy on almond trees (Prunus dulcis L.). The
results of this study showed that the nutritional contribution of treated wastewater to
irrigated soil was 35.8 kg ha
À1 of NO 3
À , 4.41 kg ha
À1 of PO 4
3À , and 149.9 kg ha
À1
of K
+ . Other similar studies on tree crops irrigated by reclaimed water have reported
that high concentrations of macro- and meso-nutrients supplied to soil through
wastewater could facilitate a significant reduction in fertiliser application [23–25].
The supply of mineral nutrients by wastewater application to cultivated species
represents a significant agronomic value of this water resource. However, this benefit
must be assessed with particular attention to the possibility of plant nutritional
Wastewater Reuse in Agriculture: Effects on Soil-Plant System Properties
83