Large-scale water reuse for agricultural irrigation in Milan from the San Rocco Waste Water Treatment Plant
4 June, 2050
Waste water source
The wastewater source is a mixture of two main streams of municipal wastewater. About 40 % of the municipal wastewater of the municipality of Milan and part of discharge of the municipality of Settimo Milanese flow into the San Rocco wastewater treatment plant. The plant started full operation in December 2004.
The water quality of the effluent is monitored extensively on a daily basis. Besides internal monitoring, also controls from the Milan town administration and the regional environmental agency verify conformity of the effluent. The Italian regulations define that E.coli might not exceed 10CFU/100ml in 80% of the samples when used for unrestricted irrigation. Some water quality parameters for the influent and effluent are visualized in the following table.
| Parameter | IN (mg/l) | OUT (mg/l) |
| BOD5 | 168 | 10 |
| Total N | 35 | 10 |
| Total P | 35 | 1 |
| TSS | 162 | 10 |
From an agronomical perspective, the reclaimed water has adequate values with low sodicity, low conductivity, low toxic ions (boron, chloride, sodium) as well as low concentration of heavy metals.
Distribution System
Pumps bring the water from the San Rocco reclamation facility towards two channels located 1.3 km further. From there, the water is provided to the fields via an extensive (already-existing) network of open canals. This water transport is gravity –based.
Farming system
The main crops irrigated with reclaimed water in the area are corn (45%), rice (15%) and meadows and grasslands (40%). The area is located South of Milan and characterised by extensive and traditional forage crops and cereals. The first are usually irrigated by high pressure jets or low-pressure pivots, while grassland and rice are flooded. This agricultural area of particular landscape-environmental value is equally marked by the presence of a dense hydrographic network of irrigation ditches geb by the canal Roggia Ticinello.
Waste water treatment description
Nutrient removal : Tertiary treatment technologies remove Nitrogen and Phosphorus to avoid eutrophication in the Po valley, although relevant fertilizers for crops. N removal is performed by activated sludge recirculation with nitrification-oxidation followed by denitrification followed by the final decantation P removal is carried out by chemical precipitation and gravity sand filtering.
Pesticide removal : none
Disinfection : Disinfection takes place using UV radiation. A low UV dose is applied for water discharge of the effluent in the Lambro Meridionale river during the winter, while a higher UV dose is needed when the effluent is reused for agriculture or discharged in the river during the summer.
Suspended solids removal : The tertiary rapid sand filtration removes besides P, the suspended solids.
Other : Odour removal
Capacity
In 2011, 72.8 hm3 water was treated in the facility of San Rocco. About half of this volume was produced during the irrigation period (during the summer months). Furthermore, a share of this volume was discharged into the river, resulting in 11.4 hm3 of annual reclaimed water for irrigation.
Extent of the agricultural beneficiaries
24,630 ha agricultural area is irrigated with water originating from the San Rocco reclamation facility.
Costs
The total capital cost for the wastewater treatment plant (including reclamation facility) of San Rocco amounted 136.2 million euros. The Milan town administration financed this amount.
Operational costs are estimated at 0.115 euro/m³, from which energy represents the largest component (> 40% of the operational costs).
Type of agreement
The farmer are grouped in farmers’ associations in charge of the agricultural irrigation. The Lombardy region delivers the reclaimed water for free to the farmers, and only charges the pumping costs to distribute the water from the reclamation facility to the main channels (27,000 euros/year for the farmers associations).
Scientific results
Mazzini, R., Pedrazzi, L. and Lazarova, V. 2013. Production of high quality recycled water for agricultural irrigation in Milan. In: Lazarova, V., Asano, T., Bahri, A. and Anderson, J. (Eds) Milestones in water reuse: the best success stories. London: IWA publishing, p. 179- 190.
Castiglioni, S., Bagnati, R., Fanelli, R., Pomati, F., Calamari, D., & Zuccato, E. (2006). Removal of Pharmaceuticals in Sewage Treatment Plants in Italy. Environmental Science & Technology, 40, 357–363. https://doi.org/10.1021/es050991m
