• The water supply is a corporation formed by plants and human resources and it has the purpose to gain and to distribute drinkable water to a community, always in a sufficient quantity and fit to the human consumption according to the laws in force.
The water supply can have different institutional forms:
• management directed by public corporation (Commune)
• municipalized firms or stock companies to total public control
• management submitted to the privacies (S.p.A.)
Anyway since it supplies essential goods for the life of the citizens, it doesn't have purpose of profit but it has to assure the water
restocking with the rates as low as possible according to the continuity and the quality of the supplied service.
Water supply can be assimilated to:
• An extractive industry: when it gains the water and it
distributes it as it is in nature (f.e. ancient Roman aqueducts)
• A chemical industry: when it gains a raw water and it submits it to complexes treatments to make it drinkable (f.e. aqueducts which use waters of surface)
The greater part of the existing aqueducts place in intermediate position among the extreme cases above pointed out.
MILAN WATER SUPPLY
• Milan is situated in the center of the Po river
plain, in a zone very rich in waters both superficial and underground
• The most abundant and proper resource for the drinkable use is contained in the underground water table and it is which that the Milaneses have been used for a long time
The water table
– The subsoil of the Milan lowland is constituted by sandy gravelly dregs, in which are intercalated lenses and clay benches and conglomerates, which are formed during the quaternary era.
– After these last, there are the sediments of the Pliocene, which, for example, in correspondence of the city
center, are about 800 meters under the sea level.
– From the hydrogeological point of view those that interest are the loose deposits of the continental quaternary and more particularly the first 100-120 meters from the plan of country, which contain the principal water resources exploited («traditional acquifer»)
Historical information on the aqueduct
• The public water supply has been constituted in 1888.
• The aqueduct uses wells which draw water from the “traditional” acquifer among 40 and 110 meters deep from the plan of country.
In the last years water is drawn by the acquifer “deep” among 110 and 180m
• The Milanese aqueduct, extractive type initially, from over one decade is endowed with treatment system and about 80% of the distributed water is treated.
• Up to June 30th 2003 the aqueduct has been managed directly from the Ufficio Tecnico Comunale ; afterwards it has been entrusted to MM SpA, a society 100% controlled by Comune di Milano.
TYPE STRUCTURE OF AN PUMPING STATION
OPERATION SCHEME – A.P. SAN SIRO PLANT
SAN SIRO PLANT
Types of well
Scheme multicolumn
well
-
Lambro
Plant
MAP OF PLANTS AND WELLS
CHANGES AT WATER-TABLE LEVELS
The quantitative problem
CHANGES AT WATER-TABLE LEVELS
The quantitative problem
The water-table chemical pollution
• The main contaminants:
– Chromium hexavalent
– Organochlorurate compounds :
trichloroethylene, tetrachloroethylene, chloroform etc.
– Pesticide: atrazine,simazine,
2,6-dichlorobenzamide, bentazone etc.
Italian legislation concerning the drinkable water quality
• The Italian laws receive the European
Community directives about the quality of waters destined to the human consumption.
• The DPR 236 /88 applied the Directive CE of 1980
• The DLgs 31/01 applies the Directive n°83
of 3 november 1998 and came into force on
December 25th 2003
TELEMETRY SYSTEM FOR PLANTS’ MANAGEMENT
CIVIC DISTRIBUTIVE HYDRICAL NETWORK
Pumping station scheme with different
type water treatment plants
MAP OF WATERWORKS WITH TREATMENT SYSTEM
Water supply principal data- 2008
SERVED COMMUNES Milano and part of Corsico and Peschiera Borromeo RESIDENT POPULATION 1.330.000
TYPE OF USED WATER 100 % water of water table
NUMBER OF PUMPING STATIONS 31
TOTAL NUMBER OF WELLS 570
TOTAL VOLUME OF ACCUMULATION TUBS mc. 180.000 TOTAL VOLUME OF PUMPED WATER IN ONE YEAR mc. 250.000.000
DAILY WATER ENDOWMENT FOR INHABITANT l/g ab 514
AVERAGE FLOW SUPPLIED mc/s 7,92
MAXIMUM FLOW SUPPLIED mc/s 21
AVERAGE DAILY VOLUME PUMPED about mc/g 680.000
MAXIMUM DAILY VOLUME PUMPED about mc/g 950.000
MINIMUM VOLUME PUMPED about mc/g 450.000
LENGTH OF THE DISTRIBUTIVE NETWORK Km. 2.340
MATERIALS USED IN THE NETWORK Steel, Gray cast iron e Spheroidal cast iron
USED DIAMETERS from 80 mm. to 1200 mm.
NETWORK LEAKS 7,92% of volume pumped in network
FLOW OF WELL ELECTROPUMPS l/s from 30 to 40 FLOW OF WATERWORKS ELECTROPUMPS l/s from 250 to 400 RADIO-CONTROL PLANTS OF PUMPING STATION n° 5
RADIO-CONTROLLED AND PLANTS AUTOMIZED n° 28 su 31
ACTIVATED CARBON TREATMENT SYSTEM n° 16
TREATMENT SYSTEM BY STRIPPING TOWERS n° 2
TREATMENT SYSTEM WITH STRIPPING TOWERS AND ACTIVATED CARBON FILTERS n° 3
PERCENTAGE OF TREATED WATER 80% of water
QUADRO DEI TRATTAMENTI
Volumi trattati suddivisi per tipologia di trattamenti
Nel corso del 2007 sono stati erogati 236.577.855 m3 dei quali 181.676.557 trattati.
In particolare sono stati prodotti:
con filtrazioni su carboni attivi 129.476.866;
con torri d’aerazione 31.823.819;
con carboni attivi e successiva aerazione in serie 20.376.572;
con osmosi inversa ( 2 linee funzionanti ) 1.342.600.
Carboni attivi Aerazione
Carboni attivi + aerazione
Osmosi inversa
Schema delle torri di aerazione
Schema struttura di filtrazione dell’aria
Dati dimensionali torri aerazione
• Tipo Torre A) B) C)
• Materiale inox inox polietilene
• Altezza 5,75 6,00 7,00
• Diametro 3,00 3,00 3,00
• Altezza Letto 2,00 3,00 2,00
• Altezza Camino 1,30 1,00 1,00
• Diametro Camino 2,00 1,20 1,60-0,70
• Superf.di Contatto 1555m2 2940m2 1400m2
• Numero Ugelli 40 30 81
• Portata Acqua 360mc/h 360mc/h 360mc/h
• Portata Aria 14.000mc/h 16.000mc/h 14.400mc/h
• Rapporto Aria/Acqua 38,88 44,44 40
• Pressione Ugelli 1 bar 1 bar 1 bar
Efficienza torri di aerazione
IMPIANTO SOMMA C.O.V. SOMMA C.O.V. EFFICIENZA DIFFERENZA INGRESSO=E USCITA=U (E-U)/Ex100 DAL 95%
NOVARA 73,21 ppb 5,17 ppb 92,93 % - 2,07 % CHIUSA- 144,66 ppb 6,31 ppb 95,63 % + 0,63 % BELLA
CIMABUE 110,42 ppb 10,54 ppb 90,45 % - 4,55 % COMASINA 132 ppb 3,28 ppb 95,96 % + 0,96 % SUZZANI 82,23 ppb 8,76 ppb 89,34 % - 5,66 % VIALBA 46,23 ppb 2,08 ppb 95,50 % +0,50%
Impianto immissione CO 2 Suzzani
Impianti a osmosi inversa
• L’osmosi inversa è un processo di filtrazione a livello molecolare o ionico, che utilizza membrane semi-permeabili, cioè permeabili all’acqua in entrambe le direzioni ma non ai soluti.
• Poiché i soluti non possono attraversare la membrana, l’acqua fluisce verso la soluzione a concentrazione maggiore fino a raggiungere l’equilibrio.(Osmosi diretta)
• Applicando una pressione al comparto ove la concentrazione salina è più elevata, si inverte il flusso dell’acqua, che, attraversando la membrana, lascia i sali contenuti nella zona di partenza e diventa sempre più “ pulita” (osmosi inversa).
Aumentando la pressione aumenta la quantità di acqua recuperata.
• A Milano l’ Osmosi Inversa è utilizzata per abbattere nitrati e cromo esavalente, anche se i nitrati, in tutta la città, sono largamente inferiori al valore di parametro di 50 mg/l. L’Osmosi Inversa dell’impianto Gorla può trattare fino a 148 l/s su 350 l/s in entrata. La concentrazione dei nitrati in entrata è mediamente attorno a 38 - 42 mg/l . Il permeato, cioè l’acqua trattata, contiene un residuo di circa 2- 3 mg/l, viene miscelato con l’acqua non sottoposta a osmosi, mentre l’eluato, che contiene il concentrato di sali, è scaricato in fognatura.
Il risultato raggiunto è una riduzione dei nitrati ad una concentrazione di circa 25 – 28 mg/l.
• Lo scopo è distribuire un’ acqua non solo a norma di legge ma anche veramente pregiata, non inferiore alle minerali.
• I costi del trattamento sono in linea con quelli di impianti analoghi, indicati nelle memorie tecniche. Infatti il costo risulta di circa 0,11 €/ m3 = 212 £ / m3 Rautenbach [Acqua 5-279-1986] indicava 500 £ / m3.
Filtri a carboni attivi S.Siro
Impianto a osmosi inversa Centrale Gorla
Osmosi inversa Gorla
MAP OF PLANTS WITH TREATMENT SYSTEM
