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Analytical results of Hera's checks

Given its quality, water supplied by Hera may be classified as 'low mineralised' water with a low sodium content. Local health authority checks confirm the excellent quality of the tap water supplied by Hera.

Tap water quality is described via a table that shows relative values for some parameters. The considered parameters allow mains water to be characterised from a qualitative standpoint. Where necessary, they also allow comparison with the main characteristics of mineral water brands. Parameters are selected also on the basis of international water reports published by other multiutilities. Data is presented in a way that compares it with the limits established by relevant standards.

Concerning water distribution, note that Hera is responsible up to the meter (as per art. 5 of Italian Legislative Decree 31/2001); the data provided cannot, therefore, take into account any changes to qualitative parameters caused by the characteristics of the piping in customers' homes.

Analytical results of Hera's checks

Values were calculated as weighted averages (on distributed volumes) of outcomes of analyses performed by Hera. These analyses were made at network points deemed suitable for providing a concise, reliable picture of distributed water quality. These points were chosen as they were representative – in terms of position, network interconnections, and in-pipe flow – of the characteristics of the water in the entire distribution system. Concerning the parameters shown in the following table, Hera performed 60,945 analyses in 2018 at representative network points.

Water quality: average concentrations measured by Hera (2018)
 Italian legislative decree n. 31/2001Prov. BolognaProv. FerraraProv. Forlì-CesenaProv. ModenaProv. PaduaProv. Pesaro-UrbinoProv. RavennaProv. RiminiProv. Trieste
Alkalinity of bicarbonates (mg/L)-298223235245295293224246212

Total alkalinity


Ammonium (mg/L)0.50<0.02 3<0.02 30.020.02<0.05 3<0.05 30.020.02<0.05 3
Arsenic (µg/L)10<1 31<1 3<1 31<3 3<1 31<1 3
Cadmium (µg/L)25<0.5 4<0.5 4<0.5 4<0.5 4<0.1 4<0.5 4<0.5 4<0.5 4<0.5 4
Calcium (mg/L)-9163631056194597057
Chlorite (µg/L)2700188311263<100 3260154360285< LR
Residual chlorine (mg/L)-
Chloride (mg/L)25035281789934322516
Hydrogen ion concentration (pH)6.5–
Conductivity (µScm-1)2,500606471433810456600482490371
Total hardness (F°)501302122332530212419
Fluoride (mg/L) 21.50<0.10 3<0.10 3<0.10 3<0.10 3<0.10 30.2<0.10 30.1<0.10 3



Manganese (µg/L)503<5 3<5 3<5 313<5 3<5 3<5 3
Nitrate (mg/L)25065161575786
Nitrite (mg/L) 20.50<0.02 3<0.02 3<0.02 3<0.02 3<0.02 3<0.04 3<0.02 30.01<0.02 3
Lead (µg/L)210<1 4<1 4<1 4<1 4<1 4<3 4<1 4<1 4<1 4
Potassium (mg/L)-<1 4
Dry residue at 180° (mg/L)1,5001407319309542310424331367261
Sodium (mg/L)2002622135752723219
Sulphate (mg/L)2506537331202168424213
Total Trihalomethanes (µg/L)230216116664

1 For total hardness and dry residue at 180 °C, Italian Legislative Decree 31/2001 states a recommended value.
2 Parameters shown in part B of Annex 1 of Italian Legislative Decree 31/2001. The others are shown in part C of Annex 1 and classified by the “indicator parameters” regulation (see p.24). For chlorites the mains water limit was redefined by Italian Legislative Decree of 5 September 2006.
3 Absent or lower than instrument detection threshold.
4 Absent or lower the instrument detection threshold in the analyses carried out on the outflow of the treatment plants and therefore not repeated in the distribution network.


Analyses results are well within regulations and comparable with those of mineral water

As can be observed, all values are well within regulatory limits. If we classify the mains water based on the model applied to mineral water, we can state that it is low in mineral content and low in sodium content, except for the water distributed in Modena, which can be defined as mineral water.

Higher average values for chloride, sodium, and nitrate in the Modena area are due to the salinity of the aquifer water. Higher average chlorate values in the Ravenna and Ferrara areas are essentially caused by the use of higher quantities of chlorine dioxide used to ensure disinfection coverage along very long distribution networks that hold the water in the pipes for a long time. In the Trieste area, hardness values are typical of those of 'soft' waters.

At the local level, certain parameters of historical relevance deemed important for the characteristics of the water at source and/or the treatment methods, are also monitored. For example, checks on tetrachloroethylene+trichloroethylene (organohalogenated solvents) are performed in the province of Bologna because they are present in aquifers due to past human-made environmental pollution (these compounds do not occur naturally). The same goes for the pesticides found in the waters of the River Po which feed into the Pontelagoscuro plant in Ferrara. In some cases, aluminium is monitored as the salts from this metal are used as flocculants in purification processes.

Water quality: average concentrations of critical parameters at local level (2018) 
 ParameterItalian legislative decree n. 31/2001Hera GroupAnalysis performed by Arpae for Health Authority
Prov. BolognaAlluminium (µg/L)2004552
Iron (µg/L)200<1012
Tetrachoroethylene + Trichloroethylene (µg/L)101.10.4
Prov. FerraraTotal pesticides (µg/L)0.50<0.02<0.02
Pesticides (µg/L)0.10<0,02<0,02
Prov. Forlì-CesenaAlluminium (µg/L)2004229
Prov. Pesaro UrbinoAlluminium (µg/L)20050 40
 Iron (µg/L)2001118
 Tetrachoroethylene + Trichloroethylene (µg/L)10<0.80.1


Checks carried out by the Group indicate that values are well within regulatory limits, thus confirming the soundness of the treatment processes. Organic pollutants, especially halogenated solvents and pesticides, are treated via filtration on active carbon, which is particularly effective in removing them. The process was implemented inside the Bologna and Ferrara treatment plants.

The following chart compares the quality of the drinking water supplied by the Hera Group with regulations. It shows the calculated ratio between the concentrations of fourteen parameters (ammonium, arsenic, chlorite, chloride, conductivity, total hardness, fluoride, manganese, nitrate, nitrite, dry residue, sodium, sulphate, trihalomethanes-total) measured at points representative of the entire distribution system and their maximum permissible concentrations in drinking water.


Across the various areas, average concentrations are below regulations, between 78% and 90%.