The water of Lake Bolsena has been downgraded as regards its ‘drinkability’.
Regional Council Resolution no. 276 of 19 May 2020 declared that the water taken from the lake in Montefiascone, Località Orto del Piatto “… can only be used in exceptional cases, where it is not possible to use other sources of supply and on condition that the water is subjected to appropriate treatment so that it meets the quality standards for human consumption …”.
This is due to the high proportion of phosphate which exceeds the legal limits (set out in annex 2 to part three, section A of Legislative Decree 152/2006).
The Resolution has as its objective the designation and classification of the surface water intended for drinking for Lake Bracciano, Lake Bolsena and Lake Vico, as well as for the rivers Mignone and Tevere.
In point 11, with reference to the risk represented by cyanobacteria (‘red algae’), it states that:
“For Lake Vico and Lake Bolsena, in order to ensure the protection of water resources and to have timely information about the potential occurrence of conditions that favour the spread of algae, the Area Authority, the manager, the local sanitary authority and the mayor, each in his own area of responsibility must provide:
- the implementation of periodic monitoring according to the criteria defined by the “national group for the management of cyanobacteria risk in water intended for human consumption” (reported in ISTISAN report 11/35, part 2, volume 2 and subsequent revisions);
- the implementation of appropriate preventive/corrective actions in order to reduce the risk of algal blooms (reduction of nutrient supply);
- the preparation of a specific plan for the management of any massive spread of algae, including monitoring and treating the supply line to remove any algae and toxins from the drinking water network”.
The high concentration of phosphates in the waters of the lake, as ascertained by ARPA Lazio, can have two causes: the discharge of waste water into the lake or intensive fertilization in the lake basin.
Let’s see what preventive and corrective measures are put in place!
