Reuse of wastewater in agriculture
As it is now clear water resources will be the increasingly current problem for a sustainable future. The reuse of wastewater, in our country, unfortunately, both regulatory and implementation, has never been addressed with serious attention.
Internationally, since 1973 the World Health Organization (WHO) deals with the issue of reuse of wastewater; subsequently with the EU directive 91/271 Europe has posed the problem of the reuse of urban waste water. In Italy, today, the subject is governed by Ministerial Decree 185/2003 (which delegates implementation to the Regions) and the Consolidated Environmental Act (TUA -Dec. Leg.vo 152/2006) art. 98 and table III Annex 5.
Here we will address the reuse for agricultural purposes and the problems related to it.
Among the main issues to the reuse of wastewater in agriculture, it seems to me necessary to treat the most complex ones. Let’s analyze them in summary:
Not perfect and regular functioning of the phytodepuration plants; in the absence of a real program on phytodepuration plants these apparatuses often work in a discontinuous way, with occasional qualitative controls. The end result is an incongruous wastewater quality;
Lack of distribution networks and irrigated consortia with a concrete impossibility to use wastewater even if of verifiable quality;
Salinity values (without prejudice to the conformity especially of coliforms) is not always adequate for some types of soils for which a prior pedological and agronomic study should be done for irrigation use with these waters.
Above all the qualitative aspects linked to the quantity and quality of the salts (without prejudice to the other conditions) place serious limits on the use of these waters.
Consider that wastewater has average values of electrical conductivity (with seasonal fluctuations) around 2,550 – 3,500 μS / cm, SAR values between 3 and 12, pH between 5.5 and 9.5 and the possibility of the presence of heavy metals (such as Cr, Pb, etc.). In these conditions, the use of waste water without two essential conditions is unthinkable:
The first condition is a certificate of suitability for irrigation that can be issued only in the presence of a serious and constant monitoring of waste water leaving the plants;
The second condition is, as mentioned, a serious study of the use of waste water taking into account some essential factors: nature of the soils and characteristics of thermopluviometric, broad-leaved, shrub-like, tree plants, etc.), methods of water distribution (it is not advisable to sprinkle for the above issues), etc.
It is evident that in the absence of concrete implementing decrees and certain rules on the reuse of waste water we continue to talk about sustainable use of the precious water resource but in fact this is lost at sea as much hope for an eco-sustainable future of our country.