Efficienza della filtrazione naturale per approvvigionamento idrico da falde fratturate del Salento

In Puglia several coastal aquifers are polluted by uncontrolled discharges of domestic wastes and sea water intrusion. The Italian rule D. Lgs. 152/99 and the European Community Directive 2000/60/EC, known as the Water Frame Directive, encourage basic and supplementary measures for water resources protection such as rehabilitation projects and artificial aquifers recharge (see (xiii) and (xiv), part B annex VI). Moreover, in the semiarid environments the water derived from municipal treatment plants can conveniently be reclaimed for groundwater artificial recharge. Treated wastewater injections could improve groundwater quality by reducing the extent of seawater intrusion and increasing the groundwater storage. An experimental study has been carried out in the Salento Region where the Nardò injection sink has been used in the last 11 years as a natural way to increase groundwater replenishment. A mathematical model has been applied to simulate the effect of 140 l/s treated waste injection in the sink and to study contaminant pathways and concentrations in the fractured aquifer. Moreover water sampled in monitoring wells positioned at different distances from injection allowed the inactivation times for pathogens released in ground water to be estimated. The rates for pathogen inactivation have been also estimated by means laboratory tests carried out on horizontal pilot-plants able to reproduce waste filtration through fractures. Model results allowed two zones around the sink to be drawn by means the set back distances calculation in every direction and, the minimum distances required for virus (zone A) and fecal coliforms (zone B) inactivation in fractures were estimated in the case studied.