Improvement of denitrification rates in confined zones in fractured subsoils under continuous wastewater injection

An attempt to improve the natural biodegradation rate in a fractured aquifer (Nardò (Le), Southern Italy) subject since ’91 to the injection of 12000 m3/d of treated municipal wastewater , has been carried out through tests on pilot plants. The lab experiments showed that a complete nitrogen removal can be realized after 10 d of infiltration in fractures by adding whey in the influent waste. The lab results have been used in a mathematical model in order to simulate ground water quality changes caused by the addition of whey in the injecting water. The analytical parameters of ground water sampled in monitoring wells located at different distances from the injection site, have been compared with mathematical model results. Moreover for preserving such resource from pollution, the mathematical model allowed two areas, around the injection site to be drawn. These areas, where withdrawals would be prohibited, are required to avoid infections by pathogens and bacteria in ground water due to incomplete biodegradation processes. The experimental results can be useful to identify standardized methodology for artificial ground water recharge which could be required for aquifer clean up (Water Frame Directive 2000/60).