The paper summarises the research carried out on wastewater reservoirs (WWRs) operation during the period 1999–2005 at Grammichele and Caltagirone sites (Eastern Sicily). The wastewater treatment feasibility in WWRs under different (continuous and discontinuous) operation modalities is explored. The sampling monitoring program for the case studies is presented along with wastewater quality modelling to prove the systems reliability to microbiological and organic matter removal. The operational parameter MRT%FE is introduced and combined with first order kinetics to model the concentration of Escherichia coli in WWRs. Results point out that WWRs, properly designed and managed, are a valid technique for wastewater reclamation for agricultural irrigation according to the restrictive Italian standards. In particular, the reliability of wastewater storage in terms of bacteriological removal results enhanced during batch operation as confirmed by the higher values of the die-off coefficient.