In a 3-year joint research project, approved in 1995 by the European Commission, methods for advanced treatment and disinfection of municipal wastewater to permit reuse in agriculture were investigated. Pathogen inactivation, disinfection by-products (DBP) formation and the cost effectiveness of disinfection methods involving UV rays, ozone (O3) and peracetic acid (PAA) were evaluated. The investigation was carried out on municipal effluents which had received different degrees of treatment (secondary, clarified, clarified-filtered) in a 100 m3/h pilot plant that was designed, built and operated at West Bari (S. Italy) municipal wastewater treatment plant. Under the experimental conditions investigated, the WHO microbial guideline for unrestricted reuse of wastewater in agriculture (1,000 CFU/100ml for Faecal Coliforms) was easily achieved with all three disinfectants, while the corresponding Italian standard (2 CFU/100ml) was effectively met only with UV at an O&M cost in the range 17.5-35 EURO/1000m3. Log-inactivation values ≥ 5 for both UV and PAA and ≥ 3 for O3 were obtained; selected pathogens were affected by UV and, in part, by O3. No DBPs were detected with UV and PAA, while limited formation of aldehydes was found with O3.

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