Comparison of advanced disinfecting methods for municipal wastewater reuse in agriculture

Abstract

The experimental investigation carried out jointly by Italian and Israeli teams within a 3-year research project funded by the European Commission on alternative disinfection methods for reusing municipal wastewater in agriculture is described. Disinfection effectiveness of UV rays, ozone (O3) and peracetic acid (PAA) at pilot scale and hydrogen peroxide (H2O2) plus silver (Ag+) or copper (Cu+2) at laboratory scale was compared for tertiary municipal effluents. Pilot plant results indicated that the well known California limit (2 CFU/100ml of Total Coliforms) was effectively met with reasonable UV doses of 100–160 mWs/cm2 or with exceedingly high PAA dosage (400 PPM); the related WHO microbial guideline (1,000 CFU/100 ml of Fecal Coliforms) was easily met with all three disinfectants (UV, PAA, O3); maximum log-inactivation values were ≥5 for UV and PAA and ≤4 for O3. Laboratory results with tertiary effluents demonstrated that Ag+ was able to inactivate target bacteria (E. coli-B, E. coli-K12), while H2O2 was more effective than Ag+ against MS-2 phages. Copper (250 μg/l) had no bactericidal effect but possessed an appreciable virucidal effect. When hydrogen peroxide and copper were combined, a pronounced increase in both bactericidal and virucidal effects was obtained.