Disinfection with peracetic acid for domestic sewage re-use in agriculture

This paper describes a four-month pilot study on peracetic acid disinfectio n of unchlorinated tertiary effluent for unrestricted re-use in agriculture carried out at West Bari (Italy) sewage-treatment works. Dosages and conta ct times ranging from 1 to 500 mg/l and 5 to 60 mins, respectively, indicat ed that 10 mg/l of peracetic acid, with a 30-min contact time, achieved the WHO faecal coliform guideline (1000 CFU/100 ml). Much higher doses (greate r than or equal to 400 mg/l and 30 mins) were required to meet the correspo nding Californian limit of two colony-forming units/100 ml, which has also been adopted in Italy. Efficient mixing of the disinfectant (in one shot ad dition) was mandatory - particularly at lower dosages (1-10 mg/l) where the re was a higher concentration of suspended solids (>5 mg/l).