The elimination of helminth ova, faecal coliforms, Salmonella and protozoan cysts by various physicochemical processes in wastewater and sludge

Abstract

The removal of helminth ova, faecal coliforms, Salmonella and protozoan cysts by the application of physicochemical treatment processes to municipal wastewater and sludge was studied. In the first case, the advanced primary treatment (APT) process was studied, as well as filtration of the APT effluent. The APT sludge was treated with either lime or acid. The initial values of helminth ova, faecal coliforms, Salmonella and protozoan cysts in the wastewater were 23-27 eggs/L, 7.8 x 10(7)-6.5 x 10(8) MPN/100 mL, 4.5 x 10(5)-2.4 x 10(6) MPN/100 mL, and 1,007-1,814 cysts/L respectively. After APT treatment, 96% of the helminth ova, 1 log of faecal coliforms and Salmonella, and 67% of the protozoan cysts were eliminated. To reduce the concentration of helminth ova from values > 1.2 ova/L to < 1 ova/L an additional filtration step was required. In the sludge, the initial values of helminth ova, faecal coliforms and Salmonella were 65-120 ova/g TS, 8.3 x 10(7)-1.4 x 10(11) MPN/g TS and 3.6 x 10(6)-2.4 x 10(10) MPN/g TS respectively. A 97% reduction of the helminth and an 8.5 log reduction of faecal coliforms and Salmonella was achieved by alkaline stabilisation, compared with a 98% and 4.5 log reduction by acid treatment.