Reduction of helminth ova and faecal coliforms in biological sludge, using a biodegradable acid (PAA)

摘要

One of the main problems related with water treatment is the production of sludge with a high microbial concentration. Particularly, in developing countries and tropical regions diseases caused by parasites, such as helminth ova, may be transmitted through sludge. One way to control and prevent these diseases is by treating the sludge to produce biosolids that can be beneficially reused. To accomplish this, peracetic acid (PAA) can be used due to its biodegradability and biocide behaviour against pathogens such as helminth ova. In this study, five different doses of PAA (0, 250, 500, 750 and 1000 ppm), were applied to biological sludge, with a 30 minute contact time, to determine the effect on helminth ova and faecal coliforms. Initial concentrations of faecal coliforms and helminth ova in sludge were 2.7x10~6 MPN/g TS and 63 ova/g TS, respectively. Results showed that faecal coliforms were reduced between 3.4 and 6.0 logarithmic units, reaching concentrations below the detection limits with the doses of 750 and 1000 ppm. Regarding helminth ova, the inactivation efficiency ranged from 34 to 90%. Based on the results, it is possible to produce biosolids by applying peracetic acid to biological sludge in doses of 500 ppm.