Estudo sobre a ocorrência de ovos de helmintos e viabilidade de Ascaris sp em lodos aneróbicos in natura e submetidos à higienização por caleção e por tratamento térmico

Abstract

This study aims at the characterisation of anerobic sludge regarding the presence of helminths eggs and viability of Ascaris sp eggs in sludges in natura and sanitization using lime and termic treatment, besides the identification and counting of helminth eggs in different types ofsludges. For the experiment of sanitization with lime, the sludge was obtained from an UASB reactor, in demonstration scale, after being dewatered in drying bed, with three dosages of hydrated lime (30, 40 and 50 %) being used. The experiments of termic treatment were carried out in pilot- and demonstration scale treatment plants, with raw sludge (in natura) from UASB reactors being used. For these experiments, Ascaris lumbricoides eggs were used as indicator organism. For the study regarding the presence of helminth eggs and viability of Ascaris speggs, three types of sludges were used, two of them being obtained from the UASB reactor, after being dewatered in drying beds, while the third one originated from an Primary Sludge Anaerobic Digester, after being dewatered in centrifuges. The sanitization of sludge with lime was 100% efficient in the inactivation of Ascaris sp eggs, after 30 days contact time, for the three chemical dosages tested. Regarding the termic treatment, the total inactivation of viable eggs was observed for heating times around 4 to 5 hours and temperatures close to 70º C. The results concerning the total amount of eggs indicated not only the inactivation of viable eggs, but also its possible destruction. In relation to the characterization of different types of sludge, the presence of helminth eggs was detected in all samples, with prevalence of Ascaris sp eggs. In two types of sludge, more than a half of eggs were viable.