Persistence of fecal contamination indicators and pathogens in class b biosolids applied to sugarcane fields

Abstract

Agricultural recycling of human Class B biosolids in sugarcane (Saccharum spp.) crop is a promising alternative to reduce the costs of biosolids disposal. However, the presence of fecal contamination indicators such as thermotolerant coliforms and pathogenic organisms such as enterovirus and Ascaris spp. in biosolids impose barriers to effective and widespread use of biosolids as fertilizer. In addition, there is a scarcity of studies that investigate the persistence of these organisms in tropical soils. This study aimed to evaluate the persistence of pathogenic and fecal indicators for 258 d in a tropical clayey soil amended with human Class B biosolids and cultivated with sugarcane. Treatments were immediate incorporation of biosolids into soil after application (T1) or superficial application of biosolids followed by incorporation after 35 d (T2), emulating the typical procedure in sugarcane fields. Thermotolerant coliforms were estimated to persist for 437 d in T1 and 398 d in T2. For enterovirus, mean estimated persistence time in soil was 26 d for T1, but the sampling frequency was insufficient in T2 for persistence analysis. After 35 d, no enterovirus was detected in any sample. Mean estimated persistence time for viable Ascaris spp. eggs in soil was 22 d in T1 and 41 d in T2.