Persistence of Fecal Contamination Indicators and Pathogens in Class B Biosolids Applied to Sugarcane Fields.

Agricultural recycling of human Class B biosolids in sugarcane ( 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 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 spp. eggs in soil was 22 d in T1 and 41 d in T2.

Persistence of Ascaris spp. Ova in Tropical Soil Cultivated with Eucalyptus and Fertilized with Municipal Biosolids.

In many countries, the main reason for severely restricting or outright banning the land application of class B biosolids is the lack of risk assessment for adverse human health impacts. Among pathogens that are not often studied are helminth ova, including that of the spp. Almost all of the knowledge about the persistence of spp. ova in soils fertilized with biosolids is based on studies developed in North America, Europe, and Asia. These studies have almost always been conducted under temperate climate conditions, which may cause erroneous interpretations when the conclusions are extrapolated to tropical regions such as those found in Brazil. This team evaluated the persistence of viable spp. ova in a sandy Quartzipsamment tropical soil, previously planted with × hybrid () and fertilized with biosolids, over a 52-wk period. During the reporting period, the average temperature of soil and biosolids fluctuated between 15 and 30°C, and the average moisture of biosolids fluctuated between 60 and 90%. The estimated persistence time of viable spp. ova after land application was estimated at close to 7 wk, indicating that ova may not be viable for as long as it has been shown to be in studies of more temperate areas. The relationship of temperature with persistence of viable spp. ova in a tropical soil was stronger than moisture content, suggesting that temperature substantially contributed to their nonviability over the course of the experiment.