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

Abstract

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.

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

“…Several studies reinforce the idea that Ascaris and other helminths are heavily influenced by external environmental conditions. In a similar experiment in southwestern Brazil on Eucalyptus plantations with intercropped application of biosolids, de Faria et al (2017) observed that Ascaris egg inactivation took 7 wk. Even taking into account the disparities between sugarcane and Eucalyptus plantations, the time of inactivation for T2 was similar to results for the forest crop.…”

The Persistence of Indicators and Pathogens in Wastewater Biosolids-amended Soil

“…Average time for persistence of viable Ascaris spp. ova in biosolids-amended soil was observed to be about 7 weeks under humid temperature (70% moisture, 20°C, conventional aerobically -digested activated sludge; de Faria et al, 2017). Two Brazilian studies (Thomaz-Soccol et al (1999) and Souza et al (2008) reported that helminths ova survived longer for 180 days in biosolids-amended soil in colder region than 3 weeks in other studied regions of Brazil.…”

“…Ascaris eggs have been used as an indicator for Helminths ova and have been mostly studied. Survival of helminths ova has been observed to be dependent on soil temperature, soil type and soil conditions (Maya et al, 2010;de Faria et al, 2017). Following sections present relation of different factors on persistence of helminths in biosolids-amended soil.…”

“…Studies are available on decay behaviours of bacteria in biosolidsamended soil, but this type of information is not available extensively for viruses and protozoa. As biosolids carry both viruses and protozoa, chances of their exposures from biosolids-amended soil exist; information is useful in deciding setback distance and setback time using decay patterns information of all types of BAPs a as T 90 values of different BAPs vary widely Conduct more decay studies for different types of pathogens (Jenkins et al,1999;Schwarz et al, 2013;de Faria et al,2017) Decay patterns based on field-related data Information on decay rates for enteric pathogens in biosolidsamended soil is valuable more under laboratory conditions than under field conditions. Field studies present monitoring challenges as soil has varied physiochemical properties which could affect decay of pathogens differently; T 90 values obtained from field-related studies can be used for framing land application of biosolids guidelines Conduct more field-related studies (Pepper et al,1993;Lang et al, 2003;Zaleski et al, 2005;Eamens et al, 2006;Pourcher et al, 2007;Horswell et al, 2007;Elmahdy et al,2018) a BAP-biosolids associated pathogens…”

Ascaris spp.

“…Clearly, temperature has an overwhelming effect on the persistence of Ascaris ova in different media. Generally, persistence decreases with increasing temperature (Yadav, 2003;de Faria et al, 2017). This is a clear indication that Ascaris eggs are more likely to survive longer in the temperate environment than in the tropical environment (Katakam et al (2013).…”