Field inactivation of oocysts exposed to agricultural land

The determination of field inactivation rates of oocysts in sludge and soil is important as many land applications use sludgeas a means of fertilizing the soil. Approximately 2.5 × 10^sup 5^ oocysts were spiked into separate sentinel chamberscontaining a 1.0 g mixture of sludge and soil. The sentinelchambers were exposed to the soil surface environment for 60 daysat a depth of 10 cm in order to evaluate the field inactivationrates of oocysts. The mass balance approach was used to determinethe number of oocysts lost in the experiments. The results of thestudy showed that oocysts could survive environmental stress insoil. The mean inactivation rate of oocysts in the sentinelchambers at time intervals of 0 to 17 days, 17 to 30 days, 30 to45days, and 45 to 60 days were 0.0045, 0.0033, 0.0043, and 0.012day^sup -1^, respectively. Whereas, the mean inactivation rates ofoocysts in control units at time intervals of 0 to 17 days, 17 to30 days, 30 to 45 days, and 45 to 60 days were 0.0023, 0.0019,0.0017, and 0.0025 day^sup -1^, respectively. An average of 4.8percent of oocysts were lost in the experiments. Overall, thestudy demonstrated the presence of viable oocysts in sludge samples, which could potentially be used to fertilize agricultural land.[PUBLICATION ABSTRACT]