FIELD INACTIVATION OF OOCYSTS EXPOSED TO AGRICULTURAL LAND

摘要

The determination of field inactivation rates of oocysts in sludge and soil is important as many land applications use sludge as a means of fertilizing the soil. Approximately 2.5 x 10~5 oocysts were spiked into separate sentinel chambers containing a 1.0 g mixture of sludge and soil. The sentinel chambers were exposed to the soil surface environment for 60 days at a depth of 10 cm in order to evaluate the field inactivation rates of oocysts. The mass balance approach was used to determine the number of oocysts lost in the experiments. The results of the study showed that oocysts could survive environmental stress in soil. The mean inactivation rate of oocysts in the sentinel chambers at time intervals of 0 to 17 days, 17 to 30 days, 30 to 45days, and 45 to 60 days were 0.0045, 0.0033, 0.0043, and 0.012 day~(-1), respectively. Whereas, the mean inactivation rates of oocysts in control units at time intervals of 0 to 17 days, 17 to 30 days, 30 to 45 days, and 45 to 60 days were 0.0023, 0.0019, 0.0017, and 0.0025 day~(-1), respectively. An average of 4.8 percent of oocysts were lost in the experiments. Overall, the study demonstrated the presence of viable oocysts in sludge samples, which could potentially be used to fertilize agricultural land.