Destruction of helminth eggs (Ascaris suum) by ozone: second stage

Abstract

With the purpose of destroying helminth eggs, laboratory tests were carried out using a batch reactor of 1 L with 500 mL of eggs in suspension (1 × 105 eggs/L). In all the tests, a 36.8 mg O3/L concentration of gas-phase ozone was applied at the bottom of the reactor, with flows of 0.25 and 0.5 L/min to achieve rates of 9.2 and 18.4 mg O3/min, respectively. The results (first stage) showed that the eggs of Ascaris suum were destroyed at a pH of less than 5, with a dose of 18.4 mg O3/min., giving a 94% success rate; these results were improved when applying a pH 3 (second stage) with 18.4 mg O3/min for an hour, and 96.7% of the eggs showed damage to their external covers. In comparison with other species, total destruction was achieved in 1 hour and 45 minutes at pH 3 for the case of the Fasciola hepatica and the Strongiloides sp. The destruction of the Dypilidium caninum was completed after 3 hours. However, with regard to the Toxocara canis, eggs still remained, but they were observed to be seriously damaged. The degree of COD removal in the tests with the Ascaris suum was 75% after 2 hours. In the case of the other species, the COD removal was better since it varied from 85-94% after 2 hours of treatment. It can be concluded that during the process of oxidation in an acid environment, ozone hydrolyzes the amino acids that characterize the proteins of the layers covering the egg, and at the same time it breaks the cover of the egg and disperses the cytoplasm of the eggs into the solution, therefore making it impossible for the eggs to become reactivated.