Abstract
The settling velocities of helminth eggs of three types, namely Ascaris suum (ASC), Trichuris suis (TRI), and Oesophagostomum spp. (OES), in clean tap water are computationally determined by means of computational fluid dynamics, using the general-purpose CFD software ANSYS Fluent 18.0. The previous measurements of other authors are taken as the basis for the problem formulation and validation, whereby the latter is performed by comparing the predicted sink velocities with those measured in an Owen tube. To enable a computational treatment, the measured shapes of the eggs are parametrized by idealizing them in terms of elementary geometric forms. As the egg shapes show a variation within each class, “mean” shapes are considered. The sink velocities are obtained through the computationally obtained drag coefficients. The latter are defined by means of steady-state calculations. Predicted sink velocities are compared with the measured ones. It is observed that the calculated values show a better agreement with the measurements, for ASC and TRI, compared to the theoretical sink values delivered by the Stokes theory. However, the observed agreement is still found not to be very satisfactory, indicating the role of further parameters, such as the uncertainties in the characterization of egg shapes or flocculation effects even in clean tap water.
Highlights
The settling velocities of helminth eggs of three types, namely Ascaris suum (ASC), Trichuris suis (TRI), and Oesophagostomum spp. (OES), in clean tap water are computationally determined by means of computational fluid dynamics, using the general-purpose CFD software ANSYS
The sink velocities of helminth eggs of three types, namely Ascaris suum (ASC), Trichuris suis (TRI), and Oesophagostomum spp. (OES), in clean tap water are computationally determined by means of computational fluid dynamics
Results are compared with the experimentally obtained average sink velocities of Sengupta et al [20], and the sink velocities delivered by the Stokes law
Summary
The settling velocities of helminth eggs of three types, namely Ascaris suum (ASC), Trichuris suis (TRI), and Oesophagostomum spp. (OES), in clean tap water are computationally determined by means of computational fluid dynamics, using the general-purpose CFD software ANSYS. The sink velocities are obtained through the computationally obtained drag coefficients The latter are defined by means of steady-state calculations. It is observed that the calculated values show a better agreement with the measurements, for ASC and TRI, compared to the theoretical sink values delivered by the Stokes theory. When wastewater is used in aquaculture or agriculture, without an adequate treatment in advance, a serious health risk may occur for the farmers and consumers, due to contamination by viruses, bacteria, and parasite pathogens. Cirelli et al [1] presented the results of a reuse scenario where treated wastewater was supplied for vegetable crop irrigation in Eastern Sicily, Italy, while emphasizing the necessity of post-treatment to reduce the risk of bacterial contamination. In a quantitative microbial risk assessment on agricultural wastewater usage in the urban areas of. Microbial community dynamics were investigated in raw and treated wastewater by Cui et al [6], who suggested the anaerobic biofilm process as a cost-effective method of domestic wastewater treatment, while reporting the high potential
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