Abstract
Re-use of water containing helminth eggs during irrigation for agricultural purposes poses health risks, and likewise during research, due to the potential of spreading on contact. Therefore, polystyrene latex microspheres could be used as surrogates for chemical or biological species during colloidal transport. The aim here is to compare the settling velocities of microspheres having varied surface coatings—that is, proteins A, G and A/G; with that of real helminth eggs obtained from literature. The settling velocities of the microspheres were experimentally determined in tap- and wastewater, as well as theoretically in tap water; which was found to be within the range of mean values for those experimentally determined. There were no differences amongst the microspheres types used for settling in wastewater (i.e., A = 0.072 ± 0.02; G = 0.060 ± 0.03; A/G = 0.053 ± 0.01 mm/s). The same applied for settling in tap water (i.e., A = 0.068 ± 0.02; G = 0.047 ± 0.004; A/G = 0.095 ± 0.02 mm/s), except for microsphere G being different from microsphere A/G. All three types of microspheres settled at velocities lower than that of the wastewater particles (=0.118 ± 0.03). T-test analyses of settling velocities of microspheres in both tap- and wastewater, versus that from literature (i.e., Ascaris, Trichuris and Oesophagostomum), showed that microsphere A and A/G may surrogate for Ascaris in tap water, the same as A/G for Oesophagostomum. In wastewater however, both microspheres A and G are a good fit for Trichuris.
Highlights
The use of treated wastewater for agricultural irrigation represents an alternative to alleviate shortage of water in arid climatic zones of the earth [1]
This study indicates that Stokes’ law is a good predictive model for the settling of microspheres in tap water, given that the theoretical value is within the range of experimental values obtained
Odd as it may seem, wastewater particles were documented to settle faster than microspheres during wastewater sedimentation, and this occurrence is contrary to the outcome in published literature of real helminth eggs settling in wastewater
Summary
The use of treated wastewater for agricultural irrigation represents an alternative to alleviate shortage of water in arid climatic zones of the earth [1]. Both treated and non-treated wastewater use impose risks linked to pathogens present therein. In this regard, helminth eggs are one of the main concerns considering health and safety as they are highly infective. Helminth eggs are one of the main concerns considering health and safety as they are highly infective They are the most difficult biological parasites to inactivate in wastewater and sludge [2], due to their high resistance to environmental influences and disinfection. It is estimated that around a quarter of the total human population are infected with helminthiasis globally [6], with most transmissions by the
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