This study assesses seasonal particle size distribution (PSD) dynamics inside a waste stabilization ponds (WSP) (Buguruni, Tanzania) to understand settling dynamics of wastewater particles with an interest in helminth eggs. Results indicate that particles coming into the pond are mainly supracolloidal and settleables with 52.9% and 45.6%, respectively, in dry season and 48.9% and 49.9%, respectively, in wet season. Inflow PSD is a unimodal distribution that splits into settling and suspended PSDs, with an indication of particle breakage, as shown by the increased volume of smaller particles and hence the appearance of a bimodal distribution for the suspended particles. Up to 61.5% and 45.2% of particles that fall within the size range of helminths eggs are suspended during dry and wet seasons, respectively, with the potential to be carried in the effluent and to cause contamination.