Particle size distribution mathematical models and properties of suspended solids in a typical freshwater pond

Many countries, such as China, today are facing the scarcity and pollution issues of freshwater resources. Suspended solids, as wastewater contaminants, may contain components such as nitrogen, phosphorus, heavy metals and pathogens that are harmful to the environment and human health, it is essential to know the size distribution regularity of the solids with a view to guiding the management of freshwater resources for sustainability. Particle size distribution (PSD) mathematical models and properties of suspended solids in a typical freshwater pond were investigated in this study. Particle size was measured using a laser particle size analyzer (measurement range: 0.01-3500 μm). The power law model and the variable-β model were tested for their ability to fit the numeric distribution of suspended solids; Gaussian (i.e., normal) distribution and log-normal distribution models were used to evaluate the volumetric distribution of suspended solids. The results showed that: by number, about 80% of the particles contributed to only 10% of total particle volume, while the remaining 20% contributed about 90% of the total volume. For numeric distribution, the variable-β model (R² = 0.975 ± 0.011) was better than the power law model (R² = 0.899 ± 0.033); for the volumetric distribution, the log-normal distribution model (R² = 0.968 ± 0.020) clearly outperformed the Gaussian distribution model (R² = 0.655 ± 0.093). Overall, the variable-β model and log-normal distribution were shown to accurately describe the numerical and volumetric distribution of pond water suspended solids, respectively. PSD model parameters can be related to some compositions in the wastewater and can provide guidance for suspended solids further treatment, be it physical, biological, chemical or synthetic methods.