Effect of Particle Removal by OptiFiber® PA-13 Nylon Pile Media on Particle Size Distribution and Correlation between Turbidity and Total Suspended Solids

Studies were conducted to determine the effect of tertiary filtration on particle size distribution (PSD) and the correlation between filtrate total suspended solids (TSS) and turbidity (NTU) values. This was achieved using a bench-scale AquaDisk® tertiary filter system equipped with OptiFiber® PA-13 nylon pile cloth media. Influent was collected from 18 complete-mix, activated sludge process wastewater treatment plants (WWTPs). Results showed particle populations were redistributed by filtration. Even though the total number of particles was reduced, the relative populations of small particles (≤ 6 microns) increased in the effluent. Turbidimeters with short wavelength light sources are more sensitive to small particles, which results in an increase in the NTU/TSS ratio after filtration. Therefore, correlations between filtrate stream turbidity and TSS values may be used as a tool to evaluate filter performance and filtrate quality; however, they must be generated on a plant-by-plant basis so site-specific relationships are established