Dynamic Behavior Patterns of Particle Size Distribution of Dissolved Organic Carbon

Abstract

Humic acid (HA) is nonliving natural organic matter (NNOM) and exhibits dynamic behavior under certain shear conditions. This dynamic behavior presents a problem in water treatment as HA is a foulant and tends to disaggregate in turbulence and aggregate in the absence. The relationship between the aggregation time of NNOM found in pond water as a function of shear rate was investigated under constant 0.4 M CaCl2 concentrations. A rheometer (TA Instruments, Discovery HR 10) with a cup and bob attachment (TA Instruments, Peltier Concentric Cylinder) was utilized to induce shearing of NNOM in the range of 10 to 400 sec-1. Dynamic light scattering (DLS) was used to determine particle size distribution (PSD) patterns as the sample was allowed to relax over 120 minutes. The dynamic behavior of particles at ranges of 68.1-78.8nm, 396-459nm, and 4.8-5.56µm was explored. Additional data analysis suggests that there may be relationships between the increase or decrease of specific particles intensity or volume percentage, which were exposed to very specific shear rates.