(373j) Implications of Shear and Cation Choice on Dynamics of Nonliving Natural Organic Matter

Nonliving natural organic matter (NNOM) is a common material found in environmental water that presents a fouling problem in water treatment membranes. Humic acid (HA) falls under the category of NNOM and displays dynamic particle size characteristics in response to factors such as shear rate, pH, ionic strength, and temperature. These variables have been hypothesized to impact the aggregation and disaggregation of NNOM. The behavior of NNOM found in pond water as a function of shear rate was investigated under constant 0.4M CaCl₂ concentrations. A rheometer was used to induce shearing of the NNOM in the range of 10 to 400 sec^-1. The Particle Size Distribution (PSD) displayed a complex relationship between shear rate and relaxation behavior. Non-Newtonian behavior of the sample(s) was also explored. Preliminary data shows the disappearance of certain size ranges at specific shear rates and colloidal behavior.