Natural organic matter enhanced retention of atrazine by dialysis membranes: Implications for ultrafiltration and nanofiltration
Devitt, Erin Catherine
Master of Science
Retention of atrazine from simulated surface water was measured using dialysis membranes with molecular weight cut-offs similar to those of pressure-driven ultrafiltration and nanofiltration membranes. Atrazine was significantly retained by membranes in the nanofiltration range in the presence of organic matter (OM), presumably by association with OM. Atrazine rejection was independent of initial concentration. Increasing OM concentration increased atrazine retention. Solution chemistry was important in determining the extent of atrazine retention. Where OM aggregation increased, atrazine rejection decreased, and visa versa. Increasing salt concentration decreased atrazine rejection. This effect was stronger with calcium than with sodium and protons. It is speculated that the most likely mechanism of atrazine retention with OM is through its diffusion into the interior of the organic matrix and subsequent physical trapping. This implies that atrazine rejection in surface waters will increase with increased OM concentration and decreased hardness in the influent surface waters.
Sanitary and municipal engineering