(477e) Innovative Polymer Quantification and Management At a Large Scale Remediation Project

Contaminated sediment remediation projects typically require a physical/chemical sediment pore-water treatment plant for metals and organics.  In many cases, the sediments are thickened and dewatered for cost effective management and disposal.  The polymer used for thickening can be problematic for downstream pore-water treatment.  Specifically, this paper reports on a treatment system that experienced excessive “sticky” solids build-up in the clarifier and difficultly removing these solids through normal operations.  The polymer also increased backwashing of Granular Activated Carbon (GAC), and decreased adsorption performance of Granular Activated Carbon (GAC).  

In order to optimize thickening polymer management, this program identified the threshold of residual polymer that adversely impacted the pore-water treatment plant chemical precipitation & gravity settling unit operation.  A mathematical relationship was established between a field-utilized China Clay Procedure and laboratory particle charge density (PSD) to establish an acceptable real-time simple procedure to validate the operating range and upper threshold for polymer dosing. 

This program also quantified the impacts of residual polymer on the GAC.  Equilibrium isotherms and rapid small scale column tests (RSSCTs) were conducted to confirm that the excess polymer was causing the observations in the full-scale GAC operations.  Laboratory testing was used to quantify reduction of the bed volumes processed before both excess pressure drop and benzene breakthrough occurred.  The program evaluated chemical types and dosages to dislodge and/or oxidize the excessive polymer that adhered to the carbon in the GAC beds. 

The results of this testing were used in the field to optimize polymer dosing, which lowered operating costs and reduced system maintenance.   The results also identified the impacts of GAC cleaning (both forward maintenance dosing as well as during backwash) on both pressure drop and adsorption capacity recovery.