Framework for Evaluating Sorbent Usage Rate of Various Sorption Column Configurations with and without Bypass Blending

Abstract

Sorption systems are a prevalent technology in the field of environmental engineering for treating waters contaminated with organic and/or inorganic compounds. Examples of such contaminants include taste and odor, hardness, disinfection byproduct precursors, and arsenic.The primary operating costs for these sorption systems lie in sorbent replacement. Different column arrangements and the use of bypass blending have the potential to reduce sorbent usage. Thus, this research aimed to develop a decision framework to assist engineers and practitioners in considering when to apply single columns, parallel columns, and lead-lag series configurations, with and without bypass, based on sorbent usage rate. This framework utilized two parameters that were found to influence the overall performance of each configuration option. These parameters were a normalization of the breakthrough curve, expressed as a ratio of the mass transfer zone length to the lag length (MTZ:Lag), and the normalized treatment objective (C/Co). Based on these parameters, comparisons of the performance of various configurations, both with and without bypass, could be developed.The following conclusions were formed based on this research:• Systems operated at low MTZ:Lag ratios have the ability to yield significant savings in sorbent usage with the use of bypass over arrangements without bypass in single column or lead-lag arrangements.• Systems with high MTZ:Lag ratios can benefit from the use of a lead-lag series configuration to increase column bed life and reduce sorbent usage rate, with or without bypass.• Parallel column configurations can offer significant savings in sorbent usage, particularly in systems with higher treatment objectives and high MTZ:Lag ratios.• Single column configurations without bypass remain competitive with other configurations for systems with low MTZ:Lag ratios (< about 0.5) and low treatment objectives (<0.2). ACKNOWLEDGEMENTS

Models for predicting organic micropollutant breakthrough in carbon adsorbers based on water quality, adsorbate properties, and rapid small‐scale column tests

“…Also, considering only one point on an OMP breakthrough curve does not provide information about the spread of the mass transfer zone. Knowing the size of the mass transfer zone relative to the adsorbent bed depth is important for evaluating lead–lag and staged parallel treatment configurations, for instance (Stewart et al, 2013). Further discussion is beyond the scope of the present document, but we refer the reader to previous work on approaches to reactor configurations and assessment criteria for OMP removal (Corwin & Summers, 2012; Crittenden et al, 2012).…”