An Experimental Method for Predicting the Adsorption of Trace Organic Contaminants in Partially Saturated Granular Activated Carbon

Abstract

The pore and surface diffusion model of adsorption was used to develop an equation that indicates that the fraction of a trace contaminant removed across a granular activated carbon (GAC) column during water treatment is an exponentially decaying function of the empty bed contact time (EBCT), and a parameter φ that accounts for GAC preloading. An experimental method using partially saturated GAC harvested from a plant was proposed to allow the value for φ to be determined for GAC from that site. With this information, the ability of the GAC to remove a contaminant of interest could be predicted for different EBCTs, or for different GAC service times, potentially allowing utilities to predict how much service time is left before the GAC needs to be replaced to meet some treatment target. Two conditions of the current method are that organic loading must be relatively consistent throughout the GAC lifetime and the water temperature during model calibration should be the same as that at full scale; however, the model allows for a future modification to account for these variables. The prediction capability of the model was validated by comparing the breakthrough from independent pilot-scale tests with the predicted breakthrough calculated using the calibrated model and bench-scale tests.

Micropollutant Mass Transfer Zones in Granular Activated Carbon Contactors

“…This result suggests that GAC saturation is approximately uniform across the bed depth (Figure c), thus supporting the hypothesis of the minicolumn test that GAC harvested from almost any point in the contactor would accurately represent the full scale. In addition, this finding suggests an operational simplification to the method reported by Huang et al to predict GAC performance based on GAC service time and EBCT (eq ). Their proposed approach is to harvest the whole depth of a GAC core sample from a full-scale contactor for the minicolumn test, which enables determination of model parameter φ for the GAC from that site, which expresses the GAC exhaustion rate as a function of service time and source water characteristics.…”

“…2 When these minicolumn tests are conducted at routine intervals, the GAC exhaustion rate can be observed and modeled to determine the GAC replacement schedule. 4 A key requirement of this minicolumn test is that the median grain size that is isolated from a core sample harvested from the GAC bed must represent the entire bed depth. In other words, if the full-scale bed contains GAC particles that have different degrees of saturation ranging from completely unsaturated to fully saturated, the grains that are isolated by sieving and used in the minicolumn test will need to exhibit the same saturation profile.…”

“…Contaminant removal in the minicolumn tests has been reported to accurately simulate the removal at full scale . When these minicolumn tests are conducted at routine intervals, the GAC exhaustion rate can be observed and modeled to determine the GAC replacement schedule …”

Covalent Organic Framework Membrane for Efficient Removal of Emerging Trace Organic Contaminants from Water Environment

“…Conventional treatment strategies, such as physical adsorption [9][10][11] and oxidation processes 12,13 , have been widely employed for the elimination of organic pollutants. However, these techniques are often ineffective in ambient environments due to the stability of certain pollutants 14 .…”