EE&T has conducted numerous evaluations of GAC for removal of natural organic matter and taste- and odor-causing compounds including an ongoing RSSCT study and several others completed during the ICR. A two-year pilot GAC project was conducted at the Erie County Water Authority (ECWA) in Buffalo, NY. That work focused on performance-based testing using different types and depths of GAC. An array of PAC products was also tested using a 2-gpm conventional pilot plant. The objective of the project was to ensure that the Authority accomplished excellent taste and odor control at the lowest possible overall cost.

GAC/PAC testing at the ECWA clearly demonstrated that bituminous coal-based GAC and PAC outperformed lignite- and wood-based products for removal of 2-methylisoborneol (MIB). Geosmin was completely removed regardless of GAC type or depth, and with PAC dosages of as low as 10 mg/L, regardless of type. Detailed cost analyses showed that the bituminous-based PAC products would provide the most cost-effective taste and odor control. A year-long pilot plant treatability study was conducted by EE&T at the A.B. Jewell Water Treatment Plant in Tulsa, OK. The primary objective of the study was to reduce disinfection by-product concentrations using ozone and GAC. The GAC was first evaluated as filter media to determine whether it could provide effective reduction of the more easily adsorbed TOC. It was also used for the removal of intermittent taste and odor problems. In addition, two post-carbon adsorption systems were used, each having a number of columns in series. This arrangement allowed for the determination of the adsorptive wave front, the required empty bed contact time, and competitive adsorption. Routine isotherms were conducted to compare equilibrium predictions. As a result of this evaluation, an assessment of the feasibility of using GAC as a filtration media, association with ozone, and/or in a post-adsorption system was completed. A design report was submitted to the City detailing the process requirements, costs, and site needs.

A second year-long GAC study was conducted at the Mohawk WTP in Tulsa, OK. The work conducted at the Mohawk plant was similar to that at the A.B. Jewell plant in that a dual-train pilot system with post-carbon adsorber columns was utilized to enhance removal of natural organic matter and DBP formation potential.

EE&T also completed several pilot investigations for AwwaRF to determine the design and operational criteria for the removal of radon from groundwater by GAC adsorption. The three key factors evaluated were the determination of the capacity and empty bed contact time (EBCT) of GAC for radon removal, an assessment of radioactive build-up on the GAC including the ramifications of this build-up on disposal and worker safety issues, and the development of overall system design. The work was conducted in New Hampshire, New Jersey, and Colorado. The latter two pilots were six months in duration while the New Hampshire pilot was conducted over 18 months.