The effects of dissolved organic matter, reactor configuration, and granular activated carbon (GAC) particle size on equilibrium adsorption of trichloroethylene (TCE) were examined under simultaneous loading and early preloading conditions. Differences in isotherm capacities obtained using batch‐reactor and column‐reactor estimation methods were observed when natural background organic matter and TCE were adsorbed simultaneously onto nonpreloaded GAC. Differences in isotherms derived from the two methods were diminished, however, when the carbon was first preloaded with the background organic matter in a river water in the absence of TCE. Significant increases in isotherm slope were observed with increasing preloading time for GAC of two different particle sizes. Isotherms determined using powdered activated carbon sieved from crushed preloaded GAC had essentially parallel slopes, however, with capacities greater than the parent preloaded GAC over the concentration range of interest. The observed effects were analyzed in the context of a proposed dualistic model for interpretation of interactions among background organic matter, target solutes, and microporous adsorbents.
As part of an expansion to an average flow of 45.9 million gallons per day (174 mld), the Ypsilanti Community Utilities Authority wastewater treatment plant in the State of Michigan, USA, elected to install ultraviolet disinfection as a replacement for the existing chlorination process. This paper presents a unique methodology used in selecting the best system based on not only the life cycle costs, and O & M considerations but also the participation of the stakeholders. The Team members consisted of representatives of all departments at the Authority, and these Team members made the decision. The Team evaluated all criteria in the office, which was followed by verification at selected sites with similar types of equipment. The selected equipment then was pilot tested for validation of the dose-kill relationship under normal operation and also under reduced irradiation conditions. A low-pressure, high intensity system was selected, based on life-cycle cost, reliability, safety, and ease of operation. This paper describes the unique methodologies used in making that decision. The full-scale system is scheduled for start-up in Spring 2003.
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