PLANNING A REGIONAL GRANULAR ACTIVATED CARBON REACTIVATION FACILITY IN METROPOLITANPHOENIX

摘要

A regional reactivation facility located within the Phoenix metropolitan area could ultimatelyrnprocess the granular activated carbon (GAC) that services as much as one billion gallons per dayrnof drinking water. Cities in the metropolitan area anticipate a demand of 30 million pounds perrnyear (30 MM-lbs/yr) of GAC by 2013. Cities use, or will use, GAC in filters or post-filterrncontactors to meet Stage 2 Disinfectant and Disinfection Byproducts Rule requirements. ThernCities of Chandler, Glendale, Mesa, Peoria, Phoenix, Scottsdale and Tempe, Arizona haverncollaborated in a feasibility study for a regional reactivation facility. GAC reactivation is anrnenvironmentally friendly option that is expected to results in lower overall costs as comparedrnwith the purchase of virgin GAC. Required reactivation capacity was estimated at 36 MM-lb/yrrn(additional capacity to meet peak demand and reduce amount of onsite storage).rnThe general reactivation process involves thermal reactivation through heating spent GAC torn700-900° C under steam and carbon dioxide for ? to 2 hours. Facility technologies will includernreactivation furnaces, acid bath, and air pollution control equipment. Real estate requirements ofrn6 to 10 acres are anticipated based on design capacity, technological considerations and zoningrnand setback requirements.rnCost analysis was conducted in September of 2003 to determine savings through reactivatingrnGAC when compared to purchase of virgin GAC. Capital costs were estimated at $21.3M withrnannual operation and maintenance costs of $7.6M. These costs are equivalent to $0.32/lb ofrnreactivated GAC for a facility of this size. Costs for virgin GAC were estimated between $0.50-rn0.55/lb. Reactivating GAC is approximately 40% less than purchase of virgin GAC. Within fourrnyears capital costs will be recovered through savings from reactivation.rnAir quality concerns were evaluated using the EPA approved, SCREEN3 model. The maximumrnimpact is anticipated to be less than 3 percent of the National Ambient Air Quality Standards atrnground level, and less than 14 percent at flagpole heights. The model also indicated that thernambient air quality impact of toxic chemicals will be below current guidelines. Viable sites for locating a reactivation facility throughout Maricopa County were examined. Siternselection criteria included public concerns, accessibility, permitting requirements, proximity tornutilities, transportation and zoning.