2003-063 - Laserfiche WebLink

Home Browse Search

ODOR CONTROL STUDY • Install a VFD on the existing blower and add a second smaller blower to the existing scrubber system . Also , install an automated damper on the exhaust duct from the Dewatering Building . Operate the large blower at full speed during sludge dewatering . Operate the small blower at full speed or large blower at approximately half speed when sludge is not being dewatered . • Install a new hypochlorite storage and feed system if the existing hypochlorite generation facility is found to be inadequate upon further review , or if the new hypochlorite system is desired by the County. 4 . 0 Air Dispersion Modeling To estimate the off-site odor impacts of alternative improvements to the major sources of odorous emissions at the Central WWTF , an air dispersion model was developed for the Central WWTF and surrounding areas . The air dispersion model was developed to estimate how the alternative improvements could reduce the sulfide concentrations in surrounding communities , under worse case meteorological conditions . The air dispersion modeling was developed- using the EPA' s Industrial Source Complex Short Term model , third edition ( ISCST3 ) . The ISCST3 model is a Gaussian model capable of predicting off-site concentrations of specific compounds emanating from point and area sources using meteorological data . Local meteorological data for every day for an entire year were analyzed and used with odor emission data developed for this study as inputs to the air dispersion model. The model then calculated maximum hourly and annual average sulfide concentrations at a grid of receptors that surrounded the Central WWTF . Upper and lower atmospheric data from West Palm Beach Morrison Field were used in the model . This was the closet meteorological station with hourly wind speed and direction data . It should be noted that meteorological conditions at the Central WWTF likely vary from those at the West Palm Beach airport . However, the West Palm Beach airport data are the only data available . The model was executed assuming urban conditions and excluded calm hours . The model calculated the downwind sulfur concentrations along a receptor grid that extended for two thousand meters ( 1 . 2 miles ) in all directions from the treatment facility. The receptors were assumed to be at a height of 1 . 5 meters (4 . 9 feet) , which is considered to a typical breathing height . The model was run to calculate the first, second , and third highest 1 -hour average sulfide concentrations for an entire year. Lines of constant concentration , or isopleths , were plotted on a map of the areas surrounding the site . The second highest one-hour concentration was used to calculate the worst-case isopleths to exclude any anomalies that might be associated with the first highest one- hour concentration . 23 Indian River County, Central Wastewater Treatment Facility PBSU #071230, February 2003