PREDICTING HYDROGEN SULFIDE EMISSIONS FROM EXPANDED WASTEWATER TREATMENT PLANTS

With increased public pressure to reduce odors, many wastewater managers are taking a proactive stance by including odor control in plans for plant expansion. Odor emissions from existing units can be measured; however, odors from new units built as part of plant expansion, or from existing units receiving large increases in wastewater flow, cannot – they must be predicted.This paper will describe a method for estimating emissions from expanded plants. Emission rates from the existing plant, determined from field data collection, are scaled up based on anticipated changes in wastewater turbulence, surface area, and composition. Wastewater emission models are used to predict how changes in wastewater turbulence (increased flows) will impact emissions. Expansion plans are used directly to determine wastewater surface areas for the expanded plant. Changes in wastewater composition are based on anticipated development in the area, and on models that estimate hydrogen sulfide generation in collection systems.The method would also be useful for estimating odors from a plant which will receive increased wastewater flow without being expanded. Although the method incorporates wastewater emission models, it does not rely on them exclusively because of their limitations in predicting odor emissions.The paper presents a case study, in which field measurements from an existing 2 MGD plant are scaled up to estimate emissions from the expanded 24 MGD plant. Future emission estimates account for increased turbulence due to increased wastewater flows, increased surface areas available for volatilization, and future changes in wastewater composition as the plant receives a higher percent of residential waste.