Remarkably Low Maintenance and Effective Odor Control from Media-Based Odor Control Systems

Like many wastewater treatment plants in the county, the Las Vegas Street Wastewater Treatment Plant (LVSWWTP) in Colorado Springs, CO has come under increased public pressure to reduce odor impacts to the surrounding community. As an initial response to the complaints, two odor control systems were installed by the Colorado Springs Utilities that reduced overall odor emissions from the plant by more than 60%. Both systems are mediabased,and have remarkably low maintenance requirements. Case studies summarizing the design and operation of the systems are presented in this paper. Four types of media were used in these systems to effectively remove offensive odors.The first system was designed to move 24,000 cfm from the bar screen room and is the largest aerobic iron-based media system in the nation. The iron-based media (SulfaTreat®) removes 100% of the H2S from the airstream. But other odorous compounds in the effluent of the system were causing an unacceptable level of odor on the site. Polishing to remove these compounds has been accomplished with a thin layer of activated carbon. The mild odor in the effluent from the dual media system has not been deemed to be offensive. This dual media system is achieving a 97% to 99% reduction in odor units.The second system treats odors from the effluent flume of the primary clarifiers. At startup,the iron sponge media was removing over 99% of the H2S. The removal rate has dropped over the first 15 months of operation to around 96%. The iron sponge media has lasted longer than the design life of 1.25 years with a final H2S removal rate of 95%. Some conversion of methyl mercaptan to dimethyl disulfide appears to be occurring in this media. Odorous compounds in the effluent from the iron sponge media shortly after startup were also causing an unacceptable level of odor at the plant. A polishing system was subsequently installed. In the first compartment of the polishing system, an iron-based media (SulfaTreat®) removes most of the remaining H2S. In the second polishing compartment, a mix of activated carbon and activated alumina media impregnated with potassium permanganate (Purafil®) provides final polishing. The remaining odor in the effluent from this three-media system is slightly offensive but cannot be detected a short distance from the outlet. The overall system is reducing inlet odor units by 95% to 98%.Detailed sample data and analysis from the first year of operation shows that two-stage media-based odor control systems are effective and require little or no maintenance other than what is usually required for fans. Biofilters are touted as requiring low maintenance, but these systems definitely go a step further towards effective and easily maintained odor control systems.