A heating facility in Wisconsin required nearby lake water to be clarified and demineralized in order to produce water suitable for boiler feed. Two technologies were identified as potential solutions to the clarification portion of this process: ACTIFLO® Turbo followed by Multimedia Filters and a membrane ultrafiltration system. A carbon footprint analysis was conducted on these two options to determine which would produce fewer carbon emissions over the course of a 20-year period.
Technology Design Data
The ACTIFLO® Turbo/Multimedia Filtration and ultrafiltration options were each designed to treat 600 gpm of flow primarily for Total Suspended Solids (TSS) and Total Organic Carbon (TOC) removal, achieving target levels of about 2 mg/L of each constituent. Additionally, each design was to be able to respond to potential spikes in TSS loading due to algal blooms that could occur during the summer months. The process flow for each option prior to the demineralization step is illustrated below:
The carbon footprints of the ACTIFLO® Turbo/Multimedia Filtration and ultrafiltration options were analyzed primarily based on their energy, process, and chemical usages. While emissions costs associated with consumables were addressed and travel and freight costs were considered, they were given less weight in the analysis. The reason why this is so is because this analysis was conducted during a preliminary phase of the project's development; while energy, process and chemical use could be estimated based on experience with similar applications addressed in the past, consumables, travel and freight costs had not yet been solidified. As such, the emphasis of this exercise is on the effects of operational rather than capital costs and their effects on carbon footprint. The result of the carbon footprint analysis conducted on each treatment option is given in the figure below:
Carbon Footprint Over System Lifetime
While the greatest contributor to the carbon footprint of each technology was energy use, reagent consumption and consumables also played roles in producing carbon emissions. However, the ACTIFLO Turbo/Multimedia Filtration system has been optimized to use little energy, consume few chemicals, and has fewer components that require replacement over a 20-year period of time compared to the ultrafiltration system. As a result, the former system produces a carbon footprint that is about half that of the latter.
The ACTIFLO® Turbo/Multimedia Filtration option to clarify lake water prior to its demineralization and boiler feed water use had a carbon footprint that was 50% less than that of its alternative, membrane ultrafiltration. The ACTIFLO® Turbo's efficient design, utilizing a TURBOMIXTM draft tube to optimize tank mixing such that lower energy and chemical use is required, as well as its having few replaceable parts, is a key contributor to its smaller carbon footprint.