Bruce I. Dvorak
Date of this Version
Although water resource recovery facilities (WRRFs) reduce environmental impacts related to water quality, their construction and operation result in negative environmental impacts in other categories. Past research into Nebraska WRRFs investigated variables determining energy intensity, opportunities and barriers for energy efficiency improvements, and environmental impacts of the construction and operation phase. This leads to the research question of what design practices can be considered to reduce the environmental impacts.
The Life Cycle Assessment (LCA) methodology was used to evaluate and compare the inventory and environmental impacts of nine small WRRFs, most of which are serving slow growing or declining populations. Inventory data was collected from the facilities’ engineering design plans and utility bills and simplified to 21 lines of general representative inventory. The SimaPro v8 program used to convert inventory to environmental impact, and the Ecoinvent database was used for background data. The outputs were categorized by ten process elements to address the multi-functional nature of WRRFs and by the ten TRACI characterization factors.
The biological reactor and the conveyance elements were identified as high impact process elements. Whereas the biological reactor had low impact variability, the conveyance had high variability. Three opportunities for impact mitigation were identified. The first suggested practice is to avoid significant overdesign by planning for no lower than a 75% capacity utilization. Planning for a lower design average flow rate was shown to mitigate lifetime electricity usage and secondary process concrete, and consequently Carcinogenic and Global Warming environmental impacts. Other suggested practices were focused on the conveyance process element, namely, to reduce ductile iron piping since it was found to contribute 93% of the carcinogenic impact in the conveyance element. The suggested practices were to minimize non-process facility area and to use polyvinyl chloride pipe instead of ductile iron pipe where possible.
Advisor: Bruce I. Dvorak