Date of this Version
Hanna, S.M. (2017). Benchmarking the Energy Intensity of Small Nebraska Wastewater Treatment Plants (Master's Thesis). Department of Civil Engineering, University of Nebraska-Lincoln. Retrieved from UNL Digital Commons (Post URL Here).
To help small communities improve the energy efficiency of their wastewater treatment plants, this study created energy benchmarking models for small wastewater plants serving populations of 10,000 or less and having average flows less than 1.5 million gallons per day (MGD). The purpose of these models is to allow comparisons among plants of similar type and size, identify what factors most significantly impact energy usage, and predict potential savings from changes in key plant characteristics.
Energy usage and plant data from 83 small, mechanical wastewater plants in Nebraska were collected and used to create energy benchmarking models. Data obtained from the Pennsylvania Department of Environmental Protection on 71 small Pennsylvania wastewater plants were also used for modeling and comparisons among the two states. The development of these benchmarking equations was modeled off the American Water Works Association Research Foundation and ENERGY STAR models for large wastewater treatment plants. Separate models were created by state with an overall model created for all plant types, as well as models based off the three most common plant types (extended aeration, oxidation ditch, sequencing batch reactor).
The models predict either intensity (MWh/MG) or usage (kWh/year) for both electric use only and total energy use. Key variables found in most models include extended aeration plant type, supplemental energy usage for sludge treatment, average flow, percent design flow, climate controlled floor area, effluent ammonia-nitrogen, and influent carbonaceous biochemical oxygen demand (CBOD). The resulting models suggest that the variability of effluent NH3-N limits may be a more important parameter in determining energy usage than influent and effluent CBOD for small plants. Like past studies, flow was found to explain much of the variation in energy use. Some variables that have not shown up as significant in previous studies may only be significant for small plants. These include climate controlled floor area, supplemental energy usage for sludge treatment, and presence of dewatering equipment. Some variables, such as automatic DO controls, thought to be significant, were found not to be significant. Differences between the Nebraska and Pennsylvania models suggest these types of models may be more region specific.
Advisor: Bruce I. Dvorak