Bruce I. Dvorak
Date of this Version
Wastewater treatment plants (WWTP)s account for about 0.8% of U.S. electricity use. Small WWTPs serving communities of populations less than 10,000 accounts for 95% of treatment plants in Nebraska. These plants are significantly less efficient compared to large systems and thus improving their energy efficiency (E2) is a growing focus in efforts to reduce greenhouse gas emissions associated with their operation. Energy use of plant unit operations was evaluated for several plants and included analysis of energy for space heating. Specific infrastructure and/or operational changes reported by operators following an E2 benchmarking project were evaluated by quantifying the change in annual billed energy use. Barriers to implementing E2 improvements were ranked by operators in a one-page survey. Supplemental observations from plant assessments occurring throughout the E2 benchmarking project and fifteen subsequent energy assessments were provided.
Aeration was identified as the largest energy use (66-73%) of total process energy use and space heating accounted for 4-34% of total plant energy use. Changes were reportedly being made at 19 plants (37% of respondents), with 12 plants reporting changes recommended in the previous benchmarking letters. Energy bills collected for 13 plants reporting changes had 9 plants showing energy reductions of 4-35% and an approximate $39,000 of annual cost savings, with the largest reductions involving the use of VFDs. These plants showed an 8.5% average reduction in energy compared to a 1.2% reduction shown by 16 plants reporting to have not made changes.
Survey responses from 41 operators showed that financial related barriers and lack of time or other priorities are the largest barriers for small municipalities in making E2 improvements. Organizational issues also exist within small municipalities in which energy management is not prioritized and often is neglected. Plants reporting making changes had reported lack of staff of awareness as less of a relevant barrier compared to plants reporting to have not made changes. This may suggest that raising awareness about E2 can potentially lead to greater implementation of changes.
Advisor: Bruce I. Dvorak