Water and wastewater treatment facilities rely on complex electrical distribution systems to power critical equipment, such as pumps, blowers, and associated variable frequency drives (VFDs). These components, while essential for efficient operation, can generate significant harmonic distortion, adversely affecting the overall power quality. Harmonics can lead to equipment overheating, increased losses, reduced efficiency, and potential failures, posing risks to operational reliability and escalating maintenance costs. This presentation explores the sources of harmonic distortion in electrical systems at water and wastewater facilities and their impact on performance. It highlights the role of non-linear loads, such as VFDs as primary contributors to harmonic distortion. Key industry standards, such as IEEE 519, are discussed in relation to acceptable harmonic limits to ensure safe and efficient operations. Effective mitigation strategies are crucial to improving system performance and reducing the adverse effects of harmonics. However, deciding on the correct level and type of mitigation is not always easy since many solutions can be costly. Proposed solutions will be explored including the use of line reactors, harmonic filters (both active and passive), harmonic mitigating transformers, and various VFD technologies. The presentation concludes by underscoring the importance of a proactive approach to harmonic mitigation in water and wastewater treatment facilities. By addressing harmonic issues, facility operators can enhance energy efficiency, protect critical equipment including generators and standby sources, and ensure the long-term reliability of their electrical distribution systems.