California Wastewater Treatment Operator Practice Exam 2025 – All-in-One Guide to Master Your Certification

Tertiary treatment is the final step in wastewater treatment aimed at further improving water quality before it is released back into the environment or reused. A common method for tertiary treatment is filtration and advanced oxidation. This process involves removing any remaining suspended solids and microorganisms after secondary treatment.

Filtration typically uses various mediums (like sand or membrane filters) to effectively eliminate smaller particles and pathogens that may not have been adequately removed in previous treatment stages. Advanced oxidation processes involve the use of strong oxidizing agents, such as ozone or hydrogen peroxide, often in conjunction with ultraviolet light. This approach breaks down contaminants that are otherwise difficult to remove, resulting in treated water that meets higher quality standards.

This method stands out because it not only improves clarity and reduces residual organic matter but also targets specific pollutants that secondary treatment may leave behind. In contrast, other methods listed tend to belong to different stages of treatment or focus on different removal processes. For instance, biochemical digestion is primarily part of sludge treatment, while settling and skimming as well as flocculation and sedimentation relate more to primary and secondary treatment processes, addressing larger solids and microbial aggregates.