During 1961–1992, research on wastewater treatment prioritized high-rate, compact processes that leveraged anaerobic upflow sludge blanket concepts to simplify design and enhance throughput. Adsorption- and surface-chemistry–driven pollutant removal using silica and natural sorbents addressed dyes, fluoride, and related contaminants, emphasizing rate processes and surface transfer. Biological phosphorus removal within activated sludge began to take shape, grounded in microbial metabolism studies and metabolic pathways, while algal and natural approaches expanded orthophosphate and ammonium removal. Heavy metals removal and sludge handling incorporated extracellular polymer–mediated binding and disposal considerations, and ambient-temperature granular-bed anaerobic treatment and UASB-related concepts signaled a new era of high-rate anaerobic treatment. Historical Significance: The upflow sludge blanket concept catalyzed the emergence of high-rate anaerobic systems and became foundational for modern wastewater digestion practices. Standard methods and wastewater engineering texts established common analytical procedures and integrated disposal-and-reuse frameworks that guided policy, curricula, and design practice for decades. The Chemistry of Water Treatment Processes Involving Ozone, Hydrogen Peroxide and Ultraviolet Radiation, together with canonical analytical methods, anchored enduring approaches to treatment optimization and regulatory compliance.