After his time at the water board, Ken returned to UCL as a lecturer in the civil and municipal engineering department in 1955. Promotion to reader followed in 1963 and to professor of public health engineering in 1967. He became Chadwick Professor and Head of Department in 1984, a position he held until his retirement in 1992. He was a superb teacher at all levels, and his lectures to undergraduates were very popular. Ken played a major role in the general life of UCL, serving on many important college committees and as dean of students for two years. He fully committed himself to these tasks and gave them a lot of time and attention. He was elected a fellow of UCL in 1996 and continued to be active in the social life of the college, notably as a frequent contributor to the discussions of the Natural Sciences Club. His last visit to UCL was on the day before he died.
Ken Ives began his fundamental research in water filtration in the 1950s, and he pursued this topic during a sabbatical year at the Harvard School of Public Health, with Gordon Fair, in 1958–1959. His year at Harvard was made possible by the award of a Fulbright fellowship. Ken was a pioneer in the use of computers to model the behavior of sand filters, which were (and still are) a very important part of conventional drinking water treatment. As a result of this work, Ken showed that traditional deep-sand filters were inherently inefficient, with most of the impurities being removed in just the top layers, so that a filter would become clogged when much of its potential removal capacity remained unused. This led to the development of new designs, such as upflow or stratified filters, which gave much better performance.
At UCL Ken also carried out detailed experimental filtration studies, using specially designed columns that enabled water samples to be taken at many points throughout the depth of the filter and pressure profiles to be recorded. With this approach, he carried out investigations on the mechanisms of particle capture by grains in a filter bed, both theoretically and experimentally. Later, he used advanced fiber optic techniques and high-speed video recording to directly observe particle movements within the pores of a filter bed.