Historically, one of the most vexing problems facing designers and operators of sewage treatment plants has been the treatment and disposal of solids. In the past few years, however, a great deal has been accomplished by engineers, operators and equipment manufacturers in the improvement of systems and processes to the end that solids disposal systems now are more efficient and reliable than in the past. As an example of a modern design approach to solids disposal in large treatment works, I have chose to describe a waste treatment plant presently being designed by Brown and Caldwell for a large city in Australia. Although the treatment plant described in this paper is a large one, having an initial design capacity of 75 mgd, the solids collection, treatment and disposal systems and processes apply equally as well to small plants with design capacities ranging down to one mgd.