This module expands on the concepts of cost estimation and comparison of costs among various treatment alternatives which were presented in a previous module. The need for useful published cost data is stressed. Criteria for selecting cost references are presented, and examples of charts and graphs from several of these are used in comparing land application and conventional treatment schemes. Several critical cost factors are identified. A summary of generalized cost comparisons is made. Several pertinent cost references are listed, and the importance of keeping up to date with new reference material is pointed out to land treatment site designers. (Author/BB)