A computer program (FORTRAN, IBM 1130) is presented which can be used to compute the quasi-steady-state performance and cost of groups of conventional and advanced wastewater treatment unit processes arranged in any configuration. Each subroutine computes the performance and cost of a single unit process. An influent stream vector and decision variables are input. The program contains subroutines for simulating the following wastewater treatment processes: preliminary treatment, primary sedimentation, aerator-final settler, stream mixer, stream splitter, anaerobic digestion, vacuum filtration, gravity thickening, elutriation, sludge drying beds, trickling filter-final settler, chlorination, flotation thickening, multiple hearth incineration, raw wastewater pumping, sludge holding tanks, centrifugation, aerobic digestion, post aeration, equalization, second stage anaerobic digestion, land disposal of liquid sludge and lime addition to sludge. The report includes a program listing.