Algorithm for Optimal Activated Sludge Design

Abstract

Nonlinear design equations are used to model an activated sludge tank, final settling tank, gravity thickener, anaerobic digester, vacuum filter, pumping and aeration in terms of the design variables activated sludge solids retention time, hydraulic retention time, recycle ratio, thickener underflow suspended solids concentration, and digester solids retention time, for steady-state conditions. Nonlinear cost equations are used to model the cost of the individual unit processes in terms of unit process sizes and capacities. The Box-Complex algorithm, a numerical search technique, is then used to determine the optimum sizes of the unit process to minimize the sum of capital and operating costs for a specified design inflow, effluent quality, and equipment limitation. Less than 3 sec of execution time on a CDC CYBER 173 using an FTN compiler are required to determine the optimum.