A STEADY-STATE MODEL FOR THE SINGLE SLUDGE ACTIVATED-SLUDGE SYSTEM .1. MODEL DESCRIPTION

A steady-state model for activated sludge with or without nitrogen con trol is proposed. It pertains to real activated sludge systems in that both soluble and particulate influent organics are addressed and vari ous fractions of the mixed liquor solids are distinguished. The pseudo first-order kinetic law is used for soluble BOD removal and first-ord er kinetic for the hydrolysis of particulate organics. Biodegradation of hydrolyzed particulates is treated in a simlar way to the soluble o rganics by using an ''effective soluble BOD'' term which combines both BOD sources. Monod rate law is used for nitrification while denitrifi cation is controlled by BOD removal under anoxic conditions. The model equations are solved by an iterative procedure developed for this pro blem.