Simulation of Single‐Sludge Nitrogen Removal

Abstract

A kinetic model is presented to describe the interactions among microbial reactions that are important in single‐sludge treatment systems for nitrification/denitrification. This model describes the aerobic processes of organic carbon oxidation and nitrification and the anaerobic process of denitrification. It was used in a series of computer simulation experiments to delineate the effects of process variables on efficiency of nitrogen removal in an intermittently aerated, completely mixed, single‐sludge configuration. The effects of the following variables on nitrogen removal were studied: aeration fraction, solids retention time, hydraulic retention time, dissolved oxygen control, and the influent concentration of organic matter. Important interactions were observed between the solids retention time, aeration fraction, and influent organic matter concentration and were investigated in additional simulation experiments. Results of these experiments show the importance of solids retention time, aeration fraction, influent organic matter concentration, and dissolved oxygen control strategy to good nitrogen removal. Knowledge of the nature of the interactions among these variables is directly applicable to design and operation of single‐sludge biological treatment systems for concurrent removal of organic matter and nitrogen.