An analysis of nitrogen removal and control strategies in an alternating activated sludge process

• Published in: Water research (Oxford) Vol. 29; no. 2; pp. 535 - 544
• Main Authors: ZHAO, H, ISAACS, S.H, SOEBERG, H, KUMMER, M
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Science 1995
• Subjects: Air. Soil. Water. Waste. Feeding; Applied sciences; Biological and medical sciences; Environment. Living conditions; Exact sciences and technology; Freshwater; General purification processes; Medical sciences; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Wastewaters; Water treatment and pollution; Activated sludge; Process control; Nitrification; Denitrification; Nitrogen; Waste water purification; Modeling; Water treatment; Models; Method; Waste water
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/0043-1354(94)00174-6

Nitrogen removal in the alternating activated sludge process is described by a simplified version of the IAWQ activated sludge model No.1. The process was represented by a set of dynamic equations in terms of ammoniacal-nitrogen and oxidized nitrogen. Both nitrification and denitrification were represented in a simplified manner so that the variables were all measurable on-line. The principal disadvantage was that long-term effects such as population balance could not be described. Nevertheless it simulated pilot plant results adequately. A new analytical approach was developed by introducing the nitrification capacity and denitrification potential concepts into the alternating process analysis. From this, mathematical relationships between nitrogen removal efficiency and process operational conditions were obtained. The total nitrogen removal proved strongly dependent on the process load, nitrification rate, denitrification rate, cycle length and dissolved oxygen set point. Optimal operation required a balance between nitrification and denitrification. The different control strategies were also evaluated, resulting in a better understanding of their mechanism and effectiveness. The theoretical background to the model is described.