On-line determination of sludge settling velocity for flux-based real-time control of secondary clarifiers

• Published in: Water science and technology Vol. 54; no. 11-12; pp. 249 - 256
• Main Authors: Lynggaard-Jensen, A, Lading, L
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01.01.2006
• Subjects: Algorithms; Capacity; Clarifiers; Control; Control algorithms; Control theory; Kinetics; Mathematical models; Online Systems; Rain; Real time; Sensors; Settling rate; Settling velocity; Sewage; Sludge; Sludge settling; Sludge volume index; Suspended particulate matter; Suspended solids; Velocity; Wastewater; Wastewater treatment; Wastewater treatment plants; Water Purification - methods; Water Purification - standards
• DOI: 10.2166/wst.2006.719
• ISBN: 184339586X; 9781843395867
• ISSN: 0273-1223

The state diagram for operation of secondary clarifiers is used to design a control algorithm for the return sludge pumping and determination of the actual hydraulic capacity of the biological step of a wastewater treatment plant. On-line input for the control algorithm is derived from a sludge volume sensor and a suspended solids sensor in the form of software sensors giving values for the sludge settling characteristics - settling velocity, sludge volume index, initial settling velocity and the exponent in the Vesilind equation - allowing the control to accommodate the ever changing settling characteristics and thereby keep the suspended solids flux in the clarifiers in balance for both dry weather flows and during rain events. The control algorithm has been implemented, tested and set into normal operation on a full scale wastewater treatment plant.