Effect of Aluminium Salt Dosing on Activated Sludge Settleability Indicators: A New Settleability Model Development

Peter Ojo, Augustine Ifelebuegu

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5 Citations (Scopus)
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There has been a significant rise in the use of aluminium salts (Al3+) for the chemical precipitation of phosphates in wastewater treatment plants due to growing stricter regulatory requirements for wastewater effluent release to the environment. The modelling of the settleability of the resultant Al3+ sludge in present engineering practice for design and optimisation are still based on conventional sludge settleability models. This paper describes a novel activated sludge settleability model which is designed to analyse the effects of Al3+ dosing on activated sludge settleability indicators, zone settling velocity (ZSV), and stirred specific volume index (SSVI). The impact of Al3+ dosing concentrations on ZSV and SSVI of full scale activated sludge plant were analysed in the laboratory over a three years’ period and the exponential form of the Vesilind equation was optimised and validated to include alum chemical dosing parameters. The proposed model equation was found to effectively describe the settleability of Al3+ dosed sludge for dosing concentrations range of 0 to 100 mg/L.
Original languageEnglish
Article number179
Number of pages19
JournalWater (Switzerland)
Issue number1
Publication statusPublished - 21 Jan 2019

Bibliographical note

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution
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  • activated sludge
  • settleability
  • zone settling
  • velocity
  • alum
  • stirred sludge volume
  • index


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