Conference Publication Details
Mandatory Fields
Hannon, L., Kennelly, C., Mullins, D., Gordon, G., McCann, B., Clifford, E.
2nd IWA Specialist Conference on EcoTechnologies for Sewage Treatment Plants
Examination of Selected Alternative Settlement Tests at Small-scale Activated Sludge Plants
Optional Fields
Sludge Volume Index (SVI); Settled Sludge Volume (SSV); Performance and Monitoring Wastewater Treatment Plants; Activated Sludge.
Verona, Italy
The settling behaviour of activated sludge in wastewater treatment plants (WWTPs) is a common operational test used to assess performance and monitor changes in the treatment process. In particular, the sludge volume index (SVI) has long been recognised as a useful index of plant operation. Recent surveys of plant managers and custodians at small and medium-scale activated sludge (WWTPs) in Ireland indicate that, despite being a simple test and providing informative data, the SVI tests are generally not utilised. Similar trends can be found in other countries, particularly, at small facilities without resident staff. At all plants surveyed, a variation of volumetric settleable solids is the only routine operational settlement test being carried out; test frequency varies from daily to weekly. Most commonly, the test comprises a 30-min period of quiescent settling in an Imhoff cone (‘cone test’). The resultant volume of sludge settled is the recorded, however, cone test results are not comparable to the standard methods defined stirred settled sludge volume (SSV) test. Furthermore it cannot be used to determine SVI and is thus of limited value. The settleable solids test, on which the cone test is based, is recommended for dilute sludges, which are frequently not representative of activated sludge processes. This study compared stirred and quiescent 30-min settlement tests carried out in 1.3L and 2Lsettleometer vessels, cone tests and quiescent settling in standard 1L-graduated cylinders; activated sludge samples (n = 37) from 8 small-medium scale activated sludge plants were tested. The results show that (i) 30-min quiescent settling in an Imhoff cone generally yields higher settled volumes than quiescent settling in a 1.3L or 2L-settleometer vessel, (ii) equivalent results are derived from an Imhoff cone and a graduated cylinder and (iii) quiescent settling in 1.3L and 2L-settleometers yield higher results than stirred settling in the same vessels. A correlation is observed between the quiescent settling in the 1.3L-settleometer and SSV determined as per Standard Methods. A relationship is also presented to derive SSV from quiescent settling. This may facilitate estimation of SVI using simple apparatus. The results presented indicate that by replacing the vessel used in the ‘cone test’ with a settleometer, more meaningful information, that could significantly improve facility management, can be derived. Future work is focused on establishing that dilution can significantly reduce settlement test-time while maintaining SVI measurement accuracy.
Grant Details
EU, Enterprise Ireland (EI), NUI Galway
e funding from the European Union’s Horizon 2020 programme under grant number 689817 (INNOQUA), the Enterprise Ireland Commercialisation Fund (Grant Number: CF2332) and the College of Engineering and Informatics PhD scholarship
Publication Themes
Environment, Marine and Energy