Using Impellers to Distribute Local Nutrient Loadings in a Stratified Lake: Lake Como, Italy
Publication: Journal of Hydraulic Engineering
Volume 135, Issue 7
Abstract
The feasibility of using a vertically downward pointing impeller to remove polluted water from a coastal margin was investigated with a pilot experiment in Lake Como, Italy. The vertical jet induced by the impeller entrained surface water downward to depth, where upon reaching neutral buoyancy it intruded horizontally into the lake proper. A three-dimensional numerical hydrodynamic model was validated with results from an intensive (eight-day) field study during which rhodamine WT dye was introduced in the lee of the impeller and then tracked as it was transported into the lake. One of the major sources of pollution to the lake is the Cosia River underflow that drains a catchment adjacent to the City of Como. The numerical model, once validated, was used to show that six impellers, with the correct thrust, could be used to reduce the pollutants adjacent to the City of Como by half within two weeks; this was achieved by injecting the surface water to a depth that would intensify the Cosia River intrusion.
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Acknowledgments
This work was funded by the Como Province, Como Town Council, Como Chamber of Commerce, Cariplo Foundation, and Banca Intesa, and coordinated by Centro di Cultura Scientifica “A. Volta,” and conducted in conjunction with L’Istituto di Ricerca Sulle Acque (IRSA) in Brugherio. We wish to acknowledge the efforts of G. Casati, F. Mercalli, M. Canepa, and S. Zaffaroni from Centro Volta, and of G. Tartari and L. Valsecchi from IRSA. The assistance of G. Attwater, M. McCarthy, C. Dallimore, and R. Green during the field work is also gratefully acknowledged. S. M. particularly acknowledges many helpful conversations with P. Okely and R. Alexander regarding the analysis of horizontal transport in lakes. S.M. was the recipient of a Scholarship for International Research Fees (SIRF) from the University of Western Australia and an ad hoc scholarship from the Centre for Water Research (CWR). This paper forms CWR Reference ED1951SM.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 135 • Issue 7 • July 2009
Pages: 564 - 574
Copyright
© 2009 ASCE.
History
Received: Nov 13, 2007
Accepted: Jan 9, 2009
Published online: Apr 30, 2009
Published in print: Jul 2009
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