A series of facultative lagoons operated by Thames Water treating industrial wastewater in Thailand were found to be performing poorly, particularly with respect to the removal of biological oxygen demand (BOD). A review of the design parameters for the site found that all the lagoons are of a sufficient area for the flow and BOD load. However, observations of the lagoons suggested that there may be significant hydraulic short-circuiting. Computational fluid dynamics (CFD) modelling was therefore carried out on one of the lagoons to establish the hydraulic regime. Two consecutive simulations were carried out, both with and without baffles; the first to establish steady flow conditions, and the second using a chemical species transport model to obtain the residence time distribution (RTD). The results of the modelling indicate that the lagoons do currently suffer from significant short-circuiting, and large dead-zones are present. The installation of baffles in the CFD model improved the plug-flow characteristics of the lagoons, substantially reducing the short-circuiting and the size of the dead-zones. It has therefore been concluded that the installation of baffles in the lagoons will lead to an improvement in their performance, by increasing the retention time of the system.
Three-dimensional computational fluid dynamic modelling of a facultative lagoon
H. E. Salter, C. T. Ta, S. K. Ouki, S. C. Williams; Three-dimensional computational fluid dynamic modelling of a facultative lagoon. Water Sci Technol 1 November 2000; 42 (10-11): 335–342. doi: https://doi.org/10.2166/wst.2000.0674
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