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.

No abstract

No abstract