New flocculation centre well design for circular final clarifiers at the Tai Po Sewage Treatment Works

摘要

In the year 2012, the Drainage Services Department had adopted the new flocculation centre well (FCW) design for two circular final clarifiers at the Tai Po Sewage Treatment Works. In the existing FCW design, the suspended solids (SS) and foam may accumulate and float inside the FCW under the condition of high sewage inlet flow rate and hence this may affect the SS level in the effluent. In this paper, with the assistance of the computational fluid dynamics modelling, flow patterns and SS distribution under the existing and new FCW design were simulated and analysed in different aspects. The findings from the modelling were summarised to finalise the new FCW design. The subsequent testing of the new design was carried out in December 2012 and January 2013, respectively. The data collected in the testing provided a complete picture of the effectiveness of the new FCW design such that the experience on design procedure and testing of new FCW design could be shared.