Performance Assessment of Secondary Settling Tanks Using CFD Modeling

Abstract

Amongst the principal separation processes used to treat effluents in the water industry is the sedimentation of solid particulates from the carrier fluid known as mixed liquor by the force of gravity. New York City DEP is in the process of upgrading its Upper East River water pollution control plants (WPCP's) to incorporate biological nitrogen removal (BNR). The rectangular final settling tanks (FSTs) are a central link in the treatment process and often times a limiting factor in terms of the solids handling capacity especially when high throughput requirements need to be met. The objective of this study was to develop a 3D Computational Fluid Dynamics (CFD) model based on the exact geometry of the existing Gould II type 1170 S. Xanthos et al.FSTs in Battery "E" at the Wards Island WPCP and calibrate and validate it with insitu data collected at the site. The goal of this study is to illustrate how the different modeling approaches applied on the physical phenomena that take place in the tank affect the outcome of a CFD model and its predictions. It is common for internal baffles to be added at the inlet and within the tank to handle high flow requirements such as wet weather storms. This model has been used as a tool to assess the internal behavior of such baffles and assess the clarifier's performance based on different inlet baffle configurations.

Improving the performance of industrial clarifiers using three-dimensional computational fluid dynamics

“…Furthermore, DeClercq (2003) compared his model to the Bingham and Bokil models and concluded that the Bokil model gave the best prediction of the sludge blanket height. Over the last few years, the Bokil model has also been successfully used to model the rheology of wastewater sludge (Griborio, 2004;McCorquodale et al, 2006McCorquodale et al, , 2007Ramalingam et al, 2012;Xanthos et al, 2011;Zhou et al, 2005). It is a two-parameter model that is also relatively easy to implement in a numerical framework, and it is therefore chosen for this study.…”

“…This model was later used by Ghawi and Kris (2011) to investigate the effect of inlet baffles in terms of improving the performance of the secondary clarifiers at the Al-Dewanyia WWTP in Iraq. Xanthos et al (2011) incorporated a flocculation sub-model into a 3D CFD model to improve the Upper East River water pollution control plant in New York City. More recently, Griborio, Martinez, Stanley, Koroshec, and Coates (2012) presented a comprehensive approach including field characterization and CFD modeling for the rehabilitation of three circular centerfeed secondary clarifiers at the South Central Regional Wastewater Treatment and Disposal Board located in Delray Beach, Florida.…”

“…Even the few 3D clarifier studies (Griborio, 2004;McCorquodale et al, 2005;Ramalingam et al, 2007;Xanthos et al, 2011Xanthos et al, , 2013) focus on simple circular or rectangular geometries with a center-feed design. In comparison, the clarifiers in Freeport, TX have highly asymmetric geometry with a side-feed mechanism which necessitates coupled 3D simulations of fluid flow and solid concentration.…”

Numerical Simulation of Coal Suspension Sedimentation

“…Process release a portion of the solid from the suspension normally is carried out in settling tanks (Kowalski, 2004;Burger & Wendland, 2001;Bandrowski et al, 2001;Banaś, 2004a), that is devices using sedimentation process. The intensification of the process of sedimentation, the optimization of the process as well as the construction settlers still an important research topic (Bajcar et al, 2010(Bajcar et al, , 2011Branny & Swolkien, 2010;Rostami et al, 2011;Goula, 2008;Samaras, 2010;Xanthos, 2011;Malcher & Gzyl-Malcher, 2012;Surowiak & Brozek, 2014;Tryggavason & Zaleski, 2011).…”

Experiments and numerical modeling of baffle configuration effects on the performance of sedimentation tanks

“…There are a number of comprehensive studies on baffled tanks that investigate their hydraulic efficiency (McCorquodale and Zhou, 1993;Tamayol et al, 2010;Xanthos et al, 2010). Brescher et al (1992) considered a rectangular clarifier and showed that an intermediate (where intermediate refers to location along the tank length) baffle on the base of the tank, transverse to the main flow direction, influences the flow field and can improve efficiency.…”