The spatial significance of water quality indicators in waste stabilization ponds - limitations of residence time distribution analysis in predicting treatment efficiency

Abstract

Over the past fifty years, considerable research in waste stabilization pond operation has led to the development of a number of models used to describe the hydraulic regime and predict treatment efficiency. Models range in complexity from plug or completely mixed simplifications to computational fluid dynamics (CFD) models which are able to predict flow hydraulics at a local level. Information about the exit age of pond effluent can be used to estimate pollutant decay. However, a mechanistic approach to understanding pond operation highlights the importance of knowing both the time and spatial history of pond effluent. A CFD model of a large pond system was constructed to demonstrate various hydraulic scenarios under different boundary conditions. Two scenarios were compared to visually demonstrate the effects of differing hydraulic conditions. Typical mechanistic models were applied to each condition to quantify biological differences. This simple example indicates that integrating biological and localised flow models will lead to a more holistic understanding of pond operation and treatment efficiency.

Removal improvement of bacteria (Escherichia coli and enterococci) in maturation ponds using baffles

“…The dispersion numher 'd' is used as a descriptor of the magnitude of longitudinal dispersion within the pond, on a scale ranging from 0 (plug flow) to 00 (completely mixed condition). Dispersion number analysis of WSPs was developed from retrospective analysis of pond hydraulic performance (Sweeney et al 2003). A number of expressions have been empirically developed to predict dispersion number based on pond parameters such as length, width, depth, and flow rate (Polpresert & Bhattarai 1985).…”

Impact of Hydrodynamic Reconfiguration with Baffles on Treatment Performance in Waste Stabilisation Ponds: A Full-Scale Experiment

“…The inclusion of wind in hydrodynamics modelling of WSPs is not a recent development, with several previous studies incorporating wind into WSP models e.g., [36][37][38][39], however there is still a need to better understand the effect that environmental conditions have on the function of WSPs, including wind [40].…”

Función objetivo en el diseño de la laguna facultativa (estudio de caso)

“…Sistemas de modelado han incorporado diferentes características por ejemplo: Salter et al (2000) consideró la influencia de las mamparas en condiciones de flujo hidráulico, más tarde Sweeney et al (2003) analizó específicamente el efecto del viento en el perfil hidráulico, luego Manga et al (2004) centró sus estudios en la longitud y la localización de entrada y salida en el régimen de flujo de los sistemas lagunares. Algunos estudios donde se incluyeron los efectos combinados del viento, el impacto de mamparas así como la posición de entradas y salidas: Shilton y Harrison (2003a); Shilton y Mara (2005) y Sweeney et al (2003). Después Sah et al (2012) mencionan que es necesario desarrollar un modelo integral y calibrado para lagunas de estabilización que se utilice como una herramienta de apoyo y optimización.…”

“…Modeling systems have incorporated various features such as: Salter et al (2000) considered the influence of the screens in terms of hydraulic flow later Sweeney et al (2003) specifically examined the effect of wind on the hydraulic profile, then Manga et al (2004) focused his studies on the length and location of entry and exit in the flow regime of the lagoon systems. Some studies where the combined effects of wind, the impact of screens and the position of inputs and outputs are included: Shilton and Harrison (2003a); Shilton and Mara (2005) and Sweeney et al (2003). After Sah et al (2012) mention the need to develop a comprehensive model for calibration and stabilization ponds to be used as a support tool and…”