Study of hydraulics and mixing in roof tanks used in intermittent water supply

Abstract

Roof tanks are common in low and middle income countries, due to the intermittent water supply. Their hydraulic and water mixing behaviour has not been studied. This paper presents the results of a study on mixing and water demand in roof tanks, based on physical and numerical models. Tracer tests were carried out on a real scale transparent wall laboratory model of a roof tank, and a three-parameter residence time distribution model was applied, showing that the model that best describes mixing in roof water tanks is the one with a completely stirred flow reactor with a small portion of bypassing. This result was confirmed by computational fluid dynamic simulations and visual observation. The instantaneous water flow derived from activating typical home water-using fixtures was measured at the pipe feeding the tank, the pipe exiting the tank, and without a roof tank. Stochastic water demand patterns were generated with the measured data and used in the numerical model of a small distribution network. Based on this model it was found that water demand and pipe flow behave differently in continuous and intermittent water supply networks. The instantaneous flow rate withdrawn from the water distribution network pipes is lower in systems with roof tanks.

Quality Analysis of Atmospheric Deposits in Networks with Intermittent Service

“…Por el contrario, otros estudios existentes se focalizan en campañas de monitoreo y análisis de laboratorio para estudiar: la influencia de la temperatura y tiempo de almacenamiento en el aumento de la actividad microbiana [15]; la influencia de los depósitos en la variación de los parámetros de calidad antes y después del almacenamiento [16]; la influencia de los materiales de construcción de los depósitos y de su respectivo mantenimiento en la pérdida de calidad física, química y microbiológica del agua [17]; los efectos del servicio intermitente en depósitos de almacenamiento de agua en Tamale(Gana) [18]; el tipo de mezcla y patrones de demanda en depósitos elevados a escala de laboratorio comparando los resultados mediante técnicas computacionales [19]; la calidad del agua del grifo, depósitos privados y dispensadores de agua filtrada analizando el cloro libre residual, color, turbidez, pH, conductividad, patógenos(E.Choli), sólidos totales [20].…”

Modeling Bacterial Regrowth and Trihalomethane Formation in Water Distribution Systems

“…This assumption makes modeling the temporal variations of the bulk phase species within the tanks quite simple as it requires no extra parameters to describe it. Additionally, it applies well to all the storage components that are operated in a fill-and-draw manner [35].…”