Abstract
Granular activated carbon (GAC) filtration is an important unit operation in drinking water treatment. GAC filtration is widely used for its filtration and adsorption capabilities as a barrier for undesired organic macro- and micro-pollutants. GAC filtration consists of two successive phases: adsorption and filtration, capturing the impurities from the water in conjunction with a backwash procedure in which the suspended particles are flushed out of the system. Available literature predominantly focusses on adsorption. A less frequently discussed but nevertheless equally crucial aspect of this operation is the backwash procedure of GAC beds. To prevent accumulation of suspended particles and to avoid additional operation costs, optimal backwashing is required. Another factor is sustainability: water utilities are showing increasing interest in exploring new sustainable GAC media. As these have different bed expansion tendencies due to different GAC characteristics with varying geometries, operational developments are needed for prediction models to estimate the expansion degree during backwashing. The prediction of the bed expansion of GAC is complex as the particles are non-spherical, porous and polydisperse. Through a combination of advanced particle laboratory and fluidisation experiments, we demonstrate a new approach which leads to an improved expansion prediction model for the backwashing of GAC filters.
Highlights
Granular activated carbon (GAC) filtration is widely applied in advanced drinking water treatment plants for its filtration and adsorption capabilities as a barrier for undesired macro- and micro-pollutants [1,2,3]
In this research we developed a new approach leading to new insight into the expansion characteristics of granular activated carbon grains used in water fluidisation processes
Some researchers propose empirical models and mention low prediction errors, but it is unclear how accurate these models will remain when GAC is used for a long period of time
Summary
Granular activated carbon (GAC) filtration is widely applied in advanced drinking water treatment plants for its filtration and adsorption capabilities as a barrier for undesired macro- and micro-pollutants [1,2,3]. Netherlands to integrate activated carbon technologies in their drinking water treatment plants [4]. When a head loss setpoint is exceeded, the accumulated particles are removed from the GAC filter during the backwash phase through an up-flow water stream and additional air scouring. For reliable and safe drinking water production, a precise specification of backwash rates for filter cleaning is needed.
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