Abstract
Micropollutants can be removed in Biological Activated Carbon (BAC) filters through biodegradation, besides adsorption, when the conditions are favorable. In the present study, we build upon previous work on melamine biodegradation and activated carbon regeneration in batch experiments and assess the efficiency of this process in continuous flow lab-scale BAC filters. Melamine is frequently detected at low concentrations in surface water and is used here as a model micropollutant. BAC filters were inoculated with melamine degrading biomass and the contribution of biodegradation to melamine removal was assessed. Furthermore, we tested the effect of an additional carbon source (methanol) and the effect of contact time on melamine removal efficiency. We demonstrate that inoculation of activated carbon filters with melamine degrading biomass increases melamine removal efficiency by at least 25%. When an additional carbon source (methanol) is supplied, melamine removal is almost complete (up to 99%). Finally, through a nitrogen mass balance, we demonstrate that around 60% of the previously adsorbed melamine desorbs from the BAC surface when biodegradation rates in the liquid phase increase. Melamine desorption resulted in a partial recovery of the adsorption capacity.
Highlights
Micropollutants that are present in drinking water sources can be fully or partly removed by the use of Granular Activated Carbon (GAC) filters
The modeled breakthrough curve for adsorption shows complete breakthrough within the time-frame of the experiments (6000 Bed Volume (BV)). These results clearly demonstrate that melamine biodegradation is significantly enhanced due to the presence of an additional carbon source, which in turn contributes to extending the Biological Activated Carbon (BAC) filter lifetime
We have demonstrated that melamine biodeg radation in continuous flow lab-scale BAC filters results in higher mel amine removal and an extension of filter lifetime compared to GAC filters, where adsorption is the only removal process
Summary
Micropollutants that are present in drinking water sources can be fully or partly removed by the use of Granular Activated Carbon (GAC) filters. Increasing the role of biodegradation in the overall micropollutants removal in BAC filters can delay the saturation of the activated carbon and extend the filter lifetime, both due to a reduced loading to the BAC and due to bioregeneration. Bioregeneration is the process in which microorganisms restore at least part of the adsorption capacity of the BAC by biodegrading micropollutants, in a way that occupied adsorption sites become available for readsorption. This effect contributes to increasing the removal efficiency of non-biodegradable micropollutants (Putz et al, 2005) in these filters
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