Partial replenishment of biological activated carbon filters to improve natural organic matter removal.

Paper in proceedings, 2018

Natural organic matter (NOM) in surface waters negatively impacts drinking water
treatment and is a precursor of harmful disinfection by-products (DBPs). Granular activate carbon
(GAC) filters are integral components of many drinking water treatment plants (WTPs) due to the
ability to remove NOM and organic micro pollutants from raw waters. However, GAC filters lose
adsorption capacity and convert to biologically activated carbon (BAC) filter relatively quickly. This
paper reports on a full-scale BAC filter modification strategy to enhance short-term NOM removal.
This is achieved by adding a small amount of fresh GAC to BAC filters which increases adsorption
while maintaining biological degradation of organics by the microbes attached to the BAC. This
strategy was implemented at two treatment plants in Sweden. Modified filters showed better removal of
humic-like and protein-like NOM fractions than reference filters that did not receive fresh GAC,
indicating improved functioning of both adsorption and biological treatment. The result shows that
both biodegradation and adsorption mechanism improved within the filters.