A pilot-plant study was carried out with the water supply to Athens water works filtered through a granular
activated carbon (GAC) filter- adsorber. The objective of this study was to evaluate the performance
of GAC for the removal from drinking water of the two main groups of disinfection by -products
(DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), as well as of dissolved organic matter.
The pilot treatment facility is located at the Water Treatment Plant of EYDAP in Galatsi, Athens, and
was operated as a rapid gravity filter - adsorber. It was fed with chlorinated water, coming from the
overflow of the sedimentation tanks, and operated continuously in parallel with a full-scale sand filter.
At regular time intervals water samples were taken from both filters and analysed for THMs, HAAs
and DOC. Other parameters were measured too. The operation of the GAC filter-adsorber continued
until the GAC adsorption capacity for THMs and HAAs was almost exhausted.
The results of the analyses showed that GAC was more effective in removing the dissolved organic matter
than the smaller molecules of THMs and HAAs, fact which is in agreement with the relevant literature.
GAC was also proved more effective in removing HAAs than removing THMs. The removal of
THMs and the most part of the removal of HAAs and DOC must be attributed to adsorption by GAC,
while that of a smaller part of DOC and HAAs may be attributed to biological activity in the filter
bed, where chlorine had been totally removed by the catalytic action of the activated carbon surface.
