|Keywords||THMs, HAAs, DOC, GAC, adsorption, GAC post-filter adsorber, drinking water treatment, drinking water quality|
|Abstract||A pilot-plant study was carried out with the water supply to Athens Water Treatment Plant filtered through a granular activated carbon (GAC) post-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 (dissolved organic carbon, DOC). The pilot treatment facility is located in the utilities of Athens Water Supply and Sewerage Company (EYDAP) in Galatsi, Athens, and was operated as a rapid gravity post-filter adsorber. It was fed with chlorinated sand-filtered water and operated continously at an almost constant hydraulic loading rate, being backwashed every 6 days. A total number of 105 filter runs was completed. At regular time intervals water samples were taken from the inlet, outlet and different depths in the GAC column and were analysed for THMs, HAAs and DOC. Additionally, other parameters like bromide, free chlorine residual, soluble-UV(254) absorption, pH, temperature, turbidity were measured too. A total number of 520 analyses or measurements was performed. The operation of the GAC post-filter adsorber continued until the GAC adsorption capacity for THMs was exhausted and the breakthrough point for HAAs and DOC was reached. The total duration of the experimental cycle (adsorption cycle) was 638 days. The results of the analyses showed that the efficiency of GAC for the removal of THMs, HAAs and DOC is significant. The GAC breakthrough capacity for DOC was higher than the capacity for total-HAAs, which was higher than that for total-THMs (238,50, 4,64 and 2,83 g/kg GAC respectively). The same was observed concerning the GAC bed life, while the carbon usage rate (CUR) followed the opposite order, as expected. The higher efficiency of GAC for the removal of the dissolved organic matter than of the smaller molecules of HAAs and THMs was according to the relevant literature. The removal of THMs and the most part of the removal of HAAs and DOC should be attributed to adsorption by GAC, while that of a small part of HAAs and DOC may be attributed to biodegradation in the adsorber bed, where dechlorination, caused by the catalytic action of the activated carbon, favoured microbial growth. A comparison between the results from GAC (12x40 mesh) post-filter adsorber operation (EBCT: 14 min) and those from GAC (10x20 mesh) filter adsorber operation (EBCT: 9,5 min) that had preceded showed that GAC post-filter adsorber had a significantly higher breakthrough capacity for total-THMs, total-HAAs and DOC than GAC filter adsorber (3,5, 3 and 4,5 times higher respectively). The higher adsorption efficiency of the post-filter adsorber should be attributed to the smaller effective size of the carbon and the lower hydraulic loading rate. Also, observed desorption incidents of THMs and HAAs especially during the post-filter adsorber operation, possibly caused by pulse decreases in influent concentration or competition by strongly adsorbing organics, were favoured by the same factors.|
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|Name||Affiliation||Home page||Total pubs|
|Babi KG||Department of Environmental Studies, University of the Aegean, University Hill, Mytilene 81100, Greecefirstname.lastname@example.org||16|
|Koumenides KM||Department of Environmental Studies, University of the Aegean, University Hill, Mytilene 81100, Greece||15|
|Lekkas TD||University of the Aegean, Dept. of Environmental Studies||http://email@example.com||71|
|Makri CA||University of the Aegean, Faculty of the Environment, Dept. of Environmental Studies University Hill, 81 100 Mytilene, Greecefirstname.lastname@example.org||19|
|Nikolaou AD||Department of Marine Sciences, University of the Aegean, University Hill, 81100 Mytilene, Greeceemail@example.com||44|
|Tzoumerkas FK||EYDAP, 156 Oropou str., Galatsi, Athens, Greece||7|
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