title: The benefits of powdered activated carbon recirculation for micropollutant removal in advanced wastewater treatment.
abstract: PAC adsorption is a widespread option for the removal of organic micropollutants (OMP) from secondary effluent. For an optimal exploitation of the adsorption capacity, PAC recirculation is nowadays a common practice, although the mechanistic interrelations of the complex recirculation process are not fully resolved. In this work, extensive multi-stage batch adsorption testing with repeated PAC and coagulant dosage was performed to evaluate the continuous-flow recirculation system. Partly loaded PAC showed a distinct amount of remaining capacity, as OMP and DOC removals considerably increased with each additional adsorption stage. At a low PAC dose of 10 mg PAC L(-1), removals of benzotriazole and carbamazepine were shown to rise from <40% in the first stage up to >80% in the 11th stage at 30 min adsorption time per stage. At a high PAC dose of 30 mg PAC L(-1), OMP and DOC removals were significantly higher and reached 98% (for benzotriazole and carbamazepine) after 11 stages. Coagulant dosage showed no influence on OMP removal, whereas a major part of DOC removal can be attributed to coagulation. Multi-stage adsorption is particularly beneficial for small PAC doses and significant PAC savings are feasible. A new model approach for predicting multi-stage OMP adsorption on the basis of a single-stage adsorption experiment was developed. It proved to predict OMP removals and PAC loadings accurately and thus contributes towards understanding the PAC recirculation process.
authors.affiliation: Technische Universität Berlin, Chair of Water Quality Control, KF4, Str. des 17. Juni 135, D-10623 Berlin, Germany. Electronic address: felix.meinel@tu-berlin.de.
authors.forename: F
authors.initials: F
authors.lastname: Meinel
authors.affiliation: Technische Universität Berlin, Chair of Water Quality Control, KF4, Str. des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Zietzschmann
authors.affiliation: Technische Universität Berlin, Chair of Water Quality Control, KF4, Str. des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: A S
authors.initials: AS
authors.lastname: Ruhl
authors.affiliation: Berliner Wasserbetriebe, Research & Development, Neue Jüdenstr. 1, 10179 Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Sperlich
authors.affiliation: Technische Universität Berlin, Chair of Water Quality Control, KF4, Str. des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Jekel
mesh_terms: D000327:Adsorption; D002606:Charcoal / Q000032:analysis*; D009930:Organic Chemicals / Q000737:chemistry*; D011208:Powders; D059027:Recycling; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D011208:Powders; D014874:Water Pollutants, Chemical; D002606:Charcoal
keywords: Advanced wastewater treatment; Multi-stage adsorption; Organic micropollutants; PAC recirculation; Powdered activated carbon (PAC)