Removal of micropollutants in municipal wastewater treatment plants by powder-activated carbon

Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Duebendorf, Switzerland E-mail: .
Water Science & Technology (Impact Factor: 1.11). 09/2012; 66(10):2115-21. DOI: 10.2166/wst.2012.353
Source: PubMed


Micropollutants (MP) are only partly removed from municipal wastewater by nutrient removal plants and are seen increasingly as a threat to aquatic ecosystems and to the safety of drinking water resources. The addition of powder activated carbon (PAC) is a promising technology to complement municipal nutrient removal plants in order to achieve a significant reduction of MPs and ecotoxicity in receiving waters. This paper presents the salient outcomes of pilot- and full-scale applications of PAC addition in different flow schemes for micropollutant removal in municipal wastewater treatment plants (WWTPs). The sorption efficiency of PAC is reduced with increasing dissolved organic carbon (DOC). Adequate treatment of secondary effluent with 5-10 g DOC m(-3) requires 10-20 g PAC m(-3) of effluent. Counter-current use of PAC by recycling waste PAC from post-treatment in a contact tank with an additional clarifier to the biology tank improved the overall MP removal by 10 to 50% compared with effluent PAC application alone. A dosage of 15 g PAC m(-3) to a full-scale flocculation sand filtration system and recycling the backwash water to the biology tank showed similar MP elimination. Due to an adequate mixing regime and the addition of adapted flocculants, a good retention of the fine fraction of the PAC in the deep-bed filter were observed (1-3 g TSS m(-3); TSS: total suspended solids). With double use of PAC, only half of the PAC was required to reach MP removal efficiencies similar to the direct single dosage of PAC to the biology tank. Overall, the application of PAC in WWTPs seems to be an adequate and feasible technology for efficient MP elimination (>80%) from wastewater comparable with post ozonation.

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    • "Then, the micropollutant removals at two μGAC doses (10 and 20 g μGAC / m 3 ) are presented, as well as those of conventional wastewater quality parameters. The choice of both μGAC doses have been made based on the PAC doses tested in a previous study of this pilot (Mailler et al., 2015b), and considering the knowledge about the high efficiency of such low doses of PAC to remove micropollutants in wastewater (Boehler et al., 2012, Margot et al., 2013, Snyder et al., 2007). In addition, the influence of the μGAC dose on performances and the μGAC residence time (SRT) are also discussed, as well as the use of UV absorbance at 254 nm (UV-254) as a performance indicator. "
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    ABSTRACT: Publication dans le cadre du programme OPUR
    Science of The Total Environment 01/2016; 542(Pt A). DOI:10.1016/j.scitotenv.2015.10.153 · 4.10 Impact Factor
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    • "According to the classical Freundlich adsorption equation, a higher background adsorbate concentration would induce a higher adsorbate loading on the same PAC. This " double-stage " PAC usage strategy was demonstrated as capable of effectively exploiting PAC sorption capacity (Boehler et al., 2012). "
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    ABSTRACT: Spent granular activated carbons (sGACs) for drinking water treatments were reused via pulverizing as low-cost adsorbents for micro-pollutant adsorption from a secondary treated wastewater effluent. The changes of physicochemical characteristics of the spent carbons in relation to the fresh carbons were determined and were correlated to the molecular properties of the respective GAC influents (i.e. a surface water and a groundwater). Pore size distribution analysis showed that the carbon pore volume decreased over a wider size range due to preloading by surface water, which contains a broader molecular weight distribution of organic matter in contrast to the groundwater. However, there was still considerable capacity available on the pulverized sGACs for atrazine adsorption in demineralized water and secondary effluent, and this was particularly the case for the groundwater spent GAC. However, as compared to the fresh counterparts, the decreased surface area and the induced surface acidic groups on the pulverized sGACs contributed both to the lower uptake and the more impeded adsorption kinetic of atrazine in the demineralized water. Nonetheless, the pulverized sGACs, especially the one preloaded by surface water, was less susceptible to adsorption competition in the secondary effluent, due to its negatively charged surface which can repulse the accessibility of the co-present organic matter. This suggests the reusability of the drinking water spent GACs for micro-pollutant adsorption in the treated wastewater. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Environmental Management 09/2015; 160. DOI:10.1016/j.jenvman.2015.06.011 · 2.72 Impact Factor
    • "The third group includes well-adsorbing OMPs, which were removed by >80% with high PAC doses and could also be removed by >50% with a medium PAC dose of 20 mg/L (bezafibrate, diclofenac, benzotriazole , carbamazepine, methylbenzotriazole, metoprolol). Overall , the OMP removals of this study are in the same range as literature reports of direct addition of PAC to a sand filter (Magdeburg et al., 2014), but tend to be slightly lower than those achieved in other PAC applications (B€ ohler et al., 2012; Mailler et al., 2015; Margot et al., 2013). The comparably low OMP removals might be attributed to the high DOC concentrations and short PAC contact time in the filter. "
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    ABSTRACT: Direct addition of powdered activated carbon (PAC) to a deep-bed filter was investigated at pilot-scale as a single advanced treatment stage for simultaneous removal of organic micropollutants (OMPs) and phosphorus from secondary effluent. PAC doses of 10-50 mg/L were assessed with regard to their impacts on filter performance and removal of 15 selected OMPs over a period of 18 months. The PAC was effectively retained by the filter and had no negative effect on filter head loss. Filter runtime until particle breakthrough depended mainly on coagulant dose and did not decrease significantly due to the additional PAC load. Removal of suspended solids and phosphorus by coagulation was effective independent of the PAC dose. A PAC dose of 35 mg/L PAC was suitable to remove well-adsorbing OMPs (e.g. carbamazepine, diclofenac) by >80% and medium adsorbing OMPs (e.g. primidone, sulfamethoxazole) by 50-80%. Median removals were 50-80% for well-adsorbing and 30-50% for medium adsorbing OMPs with 20 mg/L PAC. Abatement of all OMPs was low (<50%) with 10 mg/L PAC, possibly because of the high effluent organic matter content (median dissolved organic carbon (DOC) concentrations of 11.2 mg/L). In addition to adsorptive removal, relevant concentration decreases of certain OMPs (e.g. 4-formylaminoantipyrine) were attributed to biological transformation in the filter. Adsorption onto accumulating PAC in the top layer of the filter bed led to improved OMP adsorption with increasing filter runtime. The comparison of OMP removal in the pilot filter with laboratory adsorption tests demonstrates that batch test results can be applied to estimate adsorptive OMP removal in real applications. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Water Research 07/2015; 84:58-65. DOI:10.1016/j.watres.2015.07.023 · 5.53 Impact Factor
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