Removal of highly polar micropollutants from wastewater by powdered activated carbon

Abstract

Due to concerns about ecotoxicological effects of pharmaceuticals and other micropollutants released from wastewater treatment plants, activated carbon adsorption is one of the few processes to effectively reduce the concentrations of micropollutants in wastewater. Although aimed mainly at apolar compounds, polar compounds are also simultaneously removed to a certain extent, which has rarely been studied before. In this study, adsorption isotherm and batch kinetic data were collected with two powdered activated carbons (PACs) to assess the removal of the polar pharmaceuticals 5-fluorouracil (5-Fu) and cytarabine (CytR) from ultrapure water and wastewater treatment plant effluent. At pH 7.8, single-solute adsorption isotherm data for the weak acid 5-Fu and the weak base CytR showed that their adsorption capacities were about 1 order of magnitude lower than those of the less polar endocrine disrupting chemicals bisphenol A (BPA) and 17-α-ethinylestradiol (EE2). To remove 90 % of the adsorbate from a single-solute solution 14, 18, 70, and 87 mg L(-1) of HOK Super is required for EE2, BPA, CytR, and 5-Fu, respectively. Effects of solution pH, ionic strength, temperature, and effluent organic matter (EfOM) on 5-Fu and CytR adsorption were evaluated for one PAC. Among the studied factors, the presence of EfOM had the highest effect, due to a strong competition on 5-Fu and CytR adsorption. Adsorption isotherm and kinetic data and their modeling with a homogeneous surface diffusion model showed that removal percentage in the presence of EfOM was independent on the initial concentration of the ionizable compounds 5-Fu and CytR. These results are similar to neutral organic compounds in the presence of natural organic matter. Overall, results showed that PAC doses sufficient to remove >90 % of apolar adsorbates were able to remove no more than 50 % of the polar adsorbates 5-Fu and CytR and that the contact time is a critical parameter.

Removal of emerging pollutants through Granular Activated Carbon

“…These findings are in accordance with the results of batch equilibrium studies performed by others [18][19][20]. Interestingly enough, similar results for the target compounds were recorded in a previous study performed with PAC at wastewater samples, where at a PAC dose of 50 mg/L the removal rates of the ECs examined were 75-90% for BPA, 72-75% for KFN, 65-73% for NPX and around 60% for IBU, while the results for TCS were controversial [6].…”

“…It should be mentioned that Thomas model assumes Langmuir isotherm. Based on data from studies establishing equilibrium adsorption capacities for the target compounds [18][19][20] both Langmuir and Freundlich kinetics presented satisfactory fitting to the experimental data, although Freundlich exhibit better fit at low target compounds' concentrations (to the order of few lg/L). Therefore…”

Super-fine powdered activated carbon (SPAC) for efficient removal of micropollutants from wastewater treatment plant effluent

“…3), suggesting adverse effects of competing wastewater matrix components on the adsorption of target micropollutant. It is largely acknowledged that background organic matter reduces the number of adsorption sites available for micropollutants, either through direct competition for adsorption sites and/or pore blocking, and consequently decreases the adsorption efficiency of PAC (de Ridder et al, 2011;Delgado et al, 2012;Kovalova et al, 2013a;Mailler et al, 2014;Margot et al, 2013). This effect is well illustrated in Fig.…”

The SOLUTIONS project: Challenges and responses for present and future emerging pollutants in land and water resources management

“…A number of European utilities in Switzerland, Germany and the Netherlands among others are therefore reviewing or considering implementation of additional technologies to enhance the removal of emerging compounds in wastewater effluents. While technologies such as advanced oxidation or activated carbon treatment have been demonstrated as technically successful (Boehler et al, 2012;Hollender et al, 2009;Kovalova et al, 2013;Zimmermann et al, 2011), it is necessary to evaluate their influence on environmental impacts and on human health risks to justify such enormous investments. Pilot water treatment plants will allow the evaluation of abatement options with respect to removal of emerging pollutants and address human health relevant exposure pathways via drinking water and fish consumption including mixture toxicity considerations and options for data gap handling.…”