Simulating Effluent Organic Matter Competition in Micropollutant Adsorption onto Activated Carbon Using a Surrogate Competitor

Adsorption onto activated carbon is a promising option for removing organic micropollutants (OMPs) from wastewater treatment plant (WWTP) effluents. The heterogeneity of activated carbons and adsorption competition between OMPs and adsorbable compounds of the effluent organic matter (EfOM) complicate the prediction of OMP removals. Thus, reliable and simple test systems are desirable. For this study, batch experiments with powdered activated carbon (PAC) were carried out to examine methyl orange (MO) as a selected surrogate competitor to simulate EfOM adsorption competition. MO solutions were spiked with carbamazepine (CBZ) as an indicator substance for well-adsorbing OMPs. On the basis of CBZ adsorption isotherms in WWTP effluents, MO concentrations for batch test solutions with identical adsorption competition toward CBZ were calculated. The calculations were performed according to an empirical model of CBZ adsorption in the presence of MO, since predictions employing the ideal adsorbed solution theory (IAST) proved to be inaccurate. Comparative batch tests with five different PACs were conducted with WWTP effluent and respective MO batch test solutions. Except for one PAC, the achieved CBZ removals were very similar in WWTP effluent and the test solution. Additionally, a universal correlation between MO and CBZ removals was found for four PACs

Influence of Wastewater Particles on Ozone Degradation of Trace Organic Contaminants

In this Article, we demonstrate the influence of effluent particles (in the range of <50 μm) on ozone degradation of trace organic contaminants (TrOCs) and effluent-quality parameters. Secondary effluent was filtered through different pore-size filters and ozonated at various ozone doses. Degradation of both ozone-reactive and ozone-refractory contaminants improved following ozonation of effluent filtered with smaller pore size filters, indicating that particles in this range may adversely affect ozonation. The inhibitory effect of particles was attributed to their reaction with ozone, reducing available ozone and HO^• radicals. In addition, increasing filtration level decreased the effluent’s (instantaneous) ozone demand and increased removal of effluent UV absorbance (UVA₂₅₄), further establishing that ozone reacts with effluent particles, in competition with dissolved matter. Moreover, ozone was shown to react with particles even during the first seconds of the process, suggesting a high rate of some ozone–particle reactions, comparable to ozone reaction with highly reactive dissolved organic matter moieties. Particle image analysis revealed that particle formation/aggregation and particle disintegration occurs simultaneously during wastewater (WW) ozonation. Our study implies that particles could affect the efficiency of WW ozonation, by increasing the effluent’s ozone demand and decreasing contaminant degradation