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The role of microplastics (MPs) as a vector of chemicals is generally recognized: a wide range of micropollutants have been detected in MPs sampled in different environmental compartments, and, due to their ubiquitous distribution, they can be transferred through aquatic and terrestrial organisms into the food chain. Providing representative models is challenging due to the intrinsic dynamic evolution characterizing the natural phenomena, which cannot be adequately investigated in lab experiments. On the other side, simulation/prediction tools are strongly required because of the long time-scale characterizing the MPs��� persistence in the environment. This article provides a review of the updated literature on mechanistic models and predictive thermodynamic methods applied (or applicable), to describe the uptake/release processes of pollutants by MPs. Intrinsic and environmental factors influencing the process kinetics and the equilibrium distribution are discussed in detail. Mechanistic models and thermodynamic prediction methods are analyzed and their potentialities for application to MPs highlighted with specific examples. Finally, a critical analysis of the limitations related to the simplifying assumptions in modeling and to the representativeness of the lab-scale data is performed to evaluate their effects on the reliability of the predictions and to identify knowledge gaps and address future research needs.

Substituted phenols are extensively produced and utilized in chemical industry and therefore they are largely present in wastewater. In this paper we considered phenolic mixtures which are representative of industrial wastewater, usually containing multiple substrates. In these conditions, degradation process is strongly affected by the complex interactions among substrates, which include enhancement, inhibition and co-metabolism so a process model is an useful tool to explore and predict the process evolution. Objective of this work was to formulate a kinetic model for the biodegradation of binary mixtures performed in a sequencing batch reactor (SBR). Two model mixtures were investigated: a 4-nitrophenol (4NP) and 2,4-dimethylphenol (2,4DMP) mixture, and a more recalcitrant mixture of 4NP and 2,4-dichlorophenol (2,4DCP). Kinetic tests were performed at different feed concentrations, with single compounds and mixtures and each biodegradation process was kinetically characterized. Haldane equation was utilised to model the substrate inhibited kinetics for single compound while for the mixtures the model was modified with a "switching function" to account the mutual substrate interaction. The proposed model was initially calibrated with a preliminary set of data to evaluate the best-fitting parameters, then validated by simulating different runs with the estimated parameters. Satisfactory results with high correlation coefficients (>= 0.98) and reliable predictions were obtained for the two investigated mixtures.

Sequencing Batch Reactors (SBR) appear to be an effective technological solution in order to obtain a versatile microorganism culture able to develop metabolic pathways required for degradation of bioresistant substances. Nevertheless, the performance of these devices is limited by the inhibitory kinetics of xenobiotic biodegradation that results in a significant reduction of the removal rate if the biomass experiences high substrate concentrations. In this work a dynamic model is formulated to describe the behavior of an SBR reactor for xenobiotic removal and to investigate the influence of the kinetic parameters and the operating on the biodegradation efficiency. In particular, the model shows that for inhibitory kinetics an abrupt change from low to high substrate concentrations in the outlet stream (i.e from a high to a low process efficiency) can occur, depending on the kinetic and operating parameter values.

In this paper we report the results of an investigation on the performance of conventional and two phase partitioning bioreactors (TPPBs) operating in sequencing batch mode applied to the biodegradation of a binary mixture of 2 substituted phenols, 2,4-dimethylphenol and 4-nitrophenol. The TPPB was operated with the DuPont polymer Hytrel 8206 as the partitioning phase, which was demonstrated to be effective in the uptake and release of a variety of phenolic compounds. Partition tests were performed on both compounds, and partition coefficients of 201 and 143 were obtained in distilled water for 2,4-dimethylphenol and 4-nitrophenol, respectively. Parallel kinetic tests were carried out in conventional and TPPB bioreactors under the same operating conditions. The TPPB results showed a reduction in the aqueous phase concentration for both substrates to sub-inhibitory levels in all the tests, and the effect was more evident for 2,4-dimethylphenol as expected by the partition coefficient values. Moreover, the presence of the polymer has a marked effect on the process kinetics that are significantly increased for both substrates in comparison to the values of the conventional reactor.