Investigation of polar mobile organic compounds (PMOC) removal by reverse osmosis and nanofiltration: rejection mechanism modelling using decision tree

Abstract

Polar mobile organic compounds (PMOC) are highly polar chemicals and tend to accumulate in short water cycles. Due to their properties, PMOC might be partially eliminated by advanced water treatment technologies. The goal of this study is to investigate the rejection of 22 PMOC (highly mobile and persistent) by reverse osmosis (RO) and nanofiltration (NF) membranes. The impact of transmembrane pressure was evaluated through laboratory-scale cross-flow constant pressure filtration tests. Among the investigated experimental conditions, PMOC rejection with NF at eight bars is comparable to values obtained on RO at 15 bars. Negatively charged PMOC are highly rejected by both RO and NF membranes while guanidine-like compounds exhibit higher passage values and are strongly impacted by transmembrane pressure. In order to model the rejection mechanism, decision tree methodology was employed to link PMOC physicochemical properties to rejection values. Based on laboratory-scale results, decision trees were computed and emphasized that the NF rejection mechanism is governed by electrostatic interaction and sieving effects. In contrast, PMOC rejection on the RO membrane strongly depends on the topological polar surface area (TPSA) of the PMOC. This study suggests that micropollutant TPSA should be more investigated in order to describe RO removal efficiency. Moreover, it is shown that the decision tree is a powerful numerical tool in order to reveal the specific sequence leading to micropollutant removal by RO and NF membranes.

Occurrence, Distribution, and Environmental Behavior of Persistent, Mobile, and Toxic (PMT) and Very Persistent and Very Mobile (vPvM) Substances in the Sources of German Drinking Water

“…When advanced treatment technologies such as ozonation and AC fail to remove PMT/vPvM substances, the only sufficient options are reverse osmosis or nanofiltration, both of which always result in nonrecyclable concentrates. 71 There were three samples where 1H-benzotriazole concentrations were above the German HRIV in drinking water of 3 μg/L. If these concentrations are not reduced, either through dilution or the application of advanced treatment methods during drinking water production, the compound will be present in the finished drinking water.…”

Quantification and modelling of organic micropollutant removal by reverse osmosis (RO) drinking water treatment

“…This comparison illustrated that for small cationic MPs, the additional electrostatic interactions between compounds and membrane may influence their diffuse through the membrane which negatively charged resulting in a lower passage. As a conclusion, for removal of cationic MPs, size exclusion, electrostatic sorption [25,44,71] and Donnan exclusion [72] were considered as dominant factors.…”

“…5, all neutral HL MPs larger than 140 Da were highly or moderately removed (passage < 20%). For some compounds such as methenamine (44), gabapentin (31), metribuzin (46), pirimicarb (63), bisphenol S (13), phenobarbital (62), TCEP (71), pentoxifylline (54) and hydrochlorothiazide (35) the removal was high, and the passage was lower than 5%. This could be a result of steric and electrostatic exclusion.…”

Computing Techniques for Modeling the Retention of Polar Pharmaceutical Active Compounds by Membranes

“…In particular, Polar pharmaceuticals active compounds (PPhACs) can be highly water mobile, potentially reaching source waters and even finished drinking water. Polar pharmaceuticals active compounds (PPhACs) are highly polar chemicals and tend to accumulate due to their low degradation properties and slow adsorption kinetics in water cycles (Albergamo et al 2019;Teychene et al 2020).…”

“…Solute-membrane interactions are in turn influenced by compound characteristics (such as molecular size, polarity, charge, and hydrophobicity), membrane properties (porosity, polarity, and electrostatic charges), and operating filtration conditions (pH, pressure, permeate flux, temperature, membrane fouling, recovery, and cross-flow velocity) (Teychene et al 2020;Kim et al 2018).…”