Nghiem, L. D. (2012). N-nitrosamine removal by reverse osmosis for indirect potable water reuse -A critical review based on observations from laboratory, pilot and full-scale studies. Separation and Purification Technology, a b s t r a c t N-nitrosodimethylamine (NDMA) and several other N-nitrosamines have been identified as probable human carcinogens. Here, we review key aspects related to the occurrence and removal of N-nitrosamines by reverse osmosis (RO) membranes in the context of indirect potable water reuse. A comprehensive analysis of the existing data reveals significant variations in the rejection of NDMA by RO membranes reported in the literature, ranging from negligible up to 86%. This review article provides some insight into the reasons for such variations by examining the available data on the effects of operating conditions on NDMA rejection. Amongst several operating parameters investigated so far in the literature, feed temperature, membrane permeate flux, feed solution pH and ionic strength were found to have considerable impact on NDMA rejection by RO membranes. In particular, it has been recently shown that seasonal changes in feed temperature (e.g. from 20 to 30°C) can result in a significant decrease in NDMA rejection (from 49% to 25%). However, the combined effects of all operating parameters identified in the literature to date can only account for some of the variations in NDMA rejection that have been observed in full-scale RO plants. The impacts of membrane fouling and particularly chemical cleaning on the rejection of N-nitrosamines have not been fully investigated. Finally, this review article presents a roadmap for further research required to optimise the rejection of NDMA and other N-nitrosamines by RO membranes. Crown

No abstract

No abstract

Modelling the rejection of N-nitrosamines by a spiral-wound reverse osmosis Modelling the rejection of N-nitrosamines by a spiral-wound reverse osmosis system: mathematical model development and validation system: mathematical model development and validation

No abstract

Advanced water treatment of secondary treated effluent requires stringent quality control to achieve a water quality suitable for augmenting drinking water supplies. The removal of micropollutants such as pesticides, industrial chemicals, endocrine disrupting chemicals (EDC), pharmaceuticals, and personal care products (PPCP) is paramount. As the concentrations of individual contaminants are typically low, frequent analytical screening is both laborious and costly. We propose and validate an approach for continuous monitoring by applying passive sampling with Empore disks in vessels that were designed to slow down the water flow, and thus uptake kinetics, and ensure that the uptake is only marginally dependent on the chemicals' physicochemical properties over a relatively narrow molecular size range. This design not only assured integrative sampling over 27 days for a broad range of chemicals but also permitted the use of a suite of bioanalytical tools as sum parameters, representative of mixtures of chemicals with a common mode of toxic action. Bioassays proved to be more sensitive than chemical analysis to assess the removal of organic micropollutants by reverse osmosis, followed by UV/H₂O₂ treatment, as many individual compounds fell below the quantification limit of chemical analysis, yet still contributed to the observed mixture toxicity. Nonetheless in several cases, the responses in the bioassays were also below their quantification limits and therefore only three bioassays were evaluated here, representing nonspecific toxicity and two specific end points for estrogenicity and photosynthesis inhibition. Chemical analytical techniques were able to quantify 32 pesticides, 62 PCPPs, and 12 EDCs in reverse osmosis concentrate. However, these chemicals could explain only 1% of the nonspecific toxicity in the Microtox assay in the reverse osmosis concentrate and 0.0025% in the treated water. Likewise only 1% of the estrogenic effect in the E-SCREEN could be explained by the quantified EDCs after reverse osmosis. In comparison, >50% of the estrogenic effect can typically be explained in sewage. Herbicidal activity could be fully explained by chemical analysis as the sampling period coincided with an illegal discharge and two herbicides dominated the mixture effect. The mass balance of the reverse osmosis process matched theoretical expectations for both chemical analysis and bioanalytical tools. Overall the investigated treatment train removed >97% estrogenicity, >99% herbicidal activity, and >96% baseline toxicity, confirming the suitability of the treatment train for polishing water for indirect potable reuse. The product water was indistinguishable from local tap water in all three bioassays. This study demonstrates the suitability and robustness of passive sampling linked with bioanalytical tools for semicontinuous monitoring of advanced water treatment with respect to micropollutant removal.

Open and solid symbol indicates the result of the first and second experiment, respectively. The impact of fouling on N-nitrosamine rejection by nanofiltration (NF) and reverse osmosis 2 (RO) membranes was investigated in this study. Membrane fouling was simulated using 3 tertiary treated effluent and several model fouling solutions (that contained sodium alginate, 4 bovine serum albumin, humic acid or colloidal silica) to elucidate the changes in rejection 5 behaviour of N-nitrosamines. In general, the rejection of N-nitrosamines increased when the 6 membranes were fouled by tertiary effluent. The rejection of small molecular weight N-7 nitrosamines was most affected by membrane fouling. In particular, the rejection of N-8 nitrosodimethylamine (NDMA) by the ESPA2 membrane increased from 34 to 73% after 9 membrane fouling caused by tertiary effluent. The results also indicate that the impact was 10 less apparent for the lowest permeability membrane (i.e., ESPAB), and the rejection of N-11 nitrosamines by the ESPAB membrane was over 82% regardless of membrane fouling. The 12 effect of membrane fouling caused by model foulants on N-nitrosamine rejection was 13 considerably less than that caused by tertiary effluent. Size exclusion chromatography 14 analyses revealed that the tertiary effluent contains a high fraction of low molecular weight (< 15 500 g/mol) organic substances. It appears that these low molecular weight foulants present in 16 the tertiary effluent can restrict the solute pathway within the active skin layer of membranes, 17 resulting in the observed increase of solute rejection. 18

No abstract