N-nitrosamine rejection by nanofiltration and reverse osmosis membranes: The importance of membrane characteristics

The influence of membrane characteristics on the rejection of eight N-nitrosamines was investigated using one nanofiltration (NF), one seawater reverse osmosis (SWRO) and six low pressure reverse osmosis (LPRO) membranes. The rejection of the two lowest molecular weight N-nitrosamines, namely N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA), varied in the range from 8-82% to 23-94%, respectively. In general, the rejection of NDMA and NMEA increased with decreasing membrane permeability. The impact of membrane characteristics became less important for higher molecular weight N-nitrosamines. Among the four LPRO membranes (i.e. ESPA2, LFC3, TFC-HR and 70LW) that are commonly used for water reclamation applications, similar rejections were obtained for NDMA (37-52%) and NMEA (69-82%). In addition, rejection values of NDMA and NMEA among two LPRO membranes (i.e. ESPA2 and 70LW) were almost identical when compared under variable permeate flux and feed temperature conditions. However, it is noteworthy that the ESPABmembrane could achieve very high rejection of NDMA (as high as 71%) despite having a similar permeability to the LPRO membranes. Results reported here suggest that membrane characteristics associated with permeability such as the pore size and thickness of the active skin layer can be a key factor determining N-nitrosamine rejection

Removal of magnetic resonance imaging contrast agents through advanced water treatment plants

Stable gadolinium (Gd) complexes have been used as paramagnetic contrast agents for magnetic resonance imaging (MRI) for over 20 years, and have recently been identified as environmental contaminants. As the rare earth elements (REE), which include Gd, are able to be measured accurately at very low concentrations (e.g. Tb is measured at 7 fmol/kg in this study) using inductively coupled plasma mass spectrometry (ICP-MS), it is possible to determine the fate of this class of compounds during the production of purified recycled water from effluent. Coagulation and microfiltration have negligible removal, with the major removal step occurring across the reverse osmosis membrane where anthropogenic Gd (the amount of Gd attributable to MRI contrast agents) is reduced from 0.39 nmol/kg to 0.59 pmol/kg, a reduction of 99.85%. The RO concentrate has anthropogenic Gd concentrations of 2.6 nmol/kg, an increase in concentration in line with the design characteristics of the plant. The increased concentration in the RO concentrate may allow further development of anthropogenic Gd as a tracer of the fate of the RO concentrate in the environment

Effects of feed solution characteristics and membrane fouling on N-nitrosamine rejection by reverse osmosis membranes

Augmentation of potable water sources with reclaimed municipal wastewater is an option of increasing importance for water security in regions and countries where severe water stress occurs. Consequently, the presence of emerging trace contaminants in reclaimed water has been recognised as a critical issue due to their potential adverse health effects. Notable examples of these trace organic chemicals include N-nitrosodimethylamine (NDMA) and several other N-nitrosamines

Water reuse for vine irrigation: from research to full-scale implementation

Water scarcity is a worldwide problem, which leads to unprecedented pressure on water supply in arid and semi-arid regions. Treated wastewater is an alternative water resource, therefore, its reuse for agricultural irrigation has been growing worldwide since the beginning of the 21st century. In several regions of wine-producing countries (e.g., Australia, California – USA, Spain), wastewater reuse appears to be the most accessible alternative, both financially and technically, for agricultural uses that notably do not require drinking water. From the summer of 2022, vine irrigation full-scale implementation will start with tertiary treated municipal wastewater in the French Languedoc region. This was made possible thanks to a collaborative research project conducted between 2013 and 2018 to address all potential health and environmental risks associated with this process. This research project was conducted in the south of France, with experimental and control plots both equipped with drip irrigation systems. All the results produced during the research project demonstrated the feasibility of applying this process for vine drip irrigation while effectively managing health and environmental risks and complying with the regulation. A social acceptance and economic study were also performed in order to broaden the scope of the project scalability evaluation. HIGHLIGHTS Low cost and robust technology.; Process easy to ‘Copy and adapt’.; Consideration of environmental and health aspects.; Sustaining the wine industry at a regional scale.; First deployment at full-scale following the research project.

N-nitrosamine removal by reverse osmosis for indirect potable water reuse – A critical review based on observations from laboratory, pilot and full-scale studies

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

Nitrifier decay and recovery in a moving bed biofilm reactor (MBBR) teating reverse osmosis concentrate

A two-stage moving bed biofilm reactor (MBBR) is applied at the Bundamba advanced water treatment plant (AWTP) (Queensland, Australia) to treat the reverse osmosis concentrate (ROC) for inorganic nutrient removal. One of the operational challenges for MBBR is to cope with the large fluctuations of the ROC flow. This study investigated the decay rates of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) and biofilm detachment in MBBR during starvation for up to one month. An intermittent aeration strategy of 15 min aeration every 6 hr was applied. This study also evaluated the activity recovery of both AOB and NOB after normal operation was resumed. The results showed that the activity loss of AOB and NOB was relatively minor (< 20%) within 10 days of starvation, which ensured relative quick recovery of ammonium removal when normal operation resumed. In contrast, the AOB and NOB activity loss reached 60-80% when the starvation time was longer than 20 days, resulting in slower recovery of ammonium removal after starvation. Starvation for less than 20 days didn’t result in an apparent biomass detachment from carriers

Characterisation and removal of recalcitrants in reverse osmosis concentrates from water reclamation plants

Water reclamation plants frequently utilise reverse osmosis (RO), generating a concentrated reject stream as a by-product. The concentrate stream contains salts, and dissolved organic compounds, which are recalcitrant to biological treatment, and may have an environmental impact due to colour and embedded nitrogen. In this study, we characterise organic compounds in RO concentrates (ROC) and treated ROC (by coagulation, adsorption, and advanced oxidation) from two full-scale plants, assessing the diversity and treatability of colour and organic compounds containing nitrogen. One of the plants was from a coastal catchment, while the other was inland. Stirred cell membrane fractionation was applied to fractionate the treated ROC, and untreated ROC along with chemical analysis (DOC, DON, COD), colour, and fluorescence excitation-emission matrix (EEM) scans to characterise changes within each fraction. In both streams, the largest fraction contained 10 kDa molecules, with 17-34% of organic compounds as COD. Iron coagulation affected a wider size range, with better removal of organics (41-49% as COD) at the same molar dosage. As with iron, adsorption reduced organics of a broader size range, including organic nitrogen (26-47%). Advanced oxidation (UV/H2O2) was superior for complete decolourisation and provided superior organics removal (50-55% as COD). (C) 2011 Elsevier Ltd. All rights reserved

Monitoring reverse osmosis performance: conductivity versus fluorescence excitation-emission matrix (EEM)

This paper evaluated dissolved organic matter (DOM) rejection by reverse osmosis (RO) membranes employed in full-scale water reclamation plants with two techniques based on fluorescence to assess its suitability as a novel method for verification of membrane process integrity. Excitation-emission matrices (EEM) of feed and permeate samples from individual pressure vessels, complete stages and RO trains of two full scale plants were analysed with a fluorescence regional integration technique. Depending on the excitation-emission region quantified, DOM rejection up to around 99.5% was regularly measured and fluorescence measurements could be used as more sensitive tool compared to conductivity profiling when assessing membrane installations. A blue-shift in the fluorescence of the humic substances peak was observed and could be explained by determining size distribution of organic matter by size exclusion chromatography (SEC) with fluorescence detection. The results demonstrated that the size distribution of fluorescent DOM changed towards lower molecular weight from feed to permeate due to increased rejection of high molecular weight compounds. Preliminary trials showed rejection of high molecular weight substances and consequentially membrane integrity beyond 99.9%. We conclude that fluorescence coupled with regional integration techniques and potentially SEC is a promising sensitive technique to assess RO membrane integrity