Reverse osmosis integrity monitoring in water reuse: The challenge to verify virus removal - A review.

A reverse osmosis (RO) process is often included in the treatment train to produce high quality reuse water from treated effluent for potable purposes because of its high removal efficiency for salinity and many inorganic and organic contaminants, and importantly, it also provides an excellent barrier for pathogens. In order to ensure the continued protection of public health from pathogen contamination, monitoring RO process integrity is necessary. Due to their small sizes, viruses are the most difficult class of pathogens to be removed in physical separation processes and therefore often considered the most challenging pathogen to monitor. To-date, there is a gap between the current log credit assigned to this process (determined by integrity testing approved by regulators) and its actual log removal capability as proven in a variety of laboratory and pilot studies. Hence, there is a challenge to establish a methodology that more closely links to the theoretical performance. In this review, after introducing the notion of risk management in water reuse, we provide an overview of existing and potentially new RO integrity monitoring techniques, highlight their strengths and drawbacks, and debate their applicability to full-scale treatment plants, which open to future research opportunities.

The use of multiple tracers for tracking wastewater discharges in freshwater systems.

The assessment of potential impacts of wastewater effluent discharges in freshwater systems requires an understanding of the likely degrees of dilution and potential zones of influence. In this study, four tracers commonly present in wastewater effluents were monitored to compare their relative effectiveness in determining areas in freshwater systems that are likely to be impacted by effluent discharges. The four tracers selected were the human pharmaceutical carbamazepine, anthropogenic gadolinium, fluorescent-dissolved organic matter (fDOM), and electrical conductivity (EC). The four tracers were monitored longitudinally in two distinct freshwater systems receiving wastewater effluents, where one site had a high level of effluent dilution (effluent <1% of total flow) and the other site had a low level of effluent dilution (effluent ∼50% of total flow). At both sites, the selected tracers exhibited a similar pattern of response intensity downstream of discharge points relative to undiluted wastewater effluent, although a number of anomalies were noted between the tracers. Both EC and fDOM are non-specific to human influences, and both had a high background response, relative to the highly sensitive carbamazepine and anthropogenic gadolinium responses, although the ease of measuring EC and fDOM would make them more adaptable in highly variable systems. However, the greater sensitivity and selectivity of carbamazepine and gadolinium would make their combination with EC and fDOM as tracers of wastewater effluent discharges highly desirable to overcome potential limitations of individual tracers.

Sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in wastewater systems: are your conclusions valid? A critical review.

The analysis of 87 peer-reviewed journal articles reveals that sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in sewers and sewage treatment plant influents is mostly carried out according to existing tradition or standard laboratory protocols. Less than 5% of all studies explicitly consider internationally acknowledged guidelines or methods for the experimental design of monitoring campaigns. In the absence of a proper analysis of the system under investigation, the importance of short-term pollutant variations was typically not addressed. Therefore, due to relatively long sampling intervals, potentially inadequate sampling modes, or insufficient documentation, it remains unclear for the majority of reviewed studies whether observed variations can be attributed to "real" variations or if they simply reflect sampling artifacts. Based on results from previous and current work, the present paper demonstrates that sampling errors can lead to overinterpretation of measured data and ultimately, wrong conclusions. Depending on catchment size, sewer type, sampling setup, substance of interest, and accuracy of analytical method, avoidable sampling artifacts can range from "not significant" to "100% or more" for different compounds even within the same study. However, in most situations sampling errors can be reduced greatly, and sampling biases can be eliminated completely, by choosing an appropriate sampling mode and frequency. This is crucial, because proper sampling will help to maximize the value of measured data for the experimental assessment of the fate of PPCPs as well as for the formulation and validation of mathematical models. The trend from reporting presence or absence of a compound in "clean" water samples toward the quantification of PPCPs in raw wastewater requires not only sophisticated analytical methods but also adapted sampling methods. With increasing accuracy of chemical analyses, inappropriate sampling increasingly represents the major source of inaccuracy. A condensed step-by-step Sampling Guide is proposed as a starting point for future studies.

Sampling for PPCPs in wastewater systems: comparison of different sampling modes and optimization strategies.

The aim of this study was to assess uncertainties associated with different sampling modes when evaluating loads of pharmaceuticals and personal care products (PPCPs) in sewers and influents to sewage treatment plants (STPs). The study demonstrates that sampling uncertainty can range from "not significant" to "far greater than the uncertainty due to chemical analysis", which is site- and compound-specific and depends on the (in)accuracy of the analytical method. Conventional sampling devices operated in common time- or flow-proportional sampling modes, and applying traditional sampling intervals of 30 min or longer can result in the collection of nonrepresentative samples. At the influent of a STP, wastewater may appear as a continuous stream, but it is actually composed of a number of intermittently discharged, individual wastewater packets from household appliances, industries, or subcatchments in pressurized sewer systems. The resulting heterogeneity can cause significant short-term variations of pollutant loads. We present different experimental results and a modeling approach showing that the magnitude of sampling uncertainty depends mainly on the number of pollutant peaks and the sampling frequency; sampling intervals of 5 min or shorter may be required to properly account for temporal PPCP variations in influents of STPs. A representative sample is a prerequisite for providing meaningful analytical results and cannot be compensated with a large number of samples, accurate chemical analysis, or sophisticated statistical evaluation. This study highlights that generalizing from one case to another is difficult and hence a careful systems analysis of the catchment under investigation, or precautionary choice for a sophisticated sampling mode, is necessary to prove reproducibility.

Detection of anthropogenic gadolinium in the Brisbane River plume in Moreton Bay, Queensland, Australia.

Wastewater effluent is known to contain macro and micropollutants, which may be deleterious to environmental health. One such class of micropollutants is chelated gadolinium, which are used as MRI contrast agents. As these MRI contrast agents can be assumed to behave conservatively during estuarine mixing, it is possible to calculate how much wastewater is represented in any particular sample. In this study, the percentage contribution of wastewater at specific locations in Moreton Bay, Qld, were determined by calculating the additional anthropogenic gadolinium contribution to the total rare earth element concentrations. Wastewater contributions were measured at concentrations as low as 0.2%, demonstrating the applicability of this technique for wastewater effluent plume mapping.

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.

Determining the fraction of pharmaceutical residues in wastewater originating from a hospital.

Pharmaceutical residues in water are frequently analysed and discussed in connection with sewage treatment, ecotoxicity and, natural and drinking water quality. Among different localities hospitals are suspected, or implied, to be a major and highly variable source of pharmaceuticals that substantially contribute to the total wastewater load. In this study, the contribution of pharmaceuticals from a hospital to a sewage treatment plant (STP) serving around 45,000 inhabitants was evaluated. Approximately 200 hospital beds result in a hospital bed density of 4.4 beds per 1000 inhabitants, which is a typical value for developed world countries. Prior to sampling, a sound systems analysis was performed, and a sophisticated continuous flow-proportional sampling regime was applied. Hence, overall experimental uncertainty was reduced to a minimum, and measurements provide clear evidence that, for 28 of 59 investigated substances, over 85% of the pharmaceutical residue loads do not originate from the hospital when applying a conservative error estimation. Only for 2 substances, trimethoprim (18%) and roxithromycin (56%), was the maximum observed contribution of the hospital >15%. On average, the contribution of the hospital for the compounds detected in both, hospital effluent and sewage treatment plant influent was small and fairly constant. Five compounds were only detected in hospital wastewater, and 24 neither in the hospital wastewater nor in the total wastewater at the influent of the STP. For these compounds no experimental contribution could be calculated. For the compounds where audit data for both the national consumption and the specific hospital under investigation were available, a prediction of the fraction of pharmaceuticals originating from the hospital was performed. Three quarters of the compounds, classified with the existing audit data, were in the same "hospital contribution category" as determined by measurements. For most of the other compounds, plausible reasons could be identified to explain the observed deviations.

Detection of anthropogenic gadolinium in treated wastewater in South East Queensland, Australia.

The use of refractory gadolinium (Gd) complexes as paramagnetic contrast agents in magnetic resonance imaging has resulted in point source release of anthropogenic Gd (Gd(Anth)) into the environment, and presents opportunities to trace the fate of wastewater in natural environments. We demonstrate an inductively coupled plasma mass spectrometry (ICP-MS) technique that is capable of detecting Gd(Anth) at concentrations as low as 48 fM, approximately six orders of magnitude lower than most other micropollutants, without the need for preconcentration. Further, we establish the ubiquitous presence of Gd(Anth) in wastewater at eight separate wastewater treatment plants in Brisbane, Australia, over a 3-month time period. In contrast, there is no evidence of Gd(Anth) in tap water, or in four separate regional water supply dams in South East Queensland, Australia. It is, therefore, highly unlikely that other anthropogenic micropollutants sourced from urban wastewater would be present in the drinking water supply.