William B. Anderson

Behaviour and fate of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water treatment: a review.

This article reviews perfluoroalkyl and polyfluoroalkyl substance (PFAS) characteristics, their occurrence in surface water, and their fate in drinking water treatment processes. PFASs have been detected globally in the aquatic environment including drinking water at trace concentrations and due, in part, to their persistence in human tissue some are being investigated for regulation. They are aliphatic compounds containing saturated carbon-fluorine bonds and are resistant to chemical, physical, and biological degradation. Functional groups, carbon chain length, and hydrophilicity/hydrophobicity are some of the important structural properties of PFASs that affect their fate during drinking water treatment. Full-scale drinking water treatment plant occurrence data indicate that PFASs, if present in raw water, are not substantially removed by most drinking water treatment processes including coagulation, flocculation, sedimentation, filtration, biofiltration, oxidation (chlorination, ozonation, AOPs), UV irradiation, and low pressure membranes. Early observations suggest that activated carbon adsorption, ion exchange, and high pressure membrane filtration may be effective in controlling these contaminants. However, branched isomers and the increasingly used shorter chain PFAS replacement products may be problematic as it pertains to the accurate assessment of PFAS behaviour through drinking water treatment processes since only limited information is available for these PFASs.

Decision support systems in water and wastewater treatment process selection and design: a review

The continuously changing drivers of the water treatment industry, embodied by rigorous environmental and health regulations and the challenge of emerging contaminants, necessitates the development of decision support systems for the selection of appropriate treatment trains. This paper explores a systematic approach to developing decision support systems, which includes the analysis of the treatment problem(s), knowledge acquisition and representation, and the identification and evaluation of criteria controlling the selection of optimal treatment systems. The objective of this article is to review approaches and methods used in decision support systems developed to aid in the selection, sequencing of unit processes and design of drinking water, domestic wastewater, and industrial wastewater treatment systems. Not surprisingly, technical considerations were found to dominate the logic of the developed systems. Most of the existing decision-support tools employ heuristic knowledge. It has been determined that there is a need to develop integrated decision support systems that are generic, usable and consider a system analysis approach.

The detection of Yersinia enterocolitica in surface water by quantitative PCR amplification of the ail and yadA genes.

Yersinia enterocolitica has been detected in surface water, and drinking untreated water is a risk factor for infection. PCR-based methods have been used to detect Y. enterocolitica in various sample types, but quantitative studies have not been conducted in water. In this study, quantitative PCR (qPCR)-based methods targeting the Yersinia virulence genes ail and yadA were used to survey the Grand River watershed in southern Ontario, Canada. Initial testing of reference strains showed that ail and yadA PCR assays were specific for pathogenic biotypes of Y. enterocolitica; however the genes were also detected in one clinical Yersinia intermedia isolate. A survey of surface water from the Grand River watershed showed that both genes were detected at five sampling locations, with the ail and yadA genes detected in 38 and 21% of samples, respectively. Both genes were detected more frequently at colder water temperatures. A screening of Yersinia strains isolated from the watershed showed that the ail gene was detected in three Y. enterocolitica 1A/O:5 isolates. Results of this study show that Yersinia virulence genes were commonly detected in a watershed used as a source of drinking water, and that the occurrence of these genes was seasonal.

Endotoxin Inactivation in Water by Using Medium-Pressure UV Lamps

ABSTRACT Deionized water was spiked with various concentrations of endotoxin and exposed to UV irradiation from medium-pressure UV lamps to assess endotoxin inactivation. It was found that endotoxin inactivation was proportional to the UV dose under the conditions examined. The inactivation rate was determined to be ∼0.55 endotoxin unit/ml per mJ/cm2 of irradiation delivered.

A Computational Fluid Dynamics Based Integrated Disinfection Design Approach for Improvement of Full-scale Ozone Contactor Performance

A three-dimensional multiphase computational fluid dynamics (CFD) model has been developed, to address all the major components of ozone disinfection processes at the Charles DesBaillets Water Treatment Plant in Montréal, Canada. Good agreement was observed between the numerical results and full-scale tracer data. The CFD predicted flow fields showed that recirculation zones and short circuiting existed in the DesBaillets contactors. Installation of four additional baffles in the second chamber would significantly improve contactor mixing performance. The modeling results also indicated that ozone residuals at the cross section of the outlet of each chamber were very sensitive to the locations of monitoring points.

Effect of ozone on biopolymers in biofiltration and ultrafiltration processes.

The focus of this full-scale study was to determine the effect of ozone on biopolymer concentrations in biofiltration and ultrafiltration (UF) processes treating surface water from Lake Ontario. Ozonation was out of service for maintenance for 9 months, hence, it was possible to investigate ozones action on biologically active carbon contactors (BACCs) and UF, in terms of biopolymer removal. Given the importance of biopolymers for fouling, this fraction was quantified using a chromatographic technique. Ozone pre-treatment was observed to positively impact the active biomass in biofilters. However, since an increase of the active biomass did not result in higher biopolymer removal, active biomass concentration cannot be a surrogate for biofiltration performance. It was evident that increasing empty bed contact time (EBCT) from 4 to 19 min only had a positive effect on biopolymer removal through BACCs when ozone was out of service. However, as a mass balance experiment showed, ozone-free operation resulted in higher deposition of biopolymers on a UF membrane and slight deterioration in its performance.

Methods for determining assimilable organic carbon and some factors affecting the Van Der Kooij method

Abstract It has been demonstrated in many advanced European drinking water facilities that the application of ozone in conjunction with a subsequent granular activated carbon (GAC) treatment step results in reduced distribution system disinfectant demand. This is due, in large measure, to the removal of biodegradable organic substances by microorganisms colonizing the activated carbon. The concentration of easily biodegradable or assimilable carbon (AOC) can be measured in various ways. This paper compares available methods for measuring AOC or bacterial regrowth, and presents pilot plant results showing some factors affecting the van der Kooij method.

Removal of the cyanotoxin anatoxin-a by drinking water treatment processes: a review

Anatoxin-a (ANTX-a) is a potent alkaloid neurotoxin, produced by several species of cyanobacteria and detected throughout the world. The presence of cyanotoxins, including ANTX-a, in drinking water sources is a potential risk to public health. This article presents a thorough examination of the cumulative body of research on the use of drinking water treatment technologies for extracellular ANTX-a removal, focusing on providing an analysis of the specific operating parameters required for effective treatment and on compiling a series of best-practice recommendations for owners and operators of systems impacted by this cyanotoxin. Of the oxidants used in drinking water treatment, chlorine-based processes (chlorine, chloramines and chlorine dioxide) have been shown to be ineffective for ANTX-a treatment, while ozone, advanced oxidation processes and permanganate can be successful. High-pressure membrane filtration (nanofiltration and reverse osmosis) is likely effective, while adsorption and biofiltration may be effective but further investigation into the implementation of these processes is necessary. Given the lack of full-scale verification, a multiple-barrier approach is recommended, employing a combination of chemical and non-chemical processes.

An evaluation of methods for the isolation of Yersinia enterocolitica from surface waters in the Grand River watershed

Yersinia enterocolitica is a foodborne pathogen, but the importance of water as a route of exposure for human infection is not well known. Y. enterocolitica isolation methods were developed primarily for food and clinical samples, and may not be effective for use with environmental samples. The objective of this study was to assess the recovery of Y. enterocolitica from surface water used for drinking water treatment. Four enrichment broths and an alkaline treatment protocol were compared for the isolation of Y. enterocolitica bioserogroup 4/O:3 spiked into surface water samples. Results showed that the methods tested were not effective for the recovery of Y. enterocolitica, primarily due to inadequate inhibition of interfering background microorganisms. Using one method that showed the most potential for recovery, Yersinia spp. were isolated from rivers in southwestern Ontario, Canada, over a 17-month period. Of 200 samples analysed, Yersinia spp. were isolated from 52 samples. All river isolates belonged to non-pathogenic sub-groups, including Y. enterocolitica biotype 1A, Y. aldovae, Y. bercovieri, Y. frederiksenii, Y. intermedia, Y. kristensenii and Y. mollaretii. Results of this study show that method improvements are required to more fully understand the role of water as a source of clinically important Yersinia strains.

MODELLING OF RADIUM-226 LEACHING FROM BARIUM-RADIUM SULFATE SLUDGES

Abstract A geochemical computer model was applied to the leaching of (Ba,Ra) SO4 sludge produced in the treatment of uranium mining and milling effluents to remove 226Ra2+. Previous laboratory studies had shown the following leachant characteristics to be important: initial SO42− and Ba2+ concentrations, pH, and ionic strength. The computer simulations confirmed in a general way previous experimental data, but more importantly showed that the most significant variable was the redox state of the sludge-leachant system. Under all oxidizing conditions (Ba,Ra)SO4 remains sparingly soluble. When conditions become reducing, however, BaSO4(s) is not thermodynamically stabe and the entire mass of 226Ra2+ in the sludge can be transformed to the aqueous phase. Substantial release under reducing conditions was demonstrated in experiments involving bacteria. The use of geochemical computer models represents a fundamental approach to leaching investigations and allows identification of potentially critical environmental conditions which should be investigated experimentally.