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This study presents an updated analysis spanning over two decades (1999–2023) of climate, water quality, and operational data from two drinking water facilities in Atlantic Canada that previously experienced gradual increases in the natural organic matter (NOM) concentration and brownification. The goal was to assess the impact of recent extreme weather events on acute NOM concentration increases and drinking water treatment processes. In 2023, a dry spring combined with a warm and wet summer caused NOM in the water supplies to increase by >67% (as measured by color). To mitigate increased NOM concentration, the alum dose nearly doubled in 2023 compared to that in 2022. Disinfection byproducts were elevated following the event but remained within the compliance levels. From 1999 to 2023, the two plants responded to gradual climate change impacts and brownification, with alum dose increases of between 4.1 and 8.3 times. Equivalent CO2emissions were estimated for alum usage, which increased by 3 to 7-fold in 2023 compared to when the plants were commissioned decades prior. The plants were not only adversely impacted by climate change but also contributed to the global CO2burden. Thus, a paradigm shift toward sustainable alternatives for NOM removal is required in the water sector, and climate change adaptation and mitigation principles are urgently needed.

Little is known about microbial community, filter media characteristics and hydraulic performance changes during disruptive events in biofilters. For the first time, a series of core samplings through the filter media depth was conducted over two years to study microbiome and filter media attributes along with the hydraulic performance indicators to understand the changes and their interrelations. These samples covered baseline and disruptive events, including filter media replacement, a lake diatom bloom, and chlorination resolving the performance challenges caused by the bloom. Based on 16S rRNA gene sequencing, the ecological indices were correlated against the hydraulic performance indicator, such as filter runtime, head-loss and filter media parameters (e.g., deposited metals, biological activity, and turbidity). Hydraulic performance declined during the disruptive events reflected in the microbiome community structure as well as the biological activity of the biofilter. As expected, the highest ATP and head-loss accumulation rates were observed during the lake diatom bloom. The fresh media samples, the media replacement event, showed a distinct microbiome, as indicated by beta diversity and confirmed by PERMANOVA statistical analysis. However, the chlorination did not shift the microbial community structure compared to that of the diatom bloom. This could be because chlorination may have pushed the microbes to the lower levels or the fact that 16S rRNA sequencing does not distinguish between dead and live cells. Based on the findings of this study, replacing filter media showed a more noticeable shift in the microbial community than diatom bloom and the subsequent chlorination. A significant correlation was observed between FRT, deposited aluminum concentration, and turbidity accumulation rate on the filter media. Biological activity, as measured by adenosine triphosphate (ATP), and turbidity decreased as filter depth increased. No significant variation in alpha diversity indices such as richness, Shannon and evenness through the biofilter's depth was observed. In contrast, beta diversity indicated changes in microbial community structure through the depth of the biofilter. It is concluded that the impact of the disruptive events does not end with the hydraulic performance indicators but rather extends to the microbial community structure and diversity. The findings may contribute to further predicting performance changes in case of deviation from baselines in different water utilities.

Sodium silicates have been studied as drinking water additives for coagulation, sequestration of iron, and corrosion control, but their impact on biofilm formation has received less attention. This study investigated the impact of sodium silicate corrosion control on biomass accumulation in comparison to orthophosphate, a common corrosion inhibitor. Biofilm growth was measured by determining ATP concentrations, and bacterial communities were characterized using 16S ribosomal RNA (rRNA) sequencing. In a pilot-scale study with annular reactors (ARs) fed by cast iron pipe loops, biofilm ATP concentrations were substantially lower on polycarbonate coupons in the sodium silicate-treated AR than on those in the orthophosphate-treated AR when the water temperature exceeded 20 °C. An elevated sodium silicate dose (48 mg L−1of SiO2), however, dispersed the biofilm, resulting in elevated effluent ATP concentrations. Two separate experiments confirmed that biomass accumulation was higher in the presence of orthophosphate at high water temperatures (≥20 °C), whereas no significant differences were identified in biofilm ATP concentrations at lower water temperatures (<20 °C). Differences in bacterial communities between the orthophosphate- and sodium silicate-treated systems were not statistically significant, even though orthophosphate promoted higher biofilm growth. The genera Halomonasand Mycobacterium, however—which include opportunistic pathogens—were present at greater relative abundances in the orthophosphate- compared to the silicate-treated system.

Microorganisms were allowed to inhabit flow-through systems containing representative Pb corrosion products, Pb(iv) oxide and Pb(ii) carbonate. Local tap water was fed to the system. After 277 days of operation, distinct microbial communities were developed on the two Pb compound surfaces and both differed from those on the filter media of a full-scale biofilter, which served as the inoculum. A large proportion of the microorganisms were heavy-metal tolerant. Pyromorphite-like compounds were detected in all solid samples at the end, except for the Pb(iv) control with minimal biological activity. Pb release to the tap water increased in the test groups as compared to the controls. In continuous flow mode, fractionation of Pb in the tap water leaving the flow-through systems (the effluent) showed that most Pb was in the filtrates passing the sterile filters (0.2 μm) (Pb[ii], 73.8%; Pb[iv], 64.4%). Besides, the filtrates during ATP quantification, with most microbial cells intercepted (0.22 μm), contained 64.6 ± 13.5% (Pb[ii]) and 67.7 ± 21.6% (Pb[iv]) of the total effluent Pb. During stagnation tests, the filtrates in ATP quantification generally contained over 50% of the total Pb in the first 60 ml effluent upon water resumption. These results indicate that most of the soluble and some colloidal Pb did not co-migrate with microbial cells once released to tap water, although microbial cells and biofilm debris usually carry negative charges. Additionally, the variation of the dissolved organic carbon (DOC) did not correlate with the variation of the increased Pb or ATP in the tap water effluent. The level of planktonic microorganisms in the effluent, as reflected by ATP, did not correlate with Pb release in the Pb(ii) system while a weak correlation was observed in the Pb(iv) system. Since potential residue from the inoculum and inorganic content in tap water may complicate the Pb dissolution in the presence of biofilms, future studies are required to illustrate the interactions among these components. Overall, this study suggests that physiochemical Pb dissolution may be complicated by biological instability in distribution systems due to heavy-metal tolerant microorganisms that grow on Pb scales.

Lead release into drinking water from lead service lines, lead containing solder and plumbing fixtures continues to challenge many utilities. Corrosion inhibitors such as orthophosphate are often added to water to mitigate lead release, but their use may not be feasible for many utilities and may not be sufficient to meet regulatory limits. Thus, there is a need to identify other treatment strategies to minimize lead release. Two possible means that have not been thoroughly studied include natural organic matter (NOM) removal and hardness adjustment (e.g., water softening). Accordingly, this study employed a two-level fractional factorial design to investigate the role of NOM and hardness in conjunction with dissolved inorganic carbon (DIC), and pH, on the galvanic corrosion of lead. This study followed a “dump and fill” protocol and employed test pieces consisting of new lead and copper pipes with an external galvanic connection. Suwannee River NOM (SRNOM) increased the release of dissolved lead by an order of magnitude in collected water samples. To be precise, average dissolved lead release in the synthetic waters with and without SRNOM was 140 and 2460 μg L−1respectively (potentially significant [i.e., 0.05 < p< 0.1]; p= 0.060). Using fluorescence excitation emission matrices, it was found that the release of dissolved lead was correlated to decreases in the NOM humic-like peaks A (R2= 0.85; p= 4.4 × 10−8) and C (R2= 0.87; p= 1.3 × 10−8). It is plausible that the decrease in fluorescence was due to the quenching effect of lead–NOM complexation, providing evidence that complexation mobilized dissolved lead. Hardness and DIC did not have a significant effect on lead release, however the galvanic current between the lead and copper pipes was 28.5 μA higher when the DIC concentration was 80 mg L−1compared to 10 mg L−1(potentially significant; p= 0.051). Finally, average total lead release at a pH of 7 was 7190 μg L−1compared to only 2800 μg L−1at a pH of 8.5 (potentially significant; p= 0.089), and there was some indication that the impact of SRNOM was lower at a higher pH.

Wastewater-based surveillance methods have been implemented in several countries as a tool for monitoring SARS-CoV-2 at a community scale. A variety of methods have been used for concentrating, extracting, and detecting the virus, with no clear consensus on the most effective approach. In this note, we report preliminary findings from a study that is tracking SARS-CoV-2 in wastewater in Halifax, Nova Scotia, with a specific focus on the use of four reverse transcriptase quantitative PCR (RT-qPCR) assays for detecting the virus in wastewater. We were able to detect the virus in wastewater samples during the initial rise of cases in the Halifax region in early November 2020. Levels of the targeted SARS-CoV-2 gene fragments increased and fell in response to reported cases of COVID-19. The CDC N1 and E RT-qPCR assays demonstrated greater relative sensitivity than the CDC N2 and N3 assays for detection of SARS-CoV-2 in raw sewage samples.

Silicates have been added to drinking water for decades, mainly to control colour by dispersing oxidized iron and manganese. Silicates have been used occasionally to control lead release, but there is no consensus on whether they are effective. Moreover, there are concerns that silicates may disperse particulate lead. We evaluated the effect of sodium silicate on lead release from a model lead(ii) carbonate powder using a continuous-flow stirred-tank reactor. We tested a wide range of pH and dissolved inorganic carbon (DIC) concentrations (pH 7.5 or 9, and 5 or 50 mg C per L). We compared sodium silicate against an inhibitor-free control, a better-characterized inhibitor (orthophosphate), and a widely used sequestrant (polyphosphate). Sodium silicate did not have a statistically significant impact on lead release at pH 7.5, regardless of the DIC concentration. At pH 9 it accompanied 80% more lead release at 5 mg C per L and 21% less lead release at 50 mg C per L, compared with controls at matched pH and DIC settings. Sodium silicate did not influence the crystalline phase composition, but it did adsorb to lead(ii) carbonate. This may account for its effects at pH 9. Orthophosphate was the more effective inhibitor, yielding 33–96% less lead release than matched controls. Orthophosphate inhibition was attributed to conversion from lead(ii) carbonate to hydroxylpyromorphite (Pb5(PO4)3OH) and adsorption to lead(ii) carbonate in the absence of a phase conversion (i.e., at pH 9 with 50 mg C per L). Polyphosphate increased lead release by 540–4100%, likely due to aqueous complexation and possibly due to colloidal dispersion.

Access to clean and safe drinking water is a perpetual concern in Arctic communities because of challenging climatic conditions, limited options for the transportation of equipment and process chemicals, and the ongoing effects of colonialism. Water samples were gathered from multiple locations in a decentralized trucked drinking water system in Nunavut, Canada, over the course of one year. The results indicate that point of use drinking water quality was impacted by conditions in the source water and in individual buildings and strongly suggest that lead and copper measured at the tap were related to corrosion of onsite premise plumbing components. Humic-like substances were the dominant organic fraction in all samples, as determined by regional integration of fluorescence data. Iron and manganese levels in the source water and throughout the water system were higher in the winter and lower in the summer months. Elevated concentrations of copper (>2000 μg L–1) and lead (>5 μg L–1) were detected in tap water from some buildings. Field flow fractionation coupled with inductively coupled plasma mass spectrometry and ultraviolet–visible spectrometry was used to demonstrate the link between source water characteristics (high organics, iron and manganese) and lead and copper in point of use drinking water.

A commercially-available UV surface disinfection system used for hospital room disinfection was characterized for use as a UV-inactivation system for N95 filtering facepiece respirator (FFR) respirators. The output of light was initially characterized and assessed for its ability to penetrate through the individual N95 respirator layers. Following characterization, disinfection performance was tested using a range of model pathogens. In a series of experiments, coupons of respirator material were inoculated with Escherichia coli, Staphylococcus aureus, Geobacillus stearothermophilusspores, Bacillus cereus, Pseudomonas aeruginosa, and influenza A virus. Inoculated coupons were then treated with UV light from a low-pressure UV disinfection system during specific treatment times. Microbial enumeration was performed pre- and post-UV treatment. It was found that respirator coupons inoculated with E. coli, influenza A, P. aeruginosa, B. cereusand G. stearothermophilusresulted in below detection counts when exposed to UV fluences between 410 to 2700 mJ cm−2. In addition, UV light was unable to sufficiently penetrate all layers of respirator material, highlighting the importance of flipping respirators when exposing them to UV light. This work suggests that with further validation, UV light will be a promising touchless treatment option for frontline professionals who need to repurpose N95 respirators for subsequent use.

Drinking water samples were collected from the water source, water delivery truck, domestic water storage tanks, and at the point of use in a decentralized drinking water system in Pond Inlet, Nunavut, a predominantly Inuit community in Canada's Arctic region. The samples were analyzed for standard water quality parameters (turbidity, colour, pH, conductivity), biological water quality parameters (coliforms, adenosine triphosphate), and free and total chlorine. The microbial communities in a subset of water and biofilm samples were characterized with DNA analysis. Physiochemical characteristics at the tap were influenced by source water quality and building-specific conditions. Multiple aesthetic water quality parameters were above recommended values including turbidity and colour. Turbidity and biological activity (measured as cellular ATP) varied temporally in some locations. DNA analysis at the phylum, family, and genus level demonstrated that microbial ecology evolved from source water to tap and that individual storage tanks and taps were influenced by distinct microbial communities.

Lead and manganese are regulated in drinking water due to their neurotoxicity. These elements have been reported to co-occur in drinking water systems, in accordance with the metal-scavenging properties of MnO2. To the extent that manganese is a driver of lead release, controlling it during water treatment may reduce lead levels. We investigated transport of lead and manganese at the tap in a full-scale distribution system: consistent with a cotransport phenomenon, the two metals were detected in the same colloidal size fraction by size-exclusion chromatography with multielement detection. We also studied the effect of manganese on lead release using a model distribution system: increasing manganese from 4 to 215 μg L–1nearly doubled lead release. This effect was attributed primarily to deposition corrosion of lead by oxidized phases of manganese, and we used 16S rRNA sequencing to identify bacteria that may be relevant to this process. We explored the deposition corrosion mechanism by coupling pure lead with either MnO2-coated lead or pure lead exposed to MnO2in suspension; we observed galvanic currents in both cases. We attributed these to reduction of Mn(IV) under anaerobic conditions, and we attributed the additional current under aerobic conditions to oxygen reduction catalyzed by MnO2.

Maintaining drinking water quality during distribution requires a range of tools to ensure chemical stability at the tap. Coloured water is a primary concern, and sodium silicates have been reported to reduce colour from iron. However, the impacts of water quality and the interactions between sodium silicate and iron oxides are not well characterized in this context. We conducted a bench-scale factorial experiment (24) to evaluate the effect of sodium silicate on colour and turbidity with pH, humic acid, free chlorine, and sodium silicate as independent variables. Sodium silicate reduced colour and turbidity due to particulate iron by 113.3 Pt–Co and 4.0 NTU, respectively. Sodium silicate reduced the size of iron particles, as determined by dynamic light scattering and laser diffraction, and increased the apparent density, as assessed by electron microscopy. XRD and XPS data were consistent with increased amorphous and oxyhydroxide content in iron precipitates exposed to sodium silicate. Silicate also inhibited the adsorption of humic acid onto model iron oxides due to electrostatic repulsion: the zeta (ζ-) potentials of iron oxides in silicate-treated systems were substantially more negative.

Exposure to lead, copper, and manganese viadrinking water is a public health concern. Modeling can account for solubility due to simple inorganic ligands but generally falls short in capturing the effects of natural organic matter, particles, and colloids; environmental data are needed to understand the importance of these species. Here, we demonstrate the use of asymmetric flow field flow fractionation with UV and ICP-MS detection to separate drinking water samples into ionic species, colloids, and metal–organic complexes. Colloidal iron appeared to be more important as a transport vector for lead, copper, and manganese than natural organic matter: estimated colloidal metals concentrations (Pb, Cu, Fe, Mn >1000 kDa) were at least 3 times greater than concentrations of these metals associated with the high apparent molecular weight (∼1 kDa) organic signal. In transmission electron micrographs, two distinct populations of relatively dense colloids in the size range 50–200 nm were apparent, with morphologies typical of environmental iron oxides. Moreover, energy dispersive spectroscopy showed that sample colloids were rich in iron, copper, and oxygen. At equilibrium (e.g., during long stagnation periods in plumbing), high molecular weight organic and colloidal fractions represent additional capacity for drinking water to transport lead, which could have implications for water treatment to limit lead exposure.

Disinfection byproducts (DBPs) and algal toxins can be expensive to monitor and represent significant potential risks to human health. DBPs, including haloacetic acids and trihalomethanes, are possible or probable human carcinogens. Microcystin-LR—produced by cyanobacteria—is linked with various adverse health effects. Here we show that fluorescence spectra predict both microcystin-LR occurrence and DBP formation potential (DBPfp) in lake water. We compared models with either fluorescence spectra or a suite of water quality predictors as inputs. A regularized logistic regression model with fluorescence spectral inputs correctly classified 94% of test data with respect to microcystin-LR occurrence, with a 96% probability of correctly ranking a detect/nondetect pair. Regularized linear regression predicted DBPfp based on fluorescence inputs with a combined R2of 0.83 on test data. A gradient-boosted classifier with seven water quality inputs was comparable in detecting microcystin-LR (91% correct), as was UV254in predicting DBPfp (combined test R2= 0.84), but no single parameter matched fluorescence spectra over both predictive tasks. Results highlight the potential for multiparameter monitoring via fluorescence spectroscopy, extending previous work on predicting DBPs alone. As a high-frequency monitoring tool, this approach could supplement mass spectrometric methods that may only be applicable at low frequency due to resource limitations.

ABSTRACTDunnington DW, Spooner IS, Krkošek WH, Gagnon GA, Cornett RJ, Kurek J, White CE, Misiuk B, Tymstra D. 2018. Anthropogenic activity in the Halifax region, Nova Scotia, Canada, as recorded by bulk geochemistry of lake sediments. Lake Reserv Manage. 34:334–348.Separating the timing and effects of multiple watershed disturbances is critical to a comprehensive understanding of lakes, which is required to effectively manage lacustrine systems that may be experiencing adverse water quality changes. Advances in X-ray fluorescence (XRF) technology has led to the availability of high-resolution, high-quality bulk geochemical data for aquatic sediments, which in combination with carbon, nitrogen, δ13C, and δ15N have the potential to identify watershed-scale disturbance in lake sediment cores. We integrated documented anthropogenic disturbances and changes in bulk geochemical parameters at 8 lakes within the Halifax Regional Municipality (HRM), Nova Scotia, Canada, 6 of which serve as drinking water sources. These data reflect more than 2 centuries of anthropogenic disturbance in the HRM that included deforestation, urbanization and related development, and water-level change. Deforestation activity was documented at Lake Major and Pockwock Lake by large increases in Ti, Zr, K, and Rb (50–300%), and moderate increases in C/N (>10%). Urbanization was resolved at Lake Fletcher, Lake Lemont, and First Lake by increases in Ti, Zr, K, and Rb (10–300%), decreases in C/N (>10%), and increases in δ15N (>2.0‰). These data broadly agree with previous paleolimnological bioproxy data, in some cases identifying disturbances that were not previously identified. Collectively these data suggest that bulk geochemical parameters and lake sediment archives are a useful method for lake managers to identify causal mechanisms for possible water quality changes resulting from watershed-scale disturbance.

Utility and homeowner surveys were completed in 2015 to document the number of lead service lines (LSLs) in Canadian utilities, share utilities’ knowledge, and formulate recommendations on LSL management. LSLs represented <1 to 22% of the service line connections in the distribution systems considered (average 23 LSLs/1,000 people). With the exception of two utilities, mostly partial LSL replacements (LSLRs) were conducted by the utilities surveyed; flushing procedures post‐LSLR varied. Considering both surveys, the following recommendations are suggested: improve LSL records by registering the materials on both the public and the private sides after LSLR; harmonize flushing procedures post‐LSLR; develop a collaborative approach between contractors and utility staff to increase awareness, maintain LSL records, and ensure post‐LSLR flushing; combine funding, increased awareness, and provision of contractors to homeowners with fixed costs to increase full LSLRs; and assess the possibility of mandatory LSL detection and full LSLR at the time of house resale.

Profile, regulatory, and investigative sampling were completed in six utilities to study the impact of partial and full lead service line replacements (LSLRs) on water lead levels (WLLs) and consumer’s exposure. As compared to households with no replacement, lead release after partial LSLR (PLSLR) was generally greater in the short term (3–50 days), and comparable or lower in the medium (<2 years) and long-term (>2 years). This was mainly explained by insufficient time elapsed to stabilize scales after disturbances to the service line. One utility showed sustained lead release over 18 months after PLSLR. Moreover, the reduction in WLLs was small when analyzing results for the same households. As a comparison, full LSLR decreased WLLs drastically and immediately. The occurrence of low (0–5 μg/L) to high (≥50 μg/L) WLLs in the profiles varied between households and reflected the variability of exposure among households in the same system. Using this probability of occurrence, the distribution of WLLs of exposure was estimated for households with or without a PLSLR, and used to model young children blood lead levels (BLLs) for both groups of households. The range of modeled BLLs decreased slightly for households with PLSLR, but still overlapped the range estimated for households with no replacement. This analysis suggests that, in a system, PLSLRs do not reduce young children blood lead levels except in a fraction of households.

The main psychoactive compound in Cannabis sativa, Δ9-tetrahydrocannabinol (THC), and its metabolites are emerging organic contaminants that have been detected in waste and surface waters around the globe. This study tested the efficacy of advanced oxidation processes (i.e., direct UV photolysis or UV/H2O2processes) towards the treatment of the main human metabolite of THC, THC-COOH. Three different waters were selected to evaluate the photolysis and oxidation performance with polychromatic UV light in the range of 200–300 nm, and the effect of pH on the photooxidation of THC-COOH was also studied. The results indicated that direct UV photolysis followed pseudo first-order kinetics, with fluence-based rate constants ranging from 1.9(0.3)–2.7(0.2) × 10−3cm2mJ−1, 0.6(0.2)–1.0(0.1) × 10−3cm2mJ−1, and 0.6(0.2)–0.9(0.2) × 10−3cm2mJ−1for THC-COOH prepared in deionised (DI) water, Suwannee River humic acid (SRHA) dissolved in DI water, and natural lake water, respectively. This study found that the UV/H2O2process did not enhance the oxidation rate in comparison to direct photolysis, and no effect of pH from 5.6 ± 0.2 to 8.7 ± 0.2 was observed. Hence, the hydroxyl radical (HO) degradation pathway played a less important role in the overall oxidation of THC-COOH under the tested conditions (i.e., SRHA and lake water) than direct photolysis.

Manganese (Mn) in drinking water systems can accumulate in Mn-oxide deposits which can be resuspended and re-released leading to dirty water events. Public health concerns regarding Mn are growing due to recent studies correlating Mn in drinking water with neurotoxicity in children. Understanding the factors impacting biologically mediated Mn deposition within water supply systems is crucial to developing strategies that limit Mn in drinking water. Annular reactors containing coupons for biofilm growth were installed at the beginning (Pump House) and end (Supply Plant) of the raw water transmission pipeline at a water supply plant in Nova Scotia, Canada to investigate Mn biofouling. Water quality parameters, the concentration of Mn in bulk water and biofilm, and Mn oxidizing bacteria (MOB) within biofilms were measured. Biofilm communities were characterized by 16S rRNA sequencing. Dissolved Mn concentrations decreased (∼20%) as water travelled from the pump house to the supply plant. Despite this reduction, culturable MOB and Mn-oxides were 80% and 70% greater, respectively, in the supply plant reactor biofilm relative to the pump house. Surprisingly, sequencing analysis showed the abundance of known MOB was greater in the pump house reactor than the supply plant reactor. The biofilm community in the supply plant reactor was composed mainly (55%) of the genus Candidatus Koribacter. BLASTp analysis of Candidatus koribacter versatilisidentified four proteins homologous to multicopper oxidases, which are known to perform Mn oxidation. We suggest Candidatus Koribactermay be a novel MOB which has a considerable impact on biological Mn oxidation and Mn biofouling.

Lead is a potent neurotoxin and drinking water represents an important route of exposure, especially where legacy lead pipe is widespread. Polyphosphates are often added to drinking water to sequester iron and calcium, but they may form coordination complexes with lead, increasing its solubility. This risk is not well characterized in practice: the prevalence of lead-polyphosphate complexes in drinking water systems is not known. We used size-exclusion chromatography (SEC) with multi-element (ICP-MS) detection to compare the speciation of lead below 0.45 μm in two low-alkalinity water systems dosing phosphate-based corrosion inhibitors at different ortho : poly ratios and doses. In one system dosing polyphosphate at 0.05 mg P L−1(3 : 1 ratio), it reverted almost completely to orthophosphate during distribution. In another system dosing polyphosphate at 0.20 mg P L−1(1 : 1 ratio), it was detectable at points of use. Under the influence of polyphosphate, lead and iron were present as dissolved species strongly associated with phosphorus. Moreover, experiments with sodium hexametaphosphate confirmed our ability to detect lead as a coordination complex using SEC. In the absence of polyphosphate, lead and iron were present as colloidal particles. Orthophosphate on its own also appeared to reduce lead solubility, as estimated using paired sample profiles collected at seventeen single-unit residences. Increasing orthophosphate from 0.5 to 1.0 mg PO4L−1accompanied decreases in total lead concentrations of 38% (95% CI: 15–51%) within eight months. Analysis of recovered lead pipe corrosion scale was consistent with the presence of an insoluble lead phosphate compound: hydroxypyromorphite (Pb5(PO4)3OH).

Nutrient, oxidant and media enhancement strategies were applied to pilot-scale biofilters with the objective of enhancing biodegradation to improve effluent water quality (e.g., TOC, DOC, SUVA, THMfp, HAAfp) and filter performance (e.g., effluent turbidity and head loss). While some statistically significant (α= 0.05) differences in DOC removal and DBPfp were identified as a result of specific enhancement strategies, enhancement strategies did not result in improvements in water quality (as measured by TOC, DOC, SUVA and DBPfp) that could be considered of practical operational importance. Water quality improvements were either operationally inconsistent, small in magnitude and/or within the deviation that would be expected from the biofilters when operated under equivalent ambient (i.e., not enhanced) conditions. With respect to filter performance, enhancement strategies also occasionally resulted in a statistically significant difference in effluent turbidity and head loss. However, when identified, statistically significant mean differences in effluent turbidity were deemed not meaningful given the instrument accuracy (i.e., ±0.02 NTU), the relatively small magnitude of the mean differences, or the magnitude of the mean difference observed between biofilters operated under equivalent ambient conditions. With respect to head loss, statistically significant mean differences in head loss that were also considered meaningful given the magnitude of the deviation between ambient biofilters and the accuracy of the pressure transmitters, were largely consistent with the literature; however, the magnitude of the mean differences that showed improvement to head loss were small (10–18 cm), and likely would not be sufficient to substantially extended filter run times to have any practical operational importance.

This study investigated biomass concentrations, as measured by adenosine triphosphate (ATP), in full-scale, anthracite–sand biofilters as they acclimated to conversion from direct filtration to biofiltration. Results showed that there were three scales of biofilter biomass accumulation: an accumulation period within each filter cycle, and an accumulation period associated with adapting to chlorine-free conditions for both biomass measured at the start and end of the filter cycle. Both start- and end-of-cycle biomass reached steady state after 220 days of operation. Start-of-filter-cycle biomass accumulated at a rate of 0.008/day and reached a steady-state concentration of 59 ng ATP/cm3media. End-of-filter-cycle biomass reached an apparent steady-state concentration of 267 ng ATP/cm3media. Biomass measured over a single filter cycle had an accumulation pattern similar to start-of-filter-cycle biomass but accumulated more rapidly (1.96–4.46/day).

Three high performance size exclusion chromatography (HPSEC) columns were compared, along with mobile phase chemistry and calibration standards, for the determination of apparent molecular weight (AMW) of aquatic humic substances using a UV absorbance detector (λ = 254 nm). The addition of 10 % organic solvent did not influence peak elution times of sodium polystyrene sulfonate (PSS) standards or chromatograms of Suwannee River humic acid (SRHA) or fulvic acid (SRFA) but did result in an additional peak being detected in a treated municipal wastewater sample (WWT). Mobile phase concentration was found to have a greater effect on peak position of PSS standards and SRHA than mobile phase pH or sample injection volume. Several chemicals of known molecular weight were tested alongside PSS standards, with salicylic acid (138.1 Da) and 4-chlorobenzoic acid (156.6 Da) resulting in retention times that aligned with the PSS MW standards. Of the three columns tested, the two with comparable pore sizes (i.e., 250 and 300 Å) were found to result in similar peak elution times and highly linear calibration curves over the range of 210–17,000 Da, while the column with the smaller pore size (i.e., 100 Å) gave better peak separation in the low AMW range (i.e., < 1000 Da). Estimations of AMW of SRHA using various sets of calibration standards on one of the three columns tested ranged from 1080 to 2799 Da using 0.02 M NH4CH3CO2as eluent and 60-µL injections. AMW of SRFA ranged from 939 to 2434 Da for the same conditions.

Biofiltration has gained more attention as an alternative filtration for the removal of manganese (Mn) in both groundwater and surface water. This study investigated the potential of biofiltration as pretreatment at the Bennery Lake Water Treatment Plant located in Halifax, Nova Scotia, for the removal of manganese and dissolved organic carbon (DOC) from pH 6 natural lake water. A bench-scale study identified the effect of oxidant enhancement with hydrogen peroxide (H2O2), nutrient enhancement with phosphorus (P) and medium type (granular activated carbon (GAC) and anthracite) on a biofiltration system. Addition of both the nutrient, phosphorus (300–500 µg/l), and the oxidant, hydrogen peroxide (0·5 mg/l) enhanced the biofiltration performance, achieving 98% manganese removal and 27% (1·3 mg/l) DOC removal. Overall, the medium was not a significant factor for manganese removal, while GAC removed significantly more DOC than anthracite, although further treatment would be required for either medium to achieve lower DOC concentrations. These results show direct biofiltration of surface water at pH 6 can remove manganese below the 50 µg/l aesthetic guideline from a manganese loading of over 1 mg/l. This work highlights a potential mechanism and implication of biological roughing filtration technique for the removal of manganese and DOC from natural surface water.

Fluorescence spectroscopy shows promise as a tool for monitoring regulated disinfection by-products (DBPs) online in water treatment applications. Prediction of DBP formation viafluorescence spectroscopy was investigated using drinking water treatment plant (WTP) samples and experimental data from bench-scale advanced oxidation processes applied to a natural water matrix. L1-Regularized linear regression (lasso), boosted regression tree ensembles, principal components regression, supervised principal components, and fluorescent regional integration models were applied to data comprising instantaneous haloacetic acid (HAA) and trihalomethane (THM) concentrations and DBP formation potentials (HAAfp and THMfp) paired with fluorescence excitation–emission matrices. L1-Regularized linear regression yielded the lowest mean absolute error (MAE), assessed by cross-validation, on HAA and HAAfp data collected at the WTP (7.7 μg L−1, N= 22). Boosted regression tree ensemble predictions had the lowest MAE on WTP THM and THMfp data (13.5 μg L−1, N= 37). L1-Regularized linear regression and supervised principal components, respectively, exhibited the greatest prediction accuracy (MAE 14.9 and 9.5 μg L−1, N= 60) for HAAfp and THMfp data generated viabench-scale advanced oxidation processes. Linear models based on either fluorescent regional integration or (unsupervised) principal components were consistently less accurate than the highest-performing methods for DBP prediction.

Floc size distribution is of high operational importance as it governs the transport and removal of contaminants from drinking water. The complex nature of turbulent flow in treatment plants has limited the research to quantify the dynamics of flocculation. This paper describes the use of a submersible digital in-line holographic microscopy (DIHM) technique for the measurement of the spatial distribution of floc sizes in a direct filtration treatment facility. The DIHM tool was positioned at thirteen different locations in a flocculation tank and holograms were recorded for at least 10 minutes at each location. The acquisition of morphological details of flocs (e.g., floc counts, size distributions and floc velocities relative to the fluid motion) from the reconstructed DIHM images is discussed. The results of the spatial distribution of floc sizes indicated that the volume equivalent floc diameter measured in the flocculation tank was mostly of large-sized aggregates greater than 100 μm, which can have adverse impacts on the performance of a direct filtration process. The relative motion of flocs calculated from the DIHM analysis ranged from 0.002 to 0.008 m s−1. Results showed that the investigated DIHM technique could be used as an operational tool to evaluate flocculation performance in terms of floc sizes, which is otherwise difficult to characterize in most treatment plants. The information acquired from this tool is important to understand the fate and transport of flocs during flocculation for process optimization that can lead to minimize chemical and energy usage in treatment plants.

Conversion from direct filtration to biofiltration in a full‐scale drinking water treatment plant in Halifax, N.S., was assessed in terms of filter performance (e.g., turbidity, head loss) and water quality during a 48‐month project. Conversion was achieved by removing prechlorination, with the overall objective of reducing disinfection by‐product formation. As a result of prechlorine removal, it was hypothesized that the anthracite‐sand filters would provide both particle removal and biological treatment in a single process step. When prechlorine was removed, adenosine triphosphate concentrations on the filter media increased from ∼50 to ∼200–500 ng/cm3. Filter performance analysis revealed that conversion increased the filter effluent turbidity and reduced the filter head loss accumulation rate. Unit filter run volumes and filter run times were maintained. Water quality monitoring indicated that finished water total disinfection by‐products were reduced by ∼10–20 μg/L for trihalomethanes and ∼6–10 μg/L for haloacetic acids.

AbstractMembrane fouling is a critical problem for many nanofiltration (NF) membrane plants. This study demonstrated that the poor spaces of the NF membrane were decreased for the deposition of natural organic matter (NOM) on the membrane surface. In-line coagulation was added prior to the low-pressure filtration step to remove more organic material by microfiltration (MF), thereby improving the quality of the feed-water entering the NF membranes. Three different types of coagulants, i.e. aluminum sulfate, ferric chloride, and polyaluminum chloride, with their different levels at different pH values were used for this study. The optimal dose of each coagulant was determined, and the impact on the NF membrane was assessed by batching and running 20 L of post-coagulation MF permeate through a bench-scale NF membrane for 200 h. Ferric chloride was found to perform the best of these three tested coagulants to reduce NF pressure fouling by reduction of NOM in the NF feed-water. High performance size exclusion chromatography study revealed that higher molecular weight fractions of NOM removed preferentially due to in-line coagulation processes. The scanning electron microscopy analysis of the fouled NF membrane trial revealed that the foulant layer consisted of a very large quantity of inorganic and organic matter, bacteria, which resulted in a very rough surface topography.