Amina K. Stoddart

Direct Biofiltration for Manganese Removal from Surface Water

AbstractResearch has shown biological filtration to be a successful treatment for the removal of manganese (Mn) from groundwater and surface water. In this study, bench-scale direct biofiltration was used to remove Mn and dissolved organic carbon (DOC) from a pH 6 surface water source in Halifax, Nova Scotia, Canada. Three factors were examined for their effects on Mn and DOC removal: media type (granular activated carbon and anthracite), pH (6 and 9–11), and nutrient enhancement with phosphorus (P; 20 and 200  μg/L). pH was a significant factor in Mn removal (α=0.05). The P-enhanced pH 6 biofilters for both media obtained an average 91% Mn removal; the P-enhanced pH 9–11 filters for both media achieved an average 70% Mn removal. An average of 23% DOC removal was achieved with P enhancement, compared to 12% DOC removal without P enhancement. Mn was likely removed by biological oxidation and biogenic oxide adsorption. These results show that direct biofiltration of raw surface water at pH 6 can remove Mn t...

Role of iron and aluminum coagulant metal residuals and lead release from drinking water pipe materials

Bench-scale experiments investigated the role of iron and aluminum residuals in lead release in a low alkalinity and high (> 0.5) chloride-to-sulfate mass ratio (CSMR) in water. Lead leaching was examined for two lead-bearing plumbing materials, including harvested lead pipe and new lead: tin solder, after exposure to water with simulated aluminum sulfate, polyaluminum chloride and ferric sulfate coagulation treatments with 1-25-μM levels of iron or aluminum residuals in the water. The release of lead from systems with harvested lead pipe was highly correlated with levels of residual aluminum or iron present in samples (R2 = 0.66–0.88), consistent with sorption of lead onto the aluminum and iron hydroxides during stagnation. The results indicate that aluminum and iron coagulant residuals, at levels complying with recommended guidelines, can sometimes play a significant role in lead mobilization from premise plumbing.

Combined use of resin fractionation and high performance size exclusion chromatography for characterization of natural organic matter.

The number and complexity of natural organic matter (NOM) species limits identification of individual NOM compounds. The objective of this study was to employ several characterization techniques (resin fractionation, high performance size exclusion chromatography (HPSEC), and strategic UV254 absorbance) to samples from seven surface water sites in North America, and overcome the shortfalls of each tool. Resin fractionation indicated the samples were all high in hydrophobic acids (HOA), hydrophilic neutrals (HIN) and hydrophilic acids (HIA). Site B was the only site where HIAs were the highest NOM contributors. In the HPSEC analysis, each fraction exhibited a particular molecular weight (MW) range: 100–300 Da (HIN), 1-2 kDa (HOA), and the HIA fractions exhibited MWs between these two ranges. Strategic UV254 measurements were taken at two sites to supplement the HPSEC results, and determine the difference in UV absorbance per unit dissolved organic carbon (SUVA value). Most fractions showed SUVA values of approximately 5 L/mg-m; however, the hydrophilic bases and hydrophobic neutral fractions could not be accurately evaluated due to the very low DOC concentrations for these two fractions (< 0.2 mg/L). These methods are complimentary NOM characterization techniques, and the combined methodology addresses the analytical limits of each tool.

Prediction of disinfection by-product formation in drinking water via fluorescence spectroscopy

Fluorescence spectroscopy shows promise as a tool for monitoring regulated disinfection by-products (DBPs) online in water treatment applications. Prediction of DBP formation via fluorescence 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 via bench-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.

Lake Recovery Through Reduced Sulfate Deposition: A New Paradigm for Drinking Water Treatment

This study examined sulfate deposition in Nova Scotia from 1999 to 2015, and its association with increased pH and organic matter in two protected surface water supplies (Pockwock Lake and Lake Major) located in Halifax, Nova Scotia. The study also examined the effect of lake water chemistry on drinking water treatment processes. Sulfate deposition in the region decreased by 68%, whereas pH increased by 0.1-0.4 units over the 16-year period. Average monthly color concentrations in Pockwock Lake and Lake Major increased by 1.7 and 3.8×, respectively. Accordingly, the coagulant demand increased by 1.5 and 3.8× for the water treatment plants supplied by Pockwock Lake and Lake Major. Not only was this coagulant increase costly for the utility, it also resulted in compromised filter performance, particularly for the direct-biofiltration plant supplied by Pockwock Lake that was found to already be operating at the upper limit of the recommended direct filtration thresholds for color, total organic carbon and coagulant dose. Additionally, in 2012-2013 geosmin occurred in Pockwock Lake, which could have been attributed to reduced sulfate deposition as increases in pH favor more diverse cyanobacteria populations. Overall, this study demonstrated the impact that ambient air quality can have on drinking water supplies.

Water quality and filter performance of nutrient-, oxidant- and media-enhanced drinking water biofilters

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.

Water safety plans as a tool for drinking water regulatory frameworks in Arctic communities

Arctic communities often face drinking water supply challenges that are unique to their location. Consequently, conventional drinking water regulatory strategies often do not meet the needs of these communities. A literature review of Arctic jurisdictions was conducted to evaluate the current water management approaches and how these techniques could be applied to the territory of Nunavut in Canada. The countries included are all members of the Arctic Council and other Canadian jurisdictions considered important to the understanding of water management for Northern Canadian communities. The communities in Nunavut face many challenges in delivering safe water to customers due to remoteness, small community size and therefore staffing constraints, lack of guidelines and monitoring procedures specific to Nunavut, and water treatment and distribution systems that are vastly different than those used in southern communities. Water safety plans were explored as an alternative to water quality regulations as recent case studies have demonstrated the utility of this risk management tool, especially in the context of small communities. Iceland and Alberta both currently have regulated water safety plans (WSPs) and were examined to understand shortcomings and benefits if WSPs were to be applied as a possible strategy in Nunavut. Finally, this study discusses specific considerations that are necessary should a WSP approach be applied in Nunavut.

Correction: Potential for manganese biofouling in water transmission lines using model reactors

Correction for ‘Potential for manganese biofouling in water transmission lines using model reactors’ by Nicole E. Allward et al., Environ. Sci.: Water Res. Technol., 2018, DOI: 10.1039/c8ew00074c.