WCW26

Twenty-five years ago, the US National Research Council considered potable reuse a “solution of last resort.” Today, it is a mainstream water supply option in the western United States, and is increasingly being implemented in eastern States. In Canada, water reuse has been practiced since the 1970’s, first in the Okanagan Valley as a means of addressing nutrient loading; today, discussions regarding water reuse have re-emerged in response to modern water challenges. Alberta’s upcoming Water Amendment Act (Bill 7) and regional initiatives including the City of Calgary’s Water Scarcity Roadmap and Water Reuse Assessment signal a renewed national focus on potable reuse at home.  

Treatment technology selection is a careful balance of regulatory preference, source water quality, and public perception. The rapid implementation of reuse technologies in the United States has been enabled by extensive academic research, public engagement efforts, and demonstration facilities ranging from proof-of-concept trailers, to simple outdoor pilots, to “museum-quality” permanent installations.

Historically, potable reuse facilities relied on reverse osmosis- based advanced treatment (RBAT), which is a codified requirement in some US states (notably California). As potable reuse expands into new markets, however, carbon-based advanced treatment (CBAT) has emerged as an equivalent treatment approach, with reduced cost and operational complexity. This shift has been the subject of extensive research through the Water Research Foundation, beginning with Project #1695 (Equivalency of Advanced Treatment Trains for Potable Reuse) published in 2016, followed by numerous studies exploring treatment performance, process innovations and optimization, monitoring, and validation. Early full-scale Indirect Potable Reuse (IPR) projects, where reclaimed water is introduced into an environmental buffer (reservoir or groundwater) use CBAT, including a facility on the Upper Occoquan (VA), followed by Gwinnett County (GA), and now at Hampton Roads (VA). This enables communities to pursue potable reuse without the cost of RO membranes, or needing to dispose of RO concentrate.

Now, CBAT projects push utilities towards the last frontier: Direct Potable Reuse (DPR), where purified recycled water is introduced directly back into the drinking water supply without first passing through an environmental buffer. Starting in 2017 with the international award-winning pureALTA DPR demonstration project in Altamonte Springs, Florida, and followed thereafter by similar projects in Florida (One Water Polk), Utah (Pure SoJo), and Tennessee (multiple), CBAT is being established as a viable and cost-effective approach to DPR where desalination is not required.

This presentation will begin with an overview of potable reuse technologies and their implementation across Canada and the United States. It will then discuss our understanding of CBAT performance, starting with results from WRF 1695 and subsequent research, continuing to case studies from the CBAT DPR demonstration facilities listed above, and a sneak peek at the most recent XBAT testing data. Finally, the presentation will conclude with a brief overview of a customizable CBAT process model based on all of these data, allowing utilities to explore options for potable reuse, including what specific CBAT configurations may be best for them.

Lagoons remain the backbone of wastewater treatment infrastructure for many small and medium sized prairie communities due to their simplicity and cost-effectiveness. However, meeting increasingly stringent effluent nutrient limits, especially during cold weather, poses a significant challenge at lagoon facilities. This presentation explores approaches to post-lagoon nitrification, ammonia and phosphorus removal tailored to the unique climatic and operational constraints of the Canadian prairies. We draw on recent experience on advanced lagoon system projects including implementing post-lagoon moving bed bioreactors (MBBRs) to examine how nutrient removal unit processes can be retrofitted to existing lagoons and function effectively in low temperatures. The session will highlight practical design considerations and lessons learned.

For engineers and operators, lagoon sludge is often misdiagnosed as a simple capacity issue requiring high-cost dredging or desludging. This session presents a paradigm shift based on over 800 bathymetric sludge and sediment surveys, demonstrating that sludge accumulation is actually a key indicator of pond performance. We will dissect correlations between sludge markers and facility performance, showing how "failing" assets can often be recovered without total rehabilitation. The presentation also addresses increasing sludge contaminants and their impact on disposal logistics.
Drawing on data from successful facilities, this session equips stakeholders with evidence-based strategies to assess true dredging needs, mitigate environmental risk, and delay capital expenditure.
Attendees will learn to:
-Differentiate between capacity issues and biological inefficiencies.
-Identify risks of premature dredging versus targeted adjustments.
-Apply survey data to extend asset lifecycles.
 

Alberta’s Regional Water and Wastewater Assessment Initiative (RWWAI) brought together regional water and wastewater commissions representing over 200 municipalities and 1.07 Million Albertans to examine the current state of critical infrastructure across the province. Through data-driven analysis and collaborative engagement, the initiative explores governance, rate-setting, asset management, emergency preparedness, and long-term funding needs. This session will share early findings, highlight common challenges, and discuss how regional collaboration can support resilient, affordable water and wastewater systems over the next 5, 10, and 50 years.

Oil sands process water (OSPW), generated during bitumen extraction in northern Alberta, is produced in very large volumes and contains a complex mixture of inorganic salts, suspended solids, residual hydrocarbons, and organic contaminants. Among these, naphthenic acids (NAs) are recognized as the primary contributors to OSPW toxicity due to their structural diversity, persistence, and resistance to conventional treatment. In the absence of approved discharge regulations, OSPW is stored in tailings ponds, leading to steadily increasing volumes and significant environmental and public health concerns. Advanced oxidation processes (AOPs) such as UVC/H₂O₂ and ozonation have been investigated but are often energy‑intensive and depend on continuous chemical inputs, motivating the development of more sustainable, solar‑driven treatment technologies.
This work investigates tin oxide (SnO₂)–based photocatalysts modified with silver (Ag) for solar‑driven degradation of NAs in real OSPW. SnO₂ is an attractive photocatalyst owing to its strong oxidative potential, chemical stability, low toxicity, and favorable electronic properties. Ag is incorporated to form SnO₂/Ag heterojunctions with the objective of enhancing charge separation and suppressing electron–hole recombination. Material characterization confirmed successful heterojunction formation and uniform Ag dispersion.
Photocatalytic performance was assessed using synchronous fluorescence spectroscopy to monitor fluorescent organic compounds and conventional NA analysis to quantify removal. Raw OSPW exhibited characteristic fluorescence peaks associated with single‑ and multiring aromatics. Under simulated solar irradiation, photolysis and unmodified SnO₂ produced minimal changes in fluorescence intensity, indicating limited degradation. In contrast, an optimally Ag‑modified SnO₂/Ag catalyst produced a pronounced reduction in all major fluorescence peaks, particularly those linked to multi‑ring aromatics, demonstrating substantially enhanced photocatalytic activity. NA degradation followed similar trends, with simpler O₂‑substituted NAs being more readily oxidized than more complex and highly oxidized species. Performance decreased at both lower and higher Ag contents, with excessive Ag loading leading to increased charge recombination and light‑shielding effects, consistent with photoluminescence results. Kinetic analysis indicated pseudo‑first‑order behavior, and dark adsorption controls confirmed that removal was dominated by photocatalytic oxidation rather than sorption.
Mechanistic studies using radical scavengers identified hydroxyl radicals (^•OH) as the primary reactive species driving NA degradation. The optimized SnO₂/Ag catalyst maintained high removal efficiency over multiple reuse cycles with minimal Ag leaching, indicating good stability and reusability under solar irradiation. Toxicological assessment of treated OSPW showed a strong reduction in immunotoxic responses, demonstrating that the process not only removes target organics but also substantially mitigates biological effects. In addition, two new performance indicators were introduced to support more robust comparison of photocatalytic systems for complex industrial effluents such as OSPW.
Overall, this study demonstrates that optimally engineered SnO₂/Ag photocatalysts can deliver efficient, solar‑driven degradation of NAs and significant toxicity reduction in real OSPW. At an optimum catalyst dose of 0.5 g/L, the SnO₂/Ag (5%) catalyst achieved around 90% removal of the O₂‑NAs and a strong decrease in immunotoxic responses. These results highlight SnO₂/Ag photocatalysis as a promising and more sustainable pathway for tailings water remediation.
Oil sands process water (OSPW), generated during bitumen extraction in northern Alberta, is produced in very large volumes and contains a complex mixture of inorganic salts, suspended solids, residual hydrocarbons, and organic contaminants. Among these, naphthenic acids (NAs) are recognized as the primary contributors to OSPW toxicity due to their structural diversity, persistence, and resistance to conventional treatment. In the absence of approved discharge regulations, OSPW is stored in tailings ponds, leading to steadily increasing volumes and significant environmental and public health concerns. Advanced oxidation processes (AOPs) such as UVC/H₂O₂ and ozonation have been investigated but are often energy‑intensive and depend on continuous chemical inputs, motivating the development of more sustainable, solar‑driven treatment technologies.
This work investigates tin oxide (SnO₂)–based photocatalysts modified with silver (Ag) for solar‑driven degradation of NAs in real OSPW. SnO₂ is an attractive photocatalyst owing to its strong oxidative potential, chemical stability, low toxicity, and favorable electronic properties. Ag is incorporated to form SnO₂/Ag heterojunctions with the objective of enhancing charge separation and suppressing electron–hole recombination. Material characterization confirmed successful heterojunction formation and uniform Ag dispersion.
Photocatalytic performance was assessed using synchronous fluorescence spectroscopy to monitor fluorescent organic compounds and conventional NA analysis to quantify removal. Raw OSPW exhibited characteristic fluorescence peaks associated with single‑ and multiring aromatics. Under simulated solar irradiation, photolysis and unmodified SnO₂ produced minimal changes in fluorescence intensity, indicating limited degradation. In contrast, an optimally Ag‑modified SnO₂/Ag catalyst produced a pronounced reduction in all major fluorescence peaks, particularly those linked to multi‑ring aromatics, demonstrating substantially enhanced photocatalytic activity. NA degradation followed similar trends, with simpler O₂‑substituted NAs being more readily oxidized than more complex and highly oxidized species. Performance decreased at both lower and higher Ag contents, with excessive Ag loading leading to increased charge recombination and light‑shielding effects, consistent with photoluminescence results. Kinetic analysis indicated pseudo‑first‑order behavior, and dark adsorption controls confirmed that removal was dominated by photocatalytic oxidation rather than sorption.
Mechanistic studies using radical scavengers identified hydroxyl radicals (^•OH) as the primary reactive species driving NA degradation. The optimized SnO₂/Ag catalyst maintained high removal efficiency over multiple reuse cycles with minimal Ag leaching, indicating good stability and reusability under solar irradiation. Toxicological assessment of treated OSPW showed a strong reduction in immunotoxic responses, demonstrating that the process not only removes target organics but also substantially mitigates biological effects. In addition, two new performance indicators were introduced to support more robust comparison of photocatalytic systems for complex industrial effluents such as OSPW.
Overall, this study demonstrates that optimally engineered SnO₂/Ag photocatalysts can deliver efficient, solar‑driven degradation of NAs and significant toxicity reduction in real OSPW. At an optimum catalyst dose of 0.5 g/L, the SnO₂/Ag (5%) catalyst achieved around 90% removal of the O₂‑NAs and a strong decrease in immunotoxic responses. These results highlight SnO₂/Ag photocatalysis as a promising and more sustainable pathway for tailings water remediation.