WCW26

Each wastewater treatment facility faces unique influent characteristics, making site-specific screening evaluations critical for optimizing headworks performance. At Alexandria Renew Enterprises (AlexRenew), field testing was performed to assess existing coarse and fine mechanical screens and evaluate alternative configurations.
Using on-site screening capture testing, various combinations of coarse and fine sieve openings and geometries were tested under average dry-weather conditions. Results showed the existing coarse screens removed an average of 0.7 cubic feet of solids per million gallons (CF/MG). In contrast, a configuration of a 19 mm slotted coarse screen followed by a 6 mm perforated plate fine screen achieved an average Screen Capture Ratio of 52%—a projected threefold increase in solids removal.
Beyond capture efficiency, testing provided valuable insight into screen hydraulics, blinding tendencies, and compatibility with existing infrastructure. This approach demonstrates how field data can guide screen selection, improve debris removal, reduce downstream maintenance, and extend equipment service life.
The case underscores the value of empirical testing in headworks design. By quantifying capture rates, headloss behavior, and solids characteristics, utilities can make more informed upgrade decisions tailored to their specific flow conditions and operational priorities.

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.
 

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.