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Municipal wastewater treatment plants (WWTP) effluents are primary sources of pathogenic microorganisms and contaminants of emerging concern (CECs) released into the aquatic environment. Main concerns regarding these pollutants include transmission of waterborne diseases to humans and toxic and endocrine disrupting effects on aquatic organisms. In the coming years, WWTPs are expected to invest billions of dollars in upgrades to meet new regulatory requirements for wastewater from Environment Canada. For this reason, we investigated the performance of ozone when the technology is used for disinfection to overcome multiple risk factors such as disinfection, CEC removal, endocrine activity and toxicity for real effluents collected from three WWTPs. Two secondary effluents required mean specific ozone doses for disinfection of 0.25 and 1.04 gO3/gDOC whereas the advanced primary effluent required 1.52 gO3/gDOC to achieve a total coliform target disinfection criteria of 1000 MPN/100 ml (equivalent to 200 MPN/100 ml E. coli). At ozone doses for disinfection, CECs with high reactivity with ozone were removed at levels greater than the target CEC removal of 80% for all WWTP effluents. For the secondary effluents, ozone doses above 2.6 ± 0.6 gO3/gDOC were required to satisfy the target removal for the recalcitrant CECs. Within the disinfection ozone dose range, estrogenic activity was reduced by more than 98% and androgenic activity was removed by more than 68%, while the anti-estrogenic activity remained unchanged. Lastly, based on the luminescence inhibition of V. fischeri, ozone doses for disinfection produced secondary effluents exhibiting less than 20% inhibition, thus falling under the hazard classification “no acute/chronic toxicity”.

Salt-contaminated soil generated by industrial activities has become a problem of concern over the last decades. While existing treatment technologies for these soils are efficient, the wastewater produced remains the major drawback. In this study, a novel application of forward osmosis (FO) was tested. The FO process operated in osmotic dilution mode was investigated in order to concentrate saline soil treatment wastewater and produce valuable process water. FO was chosen for this application since it is a low-energy technology and process adapted for complex liquid streams. Results from this study indicate that FO operated in osmotic dilution mode with a 1 M CaCl 2 draw solution is able to recover 50% of the initial wastewater volume with an initial total dissolved solids concentration of 16.3 g/L. Following treatment, the draw solution can be reused as a cationic exchange solution with CaCl 2 concentrations between 0.41 M and 0.44 M. No important solute transport from the feed to the draw solution was observed, except for some potassium drawn by the draw solution. This study demonstrated the potential of integrating the FO technology in the soil treatment industry in order to enhance water reuse in water-intensive processes.

Removal of the fluoroquinolone antibiotic levofloxacin (LEVO) was studied in two oxidation processes: photocatalysis (UVC lamp (254 nm), TiO 2 ) and ozonation. LEVO ( C o = 20 mg/L) was no longer detected after an ozone dose of 20.5 mg/L and after 180 min of photocatalytic oxidation. COD removals of 59% and 70% were measured for 270 mg/L of transferred ozone dose and 300 min of photocatalytic oxidation, respectively. Extensive treatment with ozone did not result in further reduction in COD levels reaching a plateau at the above mentioned value, however increased irradiation time led to increased COD removal during photocatalytic treatment. Both treatment methods proved to be effective ways of removing antibacterial activity. From agar diffusion test with Escherichia coli , it was observed that a transferred ozone dose of at least 20.5 mg/L and 180 min of irradiation were enough to completely remove antibacterial activity. Both treatments methods were shown to efficiently remove LEVO and its antibacterial activity and show promising results as possible applications for removal of antibiotics in wastewater.

Photolytic and photocatalytic removals of 17α-ethinylestradiol (EE2) and levonorgestrel (LNG) in pharmaceutical wastewater were investigated under UVC radiation. Wastewater collected from WYETH, St-Laurent, Canada contained high concentrations of EE2 and LNG in suspension and coloring agent tartrazine in solution. Aqueous phase removals of EE2 and LNG were studied as individual contaminants in water and in complex matrices including: co-contaminants in water, in simulated synthetic wastewater and in the wastewater. After 30 min of UVC photocatalysis of the individual contaminants, removal efficiencies of EE2 and LNG were 92% and 97%, respectively, while higher photolytic removal was observed for LNG (94%) compared to EE2 (60%). Hydroxyl radicals were shown to contribute significantly to the removal of both compounds in water. In contrast to EE2, photolytic removal of LNG was higher than its photocatalytic removal efficiencies in all complex matrices. Higher photolytic removal of LNG was attributed to the fact that it absorbs UVC radiation considerably more than EE2. Lower photocatalytic removals of LNG in complex matrices compared to its photocatalytic removal as an individual contaminant was due to the presence of EE2 at concentrations up to five times larger than LNG in water, thus leading to increased competition for hydroxyl radicals and retarding LNG removal. In the wastewater matrix photocatalytic removals for EE2 and LNG were similar at 48%, whereas the photolytic removal of LNG (76%) was higher than EE2 (29%). The applicability of UVC processes for reduction of hormone content in similar wastewaters was demonstrated.