Advancing wastewater treatment with UV/peracetic acid-biofiltration synergy
by
S Ajaz, M J Radke, A A Hassan, P Kaparaju, R N Michael, F D L Leusch
Graphical abstract
Project summary
The presence of organic micropollutants (OMPs) in wastewater is a growing environmental concern due to their persistence and potential health risks to aquatic life and humans. Conventional wastewater treatment plants are often ineffective at removing these contaminants, necessitating advanced treatment solutions. This study evaluates a novel approach that combines UV/peracetic acid (UV/PAA) advanced oxidation process (AOP) with biological activated carbon (BAC) filtration to degrade OMPs and reduce toxicity in secondary treated wastewater.
The study was conducted in two phases: Phase 1 using UV/H₂O₂ pretreatment and Phase 2 using UV/PAA pretreatment. Both treatments were followed by BAC filtration operating at a 10-minute empty bed contact time. Targeted chemical analysis and a suite of bioassays were used to evaluate the performance of each process in degrading OMPs and mitigating toxicity.
Key findings
1. Degradation of OMPs:
- UV/PAA pretreatment outperformed UV/H₂O₂ in degrading OMPs such as carbamazepine (65%), diuron (52%), trimethoprim (44.5%), and venlafaxine (42.5%).
- UV/PAA pretreatment significantly enhanced the degradation of carbamazepine, attributed to the formation of selective acetyl(per)oxyl radicals, which effectively target electron-rich moieties in OMPs.
- The selective reactivity of UV/PAA proved advantageous in mitigating OMPs in diverse water matrices with radical scavengers like natural organic matter and inorganic ions.
the degradation of carbamazepine, attributed to the formation of selective acetyl(per)oxyl radicals, which effectively target electron-rich moieties in OMPs.
- The selective reactivity of UV/PAA proved advantageous in mitigating OMPs in diverse water matrices with radical scavengers like natural organic matter and inorganic ions.
2. Toxicity reduction:
- Biofiltration following UV/PAA pretreatment reduced algal toxicity by 63% and estrogenic load by over 60%, lowering estrogenicity risks from high to moderate levels based on risk quotient (RQ) assessments.
- While both pretreatments mitigated bacterial toxicity caused by toxic by-products of advanced oxidation processes, UV/ H₂O₂ pretreatment achieved a greater reduction (25%) compared to UV/PAA (3%).
3. Microbial community dynamics:
- Microbial analysis revealed that BAC filters supported the growth of OMP- degrading bacteria such as Pseudomonas, Mycobacterium, and Rhodococcus.
-UV/PAA pretreatment facilitated the growth of species like Acinetobacter and Anaerolinea, which are effective at degrading estrogens and other OMPs.
Conclusion
The UV/PAA-biofiltration approach offers a promising solution for advanced wastewater treatment. UV/PAA outperformed UV/H₂O₂ in degrading a wide range of OMPs, achieving significant removal efficiencies for key contaminants like carbamazepine and diuron. UV/PAA-biofiltration effectively reduced toxicity, with significant reductions in photosynthesis inhibition and algal toxicity. Interestingly, control biofilters outperformed AOP-pretreated biofilters in reducing bacterial toxicity. Microbial analysis highlighted that UV/PAA pretreatment promoted the growth of specialised OMP-degrading microbial communities.
This combined UV/PAA-biofiltration method addresses key challenges in tertiary wastewater treatment, offering an efficient and sustainable solution for mitigating OMPs and reducing toxicity in treated effluents.
Figure 1: Schematic of bench-scale UV advanced oxidation pretreatment with biofiltration setup
Authors
Sana Ajaza, Mikaela J. Radkea, Ashraf Aly Hassanb, Prasad Kaparajuc, Ruby N. Michaelc, Frederic D.L. Leuscha
a Australian Rivers Institute, School of Environment and Science, Griffith University, Parklands Dr, Southport, Queensland 4222, Australia
b Department of Civil and Environmental Engineering, College of Engineering, United Arab Emirates University, Al Ain, PO Box 15551, United Arab Emirates
c School of Engineering and Built Environment, Nathan Campus, Griffith University, Brisbane, QLD 4111, Australia
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