Modifying gas transfer membranes with nanoscale zero-valent iron: effects on membrane material properties, treatment performance, and biofilm thickness.

Excessive membrane biofilm growth on membrane fibers depends on various factors, with membrane properties playing a pivotal role in influencing microbial affinity for the membrane. To investigate the antibacterial impact of nano-sized zero-valent iron (nZVI) on membrane biofilm structure, pristine (polyvinylidene fluoride (PVDF)) only: HF-0 (PVDF:20/nZVI:0 w/w) and four gas transfer membranes (PVDF:nZVI at different concentrations: HF-1 (PVDF:20/nZVI:0.25 w/w), HF-2 (PVDF:20/nZVI:0.50 w/w), HF-3 (PVDF:20/nZVI:0.75 w/w), HF-4 (PVDF:20/nZVI:1.0 w/w)) were produced. These membranes were assessed for surface morphology, porosity, gas permeability, and biofilm thickness, which ultimately affect biochemical reaction rates in membrane biofilm reactors (MBfRs). Various MBfRs utilizing these gas transfer membranes were operated at different hydraulic retention times (HRTs) and oxygen pressures to assess chemical oxygen demand (COD) removal efficiency and nitrification performance. Incorporating nZVI into the PVDF polymer solution increased surface hydrophilicity and porosity but reduced Young's Modulus and oxygen diffusion coefficients. Confocal laser scanning microscopy (CLSM) analysis revealed an average biofilm thickness of 700 µm in HF-0, HF-1, and HF-3, with a 100 µm decrease in HF-2, even though Escherichia coli growth was observed in HF-3 fibers. Regardless of nZVI dosage, a significant decline in COD removal and nitrification rates occurred at low HRTs and gas pressures.

Oxytetracycline and paracetamol biodegradation performance in the same enriched feed medium with aerobic nitrification/anaerobic denitrification SBR.

Pharmaceuticals such as oxytetracycline and paracetamol are extensive chemicals in the aquatic systems. In this study, the removal performance of oxytetracycline and paracetamol was investigated in the same enriched feed water medium by sequencing batch aerobic/anaerobic reactor system. In this context, oxytetracycline and paracetamol in the aerobic phase were removed by a maximum of 66 and 99.8% respectively. At the same time, nitrification and denitrification removals were obtained as 95% and 98%, respectively. On the other hand, oxytetracycline and equivalent O2 flux of oxytetracycline maximum were calculated as 1.18 and 2.14 mg/L.d and the maximum removal volumetric flux of paracetamol and its O2 equivalent flux were determined approximately as 136 and 303 mg/L.d, simultaneously. In addition, oxytetracycline and paracetamol were given to the system in an amount of maximum 1 and 500 mg/L, respectively. Paracetamol has not significantly affected nitrification and denitrification up to 120 mg/L, but 500 mg/L paracetamol has completely finished denitrification in this system. On the other hand, the water environment of sequencing batc reactor has turned into a pitch dark state at 500 mg/L paracetamol feeding. As a result, aerobic bacteria preferred paracetamol rather than oxytetracycline. In other words, aerobic bacteria preferred paracetamol/oxytetracycline as the second electron acceptor after O2.

Comprehensive evaluation of autohydrogenotrophic membrane biofilm reactor treating OTC-enriched water medium.

In the recent years, there has been considerable debate about the potential impacts of antibiotics present in various environments on the public health and ecology. Oxytetracycline (OTC) is one of tetracycline antibiotic group used for growth and treatment of animals and humans. In this study, OTC and nitrate (NO3-N) were simultaneously reduced using a hydrogen-based membrane biofilm reactor (H2-MBfR). The system successfully accomplished OTC and nitrate removals. The fluxes of OTC and NO3-N were 8.96 mg OTC/m2 day and 1100 mg N/m2 day, respectively. On the other hand, the fluxes of H2 utilized for OTC and NO3-N reductions were calculated as maximum values of 1.71 and 395 mg H2/m2 day, respectively. The concentrations of transformation products of OTC formed at ppb levels. The dominant species in all the experimental periods with OTC biodegradation referred to Naxibacter sp., Uncultured Beta proteobacterium, Janthinobacterium sp. and Alicycliphilus denitrificans in autotrophic biofilm community degrading OTC.

Degradation of oxytetracycline under autotrophic nitrifying conditions in a membrane aerated biofilm reactor and community fingerprinting.

Pharmaceuticals in waterbodies are a growing concern due to their extensive uses and adverse effects on aquatic life. Oxytetracycline (OTC) is one of tetracycline antibiotic group used for treatment of animals and humans. This study evaluates the simultaneous oxidation of OTC and ammonium under autotrophic nitrifying conditions by using a membrane aerated biofilm reactor (MABR) as it provides an appropriate environment for the antibiotic-degrading bacteria. The results showed that MABR achieved fluxes of 1.62 mg OTC/m2.d and 1117 mg N/m2.d while the fluxes of O2 (JOTC-O2) utilized for OTC and NH4-N (JNH4-N-O2) oxidation were calculated to be 2.94 and 5105 mg O2/m2.d, respectively. Three transformation products, 4-Epi-OTC, α-Apo-OTC and ß-Apo-OTC, were identified and measured at ppb levels. The biofilm community comprised of Bacteria environmental samples, b-proteobacteria, CFB group bacteria, g-proteobacteria, d-proteobacteria and a-proteobacteria.