Bisphenols in water: Occurrence, effects, and mitigation strategies.

Bisphenols (bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF) and bisphenol AF (BPAF)) are widely used as additives in numerous industries and therefore they are ubiquitously present throughout the world's natural environment including water. A review of the literature is presented on their sources, pathways of entry into the environment, and especially aquatic contexts, their toxicity to humans and other organisms and the technologies for removing them from water. The treatment technologies used are mostly adsorption, biodegradation, advanced oxidation, coagulation, and membrane separation processes. In the adsorption process, several adsorbents, especially carbon-based materials, have been tested. The biodegradation process has been deployed and it involves a variety of micro-organisms. Advanced oxidation processes (AOPs) such as UV/O3-based, catalysis relevant AOPs, electrochemical AOPs and physical AOPs have been employed. Both the biodegradation process and AOPs generate by-products which may be toxic. These by-products need to be subsequently removed using other treatment processes. Effectiveness of the membrane process varies depending on the porosity, charge, hydrophobicity, and other properties of the membrane. The problems and limitations of each treatment technique are discussed and methods to overcome them are presented. Suggestions are articulated to use a combination of processes to improve the removal efficiencies.

Treatment Trends and Combined Methods in Removing Pharmaceuticals and Personal Care Products from Wastewater-A Review.

When discharged into wastewater, pharmaceuticals and personal care products (PPCPs) become microorganic contaminants and are among the largest groups of emerging pollutants. Human, animal, and aquatic organisms' exposures to PPCPs have linked them to an array of carcinogenic, mutagenic, and reproductive toxicity risks. For this reason, various methods are being implemented to remove them from water bodies. This report critically reviews these methods and suggests improvements to removal strategies. Biological, physical, and chemical methods such as biological degradation, adsorption, membrane filtration, and advanced electrical and chemical oxidation are the common methods used. However, these processes were not integrated into most studies to take advantage of the different mechanisms specific to each process and are synergistic in the removal of the PPCPs that differ in their physical and chemical characteristics (charge, molecular weight, hydrophobicity, hydrogen bonding, structure). In the review articles published to date, very little information is available on the use of such integrated methods for removing PPCPs. This report attempts to fill this gap with our knowledge.

Potential of agro-industrial produced laccase to remove ciprofloxacin.

Ciprofloxacin (CIP), a widely used antibiotic, is frequently detected in the environment due to insufficient wastewater and water treatment. Hence, novel, green and cost-effective technologies are required to enhance the removal of these pollutants. The potency of crude enzymes, especially laccases, produced by white-rot fungi was tested to assess their effectiveness to degrade CIP from water. Crude laccase alone could not oxidize CIP. The addition of syringaldehyde, a redox mediator, resulted in a decrease in antibiotic concentration up to 68.09±0.12% in 24 h, which was the highest removal efficiency achieved with 0.15 mg/mL syringaldehyde and 2 mg/mL of crude laccase (0.1 U/ml). Crude laccase oxidation of CIP was inhibited after 6 h of treatment. To compare, a pure enzyme with the same activity as the crude one removed 86% of CIP in 24 h. No inhibitory effect during the treatment was observed. The estimation of antimicrobial efficiency revealed that after 6 h of treatment, the toxicity towards Escherichia coli decreased by 30%. The wastewater treatment by the crude laccase-mediated system was estimated to significantly reduce the cost of enzymatic treatment.

Biodegradation of aflatoxin B1 with cell-free extracts of Trametes versicolor and Bacillus subtilis.

Aflatoxin B1 (AFB1) is one of the most common contaminants of poultry feed and has been linked to adverse effects on animal health and productivity. In this study, the degradation of AFB1 was studied with cell-free extracts (CFE) of Trametes versicolor and Bacillus subtilis using High-Performance Liquid chromatography (HPLC). CFE from B. subtilis and T. versicolor gave 60% and 34% of AFB1 degradation respectively, while heat-inactivated extracts showed no degradation. By-products obtained at the end of AFB1 degradation were analyzed by Liquid Chromatography with tandem mass spectrometry (LC-MS/MS). After 96 h of incubation, by-products with lower m/z values were obtained with CFE from B. subtilis as compared to that from T. versicolor, indicating a higher degradation efficiency of the former. Additionally, the detection of a by-product which could correspond to AFB1-8,9 dihydrodiol - a less toxic derivative of AFB1 - after 72 and 96 h of incubation with CFE from B. subtilis, could indicate the simultaneous detoxification along with degradation of AFB1 by B. subtilis CFE.

Ciprofloxacin removal via sequential electro-oxidation and enzymatic oxidation.

The combination of electro-oxidation and enzymatic oxidation was tested to evaluate the potency of this system to remove ciprofloxacin (CIP), a fluoroquinolone antibiotic, from water. For the electro-oxidation boron-doped diamond (BDD) and mixed metal oxides anodes were tested, at three current densities (4.42, 17.7 and 35.4 A/cm2). BDD anode at 35.4 A/cm2 exhibited the highest removal efficiency in the shortest time (>90 % removal in 6 min). For the enzymatic oxidation, laccase from Trametes versicolor was chosen. Laccase alone was not able to remove CIP; hence the influence of redox mediators was investigated. The addition of syringaldehyde (SA) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) resulted in enhanced CIP transformation. About 48.9±4.0 % of CIP remained after 4 h of treatment when SA-mediated laccase was applied and 87.8±6.6 % in the case of ABTS-mediated laccase. The coupling of enzymatic oxidation followed by electro-oxidation led to 73 % removal of the antibiotic. Additionally, the antimicrobial activity increased up to its original efficiency after the treatment. The combination of electro-oxidation followed by enzymatic oxidation led to 97-99 % removal of CIP. There was no antimicrobial activity of the solution after the treatment. The tests with wastewater confirmed the efficacy of the system to remove CIP from the complex matrix.

Appearance of ciprofloxacin/chlortetracycline-resistant bacteria in waters of Québec City in Canada.

Most of the waterborne fecal pathogens belong to the family of Gram-negative bacteria. Hence, minimal inhibitory concentrations of chlortetracycline and ciprofloxacin antibiotics towards Gram-negative representative, Enterobacter aerogenes were estimated, which were 7 µg/ml and 0.125 µg/ml, respectively. The combined antimicrobial effect of chlortetracycline and ciprofloxacin against E. aerogenes was also investigated to establish their potential interaction towards the pathogens present in water. Eventually, the water samples obtained from various drinking water treatment plants from Québec municipality were tested for the occurrence of chlortetracycline-, ciprofloxacin- and chlortetracycline/ciprofloxacin-resistant strains.

Ciprofloxacin-metal complexes -stability and toxicity tests in the presence of humic substances.

The co-contamination of ciprofloxacin (CIP) with metal ions results in alteration of CIP mobility, antimicrobial activity and distribution/development of the antibiotic-resistance genes. In this study, the stability of five CIP-Me complexes [Me = Al(III), Co(II), Cu(II), Fe(III), Mg] was investigated in the presence of humic substances (HS) at two temperatures 18 ±â€¯2 °C and 4 ±â€¯1 °C for seven days period. The most stable complexes were CIP-Al, CIP-Cu, and CIP-Co with the stability constants (K) at 18 °C 35.5 ±â€¯1.4 11.5 ±â€¯1.5 and 11.7 ±â€¯1.5 respectively. At lower temperature (4 °C), the stability constants decreased: 1-fold for CIP-Al, 14-fold for CIP-Co and 2-fold for CIP-Cu. The presence of humic substances decreased the stability of complexes. The chemical reactions of Fe3+ in water at circumneutral pH resulted in stability alteration. The formation of CIP-Mg complexes at lower temperatures and in the presence of HS was limited. In ultrapure water, CIP-Me complexes exhibit higher toxicity towards Gram-negative Enterobacter aeruginosa (ranged between 0.125 and 0.5 µg/ml). However, the presence of HS reduced the antimicrobial activity of CIP-Me complexes by at least 2-fold. Gram-positive representative, Bacillus subtilis was not affected by the presence of metal ions and/or HS. The toxicity toward B. subtilis for the complexes was equal to toxicity of CIP alone (MIC = 0.25 µg/ml). This suggested the different susceptibility to CIP and its complexes.