Evaluation of a recirculating hydroponic bed bioreactor for removal of contaminants of emerging concern from tertiary-treated wastewater effluent

Photolytic transformation of trace organic compounds: Roles of direct photolysis and indirect photolysis by singlet oxygen

Both direct and indirect solar photolysis contribute to the in-situ attenuation of trace organic compounds (TOrCs) in surface waters, including those that are impacted by treated wastewater. In particular, the formation of singlet oxygen (1O2) from photosensitizers may play a role in the degradation of specific TOrCs. Quantification of the kinetics of photolytic processes is essential for anticipation of TOrC attenuation in sunlit waters. In this work, quantum yields for direct photolysis in sunlight and ultraviolet A light (290-400 nm), and second-order rate constants for TOrC reactions with 1O2 were determined for sixteen TOrCs that are ubiquitous in effluent-receiving surface waters. Six of the sixteen TOrCs (prednisone, dexamethasone, benzophenone, hydrocortisone, hydrochlorothiazide, and furosemide) were transformed via direct photolysis. Compounds that reacted readily with 1O2 included furosemide, propylparaben, and diltiazem. Second-order rate constants for reactions with 1O2 were determined using a kinetic model applied to a batch reactor and confirmed by measurement of kinetic solvent isotope effects (KSIE) in deuterated water (D2O). A reactor model that combined direct and indirect photolysis was used to predict TOrC in chemically complex solutions containing natural organic matter (NOM) or effluent organic matter (EfOM), using the measured direct photolysis quantum yield and reaction rate constant with 1O2.

Preparation and evaluation of a coated smectite clay-based material modified with epichlorohydrin-dimethylamine for the diclofenac removal

This study reports the analysis of diclofenac removal from aqueous solution using a novel adsorbent coating with amphoteric surface. This adsorbent coating was improved using a new amphoteric ratio to increase its performance for the removal of pharmaceuticals such as diclofenac. The adsorbent coating was formulated using acrylic polymer emulsion, smectite-based clay powder and epichlorohydrin-dimethylamine to obtain a layer form via the implementation of a facile synthesis method. In a previous study, this adsorbent coating was successful to remove cationic and anionic dyes. Therefore, this research aimed to further investigate and test its application in the removal of other emerging water pollutants like pharmaceuticals. SEM, EDX, and FTIR analyses were carried out for the characterization of this novel adsorbent. The effects of adsorbent composition, diclofenac concentration, temperature, and solution pH were studied and modeled. The best conditions to improve the diclofenac adsorption was 303 K and pH 3 where the adsorption capacity was 25.59 mg/g. Adsorption isotherms and kinetics were quantified and modeled, and the corresponding adsorption mechanism was also analyzed. Diclofenac adsorption with this novel material was exothermic and spontaneous. This alternative adsorbent is promising for diclofenac removal from industrial wastewater systems.

New roles for Bacillus thuringiensis in the removal of environmental pollutants

For a long time, the well-known Gram-positive bacterium Bacillus thuringiensis (Bt) has been extensively studied and developed as a biological insecticide for Lepidoptera and Coleoptera pests due to its ability to secrete a large number of specific insecticidal proteins. In recent years, studies have found that Bt strains can also potentially biodegrade residual pollutants in the environment. Many researchers have isolated Bt strains from multiple sites polluted by exogenous compounds and characterized and identified their xenobiotic-degrading potential. Furthermore, its pathway for degradation was also investigated at molecular level, and a number of major genes/enzymes responsible for degradation have been explored. At present, a variety of xenobiotics involved in degradation in Bt have been reported, including inorganic pollutants (used in the field of heavy metal biosorption and recovery and precious metal recovery and regeneration), pesticides (chlorpyrifos, cypermethrin, 2,2-dichloropropionic acid, etc.), organic tin, petroleum and polycyclic aromatic hydrocarbons, reactive dyes (congo red, methyl orange, methyl blue, etc.), and ibuprofen, among others. In this paper, the biodegrading ability of Bt is reviewed according to the categories of related pollutants, so as to emphasize that Bt is a powerful agent for removing environmental pollutants.

Environmental persistence, detection, and mitigation of endocrine disrupting contaminants in wastewater treatment plants – a review with a focus on tertiary treatment technologies

Endocrine disrupting chemicals are a group of contaminants that have severe effects on humans and animals when exposed, like cancer and alterations to the nervous and reproductive systems.

Investigation of EG-Bi2S3 nanorods photocatalytic activity under visible light for dye degradation from aquatic system

Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃ were synthesized by employing solvothermal route. X-ray diffraction, UV-vis absorption, photoluminescence, Raman, scanning electron microscopic studies confirmed the structural, optical, morphological behaviors. The XRD pattern of Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃ was correlated well with JCPDS # 65-2435. The crystallite size was found to be 57, 49, and 40 nm. The photoluminescence spectra showed semiconducting property of prepared Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃. The absorption spectra of Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃ nanorods were well matched with the spectra of a previous report. The bandgap values of Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃ were calculated to be 1.56, 1.45, and 1.3 eV in reducing order. The morphology of Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃ samples showed the development of nanorods. The 10 ml EG-Bi₂S₃ sample showed better development of nanorods with the addition of ethylene glycol. The agglomeration was considerably reduced with the mixing of solvent. Bi₂S₃, 5 ml EG-Bi₂S₃, and 10 ml EG-Bi₂S₃ catalysts were added to the methylene blue dye solution and its photocatalytic properties were investigated by reducing toxic pollutants under light. The 10 ml EG-Bi₂S₃ sample with neutral pH and 0.1 g of catalyst was added and investigated which showed 86% of efficiency towards dye degradation. The narrow bandgap, defined morphology of 10 ml EG-Bi₂S₃, made a positive result towards efficient photocatalytic activity.

Nanomaterial Synthesis in Ionic Liquids and Their Use on the Photocatalytic Degradation of Emerging Pollutants

The unique properties of ionic liquids make them suitable candidates to prepare nanoscale materials. A simple method that uses exclusively a corresponding bulk material and an ionic liquid—in this case, [P_6,6,6,14]Cl—was used to prepare AgCl nanoparticles and AgCl@Fe₃O₄ or TiO₂@Fe₃O₄ magnetic nanocomposites. The prepared nanomaterials were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy. The photodegradation of atenolol as a model pharmaceutical pollutant in wastewater was investigated under ultraviolet–visible light irradiation using the different synthesized nanocatalysts. In the presence of 0.75 g·L⁻¹ AgCl nanoparticles, a practically complete degradation of 10 ppm of atenolol was obtained after 30 min, following pseudo-first-order reaction kinetics. The effect of different variables (concentrations, pH, oxidant agents, etc.) was analyzed. The recyclability of the nanocatalyst was tested and found to be successful. A degradation mechanism was also proposed. In order to improve the recovery stage of the nanocatalyst, the use of magnetic nanocomposites is proposed. Under the same experimental conditions, a slightly lower and slower degradation was achieved with an easier separation. The main conclusions of the paper are the suitability of the use of ionic liquids to prepare different nanocatalysts and the effectiveness of these at degrading an emerging pollutant in wastewater treatment.