Combining TiO2-photocatalysis and wetland reactors for the efficient treatment of pesticides

Advanced catalytic oxidation coupled to biological systems to treat pesticide-contaminated water: A review on technological trends and future challenges

This article had the one and only objective of consolidating the couplings of advanced oxidation processes and biological systems in the decontamination of wastewater with pesticide content reported in the Scopus and Web of Science databases, through a critical analysis of which have been the most used, what methodologies have been implemented to develop them, identifying the objectives of each work, determining the success of the research and where the main niches of knowledge are, which can lead to the generation of new scientific knowledge as well as future trends. A co-occurrence analysis was carried out through the VOSViewer software to determine the most associated key words with the treatment configurations described above. Fenton and Photo-Fenton processes, heterogeneous photocatalysis TiO₂/UV, electrocatalysis, ozonization and a particular case of hydrodynamic cavitation-ozone as main advanced oxidation processes, together with advanced biological processes such as sequential batch bioreactor (SBR), membrane bioreactor (MBR), mobile bed biofilm reactor (MBBR); biodegradability and toxicity tests with bacterial strains and surface wetlands, whose treatment philosophy is activated sludge. The main future trends are the reuse of treated wastewater, the analysis and control of costs towards the efficient use of resources and the primary study of the byproducts generated in advanced oxidation to improve the efficiencies in the coupling.

Evaluation of the Removal of Organic Matter and Nutrients in the Co-Treatment of Fruit and Vegetable Waste Using a Bioreactor-Constructed Wetlands System

This article presents the application of a novel system for the treatment of fruit and vegetable waste (FVW) using the combination of treatment by the application of the liquid fraction to an anaerobic hydrolytic bioreactor and a constructed wetland. The batch-fed anaerobic bioreactor (AB) had an average organic loading rate of 44 g COD/L-d and a hydraulic residence time (HRT) of 24 h for the degradation of the liquid fraction of the FVW with an average COD removal of 55%. Subsequently, the constructed wetlands (CWs) were fed a subsurface vertical flow of the effluent from the AB by stepwise concentration increments from 1 to 12 g COD/L and a HRT = 72 h until the limit conditions of the operation were identified. For the tropical ornamental species of the CWs in red volcanic gravel (RVG) and RVG + polyethylene (PE) supports, the monoculture of Hippeastrum rutilum and Spathiphyllum wallisii presented removals of COD, Tot-P, and TKN of 90%, 80%, and 85%, respectively. The polycultures with both species exceeded 90% effectiveness. At the end of both processes, a concentration of ~0.5 g COD/L was achieved, confirming that the use of these technologies together constitutes an efficient system for the treatment of the liquid fraction of FVW.

New insights for enhancing the performance of constructed wetlands at low temperatures

Constructed wetlands (CWs) have been widely utilized for various types of wastewater treatment due to their merits, including high cost-effectiveness and easy operation. However, a few intrinsic drawbacks have always restricted their application and long-term stability, especially their weak performance at temperatures under 10 °C (low temperatures) due to the deterioration of microbial assimilation and plant uptake processes. The existing modifications to improve CWs performance from the direct optimization of internal components to the indirect adjunction of external resources promoted the wastewater treatment efficiency to a certain degree, but the sustainability and sufficiency of pollutants removal remains a challenge. With the goal of optimizing CW components, the integrity of the CW ecosystem and the removal of emerging pollutants, future directions for research should include radiation plant breeding, improvements to CW ecosystems, and the combination or integration of certain treatment processes with CWs to enhance wastewater treatment effects at low temperatures.

Petroleomic analysis of the treatment of naphthenic organics in oil sands process-affected water with buoyant photocatalysts

The persistence of toxicity associated with the soluble naphthenic organic compounds (NOCs) of oil sands process-affected water (OSPW) implies that a treatment solution may be necessary to enable safe return of this water to the environment. Due to recent advances in high-resolution mass spectrometry (HRMS), the majority of the toxicity of OSPW is currently understood to derive from a subset of toxic classes, comprising only a minority of the total NOCs. Herein, oxidative treatment of OSPW with buoyant photocatalysts was evaluated under a petroleomics paradigm: chemical changes across acid-, base- and neutral-extractable organic fractions were tracked throughout the treatment with both positive and negative ion mode electrospray ionization (ESI) Orbitrap MS. Elimination of detected OS⁺ and NO⁺ classes of concern in the earliest stages of the treatment, along with preferential degradation of high carbon-numbered O₂^- acids, suggest that photocatalysis may detoxify OSPW with higher efficiency than previously thought. Application of petroleomic level analysis offers unprecedented insights into the treatment of petroleum impacted water, allowing reaction trends to be followed across multiple fractions and thousands of compounds simultaneously.

A review on the application of constructed wetlands for the removal of priority substances and contaminants of emerging concern listed in recently launched EU legislation

The presence of organic pollutants in the aquatic environment, usually found at trace concentrations (i.e., between ng L^-1 and μg L^-1 or even lower, known as micropollutants), has been highlighted in recent decades as a worldwide environmental concern due to their difficult elimination by conventional water and wastewater treatment processes. The relevant information on constructed wetlands (CWs) and their application for the removal of a specific group of pollutants, 41 organic priority substances/classes of substances (PSs) and 8 certain other substances with environmental quality standards (EQS) listed in Directive 2013/39/EU as well as 17 contaminants of emerging concern (CECs) of the Watch List of Decision 2015/495/EU, is herein reviewed. Studies were found for 24 PSs and 2 other substances with EQS: octylphenol, nonylphenol, perfluorooctane sulfonic acid, di(2-ethylhexyl)phthalate, trichloromethane, dichloromethane, 1,2-dichloroethane, pentachlorobenzene, benzene, polychlorinated dibenzo-p-dioxins, naphthalene, fluoranthene, trifluralin, alachlor, isoproturon, diuron, tributyltin compounds, simazine, atrazine, chlorpyrifos (chlorpyrifos-ethyl), chlorfenvinphos, hexachlorobenzene, pentachlorophenol, endosulfan, dichlorodiphenyltrichloroethane (or DDT) and dieldrin. A few reports were also published for 8 CECs: imidacloprid, erythromycin, clarithromycin, azithromycin, diclofenac, estrone, 17-beta-estradiol and 17-alpha-ethinylestradiol. No references were found for the other 17 PSs, 6 certain other substances with EQS and 9 CECs listed in EU legislation.

Evaluation of an alternative method for wastewater treatment containing pesticides using solar photocatalytic oxidation and constructed wetlands

The present study proposes an integrated system based on the synergetic action of solar photocatalytic oxidation with surface flow constructed wetlands for the purification of wastewater contaminated with pesticides. Experiments were conducted at pilot scale using simulated wastewater containing the herbicide clopyralid. Three photocatalytic methods under solar light were investigated: the photo-Fenton and the ferrioxalate reagent as well as the combination of photo-Fenton with TiO₂ P25, which all led to similar mineralization rates. The subsequent treatment in constructed wetlands resulted in further decrease of DOC and inorganic ions concentrations, especially of NO₃^-. Clopyralid was absent in the outlet of the wetlands, while the concentration of the detected intermediates was remarkably low. These findings are in good agreement with the results of phytotoxicity of the wastewater, after treatment with the ferrioxalate/wetlands process, which was significantly reduced. Thus, this integrated system based on solar photocatalysis and constructed wetlands has the potential to effectively detoxify wastewater containing pesticides, producing a purified effluent which could be exploited for reuse applications.

Photophysical property and photocatalytic activity of new Gd(2)InSbO(7) and Gd(2)FeSbO(7) compounds under visible light irradiation

Gd₂InSbO₇ and Gd₂FeSbO₇ were synthesized first, and their structural and photocatalytic properties were studied. The lattice parameters and the band gaps for Gd₂InSbO₇ and Gd₂FeSbO₇ were 10.449546 Å, 10.276026 Å, 2.897 eV and 2.151 eV. The photocatalytic degradation of rhodamine B was performed with Gd₂InSbO₇ and Gd₂FeSbO₇ under visible light irradiation. Gd₂InSbO₇ and Gd₂FeSbO₇ had higher catalytic activity compared with Bi₂InTaO₇. Gd₂FeSbO₇ exhibited higher catalytic activity than Gd₂InSbO₇. The photocatalytic degradation of rhodamine B followed with the first-order reaction kinetics, and the first-order rate constant k was 0.01606, 0.02220 or 0.00329 min⁻¹ with Gd₂InSbO₇, Gd₂FeSbO₇ or Bi₂InTaO₇ as photocatalyst. Complete removal of rhodamine B was observed after visible light irradiation for 225 min or 260 min with Gd₂FeSbO₇ or Gd₂InSbO₇ as photocatalyst. The evolution of CO₂ was realized, and it indicated continuous mineralization of rhodamine B during the photocatalytic process. The possible photocatalytic degradation pathway of rhodamine B was proposed.

Degradation and detoxification of 4-nitrophenol by advanced oxidation technologies and bench-scale constructed wetlands

The degradation and detoxification towards the duckweed Lemna minor of 4-nitrophenol (4NP) was studied by means of bench-scale constructed wetlands (CWs), TiO(2)-photocatalysis and Fenton + photoFenton reactions. The main goal of this work was to compare the three treatment techniques to evaluate their possible combination for the efficient, low cost treatment of 4NP effluents. In CWs, adsorption on the substrate of 4NP was found to achieve 34-45%. Low concentrations (up to 100 ppm) of 4NP were successfully treated by CWs in 8-12 h. The microbial degradation of 4NP started after a lag phase which was longer with higher initial concentrations of the pollutant. The greatest degradation rate was found to occur at initial concentrations of 4NP between 60 and 90 ppm. Solar TiO(2)-photocatalysis was faster than the CWs. The greatest removals in terms of mass of 4NP removed after 6 h of irradiation were found to occur at 4NP concentrations of about 200 ppm. Fenton reaction provided complete 4NP degradation up to 500 ppm in only 30 min but TOC was removed by only about 40%. The resulting toxicities were below 20% for initial 4NP concentrations below 300 ppm. It was the Fenton + photoFenton combination (180 min in total) that provided TOC reductions up to 80% and negative L. minor growth inhibition for almost all the 4NP concentrations tested. The combination of solar TiO(2)-photocatalysis (6 h) with CWs (16 h) was able to completely treat and detoxify 4NP effluents with concentrations as high as 200 ppm of the organic.

Characterization of intermediate products of solar photocatalytic degradation of ranitidine at pilot-scale

In the present study the mechanisms of solar photodegradation of H(2)-receptor antagonist ranitidine (RNTD) were studied in a well-defined system of a pilot plant scale Compound Parabolic Collector (CPC) reactor. Two types of heterogeneous photocatalytic experiments were performed: catalysed by titanium-dioxide (TiO(2)) semiconductor and by Fenton reagent (Fe(2+)/H(2)O(2)), each one with distilled water and synthetic wastewater effluent matrix. Complete disappearance of the parent compounds and discreet mineralization were attained in all experiments. Furthermore, kinetic parameters, main intermediate products, release of heteroatoms and formation of carboxylic acids are discussed. The main intermediate products of photocatalytic degradation of RNTD have been structurally elucidated by tandem mass spectrometry (MS(2)) experiments performed at quadrupole-time of flight (QqToF) mass analyzer coupled to ultra-performance liquid chromatograph (UPLC). RNTD displayed high reactivity towards OH radicals, although a product of conduction band electrons reduction was also present in the experiment with TiO(2). In the absence of standards, quantification of intermediates was not possible and only qualitative profiles of their evolution could be determined. The proposed TiO(2) and photo-Fenton degradation routes of RNTD are reported for the first time.

Occurrence and removal of fungicides in municipal sewage treatment plant

This work reports the occurrence and the removal of widely used fungicides, in municipal sewage treatment plant receiving combined sewage discharges and operating with primary (mechanical), secondary (activated sludge) and tertiary (sand filtration and chlorination) treatments that are commonly applied in Greece. Target analytes included compounds belonging to triazoles and anilino-pyrimidines. Analytical determination in wastewaters and river water samples was carried out by means of solid-phase extraction followed by gas chromatography equipped with flame thermionic and mass spectrometric detection. The fungicides tebuconazole and cyproconazole were more frequently detected in influent and effluent samples at concentrations up to 1893 and 1735 ng L(-1), respectively. Effluent concentrations were below 691.1 ng L(-1) recorded for tebuconazole. With the exception of triadimefon, all the azole fungicides and pyrimethanil showed relatively low removal efficiencies after secondary and tertiary treatments. Mean removal rates of the fungicides after secondary treatment ranged between 31% for pyrimethanil and 65% for triadimefon. Mean overall removal efficiencies after tertiary treatment ranged between 46% for pyrimethanil and 93% for triadimefon. The findings demonstrate that significant levels of fungicides enter river waterways and that only some of these compounds are being reduced in low levels by municipal wastewater treatment processes.