Prospects of industrial membrane concentrates: treatment of landfill leachates by coupling reverse osmosis and wet air oxidation.

Stabilized landfill leachates are characterized by a high chemical oxygen demand and limited biodegradability. This study investigates the removal of the organic fraction (chemical oxygen demand and total organic carbon) using a treatment approach that couples membrane processes and wet air oxidation (operating at 200-300 °C and 18 MPa). The aim is to address the challenges posed by landfill leachate membrane concentrates considering variations throughout the year across three different seasons. The efficiency of the treatment path was assessed through the removal of the chemical oxygen demand and total organic carbon, with additional insights provided by fluorescence spectroscopy to evaluate the degradation of the organic compounds' complexity. The most favorable results were achieved at the highest temperature (300 °C) with removals over 90% for total organic carbon and 87% for chemical oxygen demand, along with a complete elimination of fluorescence. The coupling of membrane processes and wet air oxidation has demonstrated its effectiveness in degrading the organic compounds of landfill leachates. The overall mass balance on the treatment path indicates the feasibility of discharging the treated effluent into the environment, meeting regulatory thresholds for total organic carbon and chemical oxygen concentrations.

Treatment technologies and degradation pathways of glyphosate: A critical review.

Glyphosate is one of the most widely used post-emergence broad-spectrum herbicides in the world. This molecule has been frequently detected in aqueous environment and can cause adverse effects to plants, animals, microorganisms, and humans. This review offers a comparative assessment of current treatment methods (physical, biological, and advanced oxidation process) for glyphosate wastewaters, considering their advantages and drawbacks. As for other molecules, adsorption does not destroy glyphosate. It can be used before other processes, if glyphosate concentrations are very high, or after, to decrease the final concentration of glyphosate and its by-products. Most of biological and oxidation processes can destroy glyphosate molecules, leading to by-products (the main ones being AMAP and sarcosine) that can be or not affected by these processes. This point is of major importance to control process efficiency. That is the reason why a specific focus on glyphosate degradation pathways by biological treatment or different advanced oxidation processes is proposed. However, one process is usually not efficient enough to reach the required standards. Therefore, the combination of processes (for instance biological and oxidation ones) seems to be high-performance technologies for the treatment of glyphosate-containing wastewater, due to their potential to overcome some drawbacks of each individual process. Finally, this review provides indications for future work for different treatment processes to increase their performances and gives some insights into the treatment of glyphosate or other organic contaminants in wastewater.

Kinetic study of glyphosate degradation in wet air oxidation conditions.

Glyphosate is one of the most widely used herbicides in the world against perennial and annual weeds. It has been reported to be a micro pollutant, and its degradation in different wastewater treatment processes must be studied. For that purpose, the kinetics of wet air oxidation of glyphosate was studied in an autoclave reactor at a temperature range of 423-523 K and under a total pressure of 15 MPa. Oxidation reactions obeyed the first-order kinetics with respect to glyphosate concentration. The activation energy for glyphosate oxidation was found to be equal to 68.4 kJ mol-1. Furthermore, the possible reaction intermediates and main end products of glyphosate degradation in the wet air oxidation process were identified and quantified using UV-spectrophotometry and liquid chromatography coupled to high resolution mass spectrometry. A degradation pathway for glyphosate oxidation was proposed.

Experimental coupling and modelling of wet air oxidation and packed-bed biofilm reactor as an enhanced phenol removal technology.

Experimental coupling of wet air oxidation process and aerobic packed-bed biofilm reactor is presented. It has been tested on phenol as a model refractory compound. At 30 MPa and 250 °C, wet air oxidation batch experiments led to a phenol degradation of 97% and a total organic carbon removal of 84%. This total organic carbon was mainly due to acetic acid. To study the interest of coupling processes, wet air oxidation effluent was treated in a biological treatment process. This step was made up of two packed-bed biofilm reactors in series: the first one acclimated to phenol and the second one to acetic acid. After biological treatment, phenol and total organic carbon removal was 99 and 97% respectively. Thanks to parameters from literature, previous studies (kinetic and thermodynamic) and experimental data from this work (hydrodynamic parameters and biomass characteristics), both treatment steps were modelled. This modelling allows the simulation of the coupling process. Experimental results were finally well reproduced by the continuous coupled process model: relative error on phenol removal efficiency was 1 and 5.5% for wet air oxidation process and packed-bed biofilm reactor respectively.

Thermodynamic and kinetic study of phenol degradation by a non-catalytic wet air oxidation process.

This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350°C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H(2)O and CO(2). The Arrhenius law data obtained for the phenol disappearance are the following: k=1.8×10(6)±3.9×10(5)M(-1)s(-1) (pre-exponential factor) and E(a)=77±8 kJ mol(-1) (activation energy).