Analysis of the concentration polarization and fouling dynamic resistances under reverse osmosis membrane treatment of olive mill wastewater

Engineered nanomaterials for (waste)water treatment - A scientometric assessment and sustainability aspects

Application of nanomaterials for the treatment of effluents originated from various industrial and non-industrial sources, has been rapidly developed in recent decades. In this situation, there is a need for conclusive studies to identify the current status of the knowledge in this field and to promote the commercialization of such technologies by providing recommendations for future studies. In the present manuscript, a scientometric assessment on the progress made in this field has been performed and the results have been organized and discussed in terms of science statistics, research hotspots and trends, as well as the relevant sustainability aspects. Based on a set of keywords, identified through a pre-literature analysis, a total of 6539 documents were retrieved from the Web of Science (WoS) database and analyzed to achieve the main goals of this study. The results demonstrate that the studies in this field have been initiated since the beginning of the 2000s but were mainly performed in lab and pilot scales. Also, China and Iran were identified as the most contributing countries in this scientific area in terms of the number of publications. Among various types of engineered nanomaterials (ENMs), there has been especial attention for the application of iron-based nanomaterials as well as carbonaceous structures (such as graphene oxide and biochar). Besides, there are not still strong collaborations formed among researchers in this area worldwide. Regarding the research hotspots, the synthesis of green and sustainable nanomaterials (e.g., biosynthesis approaches) has received attention in recent years. The results can also demonstrate that the most widely studied pathway for the removal of pollutants from (waste)waters involves the adsorption of the pollutants using ENMs. Treatment of contaminants of emerging concern (CECs) as well as exploring the mechanisms involved in the treatment of contaminated (waste)waters using ENMs and the possible by-products are considered the current trends in the literature. Regarding the sustainability aspects of ENMs for (waste)water treatment, the results achieved in this study calls for in-depth sustainability studies, which consider parameters such as economic, environmental, and social aspects of nanomaterials utilization for (waste)water treatment purposes, besides the technical parameters, to push transferring such technologies from lab and pilot scales to large and real-scale applications.

An integrated electrocoagulation-nanofiltration process for carwash wastewater reuse

In the present work, advanced treatment of carwash wastewater with an integrated electrocoagulation-nanofiltration (EC-NF) process to reuse the treated wastewater as rinsing water was investigated. The wastewater was pretreated by EC process under various operating parameters such as temperature (25 °C, 35 °C, 45 °C), stirring speed (150 rpm, 250 rpm, 350 rpm), and electrode connection mode (MP-P, MP-S, BP-S) using Fe electrode. The best results were achieved at 25 °C, 250 rpm and MP-P connection mode for EC, considering both pollutant removals and energy consumptions. EC sludge was characterized scanning electron microscopy-energy dispersive index (ESEM-EDX) analysis. The pretreated carwash wastewater using EC process was further treated by NF process using NF 270 and Desal 5DL membranes. Desal 5 DL membrane provided the highest treatment performance for chloride (92%), conductivity (80%) and total hardness (90%) parameters for EC-NF process. Resistance in series model was used for a deeper discussion of the reasons for flux decline. In addition, Fourier transform infrared (FTIR) spectroscopy and contact angle measurements were conducted for membrane fouling characterization. The foulants mainly accumulated on the membrane surface forming a cake layer and lower extent of membrane fouling was occurred for both membranes. As a result, this study showed that the water quality for reuse in carwashing process could be achieved with an integrated EC-NF process.

Rapid decontamination of tetracycline hydrolysis product using electrochemical CNT filter: Mechanism, impacting factors and pathways

In this study, electrooxidation of the tetracycline hydrolysis products was investigated using a carbon nanotube (CNT) electrochemical filter and 4-epianhydrochlortetracycline (EACTC) as a model compound. Electrochemical filtration of 10 μmol L^-1 EACTC at a voltage of 2.5 V and a flow rate of 1.5 mL min^-1 (hydraulic residence time <3 s) provided an oxidation flux of 1251 ± 28 μmol h^-1 m^-2. Replacement of the Ti cathode with a CNT filter cathode increased the EACTC oxidative flux by 1.3 fold at a voltage of 2.5 V. The electrochemical filtration process is effective for the degradation of EACTC and the reduction of the antimicrobial activity based on liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) analysis and luminescent bacteria test. The high oxidation flux within 300 min (1212-1263 μmol h^-1 m^-2) and affordable cost (0.25 kWh m^-3) at a voltage of 2.5 V show the potential application of the electrochemical filtration system as a promising unit for EACTC degradation. These findings provided new insights into the rational design principles of novel continuous-flow filtration system aimed to efficiently remove hydrolysis products of the antibiotic tetracycline.

Modeling and optimizing electro-persulfate processes using Fe and Al electrodes for paper industry wastewater treatment

In this study, the treatment of paper industry wastewaters by the electrocoagulation (EC) process with a strong oxidant, persulfate addition, was investigated. Persulfate was activated by dissolution of Fe and Al from electrodes during the process. Central composite design method, being one of the response surface methods, was applied for the optimization of process parameters and the development of a mathematical model for chemical oxygen demand (COD) removal from paper industry wastewaters. The effects of S₂O₈ ^-2/COD ratio, current, pH, and reaction time, being the variables of process, were assessed on the efficiency of contaminant removal. For COD removal in EC processes in which Fe and Al electrodes were used, the model's correlation coefficients (R²) were determined as 90.14% and 87.46%, respectively. As the result of experimental study actualized under optimum conditions determined by the model in order to obtain maximum contaminant removal, COD removal efficiencies were determined as 63.5% and 72.8% respectively for the Fe electrode (S₂O₈ ^-2/COD ratio: 1.25, current: 4.14 A, pH: 6, and reaction time: 5 minutes), and the Al electrode (S₂O₈ ^-2/COD ratio: 0.5, current: 4.25 A, pH: 7.25, and reaction time: 25 minutes). Electro-activated persulfate process is an appropriate treatment alternative for COD removal from paper industry wastewaters.

Integration of Green Energy and Advanced Energy-Efficient Technologies for Municipal Wastewater Treatment Plants

Wastewater treatment can consume a large amount of energy to meet discharge standards. However, wastewater also contains resources which could be recovered for secondary uses under proper treatment. Hence, the goal of this paper is to review the available green energy and biomass energy that can be utilized in wastewater treatment plants. Comprehensive elucidation of energy-efficient technologies for wastewater treatment plants are revealed. For these energy-efficient technologies, this review provides an introduction and current application status of these technologies as well as key performance indicators for the integration of green energy and energy-efficient technologies. There are several assessment perspectives summarized in the evaluation of the integration of green energy and energy-efficient technologies in wastewater treatment plants. To overcome the challenges in wastewater treatment plants, the Internet of Things (IoT) and green chemistry technologies for the water and energy nexus are proposed. The findings of this review are highly beneficial for the development of green energy and energy-efficient wastewater treatment plants. Future research should investigate the integration of green infrastructure and ecologically advanced treatment technologies to explore the potential benefits and advantages.

Analysis of the Flux Performance of Different RO/NF Membranes in the Treatment of Agroindustrial Wastewater by Means of the Boundary Flux Theory

Dynamic membrane system behaviour must be adequately addressed to avoid process unfeasibility. The lack of proper analysis will mean relying on erroneous permeate flux values in the system design, which will lead to quick and/or steady high fouling rates. In this paper, the authors present additional data supporting the boundary flux theory as a helpful tool for membrane engineers to carefully avoid process failures. By fitting the dynamic permeate flux data to the boundary flux model, it was possible to calculate the β fouling index for the three selected membranes (one nanofiltration (NF) and two reverse osmosis (RO) ones). The dynamic flux given by the low-pressure RO membrane did not follow sub-boundary operating conditions, since a sharp flux loss was measured throughout the whole operating cycle, pinpointing that supra-boundary flux conditions were governing the system. This was supported by the calculated value of the β fouling parameter, which resulted to be in the order of ten times higher for this membrane. However, the values of β→0 for the SC-RO and DK-NF ones, supported by the very low value of the sub-boundary fouling parameter α (0.002 and 0.007 L·h^-1·m^-2·bar^-2, respectively), ensure nearly boundary operating conditions for these membranes.