The current concept for cooling the indoors is far from ideal with respect to the total energy consumed and waste discharged. A novel concept for improving the energy efficiency is proposed via hybridizing the heat pump with a membrane distillation (MD) unit for simultaneous space cooling and water treatment. MD is well-acknowledged for utilizing low-quality waste heat for water treatment, which makes it feasible for coupling with a heat pump to make use of both the hot and cold reservoirs of the pump. Accordingly, the objective of the current effort was to investigate via experiments the efficacy of a thermoelectric heat pump coupled with a sweep-gas MD system (T-SGMD) by measuring the cooling capacity, condensate production and power consumption. The results from this study can be extended to other heat pumps. Three key highlights emanated from this study. Firstly, condensate production per unit energy consumed can be doubled with the T-SGMD system relative to thermoelectric dehumidification alone. Secondly, cool air recycle affected the condensate flux the most without a drastic loss of cooling compared to other tested parameters during the operation of the T-SGMD. Lastly, the T-SGMD system was able to provide an increase in condensate produced per unit energy without a loss in cooling capacity per unit energy input. These advantages of coupling heat pumps with MD, leveraging on the current advancements in MD, is promising for a hybridized system for decentralized water treatment, dehumidification and space cooling.
Hydrogels are being investigated recently for wastewater treatment. These polymeric networks permit their functional group alterations imparting high binding affinity for different contaminants in wastewater. Their innate ability to imbibe huge volume of water qualifies it for a smart material for water remediation. In this review recent advancements in the modifications and types of hydrogels with particular emphasis on adsorption capacity of metal ions and dyes is presented. In addition, through a comparative approach, adsorption mechanism, kinetic, isotherm and related thermodynamics parameters of the modified hydrogels have been discussed. It gives a detailed account of the work done by different authors on the synthesis, composition, functionality and contaminant removal mechanism. It also provides an indepth perspective on the advantages and limitations in the application of hydrogels for wastewater treatment.
Water scarcity motivated the scientific researcher to develop efficient technologies for the wastewater treatment for its reuse. Ionic liquids have been applied to many industrial and analytical separation processes, but their applications in the wastewater treatment, especially in the removal of organic pollutants, are still not well explored. Potential applications of ionic liquids include solvent extraction, solvent membrane technologies and ionic liquidmodified materials that are mainly used as adsorbents. Aforementioned technologies have been examined for the abatement of phenol, chloro and nitrophenols, toluene, bisphenol A, phthalates, pesticides, dyes, and pharmaceuticals etc. Present review enlightens the application of different ionic liquids in wastewater treatment and suggests the versatility of ionic liquids in the development of rapid, effective and selective removal processes for the variety of organic pollutants. Implementation of ionic liquid based technologies for wastewater treatment have lots of challenges including the selection of nonhazardous ionic liquids, technological applications, high testing requirements for individual uses and scalingup of the entire pollutant removal, disposal, and ionic liquid regeneration process. Toxicity assessment of water soluble ionic liquids (ILs) is the major issue due to the widespread application of ILs and hence more exposure of environment by ILs. The development of effective technologies for the recoverytreatment of wastewater contaminated with ILs is necessary from the environmental point of view. Furthermore, the cost factor is the major challenge associated with ionic liquidbased technologies.
Microorganisms are responsible for the conversion and breakdown of organic compounds and contaminants in bioreactors designed for the treatment of different types of waste. Organized in highly complex communities, they are the heart of every wastewater treatment plant and solid residue landfill. The detailed characterization of these communities and their taxonomic classification based on phylogenetic data are of great utility in monitoring the responses of the system to changing operational parameters and the development and optimization of favorable conditions within the bioreactors these communities inhabit. Until recently, only a fraction of the microbial diversity could be assessed, limited by the available sequencing technology, which was not suited for a highthroughput implementation. With the introduction of the recent nextgeneration sequencing (NGS) methods, an enormous advance has taken place allowing researchers in microbial ecology to generate large amounts of phylogenetic data in a short time and at relatively low costs. In this review, we present and discuss how the increase in available information has influenced recent research and the results available phylogenetic data has produced in the field of wastewater treatment. Furthermore, we introduce the data processing of NGSbased experiments, which has become more complex as the millions of sequences that a single sample can yield require the effective use of computational resources and human bioinformatics skills. To address this part of modern microbial ecology, the most popular sequencing techniques, as well as data analysis workflows, are outlined in this review article.
Contaminant removal from water involves various technologies among which adsorption is considered to be simple, effective, economical, and sustainable. In recent years, nanocomposites prepared by combining clay minerals and polymers have emerged as a novel technology for cleaning contaminated water. Here, we provide an overview of various types of claypolymer nanocomposites focusing on their synthesis processes, characteristics, and possible applications in water treatment. By evaluating various mechanisms and factors involved in the decontamination processes, we demonstrate that the nanocomposites can overcome the limitations of individual polymer and clay components such as poor specificity, pH dependence, particle size sensitivity, and low water wettability. We also discuss different regeneration and wastewater treatment options (e.g., membrane, coagulant, and barriercolumns) using claypolymer nanocomposites. Finally, we provide an economic analysis of the use of these adsorbents and suggest future research directions.
Recently, a series of new photocatalysts have been developed for to combat diverse biorecalcitrant contaminants and the inactivation of bacteria. Modeling photocatalytic processes is important to assess these materials, and to understand and optimize their performance. In this study, the recent literature is critically reviewed and analyzed to identify and compare methods of modeling photocatalytic performance. The LangmuirHinshelwood model (LH) has been used in many studies to rationalize the degradation kinetics of single contaminants because it is the simplest model including both the adsorption equilibrium and degradation rates. Other studies report the development of more sophisticated variants of the LH model that include the rates of catalyst excitation, recombination of electronhole pairs, production of reactive oxygen species (ROS), and formation of byproducts. Modified ChickWatson (CsbndW) and Hom models have been used by many researchers to include lag phases of bacteria in the description of disinfection kinetics. Artificial neural networks (ANNs) have been used to analyze the effects of operational conditions on photocatalyst performance. Moreover, response surface methodology (RSM) has been employed for experimental design, and optimization of operational conditions. We have reviewed and analyzed all available articles that model photocatalytic activity towards water pollution, summarized and put them in context, and recommended future research directions.
The development of novel technologies for wastewater treatment provides a reliable pathway to solve the growing environmental issues. Control on process cost, increment of pollutant removal efficiency, and multisystem applicability are key points which should be carefully considered. Here in this work, a novel method of ‘water splitting coagulation (WSC)’, which involves the synchronous treatment of two kinds of wastewater that contain metal and organic contaminants was proposed. As an electrical based technique, WSC utilizes ‘water splitting’ in a bipolar membrane (BM) instead of ‘water electrolysis’ on electrodes to constructively produce a flocculating constituent (Ni(OH) x (2x) ) by controlling the ‘hydroxide delivery’ and ‘cation delivery’ inside a BM and across a cation exchange membrane. The metal hydroxide is capable of absorbing textile dyes in (Dye) y Ni(OH) x (2x) form, which can be posttreated to produce useful resources. The alternative process has several advantages: 1) prevents the replacement of sacrificial anodes, 2) simultaneous removal of heavy metal and textile dyes, and 3) the recycling of valuable accompanying byproducts, and has great potential in the complex industrial wastewater treatment.
Fabricating stable mono-/multi-valent anion-selective membranes with high perm-selectivity for electrodialysis (ED) applications is critical but challengeable. In this work, we have fabricated a series of novel homogeneous monovalent anion-selective amphoteric ion-exchange membranes (AIEMs, PAES-im-Xc) based on a long-side-chain type imidazolium-functionalized poly(arylene ether sulfone) cross-linked with 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt (DAS) for ED. By tuning the mass percent of DAS added, low swelling ratio but appreciably high anion perm-selectivity (in Cl–/SO4 2– system) of optimized AIEM are achieved to values of 8.0% and 47.12 at current density of 2.5 mA cm–2, respectively. In particular, at an enhanced current density of 5.0 mA cm–2, its perm-selectivity reaches 12.5, significantly outperforming commercial monovalent anion-selective Neosepta ACS (5.27). The appreciably high perm-selectivity possibly arises from pore-size sieving effect from dense matrix structure with cross-linkings and strong electrostatic repulsion between negative fixed –SO3 – groups and negative divalent ions of SO4 2– in feeding solution. The superior performances might be particularly interesting findings that can facilitate the development of advanced mono-/bi-valent anion-selective membranes in applications of sea water desalination, resource recovery and water treatment/pretreatment etc..
Managed aquifer recharge with reclaimed water is a promising strategy for indirect potable reuse. However, residual contaminants in the treated wastewater effluent could potentially have adverse effects on human health. Hence, adequate water pretreatment is required. A multicriteria approach was used to select and evaluate suitable water pretreatment technologies that can remove these critical contaminants in wastewater effluent for MAR identified in a previous study (Yuan et al., 2017). The treatment efficiency targets were calculated based on the concentrations and the suggested limits of critical contaminants. Treatment efficiency credits were then assigned to each treatment option for the removal of critical contaminants based on literature data. Treatment units that resulted in the highest efficiency credit scores were selected and combined into treatment train options, which were evaluated in terms of treatability, cost, and sustainability. This paper proposes an approach for the selection and evaluation of water treatment options, which will be helpful to guide the future implementation of MAR projects with reclaimed water.
In an attempt to advance GO-based environmental applications, herein we probed the anti-biofouling properties and mechanisms of graphene oxide (GO) surface coating. A flexible and mechanically stable GO membrane was fabricated using vacuum filtration technique and its ability to inactivate bacterial growth and subsequent biofilm formation was investigated. Our preliminary results authenticate that the GO membrane, owing to its unique physicochemical surface properties, exhibits superior antibacterial activity against planktonic cell proliferation. An optical coherence tomography (OCT)-based nondestructive in situ monitoring of bacterial biofilm evolution and behavior revealed that the GO surface initially inhibited biofilm growth for 24 h under continuous flow conditions but was incapable of completely averting biofilm development under long-term operation (48 h). We further confirmed that the observed biofilm on the GO membrane was highly unstable and reversibly attached and could be conveniently removed from the surface under a gentle rinsing. Finally, we confirmed that upon direct bacterium-GO contact, GO simultaneously induces cellular membrane disruption and oxidative stress followed by degradation/release of intracellular organelles, thereby causing bacterial inactivation or cell death. We believe our findings will offer new understandings into the anti-biofouling properties of GO-coated membranes and highlight their potential for practical application in membrane-based water and wastewater treatment technologies.