Application of direct contact membrane distillation for saline dairy effluent treatment: performance and fouling analysis

Construction of direct Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst with enhanced visible light activity towards the degradation of methylene blue

Construction of the Z-scheme heterojunction photocatalyst achieved highly improved photocatalytic ability by its high redox ability of the photoinduced e^--h⁺ pairs. In the study, Z-scheme g-C₃N₄/BiYWO₆ heterojunction photocatalyst is prepared by the single-step hydrothermal method. Further, its photocatalytic ability was assessed by degrading methylene blue under visible light exposure. Particularly, the optimized 30 wt% of g-C₃N₄ in the g-C₃N₄/BiYWO₆ composite exposes almost complete degradation after 90 min, that is ~ 3.0 times greater than the bare BiYWO₆ and g-C₃N₄ with the rate constant value 0.032 min^-1. Experimentally, the radical trapping studies indicate O₂·^- and ·OH radicals are playing a vital role in the photocatalytic degradation process. Also, the Z-scheme g-C₃N₄/BiYWO₆ heterojunction photocatalyst exhibits excellent photoelectrochemical property and it is stable after 5 cycles, which indicates its good reusability nature. These enhancements are due to the newly formed heterostructure that facilitates the migration and separation efficiency of the photoproduced e^--h⁺ pairs. Hence, the synthesized Z-scheme g-C₃N₄/BiYWO₆ heterostructure could be an excellent material for wastewater remediation works.

One-step synthesis of rod-on-plate like 1D/2D-NiMoO4/BiOI nanocomposite for an efficient visible light driven photocatalyst for pollutant degradation

Visible light active 1D/2D-NiMoO₄/BiOI nanocomposite photocatalyst has been constructed by single step solvothermal method. Various compositions of NiMoO₄/BiOI nanocomposites are prepared by loading different amounts of nickel molybdate (NiMoO₄) (1, 2, 3 wt%) to the bismuth oxy iodide (BiOI) and investigated by XRD, FTIR, SEM, EDAX, TEM, UV-vis DRS, and PL analysis. Among the as-prepared photocatalysts, 1 wt% NiMoO₄ incorporated BiOI (NMBI-1) showed superior photocatalytic activity with a rate constant of 0.0442 min^-1 for methylene blue degradation. While the bandgap values of pure BiOI and NiMoO₄ are 1.94 and 2.43 eV, respectively, the optimized NMBI-1 exhibited a lower bandgap energy of 1.64 eV, and showed about 2 and 3.7 times higher photodegradation ability than the pure NiMoO₄ and BiOI, respectively, towards MB removal under visible light. The NMBI-1 nanocomposite photocatalyst is stable even after four cycles, indicating an excellent photostability and recyclability. Charge carriers on the interface of NiMoO₄ and BiOI easily transferred via the newly formed heterojunction, thereby increasing the photocatalytic performance. Photochemically formed h⁺ and^.OH are found to be the major species in the MB removal under visible light illumination. Therefore, the 1D/2D-NiMoO₄/BiOI nanocomposite photocatalyst materials may be considered for the wastewater remediation processes.

Assessment of pilot direct contact membrane distillation regeneration of lithium chloride solution in liquid desiccant air-conditioning systems using computer simulation

Membrane distillation (MD) has been increasingly explored for treatment of various hyper saline waters, including lithium chloride (LiCl) solutions used in liquid desiccant air-conditioning (LDAC) systems. In this study, the regeneration of liquid desiccant LiCl solution by a pilot direct contact membrane distillation (DCMD) process is assessed using computer simulation. Unlike previous experimental investigations, the simulation allows to incorporate both temperature and concentration polarisation effects in the analysis of heat and mass transfer through the membrane, thus enabling the systematic assessment of the pilot DCMD regeneration of the LiCl solution. The simulation results demonstrate distinctive profiles of water flux, thermal efficiency, and LiCl concentration along the membrane under cocurrent and counter-current flow modes, and the pilot DCMD process under counter-current flow is superior to that under cocurrent flow regarding the process thermal efficiency and LiCl concentration enrichment. Moreover, for the pilot DCMD regeneration of LiCl solution under the counter-current flow, the feed inlet temperature, LiCl concentration, and especially the membrane leaf length exert profound impacts on the process performance: the process water flux halves from 12 to 6 L/(m²·h) whilst thermal efficiency decreases by 20% from 0.46 to 0.37 when the membrane leaf length increases from 0.5 to 1.5 m.

Recent technological advancements in membrane distillation and solar stills: preheating techniques, heat storage materials, and nanomaterials - a detailed review

Freshwater and energy are critical components for the growth and progress of societies. The scarcity of freshwater and rapid population growth, especially in remote countries, has led to an urgent need to develop desalination technologies in order to raise its productivity and reduce its energy consumption rates. Membrane distillation is one of the effective methods characterized by its high productivity, but its disadvantage by higher electricity consumption. Also, solar stills are one of the sustainable and economical technologies, but the disadvantage by lower productivity. Accordingly, this manuscript dealt with a comprehensive review and detailed comparison of the most important modifications and innovations that were made to the design of the membrane distillation units, which aim to reduce electricity consumption rates, as well as the design of solar stills, which aims to maximize the productivity and efficiency. This was done by providing a detailed comparison of the most important three axes of modifications and innovations that were addressed by recent previous studies on the design of membrane distillation units and solar stills, and their statement as follows: preheating technology, use of the thermal storage materials, and nanomaterials technology. Finally, based on this review, the authors make some recommendations for future work in the field of solar and membrane desalination.

Competitive effect of copper and nickel recovery with carbonate in the fluidized-bed homogeneous granulation process

With the rapid growth of the world's informatics innovation, printed circuit boards (PCBs) processing produces wastewaters with copper and nickel ions. This study aims to remove and recover copper and nickel ions from synthetic PCB wastewater using a fluidized-bed homogeneous granulation process (FBHGP). FBHGP is an advanced green technology that removes copper and nickel and transforms the sludge into a hard granule. The impacts on the removal and granulation of copper and nickel of the initial operating pH, molar ratio (MR) of precipitant to metal, and precipitant flow rate have been evaluated. The highest copper removal was attained at 97% at pH of 6.5 and 98% copper removal at an MR of 2.0 and 10 mL·min^-1. A 93% copper granulation was achieved at the same pH, while a 94% copper granulation was also achieved at the same MR and precipitant flow rate. At a pH of 7.5, 85% nickel removal and 74% granulation were attained for a nickel. At an MR of 1.75, 82% and 74% were the highest removal and granulation. While at 25 mL·min^-1, the highest removal was 83%, and 73% nickel granulation was achieved. Copper has been successfully recovered from synthetic PCB wastewater using FBHGP. At the same time, nickel needs a multi-step FBR, which is more suitable for the recovery of nickel under the same conditions applied during the same period.

Use of Membrane Technologies in Dairy Industry: An Overview

The use of treatments of segregated process streams as a water source, as well as technical fluid reuse as a source of value-added recovery products, is an emerging direction of resource recovery in several applications. Apart from the desired final product obtained in agro-food industries, one of the challenges is the recovery or separation of intermediate and/or secondary metabolites with high-added-value compounds (e.g., whey protein). In this way, processes based on membranes, such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), could be integrated to treat these agro-industrial streams, such as milk and cheese whey. Therefore, the industrial application of membrane technologies in some processing stages could be a solution, replacing traditional processes or adding them into existing treatments. Therefore, greater efficiency, yield enhancement, energy or capital expenditure reduction or even an increase in sustainability by producing less waste, as well as by-product recovery and valorization opportunities, could be possible, in line with industrial symbiosis and circular economy principles. The maturity of membrane technologies in the dairy industry was analyzed for the possible integration options of membrane processes in their filtration treatment. The reported studies and developments showed a wide window of possible applications for membrane technologies in dairy industry treatments. Therefore, the integration of membrane processes into traditional processing schemes is presented in this work. Overall, it could be highlighted that membrane providers and agro-industries will continue with a gradual implementation of membrane technology integration in the production processes, referring to the progress reported on both the scientific literature and industrial solutions commercialized.

Current available treatment technologies for saline wastewater and land-based treatment as an emerging environment-friendly technology: A review

Different industrial activities such as agro-food processing and manufacturing, leather manufacturing, and paper and pulp production generate highly saline wastewater. Direct discharge of saline wastewater has resulted in pollution of waterbodies by very high magnitudes. Consequently, an enormous number of pollutants such as heavy metals, salts, and organic matter are also released into the environment threatening the survival of human and biota. Saline wastewater also has significant effects on survival of plants, agricultural activities, and groundwater systems. Several treatments and disposal technologies are available for saline wastewater, but the selection of the most appropriate treatment and disposal technology still remains a major challenge with respect to the economic or technical constraints. Considering the sustainable management of saline wastewater, the present review is an attempt to compile the existing and emerging technologies for the treatment of saline wastewater. Among all the individual and hybrid technologies, land-based treatment systems are proven to be the most efficient technologies considering the energy demands, economic, and treatment efficiencies. Likewise, new and sustainable technologies are the need of hour integrating both the treatment and management and the resource recovery factors along with the ultimate goal of the protection in terms of human health and environmental aspect. PRACTITIONER POINTS: Physico-chemical treatment technologies for saline wastewater. Combined/Hybrid technologies for the treatment of saline wastewater. Land-based treatments as the environment friendly and sustainable method for saline wastewater treatment and disposal. Role of phytoremediation in land-based treatment.

Seawater Desalination Based on a Bubbling and Vacuum-Enhanced Direct Contact Membrane Distillation

A Bubbling and Vacuum-enhanced direct contact membrane distillation (BVDCMD) is proposed to improve the water production rate of the direct contact membrane distillation (DCMD-)based seawater desalination process. Its heat and mass transfer mechanism are theoretically analyzed, and a CFD model is established, which is verified by the published data. Four types of the noncondensable gas, “O2,” “air,” “N2,” and “H2,” are adopted as the bubbling gas, and their process enhancements under different pressure of permeate side, temperature, and NaCl concentration of feed side and flow velocities are investigated. The results show that the permeate flux increased remarkably with the decrease in the viscosity of the bubbling gas, and hence, “H2” is the best option for the bubbling gas, with the permeate flux being enhanced by 144.11% and the effective heat consumption being increased by 20.81% on average. The effective water production rate of BVDCMD is predicted to be 42.38% more than that of DCMD, proving its feasibility in the seawater desalination.

A novel thermophilic anaerobic granular sludge membrane distillation bioreactor for wastewater reclamation

Membrane distillation (MD) has a high heat requirement. Integrating MD with thermophilic bioreactors could remedy this problem. A laboratory-scale thermophilic anaerobic granular sludge membrane distillation bioreactor (ThAGS-MDBR) was used to treat wastewater with a high organic loading rate (OLR). Waste heat from ThAGS was used directly for the MD process to reduce energy consumption. The result demonstrated that the ThAGS-MDBR system achieved a high-efficiency removal of chemical oxygen demand (more 99.5%) and NH₄⁺-N (96.4%). Furthermore, the highest methane production from the proposed system was 332 mL/g COD_removed at OLR of 16 kg COD/m³/day. Specifically, an aggregate of densely packed diverse microbial communities in anaerobic granular sludge was the main mechanism for the enhancement of bioreactor tolerance with environmental changes. High-quality distillate water from ThAGS-MDBR was reclaimed in one step with total organic carbon less than 1.7 mg/L and electrical conductivity less than 120 μS/cm. Furthermore, the result of the DNA extraction kit recorded that Methanosaeta thermophila was a critical archaea for high COD removal and bioreactor stability.

Food-processing wastes

Literature published in 2018 and literature published in 2019 related to food-processing wastes treatment for industrial applications are reviewed. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following food-processing industries and applications: general, meat and poultry, fruits and vegetables, dairy and beverage, and miscellaneous treatment of food wastes. PRACTITIONER POINTS: This article summarizes literature reviews published in 2018 and in 2019 related to food processing wastes treatment for industrial applications are reviewed. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following food processing industries and applications: general, meat and poultry, fruits and vegetables, dairy and beverage, and miscellaneous treatment of food wastes.

A novel application of membrane distillation to facilitate nickel recovery from electroplating wastewater

In many years, the nickel electroplating technique has been applied to coat nickel on other materials for their increased properties. Nickel electroplating has played a vital role in our modern society but also caused considerable environmental concerns due to the mass discharge of its wastewater (i.e. containing nickel and other heavy metals) to the environment. Thus, there is a growing need for treating nickel electroplating wastewater to protect the environment and, in tandem, recover nickel for beneficial use. This study explores a novel application of membrane distillation (MD) for the treatment of nickel electroplating wastewater for a dual purpose: facilitating the nickel recovery and obtaining fresh water. The experimental results demonstrate the technical capability of MD to pre-concentrate nickel in the wastewater (i.e. hence pave the way for subsequent nickel recovery via chemical precipitation or electrodeposition) and extract fresh water. At a low operating feed temperature of 60 °C, the MD process increased the nickel content in the wastewater by more than 100-fold from 0.31 to 33 g/L with only a 20% reduction in the process water flux and obtained pure fresh water. At such high concentration factors, the membrane surface was slightly fouled by inorganic precipitates; however, membrane pore wetting was not evident, confirmed by the purity of the obtained fresh water. The fouled membrane was effectively cleaned using a 3% HCl solution to restore its surface morphology. Finally, the preliminary thermal energy analysis of the combined MD-chemical precipitation/electrodeposition process reveals a considerable reduction in energy consumption of the nickel recovery process.