Liquid Discharge Research Articles

Thermodynamic and kinetic analyses of Janus membrane scaling in membrane distillation for zero liquid discharge engineering

Scaling phenomena are the principal obstacle to the factual application of membrane distillation (MD). In this study, we fabricated a Janus membrane composed of a commercial polytetrafluoroethylene substrate, a superhydrophobic surface layer, and a hydrophilic reverse side coated by MXene nanosheets via a simple spraying method. The virgin and modified membranes were carried out and compared in zero liquid discharge (ZLD) MD experiments. MD flux analysis showed that all the membranes experienced severe flux decline during the ZLD process. Saturation index, Gibbs free energy and nucleation energy barrier were calculated to explain the observed difference in scaling behavior. Screenage assessment of the homogeneous nucleation and heterogeneous nucleation showed that the severe scaling developed from some small clusters of the new phase, wherein the thermodynamic energy barrier played a critical role in determining the anti-scaling behavior for these unsmooth surfaces. Model analysis and data fitting were used to conclude the kinetic behavior of the virgin and modified membranes in the ZLD engineering. Finally, we evaluated the reversible and irreversible scaling after twice washing. Therefore, this study may provide instructive insights to design novel anti-fouling membranes and promote practical applications such as industrial brine treatment and ZLD engineering.

Feasibility study of common effluent treatment plant for management of industrial wastewater: Case study of Bangladeshi textile industries

AbstractTextile industries play a vital role in the economy of Bangladesh contributing significantly to its gross domestic product. However, they are associated with high environmental pollution, especially water pollution. Since small‐scale textile industries cannot afford the treatment cost of discharged wastewater, they tend to contaminate water sources—both groundwater and surface water. To intervene in response to this situation, the existing treatment system was assessed in the present study. The effluents from industries under this research were analyzed for color, pH, TSS, TDS, chlorides, sulfates, COD, BOD, and total hardness. A Common Effluent Treatment Plant (CETP) with zero liquid discharge was suggested as a solution. It was observed that the water recovery in the proposed scheme by reverse osmosis and salt recovery using nanofiltration were 90%–95% and 80%–90%, respectively. Cost analysis also indicated that the cost of treating water can also be decreased by 18.7% which can show that water recovery is even more affordable for small‐scale industries. Finally, a linear programming model was developed to assist the industries with decision‐making in the selection of treatment schemes. This research revealed that a CETP using zero liquid discharge technology is a potential solution to the environmental crisis due to industrial wastewater discharge. This could ensure reduced water pollution, increased drinking water availability, improved public health, and thus could be a potential driver for environmental sustainability.

Electrodialytic crystallization to enable zero liquid discharge

The management of hypersaline brines (that is, wastewater of high salinity) is a technical challenge that has received increasing attention due to their growing volume, environmental impacts and increasingly stringent regulations. Here we present electrodialytic crystallization (EDC) as a new process to achieve brine crystallization without evaporation. In an EDC process, the brine stream recirculating between an electrodialysis cell and a crystallizer remains oversaturated via continuous electromigration of ions from the feed stream across the ion exchange membranes. We first used Na2SO4 as the model salt to demonstrate the feasibility of EDC and to perform a systematic investigation of how crystallization kinetics and crystal size distribution depend on current density and crystallization mode. We then elucidated the criterion of crystallizability and showed how it depends on salt species, membrane properties and operating conditions. Lastly, we analysed the energy consumption of an EDC-reverse osmosis treatment train for achieving zero liquid discharge of a Na2SO4 brine. Overall, this study provides a proof of concept for EDC as an electric-field driven and non-evaporative crystallization process, and lays the foundation for its future technical development and optimization. Achieving zero liquid discharge is an essential step towards the sustainability of hypersaline brine treatment. A potential method to achieve zero liquid discharge on the basis of electrodialysis crystallization is now demonstrated.

Study on the water resources and the opportunities for sustainable desalination & minimal/zero liquid discharge (MLD/ZLD) practices in Greece (Eastern Mediterranean)

Study on the water resources and the opportunities for sustainable desalination & minimal/zero liquid discharge (MLD/ZLD) practices in Greece (Eastern Mediterranean)

Pulsed gas–liquid discharge plasma catalytic degradation of bisphenol A over graphene/CdS: process parameters optimization and O3 activation mechanism analysis

In the present work, pulsed gas–liquid hybrid discharge plasma coupled with graphene/CdS catalyst was evaluated to eliminate bisphenol A (BPA) in wastewater. The optimization of a series of process parameters was performed in terms of BPA degradation performance. The experimental results demonstrated that nearly 90% of BPA (20 mg l−1) in the synthetic wastewater (pH = 7.5, σ = 10 μS m−1) was degraded by the plasma catalytic system over 0.2 g l−1 graphene/CdS at 19 kV with a 4 l min−1 air flow rate and 10 mm electrode gap within 60 min. The BPA removal rate increased with increasing the discharge voltage and decreasing the initial BPA concentration or solution conductivity. Nevertheless, either too high or too low an air flow rate, electrode gap, catalyst dosage or initial solution pH would lead to a decrease in BPA degradation. Moreover, optical emission spectroscopy was used to gain information on short-lived reactive species formed from the pulsed gas–liquid hybrid discharge plasma system. The results indicated the existence of several highly oxidative free radicals such as ·O and ·OH. Finally, the activation pathway of O3 on the catalyst surface was analyzed by density functional theory.

3D Numerical Simulation of Metal Bipolar Plate Proton Exchange Membrane Fuel Cell Considering Wavy Interlaced Flow Field

A metal bipolar plate fuel cell (FC) composed of gas distribution zones (GDZ) with ordered distribution of “dot matrix” structures, a complex waveform staggered fluid region, and the effect of cooling flow field (FF) is proposed in this investigation. The 3D multiphase model is applied to simulate the two‐phase flow in the FC. First, the cathode catalyst layer (CCL) has a higher electrochemical reaction rate (ERR) when gas diffusion layer (GDL) is anisotropic, and the ERR under channels is much higher than ribs. Increasing the thickness of GDL is not conducive to gas mass transfer, and the maximum current density reduction rate is 2.94%. Increasing the porosity of GDL is beneficial to improve the mass transport efficiency, and the liquid discharge is promoted. Second, the increase of GDL contact angle affects the cathode microporous layer and liquid saturation in CCL, and the current density is the highest when the contact angle is 120°. Finally, the volume‐of‐fluid model is utilized to analyze the drainage process in the GDZ and cathode small‐size FF. It is indicated in the results that water tends to concentrate at the outlet corner of GDZ in liquid form.

Wastewater Assessment and Biochemical Oxygen Demand Value Prediction from Mining Operations: A Case Study

Wastewater is a byproduct of industrial or household waste processes, and its contamination level must be determined before treatment. Discharges of liquid effluents generated by mining operations, one of the most prevalent forms of industrial waste water, pose a risk to human health and the environment. This study evaluates the physicochemical quality of industrial liquid effluent discharges from the Boukhadra mine (Algeria). Samples were collected from the washing water to identify the level of contamination of these liquid discharges and to measure physicochemical parameters such as temperature (T), hydrogen potential (pH), Electrical Conductivity (EC), Suspended Solids (SS), Chemical Oxygen Demand (COD), Biological Oxygen Demand for 5 days (BOD5), Oils and Greases (O&G), iron (Fe+2) and Kjeldahl Nitrogen (NTK). It was found that the concentration values of those effluents exceeded the maximum contamination limits specified by international industrial waste standards. A simple and reliable prediction model was developed to estimate DBO5, based on MES, COD, and O&G, by using classical regression analysis and fitting Design of Experiments (DOE) methodology. When comparing the analytical results, it was found that the quadratic model provided a better estimation, with a high correlation coefficient (R2) of 0.9976. The parameters determined in this study will enable engineers to quickly estimate the degree of wastewater contamination and choose adequate treatment strategies.

A demonstration project for desulfurization wastewater evaporation technology: Field test and performance analysis

Desulfurization wastewater evaporation technology is an effective approach to achieve zero liquid discharge. However, limited information is available on the practical engineering performance and related risks of the technology. In this study, we conducted a field test of desulfurization wastewater evaporation technology in a demonstration project. The results indicated the technology was highly feasible and applicable to three operating conditions with varying desulfurization wastewater flow rates. The migration characteristics of Cl were investigated, revealing that less than 3 % of Cl was released into gaseous HCl. The concentrations of other typical pollutants, such as NOx and SO2, remained unchanged after treatment, indicating that the wastewater evaporation technology did not significantly affect the distribution of gaseous pollutants or the comprehensive fly ash utilization. Moreover, the study found that the evaporation process promoted the agglomeration of particulate matter, as confirmed by larger particle sizes and XRD analysis. The total operating cost of wastewater evaporation ranged from 25 to 30 yuan per ton of wastewater, primarily consisting of coal consumption for extracting flue gas. The data obtained in this work complements and verifies existing research on wastewater evaporation technology.

Revolutionizing Water Sustainability: A Comprehensive Exploration of Zero Liquid Discharge Strategies

Sustainable water management practices have become increasingly important in the face of escalating global water scarcity. ZLD is emerging as a promising solution to eliminate liquid discharge from wastewater treatment and purification systems. It highlights the pivotal role ZLD plays in advancing sustainable water management by examining its principles, technologies, and applications. With a comprehensive assessment of ZLD technologies, a nuanced understanding of their diverse tools is provided through membrane processes, evaporation, crystallization, and biological treatment. As well as emphasizing ZLD's adaptability and effectiveness, the review points out successful applications across industries. Water scarcity can be addressed by repurposing wastewater as a resource, thus aligning with circular economy principles and advocating wide adoption of the technology in future water management plans.

Treatment of Aniline Wastewater by Membrane Distillation and Crystallization.

Aniline is a highly toxic organic pollutant with "carcinogenic, teratogenic and mutagenesis" characteristics. In the present paper, a membrane distillation and crystallization (MDCr) process was proposed to achieve zero liquid discharge (ZLD) of aniline wastewater. Hydrophobic polyvinylidene fluoride (PVDF) membranes were used in the membrane distillation (MD) process. The effects of the feed solution temperature and flow rate on the MD performance were investigated. The results showed that the flux of the MD process was up to 20 L·m-2·h-1 and the salt rejection was above 99% under the feeding condition of 60 °C and 500 mL/min. The effect of Fenton oxidation pretreatment on the removal rate of aniline in aniline wastewater was also investigated, and the possibility of realizing the ZLD of aniline wastewater in the MDCr process was verified.

Development and performance evaluation of novel silica gel-coated heat exchanger with high durability and conductivity to improve adsorption water treatment

Adsorption water treatment (AWT) has received considerable attention because it can be used to produce freshwater using low-grade heat sources. Furthermore, owing to its nearly consistent desalination performance and high-water recovery rate (>80 %), it has a high potential for use as a minimal liquid discharge process. However, a low freshwater production yield per unit volume of the AWT system is observed because the AWT system uses an adsorbent-packed heat exchanger (APHE), which has a high thermal resistance. In this study, the development and performance evaluation of a novel adsorbent-coated heat exchanger (ACHE) with high durability and conductivity is presented to enhance the heat and mass transfer rates during the adsorption and desorption processes. Binders and spray coating methods are utilized to achieve a uniform coating thickness and highly durable ACHE, and the adhesion strength is investigated using a pull-off test. The physical properties of the composite adsorbent are then examined using argon and water vapor adsorption isotherms, and the thermal conductivity is determined using the transient plane source method. Finally, the performance of the AWT process is evaluated considering the hot-water temperature and cycle time and achieves a significant superiority in the ACHE compared with the APHE.

A three-dimensional folded multistage distillation device with enhanced air convection for efficient solar interface evaporation

Solar interface evaporation technology is widely used as an effective method of vapor generation. However, the convection and condensation processes that follow vapor generation have received little attention, limiting the actual freshwater output. In this study, we designed an innovative 3D folded structure with enhanced light absorption and air convection for the multistage distillation device. It is demonstrated that the 3D folded structure increases the average air flow velocity by 3 orders of magnitude compared to the conventional flat structure. As a result, the device achieves higher evaporation efficiency with less energy input, with a 7-stage device achieving an evaporation rate of 3.22 kg m−2 h−1 at 1 kW m−2 light intensity. In addition, we have designed an effective salt tolerance strategy for the new structure, with zero liquid discharge and easier salt collection. The experiment proved the stable operation of the device in high concentration brine at 20 wt%. This new structure provides a new idea for the interface evaporator to improve fresh water production and practicality.

Treatment of brackish water for fossil power plant cooling

In this study, we evaluated the technical, economic and environmental impacts of retrofitting brackish groundwater treatment systems at existing coal- and gas-fired electric generating units (EGUs) to reduce freshwater consumption in wet cooling towers. Based on fleet averages, retrofitting brackish water treatment systems decreases unit freshwater consumption by 94–100%, while increasing the cost of electricity generation by 8–10%. The unit capacity shortfalls are less than 1.1%. The resulting cost of freshwater consumption savings by brackish water treatment is US$1.7 m−3 and US$2.9 m−3 on average for coal- and gas-fired EGUs, respectively. However, these trade-offs are highly affected by the brine disposal method. The use of thermal zero liquid discharge for brine disposal can roughly double the average cost of freshwater consumption savings. The cost-effectiveness of brackish water treatment compared with dry cooling deployment depends on how concentrated brines are managed. The identified trade-offs and their dependence fill knowledge gaps to better inform water management. This study reveals trade-offs in freshwater savings, cost and capacity shortfalls from deploying treated brackish water for wet thermoelectric cooling, as well as its cost-effectiveness, relative to dry cooling retrofit, in saving freshwater.

Numerical modeling of positive streamer propagation in alternative natural ester and traditional naphthenic oil under sub-microsecond pulsed voltages

In this paper, a two-dimensional axisymmetric numerical model of streamer discharge in alternative natural ester liquid and conventional naphthenic oil under a positive sub-microsecond impulse voltage is proposed. The model is based on the charge drift-diffusion approximation in a divergent electric field. Simulation shows that streamer propagation in naphthenic oil is divided into two stages: stage I with a small streamer velocity of 0–0.91 km s−1 and stage II with a rapidly rising streamer velocity up to 213 km s−1. In natural ester, the streamer velocity gradually slows down from 4.84 km s−1 to 2.11 km s−1. The electric field at the head of the streamer in natural ester ranges from 2.4 × 108 V m−1 to 2.5 × 108 V m−1 during propagation, which is visibly lower but more consistent than that in naphthenic oil (3.5 × 108 V m−1 to 8.4 × 108 V m−1). It is revealed that the different streamer features within the two types of oil are caused by the different competition between the Laplacian electric field and space charge effect at the streamer head. For streamer propagation in naphthenic oil, stage I is dominated by the Laplacian electric field whereas stage II is dominated by the space charge effect. In natural ester, the whole streamer propagation is dominated by the Laplacian electric field. Further, it is indicated that the streamer head consists of two specific discharging regions, i.e. the front region of the streamer head which guides new space charge accumulation and the back region of streamer head which guides density reduction of accumulated space charge. The expansion of the streamer tunnel is caused by the alternating space charges in these two regions. The work in this paper provides a theoretical reference for the practical application of alternative transformer liquids.

Lubricant‐Interface Induced Mobile Crystallization for Hypersaline Wastewater Management

AbstractHypersaline wastewater management is a crucial issue for water‐energy nexus. Evaporation‐based zero liquid discharge (ZLD) desalination shows great promise to detoxify the hypersaline wastewater. However, salt formed on the evaporation surface compromises the efficiency and continuity of desalination. Here, the study reports a photothermal lubricant‐infused surface (PLIS), capable of inducing mobile salt crystallization and eliminating salt scaling during desalination. Few nuclei initiate away from the PLIS, followed by migration inward as salt growth, leading to compact crystal. The final dewetting process leaves only scattered protrusions from crystal bottom contacting with the PLIS. Such a converged small area plus pinpoint contacting mode produce an ultralow adhesion of salt to the substrate (≈2 mN mg−1), ≈40 times lower than that on a regular‐used hydrophobic surface. The salt crystal precipitated on the PLIS can be blown off easily by air flow, refreshing the evaporating surface for continuous desalination and realizing ZLD.

Novel materials and crystallizer design for freeze concentration

When wastewater streams or seawater are desalinated, the waste product is a hypersaline brine stream which is usually disposed of or stored in evaporation ponds. Eutectic Freeze Crystallization (EFC) is a novel treatment technology for these hypersaline brines that can recover both water and dissolved salts. It works by cooling the stream to the Eutectic temperature, at which point both ice and salt will crystallize. The ice, being less dense than the solution, floats, and the salt, being denser, will sink – thus effecting a gravity separation.Theoretically, EFC can result in zero liquid discharge (ZLD) and has several advantages over conventional separation techniques, including low energy consumption; high quality products and it requires no additional chemicals. It can also be combined with other separation technologies to optimise the separation process.Although it sounds simple, an EFC process can be difficult to design and operate effectively, since each of the elements has its own complexity. Specifically, the issue of ice scaling is one of the major challenges in implementing EFC.Therefore, in this study, we focussed on ice scaling in a freeze concentration system i.e ice crystallization only; without the salt crystallization component that would define the process as an EFC process.We investigated two approaches to scaling reduction:The first was modification of the heat exchanger surface, where we investigated the effect of three different heat exchanger surfaces on ice scaling: a novel polypropylene graphite (PP GR) material, Stainless Steel 316 (SS316) and Aluminium. These three materials were tested in a small-scale Column Crystallizer (CC).The second method was by designing a Continuously Stirred Column Crystallizer (CSCC), which aimed to improve the hydrodynamics independent of pumping, to improve on the heat and mass transfer distribution across the crystallizer and to improve product purity by providing a larger product separation zone. The focus was on producing an efficient crystallizer design, bearing current industrial implementation hurdles in mind.This study confirmed that using materials of low surface energy has the potential to increase the scaling induction times and reduce the severity of ice scaling, hence improving process efficiency. The outcome of the initial, small-scale study provided the required evidence to support scaling up the column crystallizer using PP GR as an HX material of choice.The study also showed that the unique multicompartment mixing system of the novel CSCC led to high supercoolings and long induction times being attained. The column design provides a larger disengagement zone than a conventional column, which has the potential to improve the separation efficiency, and hence the product purity.In summary, with the correct choice of heat exchanger material and appropriate crystallizer design, we have shown that one of the major challenges i.e. ice scaling, can be overcome. This paves the way for EFC being able to be used for the treatment of hypersaline brines, not only at laboratory scale, but also at larger, commercial scales.

An enquiry into competitive value of sustainable manufacturing capabilities

PurposeDespite its great practical and theoretical significance, research on how and to what extent sustainable manufacturing capabilities (SMCs) provide competitive advantage to firms remains scarce. Towards bridging the gap, this paper conducts an enquiry into the competitive value of SMCs.Design/methodology/approachA theoretical framework on the competitive value of four SMCs, namely, pollution control (PC), pollution prevention (PP), product stewardship (PS) and clean technology (CT) is developed through synthesis of literature. More specifically, competitive value is characterised in terms of enabling key resources and market positioning opportunities. A case study, using a deductive qualitative approach is conducted to test the framework by analysing reported sustainable manufacturing practices (SMPs) of three multinational firms. Observed compliances and deviations to the framework are analysed and accordingly few propositions are framed.FindingsThe empirical findings largely support the conceptualisation of competitive value for PC, PP, PS and CT provided in the theoretical framework. However, a few deviations were observed for PC, PP and PS. For instance, some PC-based actions, such as co-processing and implementation of zero liquid discharge technology show characteristics of resource conservation and lead to cost benefits. Similarly, there were instances when PP demonstrated the use of non-tacit (imitable) resources and PS was employed to seek compliance to environmental regulations.Research limitations/implicationsThe results based on limited number of case firms may not be generalisable to other sectors and contexts.Practical implicationsThe study provides guidance to the manufacturing managers about the competitive value of SMPs.Originality/valueThis is a novel study that empirically investigates the competitive value of SMCs by understanding the associated sustainability impetus, enabling key resources and market positioning opportunities.

Ultrasound assisted seed preparation and subsequent application for desupersaturation of calcium sulphate as a measure for scaling control

To increase the water recovery from brine for zero liquid discharge (ZLD) desalination system, precipitation of salts and its subsequent removal is one of the desired solutions to prevent the scaling of heat exchanger or membrane surfaces, which leads to improved operation. Present work focuses on synthesis of better-quality calcium sulphate seed crystals using different strategies based on different initial sources, varying reagent concentration, washing with different solvents, varying the aging period and also providing ultrasound (US) at different stages of synthesis. It was elucidated that using only US at optimized conditions of 100 W US power, 70% duty cycle and 2 h irradiation time could reduce the supersaturation from 2.05 to 1.33 at 60 °C. Use of only seeding under optimized conditions required 4 h for reducing supersaturation from 2.02 to 1.21. The combination of US with the seeds synthesized at optimized condition resulted in the complete elimination of the supersaturation i.e. from the initial supersaturation of 2.02 to final of 1.03. Better desupersaturation is attributed to the increased nucleation rate and crystal growth by the synergy of US and seeding. Overall, an effective approach based on the combination of US and seeding for the desupersaturation of CaSO4 has been demonstrated.

Process design and technoeconomic analysis for zero liquid discharge desalination via LiBr absorption chiller integrated HDH-MEE-MVR system

A novel multipurpose seawater desalination process is presented that integrates a Lithium Bromide (LiBr) absorption chiller, humidification-dehumidification (HDH), multi-effect evaporator, and mechanical vapor recompression (MVR) to improve the energy effectiveness of conventional desalination processes. The proposed process uses the LiBr absorption chiller cycle to preheat the seawater prior to the steam generation in the multi-effect evaporators while the MVR system activates the LiBr cycle. The integration of HDH further allows to recover the excess water in the process stream and concentrates the brine effluent for zero liquid discharge processing. A stand-alone HDH desalination is comparatively studied with the integrated system to quantify their respective performances over several metrics. Technoeconomic analysis is also performed to assess the economic feasibility and a sensitivity analysis is carried out to observe the effects of changing process variables on the overall performance of these systems. The results show that the proposed process design achieves several times higher gain-output ratio compared to a conventional HDH system of equal capacity, with a levelized water production cost of $8.4/m3 and 6 kW of cooling capacity that can be used for air conditioning.

Zero Liquid Discharge and Resource Treatment of Low-Salinity Mineralized Wastewater Based on Combing Selectrodialysis with Bipolar Membrane Electrodialysis

A large amount of mine water is generated during coal production, which not only damages the surface environment and ecology but also wastes groundwater resources in the mining area, exacerbating regional water scarcity. In this work, a novel zero liquid discharge technology combining selectrodialysis (SED) and bipolar membrane electrodialysis (BMED) was developed for the resourceful treatment of low-salinity mineralized wastewater. The SED stack had demonstrated to be workable for the elimination of multivalent ions. The BMED stack converts brine into acid and base. After SED, a high pure crude salt (~98%) was attained. Furthermore, under the conditions of a current density of 20 mA/cm2, a flow velocity of 20 L/h, and an initial acid/base concentration of 0.10 mol/L, the maximum concentrations of acid and base were found to be 0.75 mol/L and 0.765 mol/L, respectively, for a feed conductivity of 55 mS/cm. The cost of the entire electrodialysis stage was evaluated to be USD 1.38/kg of NaOH. Therefore, this combined UF-RO-SED-BMED process may be an effective strategy for the sustainable treatment of low-salinity mineralized wastewater.