Zero Liquid Discharge Research Articles

Emerging and Conventional Water Desalination Technologies Powered by Renewable Energy and Energy Storage Systems toward Zero Liquid Discharge

The depletion of fossil fuels has become a significant global issue, prompting scientists to explore and refine methods for harnessing alternative energy sources. This study provides a comprehensive review of advancements and emerging technologies in the desalination industry, focusing on technological improvements and economic considerations. The analysis highlights the potential synergies of integrating multiple renewable energy systems to enhance desalination efficiency and minimise environmental consequences. The main areas of focus include aligning developing technologies like membrane distillation, pervaporation and forward osmosis with renewable energy and implementing hybrid renewable energy systems to improve the scalability and economic viability of desalination enterprises. The study also analyses obstacles related to desalination driven by renewable energy, including energy storage, fluctuations in energy supply, and deployment costs. By resolving these obstacles and investigating novel methodologies, the study enhances the understanding of how renewable energy can be used to construct more efficient, sustainable, and economical desalination systems. Thermal desalination technologies require more energy than membrane-based systems due to the significant energy requirements associated with water vaporisation. The photovoltaic-powered reverse osmosis (RO) system had the most economically favourable production cost, while MED powered via a concentrated solar power (CSP) system had the highest production cost. The study aims to guide future research and development efforts, ultimately promoting the worldwide use of renewable energy-powered desalination systems.

A Review of Renewable Energy Powered Seawater Desalination Treatment Process for Zero Waste

Freshwater resources have faced serious threats in recent decades, primarily due to rapid population growth and climate change. Seawater desalination has emerged as an essential process to ensure a sustainable supply of freshwater to meet the global demand for freshwater. However, this approach has some shortcomings, such as the disposal of brines containing high levels of contaminants creating environmental problems, and the energy-intensive nature of desalination, primarily powered by fossil fuels, which contribute to greenhouse gas emissions. Consequently, as a solution, the zero liquid discharge approach has been identified by the body of research to be one of the viable methods to solve these problems. Over 90% of freshwater and reusable salts could be recovered through this approach. Adopting renewable energy-powered systems could make zero-liquid discharge desalination plants operate in an entirely environmentally friendly and sustainable manner. This review explores the integration of renewable energy-powered systems for the optimisation of seawater desalination treatment processes for zero-waste and improved productivity. The review also examines technologies and strategies that improve the efficiency and sustainability of desalination systems. By analysing recent research, we provide insights into the advancements, challenges, and prospects for optimizing renewable energy-powered seawater desalination processes aimed at achieving zero waste.

Chloride-Salt Separation Type Nanofiltration Membranes for Efficient Crude Salt Refinement

Application of unrefined crude salt not only leads to a serious equipment scaling and a low product quality, but also increases operational risks and poses health hazards. Therefore, it is essential to refine crude salt prior to its use. However, traditional methods of crude salt refinement are energy-intensive and probably produce additional chemical by-products. In this work, membrane technology was used to accomplish the refinement of crude salt due to its unique characteristics, such as environmentally friendly and lower energy consumption. To improve the separation performance, the membranes were fabricated by simply adjusting the aqueous monomer concentration. For single-salt feed, the membrane (M10) prepared with a high ratio of 10 exhibited excellent salt rejection due to the formation of a thicker and denser PA layer. And it owned a superior MgCl2/NaCl selectivity of ∼22.0, demonstrating that the membrane can achieve outstanding selectivity for mono-/divalent ions. The selectivity of Mg2+/Na+ increased to ∼23.5 for bi-salt feed and further improved to 66.2 for multi-salt feed due to the stronger charge shielding effect. Most importantly, the membrane was also successfully applied in the refinement of crude salt. When using crude salt (NaCl 30 g/L, purity 0.90) as feed, the M10 exhibited both excellent retention of bivalent ions and permeation of univalent ions, resulting in the corresponding Mg2+/Na+ selectivity up to ∼251.6 and the tremendous enhancement in the Na+ purity of ∼0.997. This work offers a feasible strategy for crude salt refinement, and could expand to some other potential applications such as resource utilization in the salinization industry and zero-liquid discharge of industrial wastewater.

Heavy metal migration and enrichment in desulfurization wastewater during low-temperature triple effect evaporation process

Zero discharge of desulfurization wastewater from coal-fired power plants has become important. Desulfurization wastewater and gypsum from different stages of the low-temperature triple-effect evaporation process of a coal-fired power plant were collected and investigated. The results showed that after low-temperature triple-effect evaporation, the concentrations of Na+, Mg2+, K+, and Cl− in the desulfurization wastewater increased by 7.91, 7.15, 8.49, and 8.35 times, respectively. With the progress of low-temperature triple effect evaporation process, the concentrations of As, Cd, Co, Cr, Cu, Mn, Se, and Zn in the wastewater after the triple effects were 5.85, 75.44, 1.28, 2.34, 13.66, 5.58, 8.59, and 4.35 times higher than those in the raw wastewater. Mn and Se exceeded the emission limits by 40 and 10 times, respectively. After triple-effect evaporation, the concentrations of As, Cd, Co, Cr, Cu, Pb, Se, and Zn in gypsum decreased to 46%, 26%, 66%, 41%, 35%, 97%, 39%, and 51% of the raw gypsum, respectively. Compared with that of other metal sulfates, the solubility of PbSO4 was extremely low under low-temperature conditions, and some PbSO4 precipitated during the triple-effect evaporation process, leading to a gradual decrease in the Pb concentration in the liquid phase. The mercury compounds in gypsum after the first and second effects were the same as those in raw gypsum, both of which were HgS and HgO. After third effect, the mercury compound in gypsum also included HgSO4. In addition, owing to the promoting effect of the pH of desulfurization wastewater approaching 5.50 on the generation of HgS, the proportion of HgS gradually increased, and the proportion of HgO gradually decreased from the raw gypsum to the third effect gypsum. Therefore, the stability of the mercury compounds in gypsum was enhanced. It can provide a good reference for the migration and enrichment of heavy metals in the low-temperature triple-effect evaporation process, which is beneficial for the clean production and efficient utilization of coal.

Review on advanced techniques in zero liquid discharge water desalination via humidification-dehumidification within thermally-driven transport reactors

The article examines an advanced zero liquid discharge (ZLD) desalination method focusing on humidification-dehumidification (HDH) in thermally driven transport reactors. The limited availability of water, particularly in dry locations, has prompted the advancement of several desalination techniques. Reverse Osmosis (RO) is a prevalent membrane technology in the market; however, it has restrictions regarding brine disposal. ZLD technologies strive to mitigate environmental consequences by transforming saltwater into drinkable water and precious salts while minimizing waste. Membrane Distillation and Crystallization (MD-C) is notable as a highly efficient Zero Liquid Discharge (ZLD) technique. Despite its high energy consumption, it can combine MD-C with renewable or waste energy sources to improve sustainability. Freeze Desalination (FD) was reviewed for its economic efficiency, especially when utilizing cold energy from liquefied natural gas (LNG). Hybrid systems that combine Forward Osmosis (FO) and membrane distillation with condensation (MD-C) can potentially improve water recovery and decrease energy usage. The HDH desalination process imitates the natural precipitation process, examines its ability to operate at low temperatures, and highlights its potential for integration with renewable energy sources. The review discusses the HDH design, the effect of salinity on its performance, and the different dehumidification technologies. It emphasizes the significance of creative methods in achieving sustainable water management.

Reverse Osmosis Concentrated Water Treatment Technology Research

With the national “double carbon” goal, energy saving and consumption reduction strategic plan to promote, more and more enterprises will be “zero discharge” of wastewater as the ultimate goal of industrial wastewater. Reverse osmosis (RO) process is the most common way of water treatment process, in the treatment of water treatment and pure water preparation at the same time, will be accompanied by a variety of inorganic and organic pollutants contained in the by-products of concentrated water, these difficult to deal with high salt, complex composition of the reverse osmosis concentration of water, not directly discharged without treatment, not only to make a lot of water in the concentration of water to be a waste of water resources, will be a large extent on the ocean, soil and other natural environments to cause irreversible damage. Reversible damage to the ocean, soil and other natural environments. Therefore, it is of great significance to protect the environment by finding an economical and efficient treatment method for RO concentrated water. For the regeneration of fresh water resources of RO concentrated water, there have been many international reports on the development of zero liquid discharge (ZLD) or near-zero liquid discharge technology, through the membrane technology to reverse osmosis concentrated water concentration, water recycling, reduce the volume of concentrated water, and then based on the thermal technology of concentrated water desalination, evaporation and crystallization process leads to the recovery of water, and at the same time, the process of solid by-products after dehydration, purification, can also produce a considerable amount of water. At the same time, the solid by-products produced in the process can be dehydrated and purified, which can also produce considerable economic value of commodities. Concentrated water concentration process around how to achieve low-cost RO concentrated water concentration process, in the disc tube reverse osmosis (DTRO), electrodialysis (ED), membrane distillation (MD) and forward osmosis (FO) and other new membrane concentration technology field carried out a wide range of research on the concentration of further concentrated water to provide more prospects for application. Solidification crystallization through reasonable crystallization control and solid-liquid separation technology, can achieve effective separation and purification of solutes, for various industries to provide solid products in line with the quality requirements, commonly used evaporation crystallization, cooling crystallization, solvent crystallization, ion exchange methods and other ways. Through the study of reverse osmosis concentrated water concentration treatment, crystallization and solidification of the two important links of the production process plan, summarize the practicality of various technologies and advantages and disadvantages, integration of existing technologies, research suitable for reverse osmosis concentrated water resources utilization of economic technology solutions, optimize the treatment process, and ultimately realize the application of engineering examples, is the direction of the efforts of researchers in recent years.

Down flow jet-loop reactor with NF-RO membrane system for the treatment of textile wastewater

Textile industries are significant consumers of fresh water, extensively using it for washing and dyeing processes. The effluent from these operations contains various chemicals, including complex synthetic dyes, NaCl and Na2SO4 necessitating efficient treatment before discharge into water bodies. Zero Liquid Discharge (ZLD) technology facilitates complete water recovery but leads to substantial solid waste accumulation, which poses challenges for reutilization. This study introduces an innovative approach using a Downflow Jet Loop Reactor combined with ozone and activated carbon to effectively remove color and Chemical Oxygen Demand (COD) from textile effluent. Furthermore, a combination of Nanofiltration (NF) and Reverse Osmosis (RO) membrane systems ensures comprehensive purification by effectively separating inorganic salts. Experimental results demonstrated a maximum color removal of 81.25 % from the textile effluent. The fabricated PSF/PVDF NF membrane exhibited exceptional capacity for rejecting divalent salts. Additionally, the RO reject, which is a concentrated solution of salts and contaminants, was successfully reused in a dye bath for cotton fabric dyeing. This approach highlights the practicality, sustainability, and resource conservation potential within the textile production cycle. It underscores the importance of a comprehensive water treatment strategy for achieving sustainable textile production.

Removal of malachite green in wastewater and its mechanism by three-dimensional graphene oxide-based aerogels

Malachite green (MG) is a significant water pollutant due to its widespread use and harmful properties, making its effective removal crucial. Graphene oxide (GO) has emerged as a promising material for dye adsorption. Doping GO into cellulose aerogels enhances mechanical properties and prevents GO dissolution. Many reports claim the advantages of GO in adsorption, but challenges remain in understanding and optimizing the adsorption of MG in three-dimensional cellulosic GO (CLGO) aerogels. In this study, three-dimensional CLGO aerogels were prepared using the freeze-drying method. They achieved an MG maximum adsorption capacity of 33.98 mg g−1, and the adsorbent still had 97.04 % adsorption capacity at the seventh adsorption–desorption cycle. The photothermal properties of the CLGO aerogels were also studied, contributing to the development of the zero-liquid discharge (ZLD) post-processing concept. Molecular force field simulations indicated that π-π interaction is the primary force between MG and CLGO aerogels in the absorption process. We believe our research will guide the future optimization of MG specialized absorbent.

Multilayered photo-bioanode for simultaneous conversion of CO2 and industrial refractory organics into bioelectricity in a microbial fuel cell system

CO2 and toxic wastewater were converted into bioelectricity through photo-bioanode in a microbial fuel cell (MFCs). Photo-bioanode provided multifunctional regions due to four distinct layers: the first layer integrates a Fe-doped graphitic carbon nitride photocatalyst. In contrast, the second layer contains refractory organics (RO) degrading microbes. Sequentially, the third layer consists of CO2-consuming bacteria and the fourth layer accommodates exoelectrogens. The first layer not only generated plentiful electrons upon illumination but also quenched electrons from the inner layers, facilitating the degradation of RO. The second layer transformed RO into ions (NH4, NO3/NO2) and C6H12O6, sequentially transported into the third and fourth layers. Within the third layer, CO2-consuming bacteria utilized CO2 leaked from the exoelectrogenic layer, effectively curbing its accumulation in the fourth layer. Here, exoelectrogens employed ions and C6H12O6 as their energy source, producing an electricity output 1.4 times greater than the benchmark. This synergistic performance yielded a voltage of 2.5 V, a current of 2.8A, and a power yield of 1.98 W/organic loading rate (OLR). Thus, the unique layered structure of the photo-bioanode facilitated the self-development of distinct microbial communities, thereby formulating a multifunctional and highly dynamic system with zero-liquid discharge.

Directional salt crystallization system for high-efficiency solar-driven evaporation to achieve zero-liquid discharge

Solar-driven interfacial evaporation is an efficient technology for water treatment, enabling the production of freshwater and the removal of impurities. However, achieving a high evaporation rate and a long-term stable operation is challenging due to the salt accumulation on the evaporation surface. In this study, a novel three-dimensional directional salt crystallization system is proposed. The melamine sponge modified with polydopamine and carbon black was used to transport brine, absorb sunlight, and generate steam. The non-photothermal evaporation regions were innovatively constructed by placing a thermally conductive aluminum structure with the deflector paper around the sponge, which increased the effective evaporation area of the system to accelerate the evaporation of brines from the overall system, resulting in an evaporation rate of 2.20 kg m−2 h−1 under one sun irradiation in a 15 wt% NaCl solution. Moreover, the non-photothermal evaporation regions were isolated from the evaporation interface as a salt crystallization region, which completely avoided salt accumulation at the evaporation interface and ensured the long-term stable operation of the system. Salt crystals can be easily collected by replacing the deflector paper regularly, and the salt collection efficiency is over 95 % to achieve zero-liquid discharge (ZLD) treatment. More importantly, the directional salt crystallization system achieves efficient purification of heavy metal ion wastewater and dye wastewater. Consequently, the system presents a highly efficient method for ZLD seawater treatment and wastewater purification.

Efficient treatment of high-salinity aquaculture effluents through synergistic membrane distillation and VUV/UVC photolysis

Effluents from mariculture facilities typically marked contain high salinity and organic loadings, including anti-parasitic chemicals such as formaldehyde. The direct discharge of such effluents poses serious environmental risks, thus requiring the development of sustainable methods for their treatment. Within this context, a novel approach based on the synergistic integration of thermally driven membrane distillation (MD) and vacuum-ultraviolet/ultraviolet-C (VUV/UVC) photolysis is proposed for the treatment of highly polluted saline water without the need of intensive pretreatments or chemical additives. In this specific work, the performances of the proposed integrated treatment process were explored for inland mariculture effluent. The MD system was able to reclaim 90 % of the effluent as distilled water. Concurrently, salts in the MD concentrate were recovered. The subsequent polishing of the MD permeate solution via VUV/UVC photolysis allowed the abatement of the volatiles present in the MD permeate, bringing the concentrations of formaldehyde and total organic carbon (TOC) below the detection limits (0.5 mg L−1 for both techniques) within 20 min of treatment. The novel integrated system improves the purity of the recycled water and serves as an example of sustainable mariculture effluent management, advancing towards zero-liquid discharge within this field.

Vapor Pressure and Evaporation Studies of Saline Solutions on Natural and Synthetic Fabrics for Industrial Water Treatment.

In the present paper, we have conducted a comprehensive analysis of vapor pressures of both saturated and unsaturated solutions, alongside a study of evaporation using synthetic and natural fabrics for industrial applications in brackish water treatment under zero liquid discharge (ZLD) philosophy. By determining the vapor pressures of saturated solutions, we obtained results consistent with those of other researchers, extending the range of tested temperatures from 1 to 50 °C and successfully fitting the parameters of an Antoine-type equation. Similarly, positive results were achieved for unsaturated solutions, where various parameters of different equations accounting for the salt concentration were estimated, simplifying the fitting procedure. Natural evaporation tests from water surfaces using saturated solutions revealed that salts with higher associated vapor pressures exhibit higher evaporation rates. On the other hand, hydrated salts retain water in their structure and are significantly affected by ambient humidity. Evaporation studies on natural and synthetic fabrics with saturated NaCl and CuSO4·5H2O solutions showed distinct behaviors. NaCl increased both the evaporation rate and salt deposition with each cycle. In contrast, CuSO4·5H2O reduced the absorption capacity by blocking the fabric's structure, decreasing the evaporation efficiency over successive cycles.

Ultra-antiwetting Membrane for Hypersaline Water Crystallization in Membrane Distillation.

Membrane distillation (MD) has great potential in the management of hypersaline water for zero liquid discharge (ZLD) due to its high salinity tolerance. However, the membrane wetting issue significantly restricts its practical application. In this study, a composite membrane tailored for extreme concentrations and even crystallization of hypersaline water is synthesized by coating a commercial hydrophobic porous membrane with a composite film containing a dense polyamide layer, a cation exchange layer (CEL), and an anion exchange layer (AEL). When used in direct contact MD for treating a 100 g L-1 NaCl hypersaline solution, the membrane achieves supersaturation of feed solution and a salt crystal yield of 38.0%, with the permeate concentration at <5 mg L-1. The composite membrane also demonstrates ultrahigh antiwetting stability in 360 h of long-term operation. Moreover, ion diffusion analysis reveals that the ultrahigh wetting resistance of the composite membrane is attributed to the bipolar AEL and CEL that eliminate ion crossover. The literature review elucidates that the composite membrane is superior to state-of-the-art membranes. This study demonstrates the great potential of the composite membrane for direct crystallization of hypersaline water, offering a promising approach to filling the gap between reverse osmosis and conventional thermal desalination processes for ZLD application.

Zero liquid discharge management: optimizing sustainable reverse osmosis desalination practices

This study introduces a Zero Liquid Discharge (ZLD) scheme for Reverse Osmosis (RO) desalination, integrating ultra-filtration pretreatment and Electrodialysis (ED) for brine concentration. The scheme divides brine reject into fractions, directing them to an electrolyser and evaporator powered by renewable energy sources. Notable findings include the treatment plant's capability to produce 792 cubic meters of fresh water daily, while decreasing salt concentration from 4,660 ppm to 30 ppm, showcasing efficient desalination. Additionally, recycling fractions of RO unit waste to various components enhances resource efficiency. The study highlights the daily production of 2,269.27 kg of hydrogen, coupled with minimal electricity consumption of 74,885.91 kWh, thereby improving overall energy efficiency. Furthermore, the utilization of solar energy significantly reduces reliance on fossil fuels, thereby promoting sustainability and mitigating the environmental impacts associated with traditional energy sources. Solar energy is a clean, renewable resource that helps decrease greenhouse gas emissions and other pollutants, contributing to cleaner air and a healthier planet. This shift towards renewable energy is crucial in addressing climate change and ensuring a sustainable future for generations to come. In the context of desalination, emphasizing environmental preservation and water security is paramount. Desalination processes, while providing essential fresh water in arid regions, often produce brine as a byproduct. The brine, with a high salt concentration of 13,648 ppm, poses a disposal challenge that can negatively impact marine ecosystems if not managed properly. This is where Zero Liquid Discharge (ZLD) systems come into play. With a ZLD index of 2.7%, these systems ensure that all wastewater is treated and reused, leaving no liquid waste behind. ZLD technology captures and recycles every drop of water, converting waste into reusable resources, thus minimizing environmental harm. The model showcased a significant decrease in brackish water extraction from 1,200 cubic meters per day to 871.52 cubic meters per day, marking a notable 27% reduction. These results highlight the promising effectiveness of the proposed ZLD scheme in enhancing the efficiency of brackish water treatment, demonstrating its potential to significantly reduce the demand for fresh water resources while achieving sustainable desalination practices. This article will present a detailed yet a simple description of reverse osmosis and ZLD, how do they correlate and how these two technologies represent the future of water treatment.

A zero-liquid discharge process to recover all critical metals from spent NCM111 cathode material of end-of-life lithium-ion batteries: statistically optimized leaching with formic acid and in-situ crystallization

A green chemistry process has been developed to recycle cathode material from end-of-life lithium ion batteries. NCM111 (LiNi1/3Co1/3Mn1/3O2) was completely leached with 13 M formic acid to produce two groups of salts with different solubilities: sparingly soluble cobalt, manganese, and nickel (CMN) formates and highly soluble lithium formate. During leaching, CMN formate salts exceeded their solubility limit in the pregnant leach solution (PLS) and crystallized. Mixed CMN formate salts were recovered by filtering the PLS. Lithium was completely recovered by evaporating the filtered PLS then thermally decomposing the lithium formate obtained in air to lithium carbonate. The purity of the lithium carbonate was 98.1 wt%.The leaching process was optimized through response surface methodology experiments. The minimum time required to completely leach NCM111 with 13 M formic acid was 30.8 h. Optimum leaching conditions were L/S = 2.81 mL/g (equivalent to S/L = 356 g/L) and T = 95 °C. During leaching, 98% of CMN formate salts exceeded their solubility limit and crystallized from the PLS.The recycling process is simple and generates no liquid or solid waste products. The only reagent is 13 M formic acid. The only by-products are water vapour, which can be condensed and reused, and carbon dioxide gas.

Model-based zero liquid discharge desalination for land-locked arid/semi-arid regions in India

The arid and semiarid regions usually are water-stressed. The available natural groundwater resources in these areas are, at times, saline and unfit for potable use. Desalination of saline water is a possible solution in such cases. However, discharge of concentrated brine is an issue, particularly in land-locked areas. In this regard, a case study has been presented for brackish water desalination in Western Rajasthan, India. As this is a land-locked desert area, zero liquid discharge (ZLD) desalination has been considered, offering a practical and sustainable solution. This study presents a novel approach to the model-based ZLD hybrid desalination system consisting of reverse osmosis and multi-effect distillation (RO-MED) systems producing drinking quality water and common salt. The simultaneous production of common salt has the potential to bring down the cost of drinking water produced by the system. A system design has been carried out for a real case based on the raw water analysis of groundwater in Western Rajasthan. Our hybrid (RO-MED-ZLD) model results indicate that RO reduced TDS from 4419 mg/l to 22 mg/l with a 67 % recovery rate. The proposed ZLD method recovers 93 % of salt crystals from MED brine solutions, potentially reaching 99 % with adjustments.

Mineral scaling and organic fouling in electrodialytic crystallization

The management of hypersaline brine is a critical challenge to achieving a circular water economy. Traditional brine treatment technologies mainly rely on thermal evaporation, which requires intensive energy, cost, and/or areal footprint. Electrodialytic crystallization (EDC) has been recently developed as a novel process that enables brine crystallization without evaporation. However, the potential effects of mineral scaling and organic fouling on the performance of EDC have not been revealed. In this study, we systematically investigated mineral scaling and organic fouling in EDC. We demonstrate that the ion transport and crystallization efficiencies of EDC are generally unaffected by a variety of mineral scalants and organic foulants, despite an increase of energy consumption in the presence of humic acid. Further, EDC is shown to be less susceptible to gypsum scaling than RO, mainly due to the difference in concentration polarization between these two membrane processes. To mitigate gypsum scaling in an assumptive EDC-RO treatment train towards zero liquid discharge (ZLD), polyacrylic acid (PAA) is employed as an antiscalant that prevents gypsum scaling in RO while not adversely affecting EDC performance at relatively low concentration. Our study unravels the behaviors of EDC when treating feedwater with high scaling and fouling potentials, providing valuable insights for understanding mineral scaling and organic fouling when applying an ED-based technology for hypersaline brine treatment towards ZLD.

Anaerobic biodegradation enables zero liquid discharge of two-stage nanofiltration system for microelectronic wastewater treatment

Nanofiltration (NF) is a promising technology in the treatment of microelectronic wastewater. However, the treatment of concentrate derived from NF system remains a substantial technical challenge, impeding the achievement of the zero liquid discharge (ZLD) goal in microelectronic wastewater industries. Herein, a ZLD system, coupling a two-stage NF technology with anaerobic biotechnology was proposed for the treatment of tetramethylammonium hydroxide (TMAH)-contained microelectronic wastewater. The two-stage NF system exhibited favorable efficacy in the removal of conductivity (96 %), total organic carbon (TOC, 90 %), and TMAH (96 %) from microelectronic wastewater. The membrane fouling of this system was dominated by organic fouling, with the second stage NF membrane experiencing a more serious fouling compared to the first stage membrane. The anaerobic biotechnology achieved a near-complete removal of TMAH and an 80 % reduction in TOC for the first stage NF concentrate. Methyloversatilis was the key genus involved in the anaerobic treatment of the microelectronic wastewater concentrate. Specific genes, including dmd-tmd, mtbA, mttB and mttC were identified as significant players in mediating the dehydrogenase and methyl transfer pathways during the process of TMAH biodegradation. This study highlights the potential of anaerobic biodegradation to achieve ZLD in the treatment of TMAH-contained microelectronic wastewater by NF system.

Sustainable brine management: Unlocking magnesium and calcium for improved carbonation in the modified Solvay process

The extensive utilization of Reverse Osmosis (RO) in water desalination has led to the production of high-salinity brine, which poses significant environmental and societal challenges. This study presents an effective approach for the recovery of calcium and magnesium from real local RO brine. This method, serving as the initial step in a multi-treatment process, aims to efficiently manage brine and mitigate CO2 emission. Experimental outcomes demonstrate that a decarbonization pre-treatment, achieved through acidification, utilizes a near-stoichiometric ratio of sodium hydroxide to magnesium (2:1). This process, along with gradual addition of alkaline solution and adequate settling time, effectively removes more than 98 % of magnesium. Additionally, it precipitates high-purity magnesium hydroxide solids with large particles sizes (193.6 µm). In the subsequent soda ash stage, more than 97 % of calcium is successfully removed, yielding calcium carbonate with 95 % purity. Preliminary assessments of revenue generated from these products offer economic justifications for Zero Liquid Discharge implementation. Furthermore, Aspen Plus simulation for the carbonation process using the modified Solvay process revealed the significant benefits of the pretreatment process. This enhances sodium conversion efficiency, improves the production of sodium bicarbonate, and reduces impurities. These findings underscore the importance of Ca2+ and Mg2+ separation steps in improving the carbonation process.

The Scenario of Groundwater Pollution after Implementation of Zero Liquid Discharge: An Agricultural Economic Perspective

Groundwater pollution is hard to remediate in the Noyyal river region even after the implementation of Zero Liquid Discharge process. Hence, to study the status and extent of groundwater pollution in the Noyyal river region, Tiruppur district of Tamil Nadu was purposively selected and classified into 3 regions based on the distance from the river and 120 farms were selected. Tools of analysis viz., Cost benefit analysis, Resource use efficiency and decomposition analysis were undertaken to study the status of groundwater pollution and its effect on agriculture. The results showed that intensity and severity of pollution is high in the region closer to Noyyal river (less than 1 km). Income from agriculture is also low in that region due to the use of polluted groundwater for irrigation. The study revealed that Zero Liquid Discharge ensures stoppage of industrial effluents into the river and hence, river pollution is stopped. Similarly, a suitable policy is required to revamp groundwater. Hence, the suggested policy includes water storage structures like tanks, lakes, ponds etc are to be used for groundwater recharge purpose alone.