Abstract

Brine (saline wastewater) from desalination and industrial activities has received a lot of attention around the world due to its potential adverse impact on the environment and difficulty and expense to manage properly. Currently, several disposal methods have been applied; however, these methods are nowadays unsustainable. To tackle this problem, brine treatment and valorization is a promising strategy to eliminate brine discharge and recover valuable resources such as water, minerals, salts, metals, and energy. Brine valorization and resource recovery can be achieved via minimal and zero liquid discharge (MLD & ZLD) approaches. Commercially successful technologies such as reverse osmosis (RO) and distillation cannot be adopted as standalone technologies due to technical and other practical restrictions (e.g., high-energy/corrosion). New and emerging membrane, electrochemical and thermal technologies are starting to make brine valorization more practical. The extraction of specific ions from brines is technically feasible. The minerals/salts composed of major ions (i.e., Na+, Cl−, Mg2+, Ca2+) can be useful in a variety of sectors, and their sale prices are reasonable. On the other hand, the extraction of scarce metals such as lithium, rubidium, and cesium can be extremely profitable as their sale prices are much higher compared to the sale prices of common salts. The extraction of such precious metals is currently restricted to laboratory scale. The MLD/ZLD systems have high energy consumption and thus are associated with high greenhouse gas (GHG) emissions as fossil fuels are commonly burned to produce the required energy. To establish a CO2-free and circular global economy, intensive research and development efforts should continue to be directed toward brine valorization and resource recovery using MLD/ZLD systems.

In this article Brine Valorization processes are discussed in detail.

Introduction

Brine, the concentrated saline by-product of desalination and various industrial processes, is increasingly recognized as both an environmental challenge and a resource opportunity. Traditionally, brine disposal methods have been costly and unsustainable, raising concerns about ecological impacts and long-term feasibility. In response, brine valorization has emerged as a promising strategy that transforms waste into value by recovering water, salts, minerals, and even critical metals. Leveraging advanced membrane, electrochemical, and hybrid technologies, brine valorization supports circular economy principles while offering pathways to resource efficiency, cost reduction, and new economic opportunities. This article explores the processes, technologies, benefits, and challenges of brine valorization for industry and society.

Brine Valorization

Brine is a by-product of desalination and contains concentrated salt and other minerals. Developing technologies that can effectively manage and minimize brine discharge is crucial to mitigate environmental impacts in the receiving waters.

While these goals are commendable, achieving the most favorable outcomes on a large scale may be challenging.

Eliminating brine discharge entirely is a complex task as brine disposal remains a major challenge for desalination plants and the mass load of brine salts is very large.

Extracting valuable materials or resources from the brine generated during desalination or other water treatment processes helps to minimize waste and maximize the utilization of otherwise lost resources. This approach aligns with the principles of a circular economy and sustainable resource management.

Various process configurations for brine valorization are

1. Conventional Process: Incorporates thermal evaporation and
2. Modern Membrane-Based Process: Utilizes innovative technologies like Nanofiltration (NF) and Osmotically Assisted Reverse Osmosis (OARO).
3. Optimized Hybrid Process: Combines dual precipitation steps, membrane separation, and internal brine recycling.

Conventional Process Flow Steps:

• Pretreatment: Removes suspended solids and oil and grease to protect downstream equipment.
• SWRO: Produces brine of desired total dissolved solids (TDS) with substantial water recovery.
• Thermal Evaporator: Concentrates brine to higher
• Precipitation of scaling salts: Reduces scaling risks in the
• Crystallizer: Recovers desired products, leaving residual brine of very high

Modern Process Flow Steps:

• Pretreatment: Removes particulates, oil and grease and other dissolved organics, and possibly macronutrients and prepares feedwater.
• NF (Upstream): Separates divalent ions (Ca²⁺, Mg²⁺ and other trace ions) from main brine stream.

• SWRO: Produces brine at elevated TDS with reduced scaling risks (if NF is used upstream).
• OARO: Concentrates brine to higher TDS, approaching saturated
• Precipitation of scaling salts: Removes residual scaling ions post-
• Crystallizer: Recovers desired products, leaving residual brine of high

Hybrid Process Flow Steps:

• Pretreatment: Removes particulates and biofouling
• SWRO: Produces brine at certain TDS, with substantial water
• CaCO₃ Precipitation: Removes calcium carbonate to mitigate scaling risks in downstream processes.
• NF (Downstream): Reduces divalent ion
• OARO: Concentrates brine to high
• Precipitation of scaling salts: Further reduces scaling risks before
• Crystallizer: Recovers desired products, leaving residual brine of high
• Internal Recycling: Returns processed NF brine to SWRO feed, reducing intake volumes by ~10–15% and lowering intake CAPEX.

There are several steps and challenges that come into play in these brine valorization applications:

• Brine conditioning/pretreatment – addressing impurities (such as organics, hardness, ) that may harm sensitive downstream processes, impede reliable performance, or contaminate end products they otherwise would report to
• Salt splitting – separating monovalent from polyvalent ions… and then selectively/progressively segregating the ions of value being targeted from one or both of these streams

• Production/refining – reacting the segregated ions to produce the desired marketable products, at the purity and with the required physical properties
• Brine concentration – removal of excess water to increase product concentration of products, improve the economics of producing dry products or reducing disposal volumes
• Waste management – handling of non-valuable waste salts and dilute streams

There are a host of membrane, chemical/physical, ion exchange, solvent extraction, and thermal process strategies to accomplish these. Just within the membrane area, nanofiltration is very effective at the monovalent/polyvalent salt splitting. Configurations such as Osmosis-Assisted Reverse Osmosis (OARO), Counter Flow Reverse Osmosis (CFRO), Closed Circuit Reverse Osmosis (CCRO), (variants of nanofiltration and reverse osmosis) can be used to cost

effectively concentrate and speciate brines and products. Electrolytic processes coupled with membranes such as Electrodeionization (EDI), Bipolar

Electrodialysis (BPED), Electrodialysis brine concentrator (EDBC),

Electrodialysis Metathesis (EDM) are also gaining traction to help select, purify, and concentrate valuable products from the parent brine resource.

There are other challenges/constraints with these products, such as access to electricity/thermal energy required to drive the processes, dealing with non-monetizable ancillary streams/wastes, access to markets, cost competitiveness (given the energy and process mechanical intensity of these systems) relative to traditional sources (i.e., mined material or materials produced in solar ponds).

Brine valorization has several specific benefits for the desalination sector:

• Waste reduction: Instead of disposing of the brine as a waste product, brine valorization helps minimize waste and promotes a more sustainable approach to
• Supply chain resiliency: As an example, some industries are evaluating producing sodium chloride on-site from seawater to feed chloralkali and soda ash production rather than importing it from abroad.
• Resource efficiency: By extracting valuable materials from the brine, brine valorization maximizes the utilization of the available resources, contributing to resource efficiency and reducing the need for extraction from other sources.
• Economic opportunities: Brine valorization can create economic opportunities by turning the brine into valuable products. It can generate new industries, employment, and revenue streams associated with the recovery and utilization of extracted materials.
• Environmental impact: By minimizing brine discharge and extracting valuable resources, brine valorization reduces the environmental impact of desalination processes by improving water production efficiency and minimizing waste

Brine valorization is an area of active research and development, with ongoing efforts to improve the efficiency, scalability, and viability of various valorization techniques. It has the potential to transform the desalination sector into a more sustainable and resource- efficient industry, contributing to circular economy principles and addressing the environmental challenges associated with water treatment processes.

The process of extracting valuable materials from brine generated during desalination also brings broader economic benefits:

• Revenue generation: Brine valorization can create new revenue streams for desalination By extracting valuable materials from brine, such as salt,

metals, minerals, or chemicals, these resources can be sold in the market, generating additional income for the desalination facility.

• Cost reduction: Brine disposal is a significant cost for desalination plants. Instead of treating and discharging brine, valorization allows for the recovery of valuable materials, which can offset the costs associated with brine management and disposal. This can contribute to overall cost reduction and improve the economic feasibility of desalination projects.
• Resource conservation: Brine valorization promotes the efficient use of resources. Recovering valuable components from brine, such as metals or minerals, reduces the need for traditional resource extraction methods, such as mining. This can lead to cost savings and reduced environmental impacts associated with resource extraction.
• Job creation and local economic development: Brine valorization can create employment opportunities and contribute to local economic development. The establishment of brine valorization facilities and associated industries can create jobs in areas such as research and development, technology deployment, resource extraction, manufacturing, and marketing.
• Diversification of industries: Brine valorization can stimulate the growth of new industries or the expansion of existing ones. The recovered materials can be used in various sectors, such as chemical production, agriculture, manufacturing, and energy storage. This diversification can enhance regional or national economies by fostering innovation, attracting investments, and reducing dependence on traditional sectors.
• Enhanced sustainability credentials: Brine valorization aligns with sustainability goals by reducing waste generation and promoting circular economy Industries and companies that implement brine valorization practices can improve their sustainability credentials, which can enhance their reputation and competitiveness in the market.

The economic benefits of brine valorization can vary depending on factors such as the concentration and composition of the brine, the technological processes involved,

market demand for the recovered materials, and the cost of extraction and purification technologies. Additionally, the economic viability of brine valorization projects will depend on many factors including scale, infrastructure requirements, and regional market conditions. Ideally, a technoeconomic feasibility study should evaluate the

complete integrated process and business case and compare valorization against next- worst disposal options. It may be worthwhile to produce/sell intermediates at some loss to facilitate valorization of higher value co-products down the value chain.

Conclusion

The management and valorization of brine is becoming increasingly important in the water/wastewater treatment sector. Brine production is a global industry, including brackish water & seawater desalination plants, pharmaceutical industries, textile industries, oil & gas industries etc. By turning a waste stream into a valuable resource, brine valorization has the potential to generate economic value, reduce costs, promote sustainable practices, and contribute to local and regional economic development.

Rajendra Kamat (BE Chemical Engg) has 37 years of experience in the field of Process Engineering C Engineering Management. He is working as Senior Director Engineering at Worley Cluster 3 (NEH Mumbai C Vadodara). He has been involved in Proposal, FEED, BEDP and Detail engineering of various Refinery, Petrochemical, Chemical, Fertilizer, Utilities C offsite projects.

Pramod Kulkarni (BE Chemical Engg) has 31 years of experience in the field of Process Design and engineering. He is working as Head of Overall Process Department (Process, DHSE C Commissioning) at Worley NEH Mumbai. He has been involved in Proposal, FEED, BEDP, and Detail engineering of various Refinery, Petrochemical, Chemical, Fertilizer, Utilities C offsite projects.