RO Brine Treatment: Why Maximizing Reverse Osmosis Recovery Matters

A photo of a bank of reverse osmosis units at a public water utility plant.

RO Brine Treatment: Why Maximizing Reverse Osmosis Recovery Matters

Jun 27^th 2018

Treating RO brine should be approached from two directions. First, maximize the recovery of lower cost membrane systems to minimize the volume for later steps. Second, weigh brine disposal options against thermal treatment technology to determine whether you need to concentrate your brine or treat it down to solids.

Reverse osmosis (RO) is the most widely used saline wastewater treatment technology for a good reason: it is a cost-effective option for removing contaminants from water. This article will touch on how to minimize and manage RO concentrated brine.

Download a Free Periodic Table of Scaling Compounds

Key Takeaways

RO is highly effective and low cost, if correctly implemented.
Start with a detailed water chemistry analysis and try to capture variability in high and low flow.
Design a flexible treatment process that maximizes RO system recovery while avoiding scaling and fouling, and maximizing performance and reliability.
You can often treat saturated RO brine further with intelligent membrane systems, by removing scaling ions and using RO for a second time.
Evaluate your brine disposal options and complete a cost trade-off assessment for each one.
Look ahead to a future where your brine disposal options could change, and plan for those possible changes.
Contact Saltworks if you need help with any of the above.

Start with the Fundamentals: What is Your Water Chemistry?

Getting the most out of an RO system is easier when you are equipped with a comprehensive analysis of your water chemistry. This will provide essential information for the design stages, such as your scaling ions, and prepare you for any treatment challenges. Take samples during periods of high, low and normal flow and send them to a water analysis lab or to our analysis team to get help with understanding the range in your water chemistry.

Stop Fouling & Scaling on RO Membranes Before It Starts

With your water chemistry analysis in hand, devise a treatment strategy that prevents performance reductions from scaling or fouling. If scaling ions are ignored, your RO could rapidly scale or operate at low recovery, leaving performance on the table. If you plan for scaling ions, RO can be extremely reliable and optimized for performance. There are solutions for removing scaling ions. These range from the simple, such as pH control and anti-scalants, to more advanced solutions, such as selective removal of scaling ions and live monitoring of RO-normalized flux.

Choose an RO System that Can Achieve Your Performance Targets

Not all RO systems are created equally. Many factors can affect the potential recovery in your treatment process, which include:

Process controls and intelligence to monitor and correct performance: If water chemistry varies, the RO performance should also be adjusted. Do not ‘set and forget’ your RO system.
Concentrating, purging, and flushing cycles to wash away any scaling or fouling before it becomes irreversible.
Clean-in-place systems, matched to your water chemistry.
Recovery demands, which will determine pressure.
Potential accumulation of organics.

When you consider building an RO system, consult with water treatment experts who can help you determine the setup that is best suited to your needs. While RO is widely available in low cost systems, and these systems may fit your application, there are really only two categories of RO: basic and advanced. Basic RO works well for simple waters but breaks down rapidly when pushing brine concentrations. Advanced RO can push limits without compromising performance. Only pay for advanced performance if you need it, such as when you require brine volume reduction and high recovery.

It is important to factor in the costs of downstream treatment or disposal technologies as well as upstream pre-treatment when making your business decision to invest in an RO plant.

Maximize RO System Recovery Before Looking to Thermal Systems

The priority for some RO system operators is to minimize the brine volume they must treat or dispose. Treating concentrated RO brine to reduce the disposal volume further or produce zero liquid discharge solids can substantially increase capital and operating costs and requires equipment with a larger physical footprint, such as evaporators and crystallizers.

Often, concentration of RO brine is limited by scaling compounds, such as CaSO₄ or SiO₂ and other low-solubility compounds. If these scaling compounds are removed, or separated, the recovery of membrane systems can increase and reduce the volume of brine.

To reach the highest concentration levels with your RO brine, trust intelligent chemical softening systems like Saltworks’ BrineRefine. Most RO systems will hit their treatment limits near 50,000 mg/L total dissolved solids (TDS). BrineRefine removes scaling ions from the water, and enables the use of ultra-high pressure RO systems, which can reach up to 130,000 mg/L TDS brine concentrations.

Another option to maximize brine concentration is through selective ion removal with electrodialysis reversal (EDR), which can concentrate brines up to 180,000 mg/L TDS.

Trust Intelligent Automation Over Manual Management

The most advanced RO systems offer automation and systems controls that can adapt to changing water chemistries. One example is automated flux control—an intelligent RO that will increase or decrease permeate flux as it detects changes in scaling compounds. This will minimize fouling in the presence of high concentrations of scaling ions and maximize recovery when concentrations are low.

If you choose to use an RO system that requires more monitoring and manual performance adjustments, be prepared to invest more in maintenance and operating costs over the long run.

Evaluate Your Brine Disposal Options

Regardless of the RO system you choose, the concentrated RO brine needs to be managed via disposal or further treatment. There are a range of brine disposal options and their availability will depend on a variety of factors. If your brine disposal pathways are limited or cost-prohibitive, your next option is to evaluate further concentrating your brine using thermal treatment systems.

Plan Your Process with Downstream Thermal Systems in Mind

Concentrating RO brine even further requires thermal systems, such as evaporators or crystallizers. Although they cost more than RO systems, thermal systems can reduce RO brine to zero liquid discharge solids. Maximizing upstream RO recovery will minimize the size and operating cost of your thermal treatment steps.

This can be done by using a treatment strategy that minimizes the use of chemical pre-treatment; any chemicals added upstream in a treatment process will cause greater impacts on overall economics further downstream. You can avoid adding chemicals by choosing treatment technologies that do not rely on extensive pre-treatment, such as intelligent RO systems or EDR with membranes that resist organics. Alternatively, you can use BrineRefine’s intelligent chemical softening for precise dosing to both prevent scaling and avoid chemical overdosing.

Treating RO Brine: To Concentrate or To Crystallize?

The options for treating RO brine depend on whether you need zero liquid discharge or a reduction in brine volume. Download our infographic to further explore the roles of different treatment technologies for brine.

If you do not have a disposal outlet available or disposal costs more than $20/m³, concentrating brine with an industrial evaporator can offer advantages. Crystallization is usually the most expensive step in a water treatment train and should only be considered if you need to produce solids, or face disposal costs higher than $40/m³.

Look to the Future: A Rising Tide of Brine Treatment Regulations

As increasing focus is placed on water, have you considered making your treatment facility future-proof before investing? Evaluating and building in options for expansion and change are low cost while still at the drawing board. Your brine disposal costs could increase if you use a third party, you may require additional capacity, your water could change as a result of upstream production, or you may need to meet new regulatory targets.

To reduce future risks that might arise from such changes, evaluate your options and future scenarios before making an investment. Reach out to the water treatment experts at Saltworks.

About Saltworks

Saltworks Technologies is a leader in the development and delivery of solutions for industrial wastewater treatment and lithium refining. By working with customers to understand their unique challenges and focusing on continuous innovation, Saltworks’ solutions provide best-in-class performance and reliability. From its headquarters in Richmond, BC, Canada, Saltworks’ team designs, builds, and operates full-scale plants, and offers comprehensive onsite and offsite testing services with its fleet of mobile pilots.

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Treating SAGD Blowdown with the SaltMaker MultiEffect Evaporator Crystallizer

Photo of a SaltMaker evaporator crystallizer used in SAGD applications

Saltworks » Article » Page 4

Treating SAGD Blowdown With the SaltMaker MultiEffect Evaporator Crystallizer

May 4^th 2023

Steam assisted gravity drainage (SAGD) blowdown water from three operating sites was treated using Saltworks’ SaltMaker MultiEffect Evaporator Crystallizer. The energy-efficient treatment system reduces the cost of blowdown transport and disposal. MultiEffect produces a low-volume solid that can be disposed of at a Class II landfill and recovers freshwater for reuse.

SAGD and Blowdown Water Management Issues

SAGD is an enhanced oil recovery process that uses injected steam to reduce bitumen viscosity and increase oil production. This process generates produced water alongside oil production and recycles the water as much as possible before ‘blowdown’ is required. Blowdown purges dissolved solids and organics from the SAGD water balance so they do not accumulate to a detrimental level in the recovery process. The majority of SAGD operators dispose their blowdown waters in deep wells and withdraw fresh or slightly saline water to make up the loss. Increasingly, operators truck their blowdown water to deep wells, resulting in high operating costs and associated environmental impacts.

Blowdown management can be the second largest cost of production, after natural gas usage to generate steam. As a result, operators are seeking onsite solutions for treating blowdown water to remove freshwater from the blowdown for re-use, and condense all waste to solids for safer and lower cost disposal in certified landfills. Conventional crystallizer systems have been trialed with limited success due to plugging from the highly saturated mixed ionic-organic chemistry, high energy demands, and the requirement for a gas fired drier to complete the final solids production.

Dealing With SAGD Blowdown: SaltMaker MultiEffect Evaporator Crystallizer

Saltworks’ SaltMaker MultiEffect was proven to reliably treat SAGD blowdown to recover freshwater for reuse and produce solids suitable for disposal in Class II (non-hazardous) landfills. Both Once Through Steam Generator (OTSG) and evaporator blowdown were successfully trialed with four active SAGD operators.

SaltMaker MultiEffect is a low-temperature crystallizer (<90°C) that was designed from the ground up to treat and produce solids from the toughest waters. The zero liquid discharge system uses low-grade waste heat in multiple effects to reduce energy consumption and operating costs. Since there is no steam in the process, steam ticketed operators and time-consuming certifications are not required during installation and maintenance.

The SaltMaker MultiEffect uses humidification-dehumidification (HDH) principles for low-temperature operation and provides three fundamental design benefits at the expense of footprint: (1) process components are built from engineered plastics that remove concerns for corrosion and scaling/fouling; (2) high circulation rates provide a scouring effect on highly saturated flows; and (3) sensible heat transfer occurs in place of boiling, which removes troublesome tube scaling.

Also, full automation and intelligent cleaning operations built into the SaltMaker MultiEffect measure scaling potential and initiate automated cleaning cycles prior to irreversible scaling. The modular design is based on ISO shipping container blocks for low-cost and rapid dispatch, installation, and expansion. Modules can be slid in and out for simple inspection without confined spaces. A standard S125 SaltMaker MultiEffect has a capacity to remove 125 m³/day of water. Higher capacities are achieved by adding more S125 plant blocks.

Results of Four SAGD Evaporator Blowdown Treatment Pilots

Three different sources of SAGD evaporator blowdown were tested, alongside one source of OTSG blowdown. The testing included a 60-day onsite pilot test at a SAGD facility in Fort McMurray in the middle of winter. All SaltMaker MultiEffect pilot tests operated reliably, 24/7.

Saltworks’ patented non-scaling design and self-cleaning systems were paramount to operations. In addition, when coupled with the SaltMaker MultiEffect’s patented system for low-temperature solids production and extraction, the plant solved a major SAGD problem: continuous solidification and extraction of both ionic and organic components that prevents accumulation and results in gelling or plugging of conventional systems.

The project results are as follows:

High quality freshwater recovered (<500 mg/L TDS).
Continuous, reliable production and extraction of solids. Analytical tests demonstrated that solids met applicable requirements (e.g., paint filter test, leachable metals, BTEX, pH, and flashpoint) for disposal at a non-hazardous Class II landfill.
Reliable operation and non-scaling/no-plugging with automated self-cleaning, confirmed by complete plant autopsies after each trail.
Recycling of the heat through multiple effects for energy efficiency.

The pilot projects demonstrated that the SaltMaker MultiEffect reliably and efficiently recovers freshwater and produces solids from SAGD blowdown waters. Saltworks can complete a SaltMaker performance and economic assessment of your blowdown water treatment project. Contact us today to get started on your project.

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Buying an Industrial Evaporator? Ask Vendors These Five Questions

Photo of a multiple effect evaporator - Photo © Evelyn Simak (cc-by-sa/2.0)

Saltworks » Article » Page 4

Buying an Industrial Evaporator? Ask Vendors These Five Questions

Apr 6^th 2018

Before investing in an industrial evaporator for your water treatment applications, lower your risks by asking any vendor the following five questions, which cover key topics such as brine disposal, scale prevention, and cost of ownership.

1. Can you prove evaporator performance through a pilot at my site and provide a performance guarantee that covers changes in water chemistry?

Before investing in a full-scale plant, a small investment in a site pilot will pay off in a matter of months. For unique chemistries, pilots enable you to optimize costs, develop lessons learned, and ensure you have the correct treatment train. This prevents costly changes after full-scale installation start-ups. Ask a vendor how they pilot test, and if they can pilot at your site. Nothing beats operating on live water chemistry that changes along with your operations.

It is easy for vendors to make a process work behind closed doors or for a short period of time. Ask the vendor to show you how the process runs with variability in inlet conditions, prove that the machine is not scaling over time, and show you a mass balance of all inputs and outputs. Pilots are also an excellent means to test delivery, technical trust, and safety performance of your vendor.

Another tool to protect your investment is a well-written performance guarantee. It will provide a minimum capacity on which you can base your investment decision. Beware of the commonly used simple form, which has plagued many operators in the past, that references guarantees to a single chemistry data set. Your chemistry will change, and when it does, these guarantees can become invalid. Ensure that your performance guarantee accepts wide swings in water chemistry.

At Saltworks, we operate a fleet of mobile and stationary pilots. We also write performance guarantees that remain valid over your broad range of operating conditions.

2. How can I lower the total cost of ownership of my evaporator plant?

Ensure that you have reviewed opportunities for system optimization that will reduce either your capital or operating expenses. By this, we mean pre-concentration with lower cost technologies before an evaporator, and consideration of incremental cost-value trade-offs of increasing brine concentration. For example, if your TDS is below 80,000 mg/L, with a flow rate above 200 m³/day, ask about pre-concentration technologies.

Saltworks’ experts can help you with this. Modern membrane concentrators, such as our XtremeRO, can concentrate up to 130,000 mg/L, saving evaporator capacity and energy costs. However, if your flows are less than 200 m³/day, having two process plants may not make sense. Instead, it may be worth investing in a slightly larger evaporator.

In addition, you should clearly understand any chemical pre-treatment and the costs per unit inlet. Some vendors will throw a lot of chemicals at the inlet via extensive softening to make conditions easier on their evaporator. Since the chemical costs are included in your operating costs and not in the evaporator’s sale price, vendors can make their evaporator appear at a lower cost, when in fact its total cost of ownership could be much higher than originally anticipated.

At Saltworks, we like to break down the costs per unit inlet ($/m³) into four categories—capital, energy, chemicals, and labor—so that you can see where the costs go.

We work with clients to understand their goals, and cost drivers. We will then run an analysis to project out a cost-optimized treatment train that can inform the total cost of ownership.

3. How do you prevent corrosion and scaling?

Corrosion and scaling are endemic challenges that face evaporator operators. Corrosion and scaling start by suppressing capacity and increasing energy consumption, but can then lead to much downtime and maintenance. Designing for corrosion and scale is essential from day zero, so ask your vendor what they do to prevent these culprits.

Our answer to corrosion is to not build everything from titanium or exotic steels—alternative methods exist.

For instance, Saltworks’ SaltMaker family of systems provides such alternatives through smart engineering, with fiber-reinforced plastics. Our answer to scale is to avoid extensive chemical softening of the feed that adds operating costs. The SaltMaker family provides a non-chemical pre-treatment option through non-scaling design and built-in self-cleaning. We design for an evaporator plant to clean itself as it operates, rather than to suffer decaying performance and then complete an annual shutdown that requires significant manual labor for scale removal. Instead, we recommend that you clean as you treat. Read our article on minimizing minimize scale to learn more.

4. What volume reduction can I expect and how do I manage the discharge or reject?

Dealing with discharged reject brine or solids is an important topic and you should evaluate all of your brine disposal options before undertaking an industrial wastewater evaporator project. Explore the change in volume from your input and output streams, then make sure you build a plan to deal with the discharge that conforms with any environmental regulations. Also, evaluate the cost of any brine disposal options and compare them to the costs of further treatment with a crystallizer to produce solids.

Crystallizers offer the option of producing zero liquid discharge solids, rather than concentrated wastewater, that may be better suited to your project needs. In other cases, transporting or handling a liquid slurry that can be pumped, rather than solids, may be preferable. Hybrid evaporator-crystallizer technologies offer the advantage of adaptability to produce either brine or solids in a single plant, and can be upgraded to suit future treatment needs. One example of this kind of technology is the SaltMaker Evaporator Crystallizer, which can reliably operate as an evaporator or crystallizer, with built-in solids management.

Ask the vendor for their recommendations and insights for reject disposal. At Saltworks, we have helped clients source low-cost disposal options and proven safe disposal during pilots. If you pilot, ensure that you see your rejects disposed of via the same mechanism that is intended at full scale. Too often, people wait until their full-scale plants are almost built before considering residual disposal. Start with the final disposal in mind, as it could govern your economics.

5. Can you provide clear maintenance, operation, and operating cost expectations, and can I visit a reference installation and speak to one of your existing customers?

Know what you are getting into before you invest in an industrial evaporator. Running evaporators requires energy, people, attention, and chemicals. It also requires more management than membrane system assets. Ask vendors to paint a complete picture of installation and operating costs for you, and question every aspect deeply. There is nothing better than visiting an existing installation and talking to operators to secure the full picture.

Coupling site visits with analyzing the full cost of ownership, including trialing a pilot, will set help set up your project for success.

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Saltworks » Article » Page 4

Implementing an Evaporator Crystallizer Plant: What Sets the SaltMaker Apart?

Apr 6^th 2018

The SaltMaker MultiEffect evaporator crystallizer is a one-step brine treatment plant for volume minimization and zero liquid discharge (ZLD) applications. Its unique evaporative crystallizer design is built to treat the toughest waters and to simplify your brine treatment project.

Key Takeaways

The SaltMaker MultiEffect overcomes challenges that face conventional crystallizers:

Reliable solids production: A circulating slurry continuously forms and grows crystals. Solid salt is discharged to an automated bagging or binning system.
One-step treatment: No pre-treatment required. For ZLD applications, solids are produced without the need for extra process equipment, such as centrifuges or filter presses.
Resists corrosion, plugging, and scaling: High circulation rates, constantly changing saturation gradients, and non-corroding, non-stick wetted surfaces prevent reliability challenges that plague conventional crystallizers
Intelligent automation and self-cleaning: The plant has automated start, stop, and hibernate for immediate ramping from 0 to 25% capacity in one step. It operates at any capacity between 25% to 100% in dynamic capacity control mode and will detect and initiate cleaning cycles.
No single point of failure: The SaltMaker is built from redundant process sets. Even with the loss of one process set during maintenance, the plant keeps running at 92% capacity.
Modular build and scale-up: The plant is built inside ISO container frame modules for ease of delivery, installation, and expansion to suit growing project capacity needs by adding process blocks.
Low-temperature air humidification-dehumidification: The SaltMaker operates with an air cycle humidification-dehumidification process (< 90^oC), which avoids the use of pressure vessels and enables its construction from fiber reinforced plastics that withstand severely corrosive fluids. Multiple effects efficiently recycle thermal energy, opening a wide range of waste heat energy source options.

Reliable Solids Production and Extraction

The SaltMaker MultiEffect produces solids by circulating a brine slurry to continuously form and grow crystals. Salts preferentially grow on nucleation sites of suspended seed crystals rather than on heat transfer surfaces. The larger crystals settle and are discharged to a Solids Management System for automated bagging or binning. Concentrated liquor, including smaller salt seeds, is recycled back to the SaltMaker while solid salts remain behind in the bags or bins. The system notifies the operators when the bags are full and ready to be transported to a drainage rack by forklift.

The solids are then drained and pass the paint filter test, often within 24 hours of draining, after which the bag can be sent for disposal or re-use depending on the application. The Solids Management System takes the guess work out of management and improves reliability. The plant flushes and purges slurry lines to prevent clogging, discharges thick slurry to the bags only when necessary, and automatically recycles rich liquor brine and notifies operators when to change bags.

One-Step Treatment

Traditional treatment technology requires multiple steps with different technologies to treat wastewater with high salinity levels. This includes separate systems for pre-treatment, evaporation, crystallization, solids production and dewatering. The SaltMaker combines these steps into a single system that requires no pre-treatment. It can be fed water at any salinity and almost any water chemistry. Expensive chemicals, such as soda ash, that increase solids load are avoided on the front end.

For ZLD applications, the Solids Management System can be added to the SaltMaker. Brine enters the plant, which produces freshwater and solids in bags or bins. No extra processing equipment, such as centrifuges or filter presses, is required. A simplified process flow diagram comparing the SaltMaker and a conventional process used to achieve ZLD is provided below.

Built to Resist Corrosion, Plugging, and Scaling

The SaltMaker MultiEffect is predominantly built from plastics—namely gel-coated, fiber-reinforced plastics—with a low surface energy that provides resistance to corrosion and scale. The photos below showcase the different components of the SaltMaker.

The plant also operates with high circulation rates to provide scouring flows, and all wetted surfaces are exposed to continuous dynamic salinity gradients for salt saturation relief. Combined with sound engineering design, the SaltMaker prevents plugging and challenges in reliability that frequently affect conventional evaporators and crystallizers.

Intelligent Automated Operation and Cleaning

The SaltMaker MultiEffect has intelligent automated operations and self-cleaning processes. The plant can perform the following functions automatically: (1) start, (2) stop and flush, and (3) hibernate in circulation mode and ramp to 25% capacity in one step. Dynamic capacity control allows the SaltMaker to operate anywhere from 25% to 100% of rated capacity while being remotely managed via a secure internet connection.

The plant’s self-cleaning modes prevent irreversible scaling or fouling by regularly monitoring key performance metrics. It will then automatically trigger the appropriate level of cleaning, from ‘light rinse’ to ‘heavy scrub’. The SaltMaker uses distilled water as the cleaning fluid, which can be chemically augmented based on the type of scaling compounds and foulants in the brine. The wash solution is reused multiple times before being fed back to the SaltMaker for treatment once the fluid has been spent.

No Single Point of Failure

Unlike mechanical vapour recompression (MVR) technologies, where 100% of plant capacity is lost when the vapour compressor goes offline, the SaltMaker has no single point of failure. The plant is built with repeatable and redundant evaporation-condensation process sets. If a process set is down for maintenance, the plant continues to run at 92% capacity.

An Evaporation-Condensation process set: There are multiple process sets in an effect

Modular Build and Scale Up

The SaltMaker MultiEffect is built into standard ISO container frames, which allow for ease of shipping, installation and future expansion. The open-concept design also allows for easy access to processing equipment, such as pumps, for inspection and routine maintenance, without the need for any confined space entry.

Multiple inspection ports (blue outlines in the photo above) in each effect allow for convenient monitoring of scaling and fouling. Process set modules slide in and out, and cleaning is done with a power washer.

The modular design simplifies transport and assembly. The SaltMaker is shipped by standard freight, without the need for any permits of oversized loads. The system is then assembled by crane onsite, as seen in the photos below.

SaltMaker MultiEffects are built to standardized plant sizes that can be added together to expand capacity as your project grows.

Model	Capacity Based on Freshwater Removed*
Model	m³/day	Gallons/day	Gallons/minute	Barrels/day
S30	30	7900	5.5	188
S66	66	17400	12	415
S100	100	26400	18	630
S125	125	33000	23	790

* Capacity derated by 20% to produce a 450,000 mg/L total solids slurry and by 40% to produce solids.

Low Temperature Air Humidification-Dehumidification

The SaltMaker MultiEffect is a multiple effect, thermally driven evaporator-crystallizer. It can use a variety of thermal sources: steam, low-grade waste heat, and gas or liquid fuel-fired low-pressure water heaters. It operates at atmospheric pressure and temperatures of less than 90^oC, employing humidification-dehumidification air cycles that do not require a vacuum, pressure or boiling water on any heat transfer surfaces. Steam ticketed operators or pressure vessel certifications are not required.

In each of the effects, thermal energy is recycled, brine is concentrated, and freshwater is produced. Initial heat input to the plant at, for example, 92^oC is used to evaporate and condense water in multiple effects, with the temperature being downgraded in each effect while the heat is recycled. This multiple effect process enables one unit of heat to produce four units of volume reduction, as shown the process diagram below.

Warm brine flows at high volumetric velocities through the system, and is sprayed into non-stick packing material of the evaporator modules. Approximately 1–2% of each droplet is evaporated to become freshwater vapour, while the droplet is concentrated and cooled. The droplet is pumped through the system again to recapture heat and further evaporate.

Air is the vapour carrier, with the fan module providing the motive force. Water vapour condenses into freshwater liquid at the radiator modules, which also transfers the latent heat of condensation to the next effect for energy efficiency. The final effect can be open or closed to atmosphere, providing cooling and heat rejection.

As water is evaporated, the brine is concentrated. Solid salts form on smaller salt seeds as saturation is exceeded. The smaller salt seeds are recycled from the Solids Management System (SMS) described above, with larger crystals forming and then discharging back to the SMS. This continuous cycling enables salt crystal growth and prevents the need for complex multi-step processes. The SMS is seamlessly integrated into the SaltMaker process, controls, and modular skids, so a single package can be delivered and operated.

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Selecting the Right Industrial Wastewater Evaporator or Crystallizer

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Saltworks » Article » Page 4

Selecting the Right Industrial Wastewater Evaporator or Crystallizer

Comparing evaporator and crystallizer technologies used for zero and minimal liquid discharge

Apr 6^th 2018

Four fundamental types of industrial evaporators and crystallizers are used for wastewater treatment, brine management, or improving water reuse. Lower your risks and improve costs by understanding the trade-offs between the different evaporator types and choosing the right fit for achieving zero and minimal liquid discharge.

Key Takeaways

Before investing in an evaporator or crystallizer, reduce costs by maximizing the freshwater recovery achieved by upstream membrane systems.
Understand the application and fit for different industrial evaporator/crystallizer types before deciding on the suitable technology for your project.
Protect your investment by engaging experts to help you prevent scale and corrosion, which diminishes evaporator performance.
Avoid extensive chemical pre-treatment, which drives up operating costs.
Traditionally, evaporators were used to concentrate saltwater, and crystallizers were used to produce solids. However, modern evaporator-crystallizer hybrids can do both.

Get the Most out of Membrane Treatment Systems Before Considering Evaporators

Reverse osmosis (RO) systems are usually the most cost-effective water treatment solution. If the concentration of total dissolved solids (TDS) is less than 70,000 mg/L, even if you have reached scaling limits, you still have options to further utilize RO and concentrate brines up to 130,000 mg/L. This will reduce your total costs by lowering the size of the downstream evaporator and the energy it consumes. To optimize your project economics, ensure that you maximize the performance of your RO system before considering evaporators or other thermal treatment systems.

The Four Major Types of Industrial Evaporators

Evaporators treat wastewater by heating it, evaporating volatile solvents—including water—from the solution, and then cooling and condensing the vapour to produce a liquid that is mostly freshwater. This leaves behind non-volatile solutes such as inorganic salts and organic compounds in a much more concentrated wastewater stream, with a much smaller volume.

There are four common industrial wastewater evaporators, as listed below.

1. Mechanical Vapour-Recompresssion (MVR) Evaporators

MVR evaporators use a blower, compressor or jet ejector to compress, and thus, increase the pressure of the vapour produced. This increase in pressure results in an increase in the condensation temperature of the vapour. This vapour is then condensed in a heat exchanger, returning heat to the evaporating water in the next stage. This forms a cyclical process that recycles thermal energy, but requires electrical energy to run the large vapour compressor.

Tips for choosing an MVR evaporator:

Ensure that the vapour compressor you select can handle high rotation speeds and stands up to severe vibrations.
Consider redundancy, since compressor failures can occur.

2. Multiple Effect Evaporators

A multiple effect evaporator combines two or more vessels, each maintained at a lower pressure than the last. Heat energy is supplied to the first vessel where evaporation occurs at a relatively higher temperature. Vapours from the first vessel move to the second vessel due to the pressure difference, where the vapour is condensed. This releases heat that is used to evaporate wastewater in a subsequent vessel. Temperature is lowered in each effect as the heat energy is recycled, and eventually rejected close to atmospheric temperature.

Tips for choosing a multiple effect evaporator:

Specify non-scaling and non-corroding materials of construction to improve long-term performance.
Ask about tube scaling on your specific water, and how it can be prevented.
Plan for maintenance access to any of the vessels, including access to the tubes for cleaning, as well as confined-space entry points and safety equipment.

3. Atmospheric Evaporators

Atmospheric evaporators release their evaporated freshwater directly to atmosphere. Energy consumption is much higher, since the water vapour formed during the evaporation process is not condensed, eliminating the opportunity to reuse the energy.

Tips for choosing an atmospheric evaporator:

Ensure that you have an abundant source of waste heat, to make the atmospheric evaporator more economic.
Verify the concentrations of ammonia and volatile organic compounds, such as benzene, toluene, methanol and others. They will create air pollution and odors if evaporated.
Plan for corrosion-proof specifications and confined space entry during maintenance.

4. Humidification-Dehumidification Evaporators

Humidification-dehumidification (HDH) evaporators operate similarly to multiple-effect evaporators, although they recycle heat across the effects at lower temperatures.

These evaporators have the following advantages:

Operate at atmospheric pressure, avoiding both pressure vessels and vacuums, resulting in simpler permitting and maintenance.
Constructed with non-metallic materials that leverage reinforced fiberglass to avoid corrosion and reduce scaling potential. This provides reduced surface energy, which acts like Teflon in a frying pan, to decrease the sticking potential of salt.
The volumetric chambers used in HDH evaporators cost less than steam-based chambers and are less prone to corrosion, although they are roughly three times larger.

Combining the Advantages of Each Evaporator

The SaltMaker MultiEffect evaporator crystallizer combines three of the above industrial evaporator designs. First, it leverages the HDH cycle so it can be constructed from lower cost, fiber-reinforced plastics, which enable easy maintenance and reduce the risk of scaling and corrosion. The SaltMaker also comes in two optional configurations:

The multiple-effect configuration enables greater energy efficiency and recycles the 80–95°C heat through four or five effects.
The open-to-atmosphere configuration can use low-grade waste heat of 60°C or more and offers a higher treatment capacity per unit of plant size.

The SaltMaker is also designed for dual operation:

As an evaporator to concentrate brines.
As a crystallizer to produce and extract solids.

Read more in the table below about the advantages that the SaltMaker design offers, compared to conventional evaporator and crystallizer designs.

Contact Saltworks for help with selecting the suitable industrial evaporator for your project.

Evaporators	Fit & Tips	Installation/Operability	Economic Sweet Spot
Mechanical Vapor Recompression (MVR)	Widely used where appropriate, namely on non-scaling flows as a concentrator of up to 20% salt mass (80% water). Ensure metallurgy and maintenance access/chemical cleans are planned for during design phase.	Custom designed and built to each need. Must consider chemical pre-treatment for scale. Pressure vessels and high-speed compressor operating on “wet” vapour represent a severe and common single point of failure risk.	No low-grade waste heat and thermal energy is expensive, while electric power is available. Low scaling potential brines, or chemical pre-treatment included.
Multiple Effect Evaporators	More common where heat recycling is desired and non-scaling flows need to be concentrated up to 20% salt mass. Ensure metallurgy and maintenance access. Ensure chemical cleans are planned for during design phase.	Custom designed and built to each need. Must consider chemical pre-treatment for scaling. Considered very reliable due to reliance on thermal energy and cooling source, rather than compressor.	Low-pressure steam is available at low cost. Brine has low scaling potential or requires extensive chemical pre-treatment.
Atmospheric Evaporators	Carefully check for volatile potential in discharge to prevent a stranded investment. Commonly only able to concentrate to 15–18% salt mass. Consider if low grade waste heat is abundant. Scaling can be more troublesome due to air injection.	Low cost and easy to install; however, a plume will be present, and this could include odors and release of damaging volatiles. Some of these plants have been shut down after less than one year of use due to stakeholder concerns of air pollution and health hazards.	Non-volatile, low scaling potential water source with abundant waste heat and ability to form a vapour plume to air.
Humidification Dehumidification (HDH)	More suitable on scaling flows, and pre-treatment costs can be avoided in intelligently designed plants with self-cleaning, such as the SaltMaker. Requires more footprint than conventional steam-based evaporators (2x ground footprint). Concentrates to 30% salt mass with ease, or produces solids due to non-corroding, non-stick materials.	Plan for space requirements, and modular installation in the case of SaltMaker. No steam ticketed operators required; however, basic handy person, process understanding, and computer skills required.	Desire to concentrate higher than conventional evaporators, or produce solids and achieve zero liquid discharge. Ability to stage investment and expand production capacity in the future by adding modules. Thermal energy is reasonably priced (SaltMaker) or waste heat abundant (AirBreather).

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How to Avoid Day Zero with Zero Liquid Discharge

Photo of the Theewaterskloof Dam during the Cape Town water level crisis

Saltworks » Article » Page 4

How to Avoid Day Zero With Zero Liquid Discharge

Mar 15^th 2018

Much discussion has centered around how the residents of Cape Town can reduce their intake to prevent Day Zero (i.e. severe water restrictions). But what about industries? New technology offers options for industrial facilities to make more clean water from wastewater by achieving the pinnacle of water treatment targets: zero liquid discharge (ZLD).

Nearly four million people living in and around Cape Town are grappling with the city’s worst drought in 85 years, which has been caused by alarmingly low rainfall over three consecutive years. While several areas around the world have been under stressed water conditions for extended periods, Cape Town is the first major city in the world to be affected this harshly by a water crisis in the recent past.

Download A Free ZLD Infographic

Response to Day Zero

The city has attempted to provide temporary relief to its residents by setting up water stations at various locations and is asking residents to consume less than 50 litres per day. Further extreme measures may be necessary, as the government tries to find a long-term solution. The response to the Day Zero crisis has resulted in a push far beyond Cape Town’s municipal limits to make people aware of the amount of water they consume.

While much of water conservation efforts have been targeted at residential activities, agriculture and industry must also contribute to preserving precious water resources. Treating water on industrial or agricultural sites not only lowers water consumption through re-use, but also protects rivers and lakes—the ultimate source of freshwater. By understanding that droughts stress these water bodies, protecting them from pollution becomes even more important, as pollutants concentrate to higher levels when less water is available.

The main pollutants in agricultural and industrial wastewater are organics, salts, or both. When the concentration of these pollutants is high in effluent streams, safe disposal of this wastewater becomes challenging. However, if these pollutants can be removed from effluent streams, freshwater can be recovered and reused, or returned to the environment.

Technology: New Options for Treating Tougher Water

The good news is that water treatment technology has made significant strides and can be economically implemented at agricultural or industrial facilities that produce wastewater. Some of these innovative technologies include:

Compact and simple biological systems that use microorganisms to reduce organic matter
Reverse osmosis (RO) that uses pressure to squeeze freshwater out of wastewater via semi-permeable membranes
Electrodialysis reversal (EDR)—an electrochemical process—that utilizes the latest in membrane technology to selectively separate ions and extract them from wastewater
Evaporators and crystallizers that use heat to separate fresh water from contaminants

Each of these technologies are suited for different water chemistries and can be combined to produce a wastewater ‘treatment train’ that suits the treatment project.

ZLD: The Pinnacle of Fresh Water Recovery

Modern water treatment technology has engineered its way to the upper limits of freshwater recovery, known as zero liquid discharge (ZLD). This water treatment approach makes use of membrane systems to first concentrate salty waters to membrane limits, and then send the saltier brine to highly efficient evaporator-crystallizers. They squeeze every drop of freshwater from the salty brine until solid salt waste is the only by-product.

While stand-alone thermal systems such as large-scale evaporators and crystallizers may prove to be a costly option, combining technologies in different configurations provides a more efficient and economic solution. For example, zero liquid discharge can also be achieved by combining different technologies: RO-evaporator-crystallizer or EDR-evaporator-crystallizer configurations.

In addition, planning for zero liquid discharge from the onset can lower water sourcing costs through recycling, lower risk cost of meeting future regulatory requirements, integrating waste heat in facility design to treat water at a lower cost, enhancing stakeholder relations while protecting rivers and lakes, and enabling better relations for future expansion and new facilities. Treating wastewater can also be turned into a profit centre, for example:

Treating agricultural wastewater runoff to selectively remove sodium, while beneficially recycling both the water and agricultural by-products
Desalting oil produced water for enhanced oil recovery re-injection, whereby lower salinity injection improves oil recovery and makes money

The technologies mentioned in this article are tried and tested, and readily available for industries to adopt. Those who seek innovation and have the courage to pioneer installations will help lead the way. These innovators can bring long term de-risking benefits to their organizations in a world where the value of clean water only increases, and risks of environmental damage can result in extremely high liabilities. By adopting innovative wastewater treatment systems today, we can help prevent Day Zero tomorrow while also advancing economic development and industrial growth.

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RO & Evaporator Scale Control: The Guide to Better Performance

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RO & Evaporator Scale Control: The Guide to Better Performance

Jun 27^th 2018

Scale is a crust that forms on membranes, heat transfer surfaces, and on the inside of pipes as salts precipitate out of solution. Scale blocks flow, disrupts heat transfer, and increases energy requirements for water treatment systems. Simply stated, scale is bad news: it limits system performance and increases maintenance costs.

You can protect your plant’s productivity from scale when you are armed with an understanding of scaling water chemistry and the right technology. You can also push and maximize performance of your plant, if you understand the scaling ‘danger zone’.

Download our periodic table, which includes an easy-to-use guide and example. Keep reading below to learn more.

Download a Free Periodic Table of Scaling Compounds

How do Scaling Ions Precipitate?

Scaling occurs when ion pairs reach their solubility limits and form salts. Ion pairs comprise positive cations and negative anions, and most scale is caused by ions that are multivalent pairs. Multivalent ions, such as calcium (Ca²⁺) and sulfate (SO₄^2-), are more likely to cause scale than monovalent ions because they have lower solubilities and will precipitate earlier. Watch out, however, for one particular mono-multi pair—calcium (Ca²⁺) and fluoride (F^–)—which can also cause scale.

Our chemists and engineers use the above periodic table of scaling compounds to easily check for concentrations of ions in water that might precipitate and affect evaporator or membrane system performance.

The solubility of an individual ion pair is the most essential information to use when designing a scale management strategy. However, scaling concentration limits can be affected by the temperature, pH, and mixed-ion chemistry of the water. Ions in mixed solutions tend to have higher solubilities than pure solutions, which can be difficult to predict, even with some of the software models that are available. We treat mixed-ion effects as an extra buffer that prevents scale.

How Does Scaling Impact Evaporators & Membrane Systems?

Any heat transfer surface where scaling occurs will observe decreased efficiency and capacity. Although scaling is typically shown on metal surfaces, it can also form on membranes used in reverse osmosis systems and reduce membrane performance. In severe cases, scale can mechanically damage or rupture the membrane.

A plant that ignores scaling limits can experience equipment plugging and surface crusting, or be operating sub-optimally for leaving room to increase freshwater recovery. Time and money are wasted on either low performance or efforts to recover from a scaling event. Although carbonate scaling is easy to remove with acid, other scales take much more effort, such as using expensive chemical cleans or mechanical removal. It is best to know your water chemistry so that you can prevent scaling, rather than try to deal with it after it forms.

How to Avoid Scaling in Your Industrial Water Treatment Process

Follow these basic guidelines to help prevent scale build-up that leads to decreased performance and increased costs.

Get a complete analysis of your water chemistry to understand the concentrations of your potential scaling ions. For a few hundred dollars, you will receive analytical data that will help you understand your water. Ensure you sample during periods of both low and high concentration for a better representation of your water chemistry.
Know the scaling potential of any scaling ions in your water by using our Periodic Table of Scaling Compounds, or find a software package if you wish to be more advanced.
Design and operate your process to push recovery, but avoid exceeding solubility limits of scaling ions.
Consider automated chemical softening that uses precision dosing to minimize the risk of scale formation, while also reducing wasted chemicals that may result from manual chemical softening.
Consider adding anti-scalants that may boost your scaling ion solubilities as much as 3–4x, but be sure to use the correct anti-scalant and consider testing. Many companies will sell you anti-scalants and their performance may vary.

Contact an expert at Saltworks today to optimize your process and prevent scale formation.

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How to Manage Brine Disposal & Treatment

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How to Manage Brine Disposal & Treatment

Dec 15^th 2017

The cost and environmental impact of each option vary significantly due to many factors. Choosing management options for the waste brine requires careful consideration of applicable discharge regulations, availability of disposal methods, and the economic feasibility to treat the brine.

Understanding Your Brine Water Chemistry

Before deciding on how to manage waste brine, you should consider a water chemistry analysis to understand essential indicators, such as the salinity level (e.g. total dissolved solids), metals contaminants, and the scaling potential of the water (e.g. calcium and sulfate). This will assist in evaluating regulatory requirements as well as determining available options and their associated costs.

Water chemistry data provides the most value if you decide to treat your brine. The chemical makeup identifies the technologies that will best fit a specific brine treatment process, for example, whether to choose thermal or membrane systems. This data enables early assessments of project feasibility and economics, as well as any pre-treatment requirements and scaling and fouling risks.

Another advantage of brine chemical characterization is that it allows you to identify opportunities for beneficial resource recovery. For example, recovering ‘fertilizer water’ from a waste brine is possible. If a brine contains a mixture of sodium and hardness, electrodialysis reversal (EDR) with certain monovalent ion selective membranes could produce a water that is high in plant-nourishing hardness, with low concentrations of the pollutant sodium. This water would have a low soil adsorption ratio (SAR) that would be valuable to the agricultural industry.

Alternatively, if a brine consists mostly of sodium and chloride, it can be treated with a crystallizer to produce solids that can be used as road de-icing salts. Consider working with experts who can help you determine the most economic options for managing your brine.

Brine Treatment

Brine treatment is usually considered if discharge options are not available, brine disposal is expensive, or freshwater recovery is important. Many technology options are available to concentrate brine, reduce its volume and disposal costs, or produce solids for zero liquid discharge. Regardless of the treatment strategy you choose, it will beneficially produce freshwater.

Membrane Treatment Systems

Reverse osmosis (RO) is the membrane system most widely used to desalt brine waters. RO produces freshwater and more concentrated brine that is often referred to as RO brine, reject, or concentrate. This brine concentrate will usually reach concentrations of dissolved salts and chemicals that will be near scaling limits. This requires treatment to relieve the scaling potential if you will use a thermal system to further concentrate the brine or to produce solids. Alternatively, you could consider thermal systems that can operate under scaling conditions, such as seeded slurry evaporators or a SaltMaker, to eliminate the thermal pre-treatment step.

Conventional RO can concentrate brine to a theoretical maximum of 80,000 mg/L. This is based on the technology’s inherent osmotic pressure limit. However, the achievable output brine concentration will usually be less due to the input brine’s scaling potential. New ultra-high pressure RO (UHP RO) membranes that operate at up to 1,800 psi, compared to conventional RO’s 1,200 psi, can reduce brine volume to half that of RO; however, scaling must be even more carefully managed due to the higher pressure. Saltworks’ XtremeRO is an example of an RO/UHP RO system.

Chemical softening can be used to manage scaling. However, cost, physical footprint, and the ability to deal with varying feedwater chemistry must be considered. Technologies such as Saltworks’ automated BrineRefine system provide an economical, compact, and flexible chemical softening solution for maximizing RO and UHP RO brine concentration. Saltworks provides fully integrated solutions that combine RO or UHP RO with BrineRefine and central controls to provide a membrane-based solution that concentrates brine to levels only previously attainable by more costly thermal systems.

If your brine contains hydrocarbons or organics, electrodialysis reversal (EDR) may be a better fit than RO due to lower pre-treatment requirements. EDR is a low-pressure system that fluxes salts through ion exchange membranes, using an applied electrical charge. There are EDR systems that use anti-fouling ion exchange membranes, such as Saltworks’ FlexEDR Organix, that can operate with hydrocarbons and organics that are present in the brine.

Thermal Treatment Systems

If you are considering thermal evaporative systems, then maximizing freshwater recovery from lower-cost membrane systems before using expensive thermal systems will deliver the best project economics.

In general, there are two types of thermal systems, based on their residual outputs:

evaporators that produce concentrated, low-volume brine but do not precipitate solids; and
crystallizers that exceed salt saturation and produce solids.

For high flow-rate zero liquid discharge applications, evaporators are used to preconcentrate the brine prior to the crystallizer for final solids production. At lower flow rates, the waste brine can be sent directly to the crystallizer after treating with a membrane system.

The final disposal of residuals is important in determining whether additional process steps are required. If you have options for disposing of concentrated brine, it will usually not require further treatment. Evaporators are only reducing the volume of brine for final disposal, ensuring that you will use fewer trucks to move the brine or need less capacity in disposal wells or ponds.

However, depending on the treatment technology you use, additional treatment may be required for solid residuals before a landfill will accept them for disposal. Almost all landfills require solids to pass a paint filter test, while some landfills also require analysis of pH and leachable metals. To pass a paint filter test, the solids should be dewatered until they have no free water present. Centrifuges, filter presses, and/or dryers are required to further process solids produced by conventional crystallizers to pass the paint filter test. Other crystallizers, such as the SaltMaker MultiEffect, have their own solids management systems that produce dewatered solids in sacks without the need for centrifuges, filter presses, or dryers.

Treatment costs increase with each step that you concentrate brine toward solids, which is why it is important to carefully consider all disposal and reuse options before implementing a technological solution.

Brine Disposal

Discharging Brine into Surface Bodies of Water or Sewer Systems

If your brine meets regulatory requirements, brine discharge into the nearest body of water or to sanitary sewers is usually the lowest cost option for disposal. Discharge regulations or guidelines vary widely from region to region, or are sometimes determined on a project-specific basis.

Regulations may prohibit discharge based on any of the following:

concentrations of certain constituents of concern (e.g., maximum limits for metals, salinity, or compounds)
total mass per day of certain constituents of concern
specific properties, such as temperature and pH
volumetric flow rates
discharges only during certain time of day.

One option for complying with regulatory discharge requirements may be to dilute the brine stream with other waters that require discharge. Sufficient dilution may reduce the controlled constituents to below the allowable concentration limits. If the brine stream has only one or two constituents of concern that exceed the discharge limits, you should consider selective treatment or removal of those constituents. Low-cost solutions are available for removing certain constituents, such as using green sand for iron removal.

While discharging brine directly into surface water systems or sewers is often the most cost-effective solution, your organization should consider how discharge will impact the local environment. If regulations do not exist, studying the potential impacts of discharging the brine on local flora and fauna will help identify the benefits of treatment to protect the ecosystem or prepare for impending regulations.

Brine Disposal in the Ocean

Like discharging brine into surface bodies of water, ocean discharge is another brine disposal method that tends to be very cost-effective. In southern California, a ‘Brine Line’ allows inland plants to discharge their brine to the ocean rather than to sewer or surface waters. Due to the ocean’s naturally high salinity, the environmental risks of brine discharge are lower.

If you are considering installing a brine discharge line, you will need to acquire a permit. As part of the permit application, the regulatory body may ask for environmental studies that address the impact on local marine ecology of the brine temperature, pH, salt density, and other property differences between the brine and seawater.

Deep Well Injection of Waste Brine

Waste brine can be disposed of by injecting it into deep wells. These injection wells are installed thousands of feet underground, away from the upper aquifers that feed drinking water sources. The availability of injection wells is geology-dependent, so they are not available in all regions.

In the oil and gas industry, abandoned oil wells are often converted into disposal wells. Recently, studies have shown a correlation between deep disposal wells and increased seismic activity, as evidenced by earthquakes in Oklahoma.

Deep well capacities have also reduced, as regulations require lower injection pressures to minimize the risk of contaminating the upper water aquifers. Moreover, securing a functioning deep well is similar to drilling for oil—you take a risk and invest capital before knowing if the underground geology will meet your expectations. It is possible that deep wells, once drilled, will accept very small volumes, or exceed expectations and accept more.

Brine Evaporation Ponds

Evaporation ponds are the artificial solution to inland surface water discharge of waste brine. Under the right climatic conditions, the water evaporates, allowing you to discharge more brine to the ponds. One limitation of ponds is that they require large areas of land to increase the surface area where the water can evaporate. This can represent a future environmental liability due to either animal entry or future decommissioning.

If you need to recover solids for disposal or reuse, then multiple evaporation ponds may be necessary to rotate between brine evaporation and solids extraction. Evaporation also happens more quickly in warmer, arid climates. You should consider installing proper liners, preventing waterfowl poisoning from brine that contains metals, and developing an end-of-life closure plan if your project will be using evaporation ponds.

Brine Incineration

Waste brine can be sent to an incinerator facility, where the brine is typically mixed with other solid wastes for processing. Incineration evaporates the water, while the salts in the brine become part of the residual ash that requires further management. Incineration is popular in countries with limited availability of land for landfills.

Brine Management from Environmental Service Providers

There are companies that provide environmental services to accept waste brine. These companies will typically take ownership of the brine and charge on a dollars-per-gallon basis. This is an option you should consider if there are facilities nearby, although distance and transportation costs may reduce cost-effectiveness. Once the service provider takes ownership, they will use their own assets to either treat the brine or dispose of it.

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What is Zero Liquid Discharge & Why is it Important?

Saltworks » Article » Page 4

What is Zero Liquid Discharge & Why is it Important?

Nov 16^th 2017

Zero liquid discharge (ZLD) is an engineering approach to water treatment where all water is recovered and contaminants are reduced to solid waste.

While many water treatment processes attempt to maximize the recovery of freshwater and minimize waste, ZLD is the most demanding target because the cost and challenges of recovery increase as the wastewater gets more concentrated. Salinity, scaling compounds, and organics all increase in concentration, which add costs associated with managing these increases. ZLD is achieved by stringing together water treatment technology that can treat wastewater as the contaminants are concentrated.

Targeting ZLD for an industrial process or facility provides a number of benefits:

Lower waste volumes decrease the cost associated with waste management.
Recycling water on-site lowers water acquisition costs and risk. Recycling on-site can also result in fewer treatment needs, versus treating to meet stringent environmental discharge standards.
Reduce trucks associated with off-site wastewater disposal and their associated greenhouse gas impact and community road incident risk.
Improve environmental performance and regulatory risk profile for future permitting.
Some processes may recover valuable resources, for example, ammonium sulfate fertilizer or sodium chloride salt for ice melting.

Download a Free ZLD Infographic

Several methods of waste management are classified as ZLD, despite using different boundaries to define the point where discharge occurs. Usually, a facility or site property line that houses the industrial process is considered the border or ‘boundary condition’ where wastewater must be treated, recycled, and converted to solids for disposal to achieve zero liquid discharge.

Certain facilities send their liquid waste off-site for treatment, deep well disposal, or incineration and they consider this to qualify as ZLD. This approach eliminates the continuous discharge of liquids to surface waters or sewers, but can significantly increase cost.

Some engineers describe their designs as near-ZLD or minimal liquid discharge to highlight that they discharge low levels of wastewater, but these processes do not eliminate liquid in their waste. For some facilities, it may be more economical to approach but not achieve complete ZLD by concentrating brine to lower volumes. Furthermore, it may be possible to avoid the creation of liquid waste on-site through careful water conservation or by treating contaminants at their source before they can enter the main flow of water.

Download our ZLD infographic for detailed information on costs.

Why is Zero Liquid Discharge Important?

In a world where freshwater is an increasingly valuable resource, industrial processes threaten its availability on two fronts, unless the water is treated. Many industrial processes require water, and then reduce the availability of water for the environment or other processes, or alternately contaminate and release water that damages the local environment.

Although the history of tighter regulations on wastewater discharge can be traced back to the US Government’s Clean Water Act of 1972, India and China have been leading the drive for ZLD regulations in the last decade. Due to the heavy contamination of numerous important rivers by industrial wastewater, both countries have created regulations that require ZLD. They identified that the best means to ensure safe water supplies for the future is to protect rivers and lakes from pollution.

In Europe and North America, the drive towards ZLD has been pushed by high costs of wastewater disposal at inland facilities. These costs are driven both by regulations that limit disposal options and factors that influence the costs of disposal technologies. Tong and Elimelech suggested that, “as the severe consequences of water pollution are increasingly recognized and attract more public attention, stricter environmental regulations on wastewater discharge are expected, which will push more high-polluting industries toward ZLD.”

Another important reason to consider ZLD is the potential for recovering resources that are present in wastewater. Some organizations target ZLD for their waste because they can sell the solids that are produced or reuse them as a part of their industrial process. For example, lithium has been found in oil field brines in the USA at almost the same level as in South American salars. In another example, gypsum can be recovered from mine water and flue gas desalinization (FGD) wastewater, which can then be sold to use in drywall manufacturing.

Regardless of an organization’s motivations to target ZLD, achieving it demonstrates good economics, corporate responsibility and environmental stewardship. By operating an in-house ZLD plant, disposal costs can be reduced, more water is re-used, and fewer greenhouse gases are produced by off-site trucking, which minimizes impact on local ecosystems and the climate.

To learn more about implementing ZLD solutions, contact us.

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