Article

How to Improve FGD Economics with Chloride Removal using Selective EDR

Coal-fired power station FGD plant

How to Improve FGD Economics with Chloride Removal using Selective EDR

July 23rd 2018

Key Takeaways:

  • As regulations on FGD wastewater tighten, additional treatment is required. Often, this is chemically intense, and high cost. The best means to lower treatment costs is to reduce the volume of wastewater generated, usually by increasing internal recycle.
  • Internal recycle of FGD wastewater is limited by high chloride concentrations that inhibit sulfur dioxide absorption and can cause corrosion issues as chlorides are cycled up – this can be solved by the solution below:
  • Chlorides can be selectively removed from FGD wastewater by industrially available electrodialysis reversal (EDR) with monovalent selective membranes (mEDR). mEDR selectively transports chlorides under an electric field through monovalent anion exchange membranes while blocking sulfates. This reduces the chloride load to enable internal FGD recycle while producing a non-scaling brine of sodium/calcium chloride at greater than 90% recovery (or 10% brine waste volume).
  • 100% recycle of the low chloride treated water will not be possible due to cycling up of organics not removed by mEDR, however even partial recycle will reduce the cost of expensive FGD wastewater treatment infrastructure.
  • Highly robust monovalent ion exchange membranes with >98% selectivity should be used, such as Saltworks’ Ionflux, which prevent scaling by blocking almost all sulfates and can be cleaned with strong oxidants such as bleach.
  • mEDR can be integrated into existing FGD wastewater treatment trains, and eliminates the need for costly soda ash softening while producing a brine concentration almost equivalent to evaporators.
  • Although chlorides can be removed to less than 200 mg/L, reducing them to between 1,200 and 1,500 mg/L is more economical. Lower chloride levels can be attained at the expense of higher capital and higher energy due to reduced membrane flux below 1,200 – 1,500 mg/L Cl.
  • For more information on how EDR works, check out this blog

Coal-fired power station FGD plant

Background: FGD Wastewater

Coal fired power plant flue gas desulfurization (FGD) systems are used to remove sulfur dioxide (SO2) air emissions. They create wastewater often saturated with calcium sulfate while containing both metals and chlorides. FGD water is recycled internally and then purged out of the system when chloride concentrations exceed a set level. High chloride concentrations inhibit SO2 absorption from the flue gas and create corrosion concerns with wetted equipment. Chloride blowdown levels range with operations from 10,000 mg/L to as high as 30,000 mg/L.

Power Plant Cooling Towers

Most FGD installations already include some wastewater treatment, typically referred to as ‘triple box’, wherein heavy metals and fluorides are removed via moderate pH (~pH 9) precipitation combined with polymer and coagulation, followed by a filter press. Historically the filtrate is released, however chloride, selenium, and other constituents that make up total dissolved solids (TDS) are not removed. The industry is facing new regulations that force TDS removal. The authors of this work reviewed and tested multiple options to inform an appropriate path for future development.  The top three contending options are summarized herein with their economics compared. The results show that monovalent electrodialysis reversal (mEDR) holds the greatest promise to provide a step change in FGD wastewater treatment cost reduction.

The top three contending options are all based on industrially practiced technology, however leading innovation is applied to options (1) and (3).

  • UHP RO: Chemical Softening –> Seawater 80 bar Reverse Osmosis (SWRO) –>Ultra High-Pressure 120 bar Reverse Osmosis (UHPRO)
  • EVAP: Chemical Softening –> Seawater Reverse Osmosis (SWRO) –> Evaporator
  • mEDR: Monovalent Electrodialysis (mEDR), without Chemical Softening
    1. Desalt down to 1,500 mg/L chlorides
    2. Desalt down to 500 mg/L chlorides

All options assume an upstream ‘triple box’ treatment step is already in place. All options produce a final brine reject that is either combined with fly ash for solidification and landfill disposal or sent to a ZLD system. The recovery and brine reject volume for each option is included in the analysis, however the final disposal costs of said brine is excluded and assumed to be roughly equivalent, or at least not impact the final conclusions drawn for next steps.

FGD Wastewater Treatment Options

Option 1 (UHP RO) and 2 (EVAP):

FGD wastewater treatment options 1 and 2 simplified process flow diagram is shown in Figure 1 and 2 below. They differ in their final concentration step: (1) includes ultra-high pressure reverse osmosis (UHP RO), which can produce a brine reject at 130,000 mg/L TDS and (2) includes an evaporator, which produces a more concentrated brine reject at 180,000 mg/L TDS, but at a higher cost than UHP RO.

Simplified process flow diagram of chemical softening
Figure 1. Option 1 Simplified process flow diagram: Chemical softening – SWRO – UHPRO
Simplified process flow diagram, Chemical softening
Figure 2. Option 2 Simplified process flow diagram: Chemical softening – SWRO – Evap

Both options produce treated water that is suitable for environmental discharge and leverage an upstream seawater reverse osmosis (SWRO) step, which is low cost and widely available. Based on the FGD waters tested by the authors, the chemical softening soda ash must be employed with RO and evaporators. Its cost accounts for almost 50% of the treatment total cost of ownership (capital plus operating cost; see Table 2 below).

Option 3 (mEDR):

Monovalent electrodialysis (mEDR) selectively pulls out chlorides to increase internal recycle rate and decrease wastewater volume. See Figure 3 for simplified process flow diagram.

Simplified process flow diagram, mEDR
Figure 3. Simplified process flow diagram: mEDR

mEDR builds upon traditional electrodialysis technology, the world’s second most practiced membrane desalination technology, and is enabled by recent advances in monovalent ion exchange membranes. These are manufactured from a ductile and highly conductive ion exchange polymer. Under an electrical field, these membranes selectively allow monovalent anions, such as chloride, to pass through the membrane and concentrate up in the brine reject stream while blocking multivalent ions, such as sulfate (see Figure 4). Similar to how kidneys remove waste from the human body, mEDR removes chloride in the wastewater and recycles the low chloride water back to the FGD system for reuse. 

Diagram of monovalent electrodialysis (mEDR) using FlexEDR technology
Figure 4. Monovalent electrodialysis stack

Since mEDR only moves chlorides and calcium to the brine reject, it produces a non-scaling brine composing of primarily sodium and calcium chloride. Since sulfates are prevented from entering the brine, scaling products do not form and high membrane system brine concentrations can be achieved without the need for expensive soda ash softening.

mEDR Tests on Real FGD Wastewater

The mEDR process has been tested on a micro-pilot (see Figure 5) and Saltworks’ micro-stack with real power plant FGD wastewater to prove feasibility and provide initial performance data. Full scale stacks are available in two sizes also shown in Figure 5 and results scale-up linearly based on a series of past projects.

Micro pilot of FlexEDR technology
Micro-pilot – fully automated and complete process
FlexEDR micro-stack
Micro-stack
FlexEDR stack
E100 Stack: 100 m3/day
FlexEDR stack with membranes in between
E200 Stack: 200 m3/day

Figure 5. EDR Micro-pilot and full-scale stacks

The tests show that mEDR can achieve over 90% recovery and remove more than 90% of the chlorides. The brine reject produced consisted mainly of calcium, magnesium, and sodium chloride, and greater than 150,000 mg/L TDS. The analytical results of the inlet FGD wastewater, processed water and brine reject are shown in Table 1 below. Figure 6 shows the relative removal of various ions, including the extremely high rate of chloride removal vs sulfate.

FGD water chemistry
Table 1: Water chemistry data for FGD Wastewater, processed water and reject brine
Comparison of major constituent concentrations in FGD wastewater and mEDR processed water
Figure 6: Comparison of major constituent concentrations in FGD wastewater and mEDR processed water

The test plant operated reliably without the need for chemical softening. The membranes demonstrated excellent monovalent anion selectivity – chlorides were reduced by more than 90%, while 94% of sulfates remained in the FGD water. On a molar basis, this means for every 200 chloride ions that were removed from the FGD wastewater, only 1 sulfate ion passed through the monovalent anion exchange membrane. This high monovalent selectivity is critical to realize chloride removal from FGD wastewater and concentrating calcium/magnesium/sodium chloride in the brine reject without scaling. No irreversible organic or inorganic fouling occurred, and preventive oxidant clean followed by a sodium chloride wash every 30 days will maintain performance. 

FGD Wastewater Treatment Costs

Table 2 below compares capital and operating cost of all three options based on real FGD water, test data, and vendor prices assuming 300 m3/day capacity (12.5 m3/hr). Costing is based on test data and water chemistry as shown in Table 1. The total cost of ownership is calculated assuming capital costs are depreciated over a 20-year life at 8% while adding in operating costs such as energy, chemicals, and membrane replacements. Installation, operating labour, and taxes are excluded.  The mEDR installation desalting to 1500 mg/L chlorides requires six Saltworks’ E200 stacks, while desalting to 500 mg/L requires twelve stacks. Flow rates larger than 300 m3/day are readily achievable by adding more stacks.

*Costs assume pre-filtration and balance of plant built in China to Saltworks’ specifications; Saltworks to supply membranes, stacks, process engineering (P&ID), and control PLC with program embedded

*Costs do not include: Install, labour, VAT – assumes equal impact to all options

*Costs assume economies of scale in orders and production

Table 2. Comparison of FGD wastewater treatment costs


The results show potential that:


  • mEDR can save up to 50% in capital (no need for chemical softening and thermal system) and operating cost for FGD wastewater treatment compared to options 1 and 2.
  • mEDR can remove chlorides to very low levels, however that may not be the most economically practical. Once chlorides are reduced below 1,200 to 1,500 mg/L, the membrane flux is reduced and electrical resistance increases. This increases membrane area and power to reach lower chloride levels. Results show that although mEDR can readily desalt to 500 mg/L chlorides or lower, capital cost and energy increase by 50%. Since the treated fluid is being blended with higher chloride water inside the FGD system, and mEDR pre-treatment costs are low, it may not make economic sense to reduce chlorides much lower than 1,200mg/L to 1,500 mg/L.

mEDR Full Scale Implementation

Full scale plants can be implemented as the foundation technology (electrodialysis) – is not new and production systems are in placed as shown in Figure 7 below.

Collage of Saltworks employees manufacturing a FlexEDR stack
Figure 7. Full scale production of electrodialysis stacks

Standard mEDR skids are produced consisting of 6 FlexEDR E200 stacks, each with a hydraulic treatment capacity of 200 m3/day per stack. Each stack will remove roughly 4,000 mg/L TDS per pass and multiple passes are required for higher removal. The monovalent ion exchange membranes are essential to the solution and Saltworks Ionflux membranes are recommended due to their high monovalent selectivity, robustness, and oxidant tolerance balanced with their lower cost.

 

Saltworks owns a series of mobile pilot plants that are available to demonstrate any of the three options on site – RO, EVAP, or mEDR.  The pilots are containerized (Figure 8) and recreate full scale processes including automation and controls.

Collage of FlexEDR stacks, Saltworks' employees and pilot plant delivery
Figure 8. Electrodialysis pilot plant

Conclusion

mEDR technology, based on industrially available electrodialysis, shows much promise and compelling economics for FGD wastewater treatment at up to 50% cost savings. Field pilots in specific applications are recommended to determine the following:

  • Optimum chloride reduction level for the process.
  • Characterization of purge/blowdown to prevent accumulation of deleterious matter such as organics or other ions.
  • Solidification requirements and recipe for the mEDR brine reject.

After a field pilot, full scale plants can be rapidly delivered as production is in place and electrodialysis has a long heritage of implementation. This article is intended as general guidance. Specific project needs, water chemistry, and site requirements will change economics. Contact us for further details.

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Shale Water and NORM

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Shale Water and NORM

June 14th 2018

Summary:

  • There are four types of shale waters, each with unique properties, uses, and treatment approaches.
  • If your frac or produced water contains NORM (naturally occurring radioactive material), plan to manage them by keeping them in solution, precipitation and safe handling, or dilution followed by water disposal.
  • Lithium extraction with petrolithium water only makes sense when concentrations are greater than 500 mg/L.

Stock image of Fracking machinery

Shale water management starts with understanding the distinct types of water, their uses, and their volumes. This will enable better management of the site’s water balance to ensure there is the right amount of water available when needed and excess water does not exceed your storage capacity. Practitioners also need to consider the chemistry, which may include scalants, total dissolved solids (TDS), and NORM (naturally occurring radioactive material). The water chemistry significantly impacts shale produced water treatment strategy, as well as informing end-of-life options for the waste by-products that are left behind once clean water is removed. These by-products are often referred to as reject or residuals.

The Different Types of Waters Used in Shale Gas Operations

There are four primary types of water used in shale gas operations.

 

Source water is drawn from nearby water sources, such as surface waters or groundwater, and is typically used for hydraulic fracturing (also known as ‘fracking’).

Saline Re-Use Water is the water that returns after the fracking process, with increased salinity, but can sometimes be re-used as source water. It may require mild treatment before being used for another fracking process.

Frac Flowback is the water that returns from the ground, following a fracking process. Most of it returns rapidly after the fracking process and will include chemicals employed in fracking that can change the treatment process. The flowback flow rate slows over the first week(s) while TDS concentrations increases. Some of this flowback may become saline re-used water, if needed for future fracking applications.

Produced Water also returns to the surface, like flowback, but produced water largely originates in the formation. It tends to flow more steadily over longer periods of time and will have a higher TDS.

Water Type Utilization Characteristics Treatment Volume (m3/day)
Source Water Fracking Usually locally sourced freshwater such as surface water or groundwater with little to now TDS. Chemicals and sand enhancements may be added. High during fracking process, then tapers to zero.
Saline Re-Used Water Fracking (Re-Used) TDS: 10,000 to 200,000 mg/L.

Scaling ions can be present.
If re-used in a fracking process, it is often filtered and occasionally softened (remove Barium & Calcium). Best maximized to reduce future management volumes.
Frac Flowback Re-used if source water needed, otherwise disposed or treated. TDS increases over the first week of flowback. See our Shale water treatment options here. High immediately post fracking (~70% of injected water returns), flow rate tapers down over the first week.
Produced Water Re-used if source water needed, otherwise disposed or treated. TDS varies but often as high as 100,000 to 200,000 mg/L. See our Shale water treatment options here. Ranges from 10-1000 m3/day (63-6,300 BBL/day) per well.

Safety Considerations

  • NORM: NORM are naturally occurring radioactive materials, with radium and its many forms being the most common. Not all produced water contains NORM, but they are occasionally encountered in North American shale. It is important to understand the major risks associated with handling water that contains NORM since these risks can be managed. First, ingestion of radioactive material either through inhalation or swallowing is the primary hazard. Always wear gloves and wash your hands and clothes whenever working around potentially radioactive material. Never eat food near NORM and do not bring gloves used to handle NORM into a food zone. Gamma rays given off by NORM are the second way they can be harmful – however, water is an effective insulator. Putting this into context, humans are exposed to more radiation on a 2-hour flight, than standing next to NORM containing produced water for an extended period.

Fracking
  • There can be some risk if NORM precipitate and become dried out, removing the insulating properties of water. NORM can be precipitated alongside barium, which can be achieved by adding sulfates (sodium sulfate) or carbonates (sodium carbonate) at an elevated pH (pH > 9). NORM may also precipitate as a sludge on the bottom of tanks and filter bags, and they should be checked with a radioactive test before handling for safe disposal by a certified party. Diluting NORM sludge with water can improve safety for the reasons mentioned above, however, this will create more liquid waste. The best strategy is to measure the presence of NORM in your water and develop a plan to manage them – either through precipitation removal and safe handling or water disposal.
  • Chloride Dioxide Treatment and Removal: Chloride dioxide is used in shale waters to precipitate iron with possible NORM co-precipitation. As a benchmark, the cost of removing iron using chloride dioxide varies widely from $3-$50/m3 ($0.5-$8/BBL), depending on the volume of water that needs to be treated. Chlorine dioxide will damage membrane treatment systems, so if it is being used upstream of a membrane system be sure to remove it. There are many options for this, including activated carbon (expensive) or sulfites addition (more common).

Lithium: Some oil field brines contain lithium in the 60-100 mg/L range (0.006-0.01%) and there has been some emerging excitement for the potential of harvesting lithium from oil field brines. See an overview of lithium brine extraction technologies. Saltworks holds patents on lithium extraction, has built machines for lithium companies, and has technology to selectively extract lithium across ion exchange membranes.  Saltworks has experience in this field, combined with an understanding of the costs and revenue potential. Extremely large volumes of water must be processed to harvest a meaningful mass of lithium, often pointing to a centralized system and transportation costs to reach that system. In the authors’ view, the best economics for produced water management are achieved through sound water management and treatment, rather than lithium extraction, however, this option can be reviewed if rich lithium brines are co-located with centralized high volumes of produced water.

Summary

Shale gas and oil production presents a leading energy source moving forward, yet its future and production is tightly linked to water management. Every water type, job site, and economic case is different. Contact us to review your specific situation, benefit from our expertise, and assess if your water management costs or risks can be lowered.

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Frac & Shale Water Management, Treatment Costs & Options

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Frac & Shale Produced Water Management, Treatment Costs & Options

June 14th 2018

Summary:

  • Economic shale produced water management strategies require you to explore: treatment options, treatment costs compared to disposal costs, and methods to manage risk.
  • Open-to-atmosphere evaporators offer the best economics for shale volume reduction, although it is important to ensure that: your emissions of volatile organic compounds (VOCs) are managed, a low cost heat source is available, your permit will allow it, and sufficient water volume removal can be achieved for minimal liquid discharge (MLD) or zero liquid discharge (ZLD).
  • New advanced membrane systems may be economic for shale produced water volume reduction with the TDS is lower than 80,000 mg/L.

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Source Water and Disposal Costs in Shale

Although there are many water management options available for shale operators, there is no one-size-fits-all solution. It is important to understand the costs, alternatives, and technical limitations of each option and develop a blended water management strategy to balance costs and risks. Start with identifying the costs of nearby frac/produced water disposal and source water costs. An overview of the different types of shale water can be found here. These options should then be compared to the costs of any treatment solution. For example:

Disposal: $6 to $60/m3 ($1 to $10/BBL)

Freshwater: $0.5 to $6/m3 ($0.1 to $1/BBL)

Re-use: many operators reuse flow back and produced water, and the cost is largely linked to storage, transport, and any treatment to reduce particulate load (microfiltration) and scalants (chemical softening).

 

In some cases, logistics or water hauling can dominate the cost equation, therefore treatment at the source to reduce volume may make sense.

Shale Water Treatment Options

Shale Gas Industry Banner Saltworks Technology

In general, there are three categories for treatment: 

Particulate & Hardness Removal: ($)

Technology:

  • Water hardness is removed by chemical softening and particulates are removed by bag filters. New developments in chemical softening system design remove pains of the past, such as over or under dosing, poor control, large physical footprint and lack of modularity.

Considerations:

  • Dosing: Conventional chemical softening systems use set dosing rates, which result in poor precision on constantly changing shale waters. This can lead to underdosing, which may cause scale, or overdosing, which results in wasted chemicals and increased operating costs. Modern chemical softening systems that use sensor-driven precision dosing avoid these problems by reducing waste and maintaining treatment system performance.
  • Filter Quality: Some bag filter systems are treated as disposable, resulting in higher waste, higher manual handling, and greater disposal costs. Opting for re-usable, highly robust filters with a semi-automated solids handling system can reduce these costs, and improve both the operability and environmental footprint of your particulate removal program.
  • Intervention: Whether dealing with bag filters or chemical softening, conventional systems can require high operator intervention. New technologies, such as our BrineRefine platform, come as a packaged, automated system that reduces intervention and improves the economics of this water treatment process.

lower cost evaporator crystallizer model
SaltMaker AirBreather

Volume Reduction: ($$)

Technology:

  • Open to Atmosphere Evaporators: Evaporation to atmosphere will reduce produced water volumes at a lower cost than closed evaporators (discussed later in this article). However, their fit with respect to thermal needs, air emissions, reject concentration, and permitting must be confirmed. Total cost of ownership (capital cost + operating costs) may range from $12-$24/m3 ($2-$4/BBL).

Considerations:

  • Air Emissions: Although water vapour is harmless to the environment, produced water may include volatile organic compounds (VOC) that evaporate with the water. Benzene is the most common VOC in produced water and is a regulated carcinogen. There are also volatile forms of arsenic and radium that exist as a part of organic complexes. Make sure you plan ahead for VOC management, since regulators and stakeholders will expect it. Open to Atmosphere Evaporators have been procured and then rapidly shut down due to stakeholder concerns. Invest in risk management and possibly a pilot project prior to making a large capital purchase. Saltworks’ open-to-atmosphere evaporator, AirBreather, includes a novel VOC management system that removes VOCs from the exhausted water vapor. Pilot plants are available to prove this and can be complemented with air dispersion modeling to support permitting discussions.

SaltMaker Airbreather Evaporator Crystallizer PFD
  • Energy: One cubic meter (6.3 BBL) of water requires 3.3 GJ (2.2 million BTUs) of energy to evaporate. However, the value of energy, known as ‘exergy’, depends on its temperature. It may only make sense to spend this energy if a waste heat source or a low temperature heat source is available, such as waste heat from reciprocating engine jacket cooling, exhaust, or waste gas that is flared. Water boils at 100 °C (212 °F), and most engine waste heat sources are 85-95 °C, which is not sufficient to evaporate water. However, the Saltworks’ AirBreather does not involve boiling water, instead it humidifies air. This enables the use of a much lower temperature heat source, whereas other open-to-atmosphere evaporators use submerged combustion with direct-fired gas sources, such as natural gas. There is a trade-off in that humidifying air requires larger chambers, but they operate at a lower temperature and can be constructed from engineered plastics to withstand corrosion and scaling issues.
  • Pre-treatment: Some evaporators cannot tolerate scale-causing compounds, so be sure to complete a water analysis and check with the technology vendor. The AirBreather was developed to accept any fluid without pre-treatment, and remove scale by self-cleaning before it becomes irreversible.
  • Concentration limits: Most open evaporators are limited to an upper TDS concentration of 150,000 to 250,000 mg/L, where they may start plugging with accumulated low solubility solids. It is worth determining these concentration limits before investing, since they directly impact the plant capacity. If you start with a TDS of 200,000 mg/L and can only concentrate to 250,000 mg/L this means a volume reduction of 20% will be achieved – contact us for help with making these calculations for your project. The AirBreather has no TDS limit, and can make solids due to its built-in self-cleaning and corrosion-proof construction. This means you can squeeze almost all the produced water, reducing your volume to any desired level. However, recall that rejected residual TDS waste must be managed.
  • Corrosion: After scale, corrosion is the second greatest killer of evaporators. Stainless steel will rapidly corrode when exposed to high chloride concentrations in produced waters. Super duplex stainless steel variants offer increased resistance, but they can cost more than exotic metals, such as titanium and Hastelloy, which do not corrode.  The AirBreather’s wetted parts are 95% gel-coated fiberglass and engineered plastic to entirely remove the corrosion risk. Heat exchangers are constructed with titanium but no boiling occurs on any metal surfaces, limiting scale potential. The AirBreather’s intelligent controls monitor heat exchanger performance and clean them in an automated manner before any irreversible performance degradation occurs.

Scaling found on the interior surface of pipes

Fresh Water Production: ($$ to $$$)

Technology:

  • Membranes ($): Reverse osmosis (RO) and electrodialysis reversal (EDR) are the most widely used membrane desalination technologies. However, these methods offer limited economic fit to water with mid-range TDS concentrations (less than 40,000 mg/L). New advancements in membrane systems, such as ultra high pressure reverse osmosis, can now be economic with TDS up to 80,000 mg/L. Our XtremeRO systems can concentrate produced water up to 140,000 mg/L TDS, reducing disposal volumes for minimal liquid discharge (MLD). Membrane system total cost of ownership (capital cost + operating costs) may range from $3-$9/m($0.5-$1.5/BBL), however, pre-treatment, such as BrineRefine, could change this cost equation. 

Reverse Osmosis System
  • Closed Evaporative Crystallizers ($): Closed evaporative crystallizers can offer applicability across a wide range of TDS concentrations, but they are also the most expensive treatment option due to their size and complexity. Closed systems condense water vapor and employ different methods to recycle a portion of the thermal energy or heat of condensation. This lowers their energy consumption relative to open to atmosphere evaporators but increases their relative cost. 

Humidification-Dehumidification Evaporators
  • When considering a closed evaporative crystallizer, you should also factor in:  pre-treatment for scaling, concentration limits of conventional evaporators, and corrosion risk. In addition, if freshwater is produced, it must either be stored, re-used, or released to the environment. One advantage of freshwater storage and transportation over produced water storage is that it requires less containment. Although you should check your local regulations, in many cases, freshwater may be stored in ponds, industrial water bags, or tanks and transported via a lower cost lay flat hose. Freshwater may be used by a neighboring agriculture facility or can also be discharged to the environment in some jurisdictions, noting that environmental discharge permitting in the US may take up to a year and the permit is typically only valid for a single site. These added dimensions speak to why open-to-atmosphere evaporators can be a better option if air emissions are managed and thermal energy is available.
  • Closed evaporative crystallizer total cost of ownership (capital cost + operating cost) may range from $24-$48/m3 ($4-$8/BBL), making them the most expensive treatment option.

Logistics and Residual Reject Disposal

Truck carrying brine

Logistics: Logistics and water hauling can dominate shale water management costs if a disposal outlet is not nearby. When assessing treatment and disposal options keep an understanding of logistics cost in mind, including wait times for trucks to load and unload. As a rule of thumb, it may cost $15/m3 ($94/BBL) per hour of transport once loading and unloading times are factored in. Costs also vary depending on the quality of roads in the area. It can make sense to review pre-concentration prior to transport, which lowers the volumes of the water being hauled. In many cases, there will be an economic optimum that combines re-use, storage, treatment, and transport for final reject waste disposal.

 

For example, if transport and disposal is $30/m3, and volumes can be halved for $10/m3, and solids produced afterwards for $45/m3, then it may make the most sense to pre-concentrate and halve the volumes for $10/m3 followed by transport and disposal for $30/m3. The net blended cost will be $20/m3. Preferably, the reject waste is as concentrated as possible until it reaches a cost that is just below the transport-disposal costs. It is important to note that as produced water is concentrated and its volume reduced, it can become denser with more scaling potential. Higher density waters can be beneficial for disposal wells; however, scaling waters may plug them. Technologies, such as BrineRefine, are available to reduce the scaling potential of highly concentrated brines prior to disposal, and thereby protect the disposal well asset from scaling and plugging while maintaining the beneficially high density.

BrineRefine modern chemical softening and treatment
Saltworks BrineRefine Chemical Softening System

Residual Reject Disposal: Although relatively pure water can be separated from produced waters, reject residual waste is always left behind. This will include organics (petroleum byproducts) and inorganics (mixed salt). It is important to plan for this in advance. One advantage of disposal wells is that they dispose of all residuals, and as noted above, disposal costs and volume can be limited through treatments that pre-concentrate. However, it is also possible to: (a) produce a mixed solid waste for landfill disposal; and (b) separate out the organic phase and produce refined salts for industrial re-use. This includes a combination of chemical pretreatment and staged crystallization.

 

Be sure to study and assess the lifetime of disposal options, if solids are going to be produced. Landfill waste must pass paint filter, leaching (TCLP) and radioactivity tests. Saltworks can help assess if your produced water may pass these tests through bench testing. Saltworks can also review your water’s potential to produce beneficial industrial salt for re-use – although this is unlikely to offer a secondary revenue stream through salt sales. Most salts are of low value and the costs of producing, handling and transport barely offset any revenue generated. However, industrial re-use offsets costs by avoiding the need to pay for landfill disposal.

Summary

Shale gas and oil production presents a leading energy source moving forward, yet its future and production is tightly linked to water management. Every water type, job site, and economic case is different. Contact us to review your specific situation, benefit from our expertise, and assess if your water management costs or risks can be lowered.

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Lithium Brine Extraction Technologies & Approaches

Salar de Uyuni Bolivia lithium salt lake

Lithium Brine Extraction Technologies & Approaches

June 8th 2018

Takeaways:

  • Brines from salars and salt lakes, as well as spodumene ores, are the primary source of lithium, while geothermal brines represent secondary sources.
  • Produced water from oil & gas operations is an untapped source of lithium that may be more important in the future.
  • Chemical precipitation, adsorption with inorganic ion exchange sorbents, solvent extraction and concentration with membrane technologies are the primary means of lithium recovery from brines.
  • Each lithium extraction and recovery process has unique advantages and challenges that need to be considered when determining the best fit for any project.
  • New advances in water treatment offer exciting improvements on the economics of using membrane technologies for lithium recovery.

Summary of Major Lithium Brine Resources and Dominant Recovery Processes

Resource Lithium (mg/L) Dominant Process Challenges Opportunities
Salars (Lake Brines) 200-7,000 Staged evaporation to atmosphere, concentrating and producing lithium. Large land areas and significant quantities of water used to extract lithium from lake beds.

Minimum 18 months from pond start-up to first production due to slow evaporation.
Massive resource with available natural evaporation energy.

Opportunity to hybridize evaporation with concentration and purification technologies.
Groundwater Brines 20-200 Lithium absorption-desorption on a metal oxide, following by refining. Tend to be richer in hardness than salars, making processing more challenging. Vast resources in USA, close to major lithium utilization plays.
Oil & Gas Brines 50-100 No dominant process established. Low concentration and extremely large volumes needed, while most produced waters are spread out and smaller volume. Attractiveness of oil & gas wastewater adding value.

Much of the world’s commercial lithium is still recovered today in the way it has been for half a century: by evaporating brines collected from salars and salt lakes in evaporation ponds. Recovering lithium in evaporation ponds can take a year or more and leaves behind lots of salt waste, but there are new technologies and processes that offer exciting options for lithium extraction.

 

What are the Primary Sources of Lithium?

Salar de Uyuni Bolivia lithium salt lake
Salars in Bolivia

The demand for lithium is outpacing the rate lithium is being mined from brines, due to continuing advancements in mobile devices and electric cars. Lithium is an abundant element, however, there are very few commercial resources where lithium is found in concentrations sufficient for producing useful lithium compounds. The primary sources of lithium are in brines from salars and salt lakes, and lithium-bearing spodumene ores, while geothermal brines represent the second most productive sources of lithium. Lastly, produced waters from oil & gas fields are an untapped source of lithium that may grow in importance in the future. To ensure the productivity of these lithium resources, it is essential to have lithium recovery technology and processes that are optimized to the characteristics of each individual resource, such as the concentration of lithium, the ratio of lithium to magnesium and calcium ions, and relative concentrations of other ions.

Lithium Recovery via Chemical Precipitation

Lithium recovery via conventional chemical precipitation normally starts by subjecting lithium-rich brine to a series of solar pond evaporations. This will precipitate other salts such as sodium chloride and potassium chloride, while concentrating the lithium. Lime (calcium hydroxide) is then added to the concentrated lithium brine to further remove magnesium as magnesium hydroxide, and sulfate as calcium sulfate. Any calcium in the concentrated brine is removed as calcium carbonate by adding sodium carbonate. The brine that results from these chemical precipitations is then subjected to a carbonation process, where the lithium reacts with sodium carbonate at 80-90°C to produce technical-grade lithium carbonate. This can be further purified to produce battery-grade lithium by re-dissolving the lithium carbonate, and then using an ion exchange process to remove impurities.

 

To reduce the time required for solar evaporation concentration, lithium will sometimes be precipitated as lithium phosphate, which precipitates more quickly than lithium carbonate due to its roughly 30-fold lower solubility. Lithium phosphate is then converted into battery-grade lithium hydroxide through an electrochemical process.

 

Lithium Recovery via Adsorption

Lithium selective ion exchange sorbents are a promising alternative for extracting lithium from brines. Inorganic ion exchange sorbents, such as lithium manganese oxides, spinel lithium titanium oxides, and lithium aluminum layered double hydroxide chloride, have been shown to have high lithium-selective uptake capacity. However, the recovery process requires the lithium to be in contact with these sorbents for long periods of time. Additionally, sorbents can be very expensive; they are mostly available as powders that require energy-intensive processes for lithium recovery and can degrade during the acid-driven desorption process.

A novel technique based on an electrolytic cell that contains LiFePO4/FePO4 as an electrode material has been studied to selectively recover lithium. Under an electrochemical process, lithium ions from a lithium-bearing brine are selectively intercalated into a cathode made from FePO4 to form a lithium-saturated LiFePO4. Then, the current is reversed, turning the LiFePO4 into an anode that can be used to recover lithium.

Lithium Recovery via Solvent Extraction

One approach that has been tested to selectively recover lithium from brine involves using an organic phase comprising kerosene and an extractant, such as tributyl phosphate, trioctylphosphine oxide (TOPO), and beta-diketone compounds. Although these organic phases show very high selectivity toward lithium over sodium and magnesium ions under optimized conditions, the lithium stripping phase uses solvent extraction that can result in costly equipment corrosion. In addition, the residual brine that remains after lithium extraction may require post-treatment to remove the leached solvent before it can safely be sent for disposal.

Reverse Osmosis System

Lithium Recovery Using Membrane Technologies

Reverse osmosis (RO) and nanofiltration (NF) processes have been studied for pre-concentrating or separating lithium from a lithium-bearing brine. A typical lithium brine usually contains high concentrations (for example, more than 5.0 wt%) of salt ions. The maximum salt concentration that an RO/NF process can reach is linked to the osmotic pressure, as well as the membrane’s selectivity and the mechanical stability of any associated equipment. There are automated chemical softening systems that can help membrane treatment systems reliably reach their treatment limits and improve yield, such as our BrineRefine system. Conventional NF processes cannot efficiently separate lithium without heavy pre-treatment of the brine, such as diluting the brine with a large amount of fresh water.

 

Electrodialysis systems that use monovalent-selective ion exchange membranes, such as FlexEDR Selective, have also been used to recover lithium from lithium brine containing divalent ions such as calcium, magnesium, and sulfate. The selectivity of the membranes for monovalent ions over multivalent ions is the key factor for determining the efficiency of the recovery process.

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RO Brine Treatment: Why Maximizing Reverse Osmosis Recovery Matters

A bank of Reverse Osmosis filters at a public water utility plant.

RO Brine Treatment: Why Maximizing Reverse Osmosis Recovery Matters

June 27th 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.

A bank of Reverse Osmosis filters at a public water utility plant.

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.
  • Often you can treat saturated RO brine further with intelligent membrane systems, by removing scaling ions and using RO 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 want help with any of the above.

Start with the Fundamentals: What is Your Water Chemistry?

Pipe Carrying Raw Water

Getting the most out of an RO system is easier when 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 understanding the range in your water chemistry.

Stop Fouling & Scaling on RO Membranes Before It Starts

Scale formation in a pipe

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 scaling ions are planned for, RO can be extremely reliable and optimized for performance. There are solutions for removing scaling ions. These range from the simple, like pH control and anti-scalants, to more advanced solutions, such as selective scaling ion removal and RO-normalized flux live monitoring.

Choose an RO System that Can Achieve Your Performance Targets

Not all RO systems are created equal. There are many factors that 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.
  • Concentrate, purge, and flush 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.
reverse osmosis system

When you consider building an RO system, consult with water treatment experts who can help you determine the setup best suited to your needs. While RO is widely available in low cost systems, and these systems may fit your application, there are really two categories of RO: basic and advanced. Basic RO works great for simple waters, but when it comes to pushing brine concentrations the basic ROs breakdown rapidly. 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 ions, such as CaSO4 or SiO2 and other low solubility compounds. If these scaling ions are removed, or separated, it can increase the recovery of membrane systems and reduce the volume of brine.

BrineRefine modern chemical softening and treatment

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). Brine Refine 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, which can concentrate brines up to 180,000 mg/L TDS.

Trust Intelligent Automation Over Manual Management

Automation for Water Treatment Systems

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 will increase or decrease permeate flux as it detects changes in scaling compounds. This will minimize fouling in the presence of high scaling ions and maximize recovery when concentrations of scaling ions 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

S100 SaltMaker Evaporator Crystallizer on Site

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 pretreatment, 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 it is higher cost 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? It can be very low cost to evaluate and build-in options for expansion and change, while still at the drawing board. Your brine disposal costs could increase if using 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 changes, evaluate your options and future scenarios before making an investment. This can be done with the help of water treatment experts.

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Treating SAGD Blowdown with the SaltMaker MultiEffect Evaporator Crystallizer

SaltMaker Evaporator Crystallizer for SAGD Applications

Treating SAGD Blowdown With the SaltMaker MultiEffect Evaporator Crystallizer

May 4th 2018

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 at a Class II landfill and recovers freshwater for reuse.

SaltMaker Evaporator Crystallizer for SAGD Applications
SaltMaker MultiEffect evaporator crystallizer test pilot

SAGD and Blowdown Water Management Issues

Steam assisted gravity drainage (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 looking for on-site blowdown water treatment solutions to remove freshwater from the blowdown for re-use, and condense all waste to solids for safe 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, providing three fundamental design benefits at the expense of footprint: (1) process components built from engineered plastics that remove corrosion concerns and scaling/fouling concerns; (2) high circulation rates that provide a scouring effect on highly saturated flows; and (3) sensible heat transfer 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 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 of 125 m3/day water removed. Higher capacities are achieved by adding more S125 plant blocks.

SaltMaker MultiEffect Raw blowdown (left) and condensed water (right)
SaltMaker MultiEffect condensed water (left) and raw blowdown (right).

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 reliably operated 24/7. Saltworks’ patented non-scaling design and self-cleaning systems were paramount to operations. In addition, when coupled with the SaltMaker MultiEffect patented low temperature solids production and extraction system, the plant solved a major SAGD problem: continuous solidification and extraction of both ionic and organic components preventing accumulation that results in gelling or plugging of conventional systems.

SaltMaker MultiEffect Evaporator Heat Recycling
SaltMaker Evaporator Crystallizer Brine

The project results are as follows:

  • High quality freshwater recovered (<500 mg/L TDS).
  • Continuous, reliable production and extraction of solids. Analytical tests demonstrated 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.

SaltMaker Evaporator Crystallizer Solids ZLD
SaltMaker MultiEffect solids suitable for Class II landfill disposal
SaltMaker Evaporator Crystallizer Data Table
Data from treating raw evaporator blowdown using the SaltMaker MultiEffect evaporator crystallizer

The pilot projects demonstrated that the SaltMaker MultiEffect reliably and efficiently recovers freshwater and produce 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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Article

Buying an Industrial Evaporator? Ask Vendors these Five Questions

Multiple Effect Evaporator - Photo © Evelyn Simak (cc-by-sa/2.0)

Buying an Industrial Evaporator? Ask Vendors these Five Questions

April 6th 2018

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

Multiple Effect Evaporator - Photo © Evelyn Simak (cc-by-sa/2.0)
Industrial Evaporator - Photo © Evelyn Simak (cc-by-sa/2.0)

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 the commonly used simple form that has plagued many in the past, which references guarantees to a single chemistry data set. Your chemistry will change, and when it does, these guarantees can become invalid. Ensure 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.

SaltMaker Evaporator Crystallizer Pilot
SaltMaker Evaporator Crystallizer Pilot

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. Our experts can help you with this. For example, if your TDS is below 80,000 mg/L with a flow rate above 200 m3/day, ask about pre-concentration technologies. Modern membrane concentrators, such as 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, it may not make sense to have two process plants. Instead, it may be worth investing in a slightly larger evaporator.   

Industrial Evaporator

In addition, understand any chemical pre-treatment clearly, and the costs per unit inlet. Some will throw a lot of chemicals at the inlet via extensive softening to make it easier on their evaporator. Since the chemical costs are included in your operating costs and not their sale price, they can make their evaporator appear lower cost, when in fact its total cost of ownership could be much higher than originally anticipated. We like to break down costs per unit inlet ($/m3) for four categories: capital, energy, chemicals, and labor.

At Saltworks, we will 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 total cost of ownership.

3. How do you prevent corrosion and scaling?

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

Scaling found on the interior surface of pipes
Scaling in a pipe

Our answer to corrosion is to not build everything from titanium or exotic steels – there are alternatives.  Saltworks’ SaltMaker family provides such alternatives through smart engineering with fiber-reinforced plastics. Our answer to scale is 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 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 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, which may be better suited to your project needs. In other cases, it may be preferable to transport or handle a liquid slurry that can be pumped, rather than solids. Hybrid evaporator-crystallizer technologies offer the advantage of adaptability to produce 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 you see your rejects disposed via the same mechanism intended for 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.

Humidification-Dehumidification Evaporators

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 the complete installation and operating cost picture for you, and question it deeply. There is nothing better than visiting an existing installation and talking to operators to secure the full picture.  

 

Coupling site visits with full cost of ownership review analyses, as well as a pilot, will set help set your project up for success.

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

SaltMaker-Evaporator-Crystallizer-at-Saltworks-Technologies-HQ

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

April 6th 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.

 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 pretreatment 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, unlike MVR evaporators that rely on a single vapour compressor inhaling moisture into a high-speed rotating machine. 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 around 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 (< 90oC), 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 suspended seed crystal nucleation sites 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.

SaltMaker - Automated Bagging System
Automated bagging system
SaltMaker - Automated Bagging System
Bag removed by forklift
SaltMaker - Bag of Solids
Bag of solids

One Step Treatment

Traditional treatment technology requires multiple steps with different technologies to treat wastewater with high salinity levels. This includes separate systems for pretreatment, evaporation, crystallization, solids production and dewatering. The SaltMaker combines these steps into a single system that requires no pretreatment. It can be fed water at any salinity and almost any water chemistry. Expensive chemicals that increase solids load such as soda ash are avoided on 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, fibre-reinforced plastics – with low surface energy that provides resistance to corrosion and scale. 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 reliability challenges that frequently affect conventional evaporators and crystallizers.

SaltMaker - Pipework
Pipework: UPVC and CPVC
SaltMaker - Pumps
Pumps: Engineered Plastics
SaltMaker - Modules and Tanks
Modules and Tanks: Fiber Reinforced Plastics
SaltMaker heat exchanger
Heat Exchanger: Titanium (non-boiling)

Intelligent Automated Operation and Cleaning

The SaltMaker MultiEffect has intelligent automated operations and self-cleaning processes. The plant can automatically (1) start; (2) stop and flush; and (3) hibernate in circulation mode and ramps 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 it has been spent.

No Single Point of Failure

Unlike mechanical vapor recompression (MVR) technologies, where 100% 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.

SaltMaker - Evaporation Module
Evaporation module
SaltMaker Radiator
Radiator Module
SaltMaker - Fan Module
Fan Module

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

A SaltMaker Effect
An Effect: There are multiple effects in a SaltMaker MultiEffect
S100 SaltMaker with four effects
S100 SaltMaker MultiEffect with four effects

Modular Build and Scale Up

The SaltMaker MultiEffect is built into standard ISO container frames. These modules enable factory assured quality production, ease of shipment-installation, and future expansion. The open concept design also allows easy access to processing equipment, such as pumps, for inspection and routine maintenance, without the need for any confined space entry.

Modular SaltMaker Plant Built into Standard ISO Frames
Modular SaltMaker Plant Built into Standard ISO Frames
Easy Access to Process Equipment
Easy Access to Process Equipment
SaltMaker Evaporator Effect

Multiple inspection ports in each effect allows convenient monitoring for scaling and fouling (ports are highlighted in blue). Process set modules slide in and out. Cleaning is done with a power washer.

 

The modular design simplifies transport and assembly; the SaltMaker is sent by standard freight without any permits of oversized loads and assembled by crane on-site. 

SaltMaker Onsite Pilot
SaltMaker Onsite Pilot
SaltMaker Onsite Pilot
SaltMaker Onsite Pilot

SaltMakers are built to standardized plant sizes that can be added together to expand capacity as your project grows. The models and their capacities are listed below. 

ModelCapacity Based on Freshwater Removed*
m3/dayGallons per DayGallons per MinuteBarrels per Day
S303079005.5188
S66661740012415
S1001002640018630
S1251253300023790

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

S100 SaltMaker MultiEffect Plant
S100 SaltMaker Plant: 100 m3/day freshwater removed capacity
S100 + S125 Full-Scale SaltMaker Industrial Wastewater Treatment Plants
S100 + S125 SaltMaker Plants: Capacity Increased by adding a S125 plant block 100 m3/day + 125 m3/ day = 225 m3/day freshwater removed capacity

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 less than 90oC, 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 92oC, 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 vapor condenses into freshwater liquid at the radiator modules, which also transfer 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 discharged 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. Contact us to see how the SaltMaker fits into your project.

Related Resources

chilledcrys chilled crystallizer pfd

SaltMaker ChilledCrys

Request More Information Learn More To produce solids, chilled crystallizers need to overcome a much lower thermodynamic barrier than evaporators. For very specific solution chemistries, chilled crystallization is a highly

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Article

Choosing the Right Zero Liquid Discharge Technology: Evaporators & Crystallizers

S100 SaltMaker Evaporator Crystallizer on Site

Selecting the Right Type of Industrial Wastewater Evaporator or Crystallizer

April 6th 2018

There are four fundamental types of industrial evaporators and crystallizers 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. When achieving zero liquid discharge, evaporators and crystallizers can be the right fit. 

  

 

Takeaways:

  • Before investing in an evaporator, reduce cost by maximizing recovery with upstream membrane systems.
  • Understand the application and fit for the four different industrial evaporator types before deciding on the suitable technology for your project.
  • Protect your investment by engaging experts to help you prevent scale and corrosion, which diminish 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 Membrane Systems Desalination
Membrane Treatment Systems

Reverse osmosis 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 reverse osmosis and concentrate brines up to 130,000 mg/L. This will reduce your total cost by lowering the size of the downstream evaporator and the energy it consumes. To optimize your project economics, ensure you maximize the performance of your RO system before considering evaporators or other thermal treatment systems. Contact us for a project analysis.

The Four Major Types of Industrial Evaporators

Evaporators treat wastewater by heating it to evaporate volatile solvents like water from the solution, and then cool and condense it to produce freshwater. The purpose is to concentrate non-volatile solutes like inorganic salts and organic compounds and leave behind a more concentrated wastewater stream. There are four common industrial wastewater evaporators:

Industrial Evaporator

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 the vapour compressor you select can handle high rotation speeds and stands up to severe vibrations.
  • Consider redundancy, since compressor failures are common, which will result in 0% capacity for your system.
  • MVR evaporators can work well on large flows at low TDS, however, they struggle in crystallizer mode as temperature and pressure differences must be larger.

2. Multiple Effect Evaporators

Multiple Effect Evaporator - Photo © Evelyn Simak (cc-by-sa/2.0)
Multiple Effect Evaporator - Photo © Evelyn Simak (cc-by-sa/2.0)

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 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 (HDH) Evaporators

Humidification-Dehumidification Evaporators
Humidification-Dehumidification Evaporators

Humidification-Dehumidification Evaporators operate similar 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.
  • Non-metallic construction that leverages 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

SaltMaker Evaporator Crystallizer Installed at BC Site
SaltMaker Evaporator Crystallizer Installed at BC Site

The SaltMaker Multi-Effect evaporator crystallizer combines three of the above industrial evaporator designs. First, it leverages the HDH cycle so it can be constructed from lower cost, fibre-reinforced plastics that 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 to 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:

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

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

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

EvaporatorsFit & TipsInstallation/OperabilityEconomic Sweet Spot
Mechanical Vapour
Recompression (MVR)

Widely used where a fit, namely on non-scaling flows as a concentrator up to 20% salt mass (80% water). 

 

Ensure metallurgy and maintenance access / chemical cleans are planned for during design phase.

Custom design-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 more reliable than MVR 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 in 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). 

 

Concentrate to 30% salt mass with ease, or produce 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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Article

How to Avoid Day Zero with Zero Liquid Discharge

Cape Town Water level crisis Theewaterskloof Dam

How to Avoid Day Zero with Zero Liquid Discharge

March 15th 2018

There has been much discussion about how residents of Cape Town can reduce their intake to prevent Day Zero, 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 its worst drought in 85 years that 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. 

Cape Town Water level crisis Theewaterskloof Dam
The Theewaterskloof Dam previously housed 41% of the water storage capacity available to Cape Town.

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 domestic activities, it is important that agriculture and industry also contribute to preserving our 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. 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.

mining flotation
Agriculture Wastewater Treatment

The main pollutants in agricultural and industrial wastewater are either 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) which 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.

FlexEDR Desalinates EOR Produced Water
Zero Liquid Discharge System Pilot

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 run off 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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