Arizona State University Study

Experimental Evaluation of Scale Mitigation Technologies

Arizona State University conducted an Evaluation of Alternatives to Domestic Ion Exchange (Salt based) Water Softeners.

The sudy was led by: Mara Wiest, Dr. Peter Fox, Dr. Lee Wontae, HDR, and Tim Thomure, HDR

Four technologies were tested

• Electromagnetic Water Treatment (EMT) - see below*
• Capacitive Deionization (CDI) - see below*
• Electrically Induced Precipitation (EIP) - see below*
• Scale Centurion media

Results

All four technologies demonstrated some scale mitigation.

However, the performance differential between treatment methods was pronounced. 

Scale Centurion media was the clear winner.

It exhibited markedly superior scale reduction across all three water quality conditions, consistently achieving scale inhibition efficiencies in excess of 90%.

This level of performance was both statistically robust and reproducible, establishing Scale Centurion media as significantly more effective than the alternative treatment technologies evaluated.

Study Details

The objective was to:

"identify credible alternatives to ion exchange water softeners that would provide consumers with the ability to reduce the impacts of hard water without creating the negative salinity impacts."

Methodology

Each of the four treatment devices was subjected to a standardised 21-day test protocol across three distinct water quality conditions. Testing was conducted using a recirculating flow apparatus in which water was continuously cycled across a resistive heating element, simulating the thermal and hydrodynamic conditions of a domestic or commercial water heater. Following each test period, accumulated scale deposits were recovered from both the test vessel and heating element surfaces via dissolution in a standardised acid solution. Total scale mass was quantified gravimetrically (by weighing), and residual dissolved mineral content was determined using the EDTA complexometric titration method — a well-established analytical technique for measuring water hardness.

Test Conditions

Feed water hardness ranged from approximately 180 mg/L (10.5 grains per gallon) to 250 mg/L (14.6 grains per gallon), spanning a range representative of moderately hard to hard water supplies commonly encountered in real-world applications.

Details on the other technologies tested:

*Capacitive Deionization (CDI)

Capacitive Deionization is a water desalination and purification technology that removes dissolved ions (salts) from water using electrical energy.

How it works: Water flows between two porous electrodes — typically made of activated carbon — that carry opposite electrical charges. Dissolved ions are attracted to and adsorbed onto the electrode surfaces (like a capacitor), effectively removing them from the water. When the electrodes become saturated, the electrical potential is reversed or removed, releasing the ions into a concentrated brine stream, and the electrodes are regenerated for reuse.

Key advantages:

• Energy-efficient at low to moderate salinity levels (compared to reverse osmosis)
• No high-pressure pumps or membranes required
• Electrodes are regenerable, reducing waste
• Scalable and relatively low maintenance

Limitations:

• Less effective at high salt concentrations
• Electrode degradation over time
• Co-ion expulsion can reduce efficiency (addressed by membrane-CDI variants)

Applications: Brackish water treatment, drinking water purification, wastewater recycling, and industrial process water treatment.

A popular variant, Membrane CDI (MCDI), adds ion-exchange membranes to improve efficiency and reduce unwanted ion re-release during charging cycles.

*Electrically Induced Precipitation (EIP)

Electrically Induced Precipitation is a water treatment technology that removes hardness ions and other dissolved minerals from water by using an electric field to trigger their precipitation as solid crystals or scale.

How it works: An electrical current is applied to electrodes submerged in water. At the cathode, localised alkalinity increases due to the electrochemical reduction of water, raising the local pH. This causes sparingly soluble salts — most commonly calcium carbonate (CaCO₃) and magnesium hydroxide (Mg(OH)₂) — to exceed their solubility limits and precipitate out of solution. The precipitate either deposits on the electrode surface or forms suspended crystals that can be filtered out.

Key advantages:

• Effective at removing hardness (calcium and magnesium) without chemical additives
• Can be combined with other treatment processes
• Relatively simple operation
• Produces a recoverable, often reusable mineral byproduct

Limitations:

• Electrode scaling requires periodic cleaning or regeneration
• Energy consumption can be significant at scale
• Less effective for monovalent ions (e.g. sodium, chloride)
• Performance is sensitive to water chemistry and temperature

Applications: Water softening, cooling tower water treatment, industrial process water conditioning, and prevention of scale buildup in pipework and heat exchangers.

EIP is sometimes combined with CDI or other electrochemical methods in hybrid systems, allowing simultaneous removal of both hardness ions and dissolved salts in a single treatment train.

*Electromagnetic Water Treatment (EMT)

Electromagnetic Water Treatment is a physical water conditioning technology that uses magnetic or electromagnetic fields to alter the behaviour of dissolved minerals, reducing their tendency to form hard scale deposits.

How it works: Water passes through or around a device that applies a magnetic or oscillating electromagnetic field. This is thought to affect the nucleation and crystal growth of sparingly soluble salts — particularly calcium carbonate — causing them to form soft, suspended micro-crystals (aragonite) rather than hard, adherent scale (calcite) on pipe and equipment surfaces. The suspended crystals can then pass harmlessly through the system or be flushed out.

Key advantages:

• No chemicals required
• No moving parts — passive and low maintenance
• Easy to retrofit onto existing pipework
• Low operating costs and energy consumption

Limitations:

• The underlying mechanism remains scientifically contested and not fully understood
• Effectiveness is highly variable and difficult to predict
• Does not actually remove ions from the water — only modifies crystal habit
• Performance claims are inconsistent across independent studies
• Effects may diminish if water is stored after treatment

Applications: Domestic and commercial scale prevention in boilers, heat exchangers, cooling towers, pipework, and household appliances such as washing machines and kettles.

EMT is perhaps the most controversial of the electrochemical water treatment technologies. Unlike CDI or EIP, it lacks a universally accepted mechanistic explanation, and rigorous independent validation of its efficacy remains an active area of debate in the scientific literature.