DMI-65 - Advanced Oxidation Filtration Media

• Reduce downtime
• Save on costly membrane cleaning and replacement
• Significantly improve system performance reducing initial system capital investment
• High Disinfection rate achieved
• No leaching of chemicals
• Substantial whole of life cost savings

Low Cost Iron and Manganese Treatment
DMI-65 significantly reduces the operating costs of iron and manganese removal in water filtration due to the following performance features:

Regeneration Not Required
The media operates with a continuous injection of sodium hypochlorite at low residual levels (0.1 to 0.3 ppm) which eliminates the need for regeneration with Potassium Permanganate which both cost and time expensive

Long Life
DMI-65 is not consumed in the process giving it an expected operational life of up to 10 years, providing considerable advantages over other processes or media. The media does not display a decaying capacity to do its catalytic work. Over the 5 to 10 year period, through many backwashing operations of the bed to remove retained solids, an attrition loss of the media occurs by contact between particles and mechanical abrasion.

High Load Capacity
Because of the increased surface area owing to the micro-porous structure of the matrix material, DMI-65 has higher iron and manganese load capacity which can extend the duration of filter runs and the time between backwashing, thereby reducing downtime, operating expense and wastage.

Reduced Total Water Treatment Solution costs

The use of DMI-65 in a water treatment solution for the removal or iron and manganese contributes to a reduction in the capital investment cost of the water filtration solution:

High Flow Rates
The infused technology of DMI-65 promotes the highest oxidation rate of any catalytic filtration media. This permits a significantly higher water flow rate to achieve the same level of iron and manganese removal. DMI-65 can operate at linear filtration velocities up to twice that of conventional media with a corresponding reduction in capital equipment costs.

Reduce Redundancy
Iron and Manganese contamination can materially reduce the performance of water treatment systems. The effectiveness of DMI-65 in removing iron and manganese contamination levels allows the water filtration system to function closer to rated levels thereby reducing the amount of costly overcapacity that would be acquired to achieve required output levels.

Wide Operating Environment
Stable and satisfactory performance at pH 5.8 to 8.6. and a maximum operating temperature of 113° F (45°C) reduces the need for investment to alter the operating environment.

Our Advanced Oxidation Process (“AOP”) uses the highly reactive catalytic material DMI-65 to boost the reduction/oxidation (redox) processes in water. This material promotes stronger oxidation than molecular oxygen and ordinary oxidants. Under certain conditions heavy metals may be difficult to oxidise to insoluble hydroxides, however our DMI-65 based AOP increases the rate of reaction and achieves a higher degree of purification.

In essence, the oxidants and the media work together to oxidize a dissolved solid into a suspended solid that is then filtered out in the depth of the media bed. If an element can’t be oxidized and precipitated the media can’t remove it. The media “helps” chemical reactions to occur by interacting with the oxidation reaction without being permanently altered.

Iron and manganese exist in bore water as bicarbonate. DMI-65 acts as an oxidation catalyst in the true meaning of the word and facilitates oxidation – precipitation – filtration. Strictly speaking, the media facilitates chemical reactions and does not explicitly remove anything, though once oxidised, the depth filtration aspect of the media removes the solids created by the oxidation that are then periodically backwashed out of the filter vessels.

Chlorine, fed as sodium hypochlorite or bleach (12.5% NaOCl), is the preferred oxidant since it is relatively inexpensive, readily available around the world and it is effective. Other oxidants such as hydrogen peroxide (H2O2), chlorine dioxide (ClO2) or ozone can also be used so long as a residual can be measured and maintained. Choice of oxidants needs to be subject to detailed analysis as performance varies according to the operating environment.

Another function of the Chlorine is that it keeps the media free from bacterial bio fouling or slime growth which reduce its performance. The need to add an oxidizer as part of the DMI-65 process also means that the final stage of the disinfection process of water treatment is also addressed.

For effective treatment results, DMI-65 Advanced Oxidisation Process is integrated into a complete treatment system. The treatment processes are arranged in three stages: pretreatment-conditioning, DMI-65 catalytic AOP treatment and post DMI-65 catalytic AOP treatment.

The DMI-65 Advanced Oxidation Process will work in most vertical filtration configurations.
Pre-treatment allows flexible implementation of a range of traditional processes; however significant performance improvements and cost reductions are generally achieved from the integration with the next stage, AOP. Post DMI-65 catalytic treatment stage may include fine filtration comprising 5 and 1 micron filters, a secondary filtration barrier using fine resolution filters.

Arsenic Removal
The media can also be used to remove Arsenic (As). In this case, the media does not actually remove the As but rather relies on the fact that Arsenic and Iron (Fe) readily form a complex and when the media takes out the Fe it takes the As with it. If water has As present but no Fe it will be necessary to add ferric chloride to the water. It should be noted that this only applies to inorganic As (As III and V) since not all organic As readily bonds with the Fe. As Arsenic is extremely poisonous (classified as a group 1 human carcinogenic substance), water treatment plant design must be proven through pilot testing to establish correct settings, or the use of already proven DMI-65 based arsenic removal systems.

Hydrogen Sulphide Removal
The media can also be used as a simple and low-cost technology to remove H2S. The DMI-65 Advanced Oxidation Process acts as an oxidation catalyst and facilitates the oxidation of any H2S not oxidized by the chlorine injection. The sulfur is then filtered in the media bed.

Uses

In addition to the basic human right to have access to clean and safe drinking water, most industries that use water in their production require water purification to ensure integrity of their products of the highest quality and that the performance of their processing or manufacturing equipment is not compromised.

Water for consumption or used in food processing industries needs to be clean, with iron and manganese well below regulated levels, low in hardness and alkalinity and free of undesirable taste, odours and chlorine.

Water used in processing industries and systems need water that is treated for the removal of iron and manganese in order to achieve the highest possible performance from their systems. This performance can be a measure of output or downtime for maintenance.
Impact on the environment must also be addressed. Spent water, or output from dewatering operations must have excess iron and manganese removed in order to avoid damage to the ecosystem output areas. Facilities must be compliant, chemical reduced, discharges recycled and minimised.

How DMI-65 Works as Filtration Media: The purpose of this paper is to provide users of DMI-65 catalytic water filtration media with qualitative information about how the material works, its capabilities and limitations and enable them to apply the material to water treatment processes in the appropriate manner and with confidence. The paper avoids the detailed complexity of solid surface electrochemical layers and colloidal science, quantitative physical and chemical processes and reactions. For readers having already significant knowledge in this area the paper brings more understanding of what DMI-65 is and its intended use. Newcomers to this area are provided with the bases, and perhaps motivation, for directing their more in depth studies as they might wish.

How DMI-65® Works compared to other products: In the early days of water treating, naturally occurring zeolites (such as glauconite greensand) were used to soften and remove the iron and manganese from boiler make-up and process waters. As the demand for higher quality water increased (due in part to higher pressure class boilers) the water treating industry largely moved away from these products for softening to the newly developed synthetic ion exchange resins.

However, in the case of iron and manganese removal this move was much slower and the result was that the use of glauconite greensand (greensand) filtration media continues until the present time. Greensand was and is often used as a pretreatment step prior to ion exchange processes since the iron in a feed water can and does foul the cation resin. Other processes include aeration and oxidation-filtration with standard media filters or proprietary types of media and/or filters

While there have been other iron/manganese removal products and processes developed since greensand was introduced the use of greensand continued even though there were several issues that made it a less than ideal media. It required periodic regeneration with potassium permanganate, could not be used in lower pH waters (<6.2), had a relatively low operating temperature (80^oF), and tended to soften through time resulting in pressure drop issues at higher flow rates. Additionally, the supply could occasionally become restricted due to environmental concerns with the processing facilities along the Eastern coast of the United States.

Because of these issues in the 1970s water treating companies and end-users began to express an interest in “something else” to replace the greensand. In response to their requests, scientists and researchers in Japan began to look for ways to infuse oxidizing agents to different matrix materials. It was felt that a commercially produced product could be made more powerful, have better physical properties and be more subject to improvements and/or modifications than any naturally occurring media.

Decades of further research and development of the Japanese Infusion Technology have resulted in the uniquely Australian made product, DMI-65 a granular catalytic media used to boost the advanced reduction/oxidation (redox) processes in water. The media is part of a broad category of products deriving their physical and chemical action from the interaction of their metal oxide surface with the water molecules and ions in solution. This product is revolutionary due to proprietary infusion technology that penetrates the micro pours substrate of the matrix material, allowing for a greater catalytic surface area and of a tight particle size distribution. DMI-65 has low level of fines, a tolerance to wider pH range and chemically infused catalytic surface that won’t be consumed or diminished under normal operating conditions. Last 5 – 10 years of continuous use.

How DMI-65® Filtration Media Works: It is an extremely powerful catalytic water filtration media that is designed for the removal of iron and manganese in aqueous solutions (water) without the need for potassium permanganate or chemical regeneration. The unique microporous structure of DMI-65 efficiently removes dissolve iron to the almost undetectable levels as low as 0.001 ppm and manganese to 0.001 ppm. DMI-65 acts as an oxidation catalyst with immediate oxidation and filtration of the insoluble precipitates derived from this oxidation reaction. DMI-65 can also remove Arsenic, Aluminium and other heavy metals and Hydrogen Sulfide under certain conditions.

The material is part of the broad category of products deriving their physical and chemical action from the interaction of their metal oxide surface with the water molecules and ions in solution.

Solid surface interaction with water distinguishes between adsorption as the weak van der Waal forces that hold a hydrophobic molecule in a rigid core media such as activated carbon and absorption as the weak van der Waal forces that hold a hydrophobic molecule in a swellable matrix (such as benzene) in a polymer of T-butyl styrene or absorption by liquid-liquid extraction. Ion exchange resins utilize absorption processes while interaction of DMI-65 with water molecules and ions in solution is initiated through adsorption.

Non catalytic type adsorbent materials retain target ions from water until either sites available for adsorption reach a maximum density and saturation or concentration of target ions in the treated water attain maximum acceptable concentration. At this point, the adsorbent material has to be regenerated to remove or replace the contaminant ions, or the used material is replaced with new material that is loaded in the treatment container. When the process works by swapping one type of ion for target ions from water the process is called ion exchange. This category of adsorbent and some partly absorbent materials remove the target ions from water. The larger the surface per volume of material the larger the amount of contaminant target ions which could be retained from the water.

Purely catalytic materials adsorb the reactant ions from solution bringing them in the proximity of chemical bonding. Then the reaction product moves away from the surface of catalyst. Strictly speaking catalysts facilitate chemical reactions; they do not implicitly remove anything. If the reaction product is a solid precipitate, often the product is retained in the catalytic bed, hence removed by filtration.

Many materials act in a mixed mode; with both ion exchange and catalytic action taking place. For those materials used primarily for their catalytic action, ion exchange resulting in dissolution of the catalytic layer leads to the need for periodic regeneration or reactivation to correct the matrix of ions at their active surface.

DMI-65 is a granular material of dark brown to black colour. This colour is produced by the manganese oxide in the outer layers of the granules. DMI-65 is a catalytic media in the true meaning of the word and facilitates oxidation – precipitation – filtration and does not get consumed in the reactions. Strictly speaking, the media facilitates chemical reactions and does not explicitly remove anything. Once oxidized, the depth filtration aspect of the media removes the solids that are then periodically backwashed out of the filter vessels.

The filtration media does not need regeneration or reactivation and does not display a decaying capacity to do its catalytic work. Over 5 to 10 years period, through many backwashing operations of the bed to remove retained solids, the media is degraded by contact between particles and mechanical abrasion. Then the material has to be replaced.

HOW DMI-65® WORKS: BASIC OPERATION:

The processes that take place in a bed of DMI-65 involve reduction/oxidation (redox). Redox reactions involve a transfer of electrons between species. Reduction is the gain of electrons or a decrease in the oxidation state of a molecule, atom or ion. Oxidation is the loss of electrons or an increase in the oxidation state of a molecule, atom or ion. Redox reactions occur simultaneously whereby there cannot be a reduction reaction without an oxidation reaction. The media “helps” chemical reactions to occur by interacting with the reaction without being permanently altered. An in depth discussion about redox chemistry is outside the scope of this paper, it will only deal with how the redox process applies in the removal of iron and manganese using DMI-65. The individual redox equations will be covered in the following iron and manganese removal sections.

In order to begin the process of oxidation of the ions in solution and to ensure that the oxidative layer is not compromised the media is designed to operate in the presence of chlorine or other oxidant. In this process the oxidant removes electrons and is consumed in the process. The operator needs to ensure that there is a 0.1 – 0.3 ppm free chlorine residual in the effluent water.

Chlorine, fed as sodium hypochlorite (NaOCl) or bleach (12.5% NaOCl), is the preferred oxidant since it is relatively inexpensive, readily available around the world and it is effective. Other oxidants such as hydrogen peroxide (H₂O₂), chlorine oxide (ClO₂) or ozone can also be used so long as a residual can be measured and maintained.

Another function of the chlorine is that it keeps the media free from bacterial or slime growth. The manganese oxide catalytic surface has to remain clean so that the ions in the water can come in contact with it. At the same time, the chlorine is a source of oxygen more reactive than molecular oxygen. The following chart indicates safe levels for other water constituents that could interfere with the surface interaction.

Unlike ion exchange resins where higher regenerant dosages will increase the ion exchange capacity, chlorine residuals or concentrations higher than required to oxidize the Fe and Mn do not increase the oxidative properties of the media. Additionally, since the media is often used to pretreat waters prior to an Reverse Osmosis (RO) system a higher free chlorine residual would require more extensive post treatment to reduce the residual to protect the membranes from chlorine attack.

The DMI-65 must be activated prior to being placed into service for the first time. This activation requires a higher dosage of chlorine than used during normal operation but only has to be performed once during the initial start up. The dosage rate is 10 fluid ounces of 12.5% chlorine per cubic foot (ft³) of the media. The activation only requires a soak of several hours but an overnight soak is preferred.

Once activated, the vessel(s) must be backwashed to remove the excess NaOCl and any fines. Since manganese oxide is one of the constituents used in the manufacture of the media an extended rinse is required at start up to remove any trace free manganese oxide residual left over from the manufacturing process. Once the Mn level in the backwash water reaches values of 0.05 to 0.15 ppm and the free chlorine residual is set the filter is ready to be placed into service.

Media replacement due to the decreased physical filtration properties of the Media due to physical abrasion will occur before complete degradation of the catalytic layer takes place. Under normal operating conditions media life is estimated at 5 – 10 years.

How DMI-65® Works for removing Iron (Fe) precipitation and removal using DMI 65

Iron (Fe) is the fourth most common element found in the earth’s crust and exists in a wide range of oxidation states from -2 to +6 although the most common states are ferrous (+2) and ferric (+3).

Ferrous salts are readily soluble. Before the ferrous iron, a dissolved solid commonly found as ferrous bicarbonate, can be removed by filtration it must be oxidized, become ferric hydroxide and in neutral pH waters precipitate out in the media bed. The catalytic surface of DMI-65 contains manganese oxide or exposes manganese and oxygen sites for adsorption of [Fe] ions that are in the water. The reaction of ferrous bicarbonate and NaOCl is almost instantaneous and the ferrous bicarbonate oxidizes (gives up an OH^–) to become the insoluble ferric hydroxide which is then removed through filtration in the catalytic surface of the media. The following redox reaction equation explains the process.