Q. How long will DMI-65 last in a filter system?
A. If the DMI-65 is maintained and operated according its design parameters, it will keep removing iron and manganese for up to 5 – 10 years of continuous use.

Q. How does DMI-65 last for so long?
A. Because DMI-65 is not consumed in the advanced oxidation process, it is maintained in a permanent state of catalysis.

Q. DMI-65 already in continuous operation for 5 -10 years.  When will it need replacing?
A. The DMI-65 does not display a decaying capacity to do its catalytic work. Over the 5 to 10 year period, through many periodic backwash cycles, an attrition loss of the media occurs through mechanical abrasion of contacting particles. If a decline in performance is noticeable, a simple top up of the media bed will a sufficient remedy. It is recommended that all DMI-65 filters do have the entire media bed replaced prior to 10 years of continuous operation, as the partly worn particles will homogonise with new top up media, effectively limiting the maximum performance of the oxidation process.

Q. Can DMI-65 replace old technology, or poor performing standard iron and manganese filter media?
A. The DMI-65 is a direct replacement for all catalytic, multimedia, and standard silica sand filter Medias. It is very easy to replace and improve the performance of any filter. The cost saving benefit of reducing expensive chemicals for oxidation and media regeneration will exceed the initial capital expense of the DMI-65 and labour typically in the first 12 months of operation.

Q. What filter types are compatible with DMI-65?
A. DMI-65 will work in all deep bed filters, pressure filters, rapid sand filters and slow sand filters. Where a deep filter bed of 1000mm is possible, remarkable performance is achieved.

Q. What is the optimum flux or linear velocity for iron and manganese removal with DMI-65?
A. Conservative linear velocity figures of 5 to 10m3/m2/hour is common practice for drinking water applications and particularly for manganese removal. However, it has been proven that DMI-65 can remove common concentrations of iron and manganese 2 to 4 times the linear velocity of standard medias. The infused technology of the DMI-65 promotes the highest oxidation rate of any catalytic filter media. This permits a significantly higher flux that maintains desirable performance of iron and manganese removal.

Q. How regular is the periodic back wash cycle? How much backwash water is spent?
A. A typical DMI-65 pressure filter can be automated to do a periodical backwash cycle once the vessel has reached a drop in head pressure of 50kpa. For Rapid Sand Filters, the backwash should be calibrated to the time it takes for the first spike of residual iron or manganese to break through. Typically, a DMI-65 filter will only require a 10 minute of backwash cycle, at velocity of 30 to 40m3/m2/hour, once every 24 to 48 hours.

Q. Can DMI-65 remove other soluble metals?
A. DMI-65 has been proven to effectively remove Aluminium and Arsenic. Recent lab tests have also demonstrated that DMI-65 is very effective in oxidising and retaining precipitated Copper, Lead and Zinc, which suggests the DMI-65 has a broader range of uses than originally intended for.

Q. Can the DMI-65 remove hydrogen sulphide?
A. DMI-65 can virtually remove all hydrogen sulphide where practical. The DMI-65 filter system creates a bath of oxidized water, and flows from the top of the tower through a catalytic chamber and oxidized water, then out through the bottom of the device. Hydrogen sulphide reacts with the oxidized water and is subsequently converted into elemental Sulphur and iron sulphide. The now insoluble Sulphur generated is removed from the water by mechanical filtration with DMI-65. When the Sulphur ion comes in contact with ferric iron complex, it gets oxidized to elemental Sulphur and is precipitated.

Q. Can DMI-65 remove arsenic?
A. In the case of drinking water treatment where the requirement is to reduce arsenic to a few parts per billion, the applicable technologies are limited. Low cost removal of arsenic from drinking water is likely to be confined to precipitation and adsorption. DMI-65 is used as the catalytic material to filter the arsenic precipitates. The optimal adsorption of arsenic(III) on ferrihydrite occurs at pH 8-9. So, it is understood by introducing a flocculating agent such as ferric chloride solution at concentration ratios of up to 50 parts ferric chloride as iron to one part arsenic, will overwhelm the arsenic to form a complex with iron. We use FeCl3 to form a bond with Arsenic, and as DMI-65 has a high efficiency of iron removal, it is possible to remove the arsenic through the retention of precipitated arsenic that has formed a complex with iron introduced from the ferric chloride.

Q. How does DMI-65 protect reverse osmosis membranes?
A. The efficient removal of dissolved iron and manganese to almost undetectable levels as low as 0.001mg/L materially reduces the incidence of bio-fouling of RO membranes downstream. This reduces the need for membrane replacement and keeps the treatment systems working at optimal levels. Saving production efficiency and the cost of membrane replacement and operating downtime.

Q. Does DMI-65 improve colour and odour?
A. In the case study of the Municipal Water Treatment Plant in South Africa, the tap water in the town of George was renowned for unsightly colour, odour, and taste due to the “difficult to remove” humic and fulvic acids in the raw water. After being treated by DMI-65, the colour, odour and taste of the water was of better quality than the demineralised water tested at the local pharmacy.

Q. Iron removal ok, but undesirable manganese removal?
A. Manganese is a much more difficult element to remove than iron. Oxidation Process is pH dependant and benefits from a greater detention time with DMI-65 oxidation catalyst. By increasing the pH as close to 8, lowering the flux velocity and increasing the linear passing of the filter bed depth, Manganese is simultaneously removed with iron to almost undetectable levels of 0.001mg/L.

Q. After a periodic backwash, iron and manganese removal is acceptable for a few hours, then residual break through repeatedly occurs?
A. This is the tell-tale sign that the backwash velocity is not strong enough to fully fluidise the total filter bed. Precipitated manganese will deposit in the bottom of the filter bed, instead of being released into waste and break through occurs prematurely. For bed depths of 700 – 800mm, a backwash velocity of 30m3/m2/hour is sufficient to fully fluidise the bed so that a 50% bed expansion is achieved. For deeper beds such as 1000mm, a backwash velocity of 40m3/m2/hour is required to effectively release the precipitates to waste.

Q. What is the best pH for iron and manganese removal with DMI-65?
A. While DMI-65 has a broad pH range for iron removal. Removing both precipitates simultaneously can be achieved to high performance in slightly basic waters and preferably as close to pH 8 as possible.

Q. Can the DMI-65 perform in salty water?
A. DMI-65 has a tolerance for brackish water that is limited to approximately 1000mg/L. Efficient iron removal can be maintained for many years, however salt will scale and form a crust on the catalytic surface. The high conductivity and saline concentration of sea water will not allow the catalytic surface of the DMI-65 interact with target metals and adversely the DMI-65 will degrade rapidly.

Q. Can the DMI-65 operate in high corrosive or hard water?
A. The negative chemistry associated with highly corrosive water due to low pH and excessive hardness needs to be addressed as it will damage the DMI-65 and most operating equipment.

Q. Will DMI-65 remove iron and manganese in high turbidity waters?
A. The main problem with turbidity is it causes problems with the disinfection process, which in turn can allow iron bacteria to cover the surfaces of the media, reducing the performance of the oxidation process.

Q. Can DMI-65 treat raw water with 50mg/L of iron?
A. It is very easy to treat high iron concentration waters by pre-oxidising the raw water prior to filtration with DMI-65. It is, for example, very easy to chemically oxidise, coagulate and separate 90% of total iron in a detention tank in minutes. It far more difficult to remove the remaining 10% of the total iron to almost undetectable levels. This is why DMI-65 is designed to be a high performance, low cost method of iron removal commonly coined as “DMI-65 iron polishing”.

Q. Can DMI-65 treat raw water with 3mg/L of manganese?
A. DMI-65 is the most effective catalytic media for oxidising and removing the notoriously difficult and highly nuisance contaminant. The strong oxidation of characteristics DMI-65 is comparable to ozone or peroxide. With a small amount of chlorine and attention to pH, difficult manganese is removed to often less than 0.001mg/L.

Q. Why maintain a chlorine residual level of 0.1 – 03mg/L when using DMI-65?
A. DMI-65 only requires this precise small amount of chlorine for disinfection to keep the catalytic surfaces clean, in a constant auto-catalytic state of oxidation and attracting colloidal iron and manganese. This small amount of residual chlorine is also conveniently compliant with World Health Organisation Drinking Water Guidelines and similarly approved and certified.

Q. What is the purpose of conditioning and soaking DMI-65 upon start up?
A. There is a fascinating chemical process advantage to the powerful curing of the DMI-65 catalytic surfaces – by soaking the media for at least 3 hours prior to its use. Ideally the longer the soaking and conditioning period is, the stronger and harder the catalytic surfaces become.

Q. Can other oxidants be used other than chlorine?
A. It is possible to effectively use other oxidants such as Ozone, Hydrogen Peroxide, Potassium Permanganate, even dissolved oxygen with a little caustic soda to address disinfection. However a good understanding of the stability of the chosen oxidant used is required to ensure there is always an oxidant residual maintained. Sodium Hypochlorite is easiest, most practical and lowest cost method of ensuring disinfection is not compromised.

Q. Can the media be damaged?
A. Yes, it is possible that DMI-65 can degenerate due to lack of dissolved oxygen present at the catalytic surface due to a failure in oxidant dosing. Abnormally low pH, corrosive water and excessive hardness will also complicate water matrixes, which can lead to media damage. Please consult your DMI-65 agent for advice.

Q. What is the procedure for a DMI-65 filter that is to go offline and be out service for a period of time?
A.The best practice in this situation is to fully submerge the media bed in a strong chlorine solution as recommended in the DMI-65 set up guide. Filters that have been maintained for up to 5 – 10 years continuously with seasonal offline breaks up to 6 months are maintained and ready for operation in the summer months.

Q. Is it necessary to dose chlorine in the backwash water?
A. The Advanced Oxidation Process is best maintained when pH and oxidant levels are stable and constant. This in turn promotes a continuous state of catalysis with iron and manganese. The oxidant dosing pump should be calibrated to accommodate the speed of the service flow, but also to the speed of the periodic backwash so that the same free chlorine residual is maintained at 0.1 – 0.3mg/L in the backwash and product waters.

Q. Can DMI-65 remove iron and manganese without chlorine?
A. DMI-65 can be used with other oxidants and even dissolved oxygen if disinfection is addressed with caustic soda dosing. When using oxygen, we know that diffused air is a less powerful oxidant. Injecting air under pressure will oxidise iron however certain manganese removal will ultimately fail. Even for removing iron, without guaranteed disinfection, iron bacteria can grow in the lower part of the filter bed. Iron bacteria growth will depend on level of nutrient available in the raw water.

Q. Greater chlorine dose will remove more iron and manganese?
A. This is a common misconception, as it is the DMI-65 catalytic layers that enhance the oxidation process. In fact dosing greater amounts of chlorine will likely reduce performance due to the competing sulphides introduced into the water matrix.

Q. What is the operational cost of using DMI-65 for iron and manganese removal?
A. Basic calculations can be done to determine how much chlorine is required for operational use with the DMI-65 Chlorine Injection Calculator. However, as an example, typical iron and manganese concentrated water would probably cost approximately $0.01 for every cubic meter of water processed.

Q. Does DMI-65 require chemical regeneration?
A. DMI-65 requires no chemical regeneration and does not have a high chemical demand. DMI-65 is the lowest cost, whole life solution for iron, manganese and arsenic removal from groundwater sources.

Q. Why is DMI-65 infusion technology different from other coated medias?
A. The DMI-65 infusion technology penetrates the micro-porous sub structure of the matrix material to form strong chemical bonds. The finished product is the result of advanced technology developed with the aim to be highly sustainable, effective and lowest cost of operation.

Q. How does DMI-65 retain precipitated iron and manganese?
A. Soluble iron and manganese is chemically attracted by adsorption to the surface of the media. As they oxidise and take a physical form that is of greater particle size than of the gaps in DMI-65 particles.

Q. How does DMI-65 remove the precipitated iron and manganese in the backwash?
A. The fluidisation of the media bed allows precipitated iron and manganese to escape in the backwash. The kinetic energy of the backwash is strong enough to release the partly oxidised iron and manganese that is chemically attracted by adsorption at the catalytic surface of the media.

Q. How does DMI-65 operate at higher flow rates than other catalytic medias?
A. The infusion technology promotes the highest oxidation rate of any catalytic media. Allowing for much higher filtration velocities, achieving the same or better desirable results.

Q. How does DMI-65 have a higher load capacity than other catalytic medias?
A. Because of the infusion technology and the micro-porous structure of the matrix material the DMI-65 has an increased surface area and a higher load capacity for targeted iron and manganese.

Q. Is DMI-65 safe to use for drinking water applications?
A. DMI-65 has been certified for safe use in drinking water applications according to the Water Quality Associations’ NSF ANSI 61 Standard Gold Seal Programme. Also DMI-65 is approved safe to use by the Drinking Water Inspectorate of the United Kingdom.