Iron removal utilizing “DEFERUM” technology introduction

The most common sources of iron are naturally occurring, from the weathering of iron-bearing minerals, soil, and rocks. Industrial effluent, acid-mine drainage, and landfill leachate may also contribute iron to groundwater and surface water.

Iron is not harmful, but it may cause aesthetic problems such as odour and undesirable taste. It can also damage processes and remediation equipment. Iron with concentrations of more than 0.3 mg/L in different forms can be a nuisance in the water supply, affecting the taste and appearance of the water.

Numerous groundwater remediation sites experience challenging water conditions, including high levels of dissolved iron in the water. Iron in the water results in deposits in pipelines, pumps, heaters, filters, and pressure tanks, which results in numerous maintenance issues and increased energy and maintenance costs.

Existing technologies such as phosphate treatment, ion exchange water softener filtration, oxidizing media filtration, aeration and chemical oxidation followed by filtration allow for iron removal; however, there are some limitations for each technology depending on the type of iron, its concentration in raw water, water characteristics, and filtration requirements.

Our goal is to minimize limitations of the existing iron-removal technologies and design a unique integrated treatment system for a broad range of iron concentrations and different water characteristics, in order to meet the discharge criteria and different filtration requirements.

An innovative solution for Iron removal from groundwater.... DEFERUM

DEFERUM technology (from the Latin de ferrum, "remove iron") has been designed specifically for groundwater dewatering construction applications where the water from a construction site requires filtration to remove suspended solids (TSS), turbidity, and iron, with the intention not only of complying with discharge criteria but also of eliminating some of the existing remediation limitations resulting from iron precipitation in filtration equipment. Other applications for which this technology can be utilized are mining and agricultural operations, as well as the treatment of contaminated water from domestic sources.

Membrane Filtration (UF/RO), automated controls and separation units can be combined with DEFERUM iron removal technology, allowing for the removal of both types of iron (ferrous and ferric) to below 0.3 ppm plus many other contaminants found in ground, surface and sea water applications. This technology requires only a small volume of water and minimal time to reactivate. The system uses floating media particles to remove contaminants and is less prone to clogging.

The DEFERUM, with a capacity of up to 132,500 gallons per day, can accommodate iron concentrations from 5 ppm to 75 ppm on a non-reagent basis as well as low concentrations of manganese. The combined degassing unit and aeration system can also remove odours and other gases such as hydrogen sulphide, methane, CO₂, and radon.

The DEFERUM operates based on an intensive aeration/degasification process followed by filtration. The aeration or degasification process removes gases and oxidizes bivalent iron (Fe2+) to its ferric state (Fe3+), which precipitates and can be easily filtered out. Floating polymer media, like "floating sand," removes the suspended solids by filtration. Gradual fouling and bed resistance raises the water level in the filtration chamber and activates a self-backwashing process. Using coagulation and flocculation, high concentrations of iron in backwash water precipitate and settle in the bottom of the collection tank and can then be removed by an automatic particulate filter.

System Components

DEFERUM is typically fabricated from carbon steel, stainless steel, concrete or plastic materials, and includes required piping as well as a stainless steel mesh bulkhead to enclose the filtration media.

The system does not typically contain any pumps or valves and can operate both in pressure as well as pressure-free modes. In a pressure-free mode design, electricity is required only for the feed pump (for example, well pump) and the filtrate processing pump.

Aeration/Degasification

The AKV Aerator/Degasifier part of the system is composed of a set of proprietary components fabricated from stainless steel 304L material. The units are located at the inlet to DEFERUM filter plants.

Feed water is supplied at a pressure of 3 to 4 atmospheres and the velocity of water flow reaches 180 km/h, creating a deep vacuum in the vacuum chambers. Dissolved gases are immediately released and high iron is oxidized.

The water flow draws atmospheric air into the device, causing the water to break up and expose a surface area of up to 12,000 m², where the release of dissolved gasses is greatly intensified. The water appears to boil and turns white. Gases are removed in a fraction of a second. The combination of vacuum and water breakup accelerates the process of gas removal by a factor of 1,500 to 3,000.

The gasification section of the system removes dissolved gases such as H₂S, CO₂, methane, and radon from the polluted water. Dissolved H₂S in water typically causes water to smell like rotten egg. CO₂ is the main reason for high corrosion of concrete, pipes and equipment. Methane gas, which is colourless, odourless, and tasteless, accumulates in the water systems and causes system noise, water hammering, and faucet spitting. Radon gas occurs naturally in groundwater in varying quantities and is known to be carcinogenic.

Aeration and degasification of water reduces the consumption of reagent/chemicals (e.g., chlorine) and increases pH. Also, as gas bubbles burst, they develop an inside pressure of up to 1,000 atmospheres (cavitation), which results in the heating of the water and generation of radicals and oxidants (H₂O₂, ozone, etc.). The surface of solid particles in water is instantaneously refreshed and becomes more susceptible to chemical and physical reactions.

The aeration part can be designed for flow rates from 0.3 m/hour to 240 m/hour and over. The curve shows specific energy consumption by a bore/recycling pump that supplies feed water to the ejector at a pressure of 63 psi (0.45 MPa) for certain applications. Curve 1 shows electrical energy consumption for the removal of CO₂ from water. Curve 2 indicates electrical energy consumption for raising the pH of water by the removal of CO₂.

Polymer Floating Filter Media(PFFM)

The Polymer Floating Filter Media (PFFM) is an effective alternative to traditional heavy filtering materials such as sand, clay, anthracite, etc. The PFFM is manufactured from EPA food-grade polymer material. It is chemically and physically stable and works in a wide range of temperatures and pH. It also has an extended particulate-capturing capacity of up to 500 mg/L (initial capacity) for suspended solids.

The PFFM must be conditioned, over a short period of time, to the optimum operating parameters. PFFM is an ideal filtering material for "contact" filtration, when reagents are introduced into the feed water immediately in front of the filter.

The buoyancy of the media causes it to arrange itself as a floating filter bed. Filtration can be either upward or downward in direction, depending on the application, with the "bed" restrained by a fine mesh and supported by a grid. It acts as "floating sand," while outperforming conventional sand filters by very effectively removing fine particles, over the full service flow cycle, down to 1.5 micron.

TABLE 1:         Comparative Technical Characteristics of Heavy Sand and Polymer Floating Filter Media (PFFM) and Associated Equipment

*Methods of technical modeling by D.Mintz.

Operation

Feed water is pumped from the collection tank/borehole at 65 psi (0.45 MPa) to the AKV Aerator/Degasifier connected the top of hydro-robot assembly, where intensive processes of liquid aeration and gas removal occur.

Then water flows down the hydro-robot and into the hydro-automatic filter tank filled with floating filter media where iron particles in insoluble form are removed throughout the depth of the filtering bed.

Schematic 1. Deferum components

Filtered water flows by gravity into the filtrate collector via the discharge pipe. As fouling of the filter media increases, the water level in the hydro-robot rises, causing the filter to switch into backwash mode. Iron-free water from the above-filter section drops down and expands the filtering bed, washing out the suspended solids. When the water level in the above-filter section drops down to a preset point, the hydro-robot stops the backwash and switches the filter into a new filtration cycle.

During the backwash mode, the filtering bed is expanded. The upward movement of the floating media and the reverse flow of water both create a strong stirring effect, resulting in a fast and complete regeneration of the polymer filter media.

The hydro-automatic gravity feature of the filtration process brings a significant reduction in capital, operational, and maintenance costs.

Backwash water can be collected and discharged from the system by gravity, or disposed of, or additionally treated according to the client's requirements.

Backwashing

Gradual fouling of the bed increases its resistance, raising the water level in an adjacent hydro‑robot until it reaches the top of a siphon. This draws water out of the filtration chamber at such a speed that flow through the filter bed reverses and the filter bed is backwashed. There are no sensors, electronic controls, floats, or other moving parts to worry about.

During the backwash, the filter bed is expanded by 30% to 70%, with the combination of the downward flow of filtrate and the upward buoyancy of the floating media producing a vigorous agitation and scrubbing effect, resulting in a fast regeneration of the media in 1 to 3 minutes.

The loss of water for backwash purposes normally does not exceed 1.5% to 3.0% of the daily flow of water.

The backwash of the PFFM is conducted by the reverse gravity flow of water and is 100% hydro-automatic. No electronics, pumps, compressors, or any other additional equipment is involved in the backwash process. The backwash process is based entirely on gravitational force and the difference in water levels.

Design Pointers and System Advantages

• No moving or rotating parts and no chemical reagents are used in the process, and no parts or elements need to be replaced on a regular basis.
• Combined degasifier/aeration units efficiently remove all dissolved gases and oxidize iron to a form where it can be filtered out, without the addition of any chemicals. It should be noted that these results are achieved without the use of additional equipment or the use of electricity.
• The PFFM is manufactured from a polymer material that is already certified for contact with drinking water. The filter media has a life span of over 25 years.
• The size of tank for collecting backwash water is about 15% of that found in conventional designs. Water used for backwash is about 1.5% to 3% of the daily flow rate of the filter and is available with a zero backwash water option. Backwash time is typically reduced to less than 5 minutes. No air, pumping, sensors, or electronics are required.

Case Studies

Case Study: Nita Lake Lodge, Whistler, B.C., Canada - Deferum High Iron Removal Plant

The system consists of two Deferum 250 (500 m3/day) units and has been in operation at Nita Lake Lodge Corp. at Whistler, B.C., since 2006. This system is currently removing iron from groundwater down to 0.1 ppm for discharge into a nearby fish-bearing stream.

The source of water is rain, groundwater, and runoff collected in the lodge's basement sump. This water is collected, run through an oil/water separator, and then run through Deferum for the removal of high iron, TSS, and turbidity. It is then discharged into a creek running by the lodge that feeds into Nita Lake.

Case study # 2 -  Mobile DEFERUM Ground Water Dewatering for High Iron Removal - Canada

Mobile DEFERUM 500 units are used in ground water dewatering construction applications where the water from dewatering of construction site requires filtration to remove Suspended Solids (TSS), Turbidity and High Iron, in compliance for discharge into environment.

These DEFERUM 500 mobile units effectively removing + 50 mg/l of iron from ground water.

Case study # 3 - DEFERUM "high iron removal" Piloting - Ethanol Plant, Oregon

A new Ethanol plant in Oregon had an issue with high Iron concentration in ground water supply to the plant.

The iron levels ranged between 25 and 75 ppm in this application. The borehole wells were drilled beside the Columbia River mouth as it enters into Pacific Ocean and raw water quality seemed to change with tide levels in river.

Testing conventional technologies that included oxidation of iron with chlorine and then conventional filtering out the ferric iron. The cost alone for chlorine annually to Ethanol plant would have been USD$600,000.00. With the installation of DEFERUM, this cost would be eliminated, because iron was removed without chemicals and reagents. Only some pH adjustment was done prior to the treatment.

Case study # 4 - Iron removal -remediation application

Iron removal was part of an integrated remediation pilot testing project for a site in Vancouver area. FII IRS DEFERUM was the first stage of the ground water treatment with the purpose of eliminating the fouling of piping and pumps, as well as the fouling of different components of remediation equipment such as air stripper, bag filters, and activated carbon filter.

The targets of the FII IRS DEFERUM application were:

• To reach discharge limits - less than 1 mg/L
• Approving applicability to high iron concentration (initial concentration of iron in the water was up to 15-20 mg/L)
• Optimization of the operation and design parameters
• Demonstration of technical feasibility and establish technological results

FII Filter Pilot Container with FII DEFERUM components designed, built, and shipped to the site. The components of the system included hydro-automatic gravity filtration system, backwash water treatment unit with particulate self-Indexing filter, and control system with automation direct PLC and touch screen.

During the pilot testing, contaminated ground water from water inlet collection drum was pumped out at 65 PSI to the AKV Aerator/Degasifier. Using the AKV Aero-degasifier, air (oxygen) was added to the water stream to ensure all iron was converted to a ferric state.  The low pressure zone (vacuum) in the AKV Aerator/Degasifier also helped to remove dissolved gasses in the water stream.

The high pressure water swirls inside the hydro-robot to complete its reaction. This allowed any unwanted gasses to be removed. Then water flowed into the hydro-automatic filter with floating media. Iron particles were removed throughout the depth of the floating filtering bed, and iron free water discharged by gravity.

The automated butterfly valve was used to control the backwash cycle, which was initiated when the backpressure in the media became loaded with iron indicating that it was to be back washed.

Backwashing resulted in a very highly concentrated waste stream which required further three- stages of chemical treatment.

The sump pump located in the bottom of the backwash tank was used to get the concentrated backwashing water to the chemical treatment system:

• Alum was added to coagulate the ferric iron
• Caustic was added to keep the pH correct
• Polymer was added to bond the coagulated material into flocs.

Pilot Testing Results

During the pilot testing, relatively strict result for iron in the treated water was easily achieved. All parts of pilot system functioned well. Automatic control of the process was carried out successfully. Based on long term pilot testing results the most significant features of the FII IRS DEFERUM were approved:

• Exceptional high quality of treated water (iron content below 2 ppm)
• Capability of aerator/degasifier to remove dissolved gasses and oxidize dissolved iron in single pass
• Polymer Floating Filter media had effectively filtered out oxidized iron and was exceptionally easy to backwash (approximately once a day for 2-16 minutes
• Very low backwash water volume - less than 1% of daily flow

During pilot testing, operation parameters of backwash such as pre-set point, floating filter media expansion, backwashing time and volume of the water needed for filter media backwashing were optimized.

A small volume of the backwash water was collected in the tank and then additionally treated with coagulants and flocculants to generate agglomerated particles. The large iron coagulated flocs were easily removed by automatic self-indexing filter. Collected iron on the self-indexing filter media (paper) was collected and sent to landfill.

Based on the pilot testing results, design optimization of the FII IRS DEFERUM was completed to minimize the risk of system upset and to operate with minimal supervision.  

FII IRS DEFERUM has been recognized as a reliable mean for iron removal and has a broad range of applications, including:

• Ground, surface and sea water
• Industrial and potable water treatment
• Cooling tower water filtration
• Iron removal from well water
• Wastewater purification

TABLE 2:  DEFERUM Influent Characteristics

Groundwater Characteristics (Influent)

TABLE 3:  DEFERUM Effluent Characteristics

Quality of Filtrate (Effluent)

TABLE 4: DEFERUM System Characteristics