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 MTM is granular manganese dioxide filter media used to reduce iron, manganese and hydrogen sulfide from water. Its active surface coating oxidizes and precipitates soluble iron and manganese. Hydrogen sulfide is oxidized to a sulfur. The precipitates are filtered out in the granular bed and removed by backwashing.
MTM consists of a light weight granular core with a coating of manganese dioxide. The coating provides contact filtration where the media provides the oxidizing potential. This allows for a much broader range of operation than many other iron removal media. A pH level as low as 6.2 can be treated. Dissolved oxygen is not essential. The media’s light weight reduces backwash water requirements.
When the oxidizing power of MTM is reduced, the bed will need to be regenerated with a weak solution of potassium permanganate (KMnO4), thus restoring MTM’s oxidizing capacity. A regenerating solution of 1 ½ to 2 ounces (dry weight) of potassium permanganate per cubic foot is sufficient for normal regeneration. Upon start-up a new bed should be backwashed and caution exercised to ensure that lightweight media is not backwashed to drain. A new bed should be regenerated the evening of installation. Operating the filter after its oxidizing capacity is exhausted will reduce its service life and may cause staining.
MTM requires either intermitted or continuous regeneration to maintain its oxidizing capacity. A solution of potassium permanganate (or chlorine then potassium permanganate) can be pre-fed to maintain capacity. In the later case, the manganese dioxide coating acts as a catalyst to enhance the oxidation reaction and as a buffer to reduce any excess potassium permanganate concentration and prevent it from entering the service lines. |
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Advantages
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Broad operating range for iron reduction
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Lower pressure loss through the bed with high flock holding capacity
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Effective hydrogen sulfide, iron and manganese reduction
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Light weight requires lower backwash rates and reduces pumping requirements
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Chlorine can be beneficial in extending filter run times
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Low attrition loss for long bed life
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Physical Characteristics
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Color: dark brown
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Bulk Density: 27 lbs./cu. ft.
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Specific Gravity: 1.7
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Effective Size: .60 - .70 mm
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Uniformity Coefficienty: 1.9
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Mesh Size: 12 x 35
Operational Specifications
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Water pH range: 6.2 – 8.5
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Bed depth: 24 – 36 in.
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Freeboard: 50% of bed depth (min.)
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Service flow rate: 3 – 5 gpm/sq. ft.
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Backwash flow rate: 8 – 11 gpm/sq. ft.
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Backwash expansion rate: 20 – 40% of bed depth
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