CS258570B1 - A method for removing manganese and iron from water - Google Patents

Abstract

The essence of the method for removing iron and manganese is that the treated water containing iron and manganese flows through a layer of fluidized granular material, preferably sand, while potassium permanganate is dosed into the treated water in an amount of 0.3 to 5.5 mg KMnO4 per 1 mg Mn or Fe. In the fluidized layer, both the oxidation of iron and manganese to insoluble hydrated oxides and the simultaneous separation of the formed oxides take place. The oxides are captured on the surface of the grains of the fluidized material, forming a compact layer.

Description

The present invention relates to a process for removing manganese and iron from surface and ground water in the treatment thereof for utility and drinking water.

In particular, precipitation and oxidation processes are used to remove manganese and iron from surface and ground water, which cause sensory and technological defects in drinking and process water. In the precipitation processes, the water is basified, usually with calcium hydroxide, whereby insoluble hydrated iron and manganese oxides are separated, which are further separated from the water by sedimentation and filtration, or only by filtration. At the same time, however, calcium and magnesium ions precipitate in this process, which in many cases is undesirable. Water then requires pH adjustment. In the oxidation processes, iron and manganese are converted to a higher oxidation stage by the action of oxidizing agents (C1, KMnO4, Og) and hydrated manganese oxides and ferric hydroxide are formed by hydrolysis. These are then removed from the water by conventional separation techniques such as sedimentation and filtration. Lower concentrations of manganese and iron can be removed from the water also in water dissolved by oxygen, usually on filters, which are filled with prepared sand, where the grain of the filter material is coated with a layer of burel, which catalyzes the oxidation reaction. In all the processes described above, however, the separation stage, i.e. sedimentation and filtration, or only filtration, is an integral part of the de-ironing and de-manganese process line, which are costly equipment, and the filters require cyclic washing during operation.

In addition, the usable filter speed for water-jet filters is a maximum of 7 to _m ^-2 H ^-1 m, m .h

The aforementioned drawbacks are overcome by the iron-de-ironing and de-manganese process according to the invention, which consists in that the oxidation of manganese and iron is carried out in the fluidized bed of the granular material through which the treated water flows. In the fluidized bed, iron and manganese are oxidized and the resulting iron and manganese oxides are simultaneously separated to form an oxide layer on the grains of the fluidized material. As the oxidizing agent, potassium permanganate KMnO4, which is fed to the fluidized bed or to the treated water supply to the fluidized bed, is preferably used. The optimal dose of KMnO2 for iron and manganese removal depends on the water composition, the organic content of the water and the concentration of other reducing agents. Depending on the composition of the water, the optimal dose of KMnO4 is in the range of 0.3 to 5.5 mg KMnO4 per mg Mn or 1 mg Fe.

The advantages of the process of removing iron and manganese from the water according to the invention consist mainly in the intensification of the entire process (hydraulic loading of the fluidized bed being up to 80 m / m), which leads to a reduction in the equipment in which the ironing and de-manganese are carried out. Furthermore, in the possibility of limiting the scope of use of the water filter or in many cases it can be excluded from the technological line. Another advantage is the continuity of the entire operation. The main advantage is the high efficiency of the oxidation of iron and manganese and the separation of the oxides formed in the fluidized bed, which is close to 100% at the optimum oxidant dose. The grain weight gain of the fluidized material layer due to trapped iron and manganese oxides is negligible at commonly occurring concentrations of iron and manganese in surface and groundwater, so that the ironing and de-manganese process of the invention can be operated for several years without requiring fluid bed refilling. .

Examples of embodiments of the ironing and manganese method according to the invention:

Example 1

Under laboratory conditions was run column with an inner diameter of 4 cm, filled with sand of grain size 0.4 to 0.6 mm to a height of 1.1 m. When the water flow in an amount of 1 .min ^-1 amounted expansion ratio of the fluidized layer of sand 1.7. The concentration of manganese ions in the treated water was 2.5 mg.l ^-1 and ferrous ions 0.5 mg.l ^-1 . The fluidized bed was fed potassium permanganate, so that the dose was 2.5 mg.l ^- '·. During long-term operation, the average value of the effect of removal of manganese from water was 96% and of iron 75%.

Example 2

On a pilot scale, quartz sand with a grain size of 0.4-0.7 mm was used as the fluid bed. The fluidized bed was realized in a tube with a diameter of 8 cm. The filling height at rest was 153 cm, and with a water flow through the fluidized bed at 280 l.h.sup.3, the expansion layer support was 1.7. Thus, the hydraulic loading of the fluidized bed was 55.7 m / m -1 -1

The fluidized bed treated water contained 0.8 to 0.9 mg / ml. Prior to entering the fluidized bed, potassium permanganate solution was dosed into the water for a dose of 0.9 to 0.5,

The results of the long-term follow-up are given in Table I. The experiment was performed for 240 days.

Tabulkal

Long-term monitoring of pilot plant experiment with water de-manganese in fluidized bed

Experiment Day Dose KMnO ₄ (mg.l ¹ ) Mn concentration in raw water (mg.l ¹ ) Removal effect Mn (%) 1. 0.92 0.92 100 ALIGN! 45. 0.96 0.90 96 60. 1.10 0.90 100 ALIGN! 90. 0.90 0.85 100 ALIGN! 110. 1.10 0.86 98 150 1.15 0.80 100 ALIGN! 200 0.96 0.80 100 ALIGN! 240. 0.92 0.80 100 ALIGN!

The invention can be used in water treatment plants where ground or surface water containing iron and manganese is treated into drinking or service water and where manganese or iron in the treated water would otherwise cause sensory or technological problems.

Claims (1)

Process for removing manganese and iron from water by oxidation with potassium permanganate, characterized in that the oxidation is carried out simultaneously with the separation of the resulting oxidation products in a fluidized bed of granular material through which the treated water flows, wherein the oxidizing agent is metered directly into the fluidized bed or into the treated water before entering the fluidized bed.