CS260082B1 - A method for removing manganese from water - Google Patents

Abstract

The essence of the method for removing manganese from water is that the treated water containing manganese flows through a layer of fluidized material, preferably sand, while chlorine or hypochlorite is dosed into the treated water in an amount of 1.3 to 4.0 mg Cl2 per 1 mg Mn. Chlorine or hypochlorite is dosed directly into the fluidized bed or into the treated water before it enters the fluidized bed. In the fluidized bed, both the oxidation of manganese to highly insoluble oxides and the simultaneous separation of these oxides to form a compact layer take place.

Description

The present invention relates to a process for removing manganese 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 from surface and groundwater, which causes sensory and technological defects in drinking and service water. In the precipitation processes, the water is basified, usually with calcium hydroxide, whereby insoluble manganese compounds are separated, which are further separated by sedimentation and filtration, or only by filtration. At the same time, however, calcium and magnesium ions precipitate in this process, which is undesirable in many cases.

The water then requires pH adjustment. During the oxidation processes with oxidants (Cl _2, KMnO ^, Oj) translates into a higher manganese oxidation step and hydrolysis of the resulting voluminous insoluble hydrated manganese dioxide MnO ^ or manganese MnjOj. These are again removed from the water by conventional separation processes such as sedimentation and filtration.

Lower concentrations of manganese can also be removed with oxygen dissolved in water, but only on filters that are filled with prepared sand, where the grain of the filter material is coated with a layer of manganese oxides, which catalyze oxidation by air oxygen. In all the processes described above, however, the separation stage (sedimentation and filtration, or only filtration) is an integral part of the water dewatering process line, which is a costly plant with filters requiring cyclic washing during operation. In addition, the usable filtration rate of 3 -2 -1 for water-jet filters is a maximum of 7 to 8 m / m.

The above-mentioned drawbacks are overcome by the de-manganese process according to the invention, which consists in the fact that the oxidation of manganese is carried out in the fluidized bed of the granular material through which the treated water flows. In the fluidized bed, manganese oxidation occurs and the resulting manganese oxides are separated to form a compact manganese oxide layer on the grains of the fluidized material. The base layer of manganese oxides can be formed by treatment with potassium permanganate solution KMnO4.

The resulting oxides simultaneously catalyze the oxidation of manganese Mn with chlorine, optionally chlorine, or potassium permanganate, and oxygen dissolved in water with the addition of another oxide layer. Chlorine or hypochlorite, which is metered into the fluidized bed or into the treated water supply to the fluidized bed, is preferably used as the oxidizing agent. The optimum dose of chlorine or hypochlorite to remove manganese from water depends on the water composition, the organic content of the water and the concentration of other reducing agents. Depending on the water composition, the optimum dose of chlorine or equivalent amount of hypochlorite is 1.3 to 4.0 mg of chlorine per mg of Mn.

The advantages of the water de-manganese process according to the invention consist mainly in the intensification of 3-2 -1 of the whole process (the hydraulic loading of the fluidized bed is up to 80 m / m. H), which leads to a reduction in the apparatus in which the de-manganese is performed. Furthermore, the possibility of limiting the scope of use of the water filter or, in many cases, completely removing it from the technological line. Another advantage is the continuity of the process. The main advantage is the high efficiency of oxidation of manganese and separation of formed oxides in the fluidized bed, which is close to 100% at the optimum dose of chlorine or hypochlorite. Grain weight gain of the fluidized material layer due to entrapped manganese oxides is negligible at commonly occurring manganese concentrations in surface and groundwater (maximum units of mg.l ¹ ), so that the de-manganese process according to the invention can be operated for several years layers.

The invention can be used in water treatment plants where groundwater or surface water b is treated with manganese to make it potable or service water and where manganese in the treated water would otherwise cause sensory or technological problems.

An example of an embodiment of the water de-manganese process according to the invention:

A column with an inner diameter of 4 cm was operated, packed with a layer of sand with a grain size of 0.4 to 5

0.6 mm to a height of 1.1 m. At a flow rate of 1 l.min of treated water, the expansion ratio of the fluidized sand layer was 1.7. The concentration of manganese ions in the treated water was

1.0 mg.l ^_ l. In the fluidized bed was fed sodium hypochlorite so that the final dose has been

1.3 mg.l "^ _Cl. During long-term operation, the average value of the effect of removing 4 -1 manganese from water was 80%; at a dose of 1.8 mg.lCl, then 93%.

Claims (1)

SUBJECT OF THE INVENTION Process for removing manganese from water by oxidation with chlorine or hypochlorite, 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 chlorine or hypochlorite is metered directly into the fluidized bed or into the treated water.