CS254591B1 - Filtering material especially for water treatment - Google Patents

Abstract

The issue of using a higher quality filter material, especially in water treatment, is being addressed. The filter material is polyethylene produced by gas phase polymerization and having a particle size of from 0.1 to 2 mm

Description

(54) Filter material especially for water treatment

The issue of using better filter material is addressed, especially in water treatment. The filter material is polyethylene produced by gas-phase polymerization and has a particle size of from 0.1 to 2 mm.

(11) (B1) (51, Int Cl. ⁴

B01D 39/04 C02F 1/00

The invention relates to filter material, in particular for the treatment of water.

In the treatment of drinking water, industrial water and wastewater treatment, so-called floating-fill filters are used.

To date, foam polystyrene, cork, cellular ceramic materials, and special polymer-based granulates have been used as floating filters. These materials have both functional disadvantages and are expensive.

The high cost of granular polymers suitable for water filtration is that in order to achieve the desired hydrodynamic properties of the granular polymer, the diameter of the roller granules should not exceed 1 mm. The production of such small granules is very unproductive and energy-intensive due to the high resistance of the granulation head.

The use of expanded polystyrene is complicated by the need to pre-foam the granules in hot water, which is again an energy-intensive and laborious operation. The disadvantage of cork is its chemical instability and the increasing price of this natural raw material. The production of special lightweight ceramic materials is also expensive.

The filter material according to the invention does not have these disadvantages. This filter material consists of polyethylene particles of 0.1 to 2 mm, preferably 0.4 to 2 mm, produced by gas-phase polymerization of ethylene, with a specific gravity of 950 to 970 kgm, a particle size of 0.1 to 2 mm, the largest proportion of particles in the range of 0.8 to 1.5 mm. The grains have an irregular rugged surface and do not contain a gas cavity inside. Tests have shown that this material is suitable for water filtration without further treatment.

The filter function can be further improved by removing dust fractions of less than about 0.4 mm from the polyethylene powder.

The rugged surface of the polyethylene particles ensures a favorable low shape coefficient and a desirable high voidness of the filter bed.

The material is resistant to acids, alkalis, organic solvents and bacteria. The grains are dimensionally stable, do not disintegrate during filtration and are hygienically harmless.

Polyethylene in the form of a granular powder is an intermediate in the production of granulated polyethylene for plastics purposes. This material is produced on high capacity units and its price is lower than the price of filter materials used so far. The economic advantage of using powdered polyethylene is further underlined by the fact that non-plastic material can also be used for filtering purposes. Materials that do not meet the quality requirements in terms of plastic use arise, for example, when starting up reactors, when changing the type of polyethylene produced, when equipment fails, etc. For filtration purposes, very cheap waste materials resulting from polyethylene production can also be used.

In addition to the economic advantages, the use of granular polyethylene for water filtration and the functional advantages which are evident when compared to foam polystyrene-based filter materials.

Polyethylene has 10 to 20 times higher density compared to expanded polystyrene, resulting in a higher expansion capacity when washing the filter bed. When washing the filter, it is therefore possible to use a lower water flow with better washing of trapped dirt.

Polyethylene is less compacted into lumps that are ineffective for filtration.

Polyethylene is less electrostatically charged and therefore it is relatively easy to screen through the sieves, whereas in the case of expanded polystyrene the screening is very difficult.

The invention is further illustrated by the following example of practical application.

Example

A water treatment unit with an output of 5 l / s was put into operation for water treatment. The water treatment here is as follows: coagulant, aluminum sulphate and water are fed into the raw river water. Here, rapid and slow mixing, settling and filtration through a layer of floating filter material takes place. Originally, foam polystyrene was used for filtration, which was later replaced by linear polyethylene. Comparing the operation with the two cartridges it was found that the quality of the treated water did not change. The cycle lengths between the regenerative scrubbing of the filter cartridge were extended by about 15%. Due to the higher specific gravity of the granular polyethylene, the water flow required to achieve the expansion of the filter cartridge during the regenerative -2-1 wash was significantly reduced. While in the case of polystyrene foam filling it was necessary to wash. a flow rate of 18 1 m s -2-1 in the case of granular polyethylene, a flow rate of 1.8 1 m s was sufficient. The use of granular polyethylene is also more advantageous in terms of material transport, long-term storage, material handling and fire protection during handling.

Claims (1)

SUBJECT OF THE INVENTION Filter material, in particular for water treatment, characterized in that it consists of particles of polyethylene of the size of 0.1 to 2 mm, preferably 0.4 to 2 mm, produced by gas-phase polymerization of ethylene.