DE20109443U1 - Device for decontaminating water containing traces of arsenic, manganese and iron - Google Patents

Description

Device for the decontamination of water, which
Contains traces of arsenic, manganese and iron

Description

The invention relates to a device for decontaminating water, in particular drinking water and/or groundwater, which contains traces of arsenic (As), manganese (Mn) and iron (Fe), whereby these metals are brought below the legal limits with the device according to the invention by combining a bioadsorber for iron and manganese removal and an inorganic adsorber for selective As removal. The device according to the invention comprises at least two chromatography columns through which the water to be decontaminated is passed, whereby one column contains the bioadsorber and the other column contains the inorganic adsorber.

The world's resources of high-quality drinking water are becoming increasingly scarce. As a result, many countries are already forced to rely on groundwater that contains trace elements of heavy metals and/or semi-metals or organic contaminants. On the one hand, such contamination is geogenic or it represents contamination from, for example, industrial wastewater, and on the other hand, it can be found in trace amounts in almost all natural bodies of water.

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The health relevance of certain water ingredients is officially laid down in the "Guidelines for Drinking Water Quality" based on the current state of knowledge and technology. Some water ingredients only affect the taste or smell of drinking water, such as iron and manganese, while other ingredients pose major health risks, such as arsenic, which increases the risk of cancer. New demands must therefore be placed on research and technology.

The German Drinking Water Ordinance of December 5, 1990 sets out the requirements for "water intended for human consumption." Annexes 2 and 4 of the Drinking Water Ordinance list limit values for chemical substances as well as sensory and physical-chemical parameters and limit values for assessing the quality of drinking water, which are 200 ßg/l for Fe, 50 Mn/l and 10 ^g/l for As.

The object of the invention was to develop a system for the decontamination of water, with which the amounts of Fe, Mn and As contained in the water can be reduced effectively, inexpensively and in an environmentally friendly manner to at least the values of 200 μg/l for iron, 50 ^g/l for manganese and 10 μg/l for arsenic.

The object is achieved by a device according to the claims.

The device according to the invention is characterized in that it comprises at least two chromatography columns which can be connected in series, one column containing a bioadsorber for iron and manganese removal and the second column containing an inorganic adsorber for selective As removal. Preferably, the bioadsorber is contained in column 1, through which the water is passed first, and the inorganic adsorber is contained in the subsequent column 2.

In a preferred embodiment of the invention, the device further comprises a third column (3) which is connected downstream and contains activated carbon which serves to remove other undesirable flavors and/or ingredients which cause turbidity. In particular, the activated carbon serves as a "police filter" and to remove organic contaminants. If the third column is used, a preferred embodiment consists in column 1 being connected from bottom to top and the second and third columns (2, 3) being connected one after the other from top to bottom. It is of course also possible to operate each chromatography column on its own, i.e. separately from the others.

Bioadsorbers, produced by modifying plant-based, renewable raw materials, are known for the removal of heavy metals (e.g. WO 98/48933). They are cheap, CO ₂ - neutral in terms of environmental impact and can be produced from easily accessible raw material sources. In addition, the

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The binding capacity of many bioadsorbers can be increased by chemical modifications (e.g. phosphorylation). The binding principle is based on both ion exchange processes and physisorption. Furthermore, a bioadsorber is easy to dispose of. For example, a bioadsorber loaded with heavy metals after decontamination is either regenerated for reuse using known methods or disposed of, e.g. by incineration or composting, whereby biodegradability does not pose any problems.

A known bioadsorber (ion exchanger) suitable per se for the removal of heavy metals is, for example, a chemically modified wood granulate (WO 99/2 83 72 A) which was obtained from wood chips and which was modified with phosphoric acid or ammonium phosphates and urea and possibly sulfur. Another bioadsorber is described in DE 42 39 74 9 C2, which is a phosphorylated wood, which is wood flour with a grain size of 0.05 to 3 mm, which was modified with phosphoric acid or ammonium dihydrogen phosphate, water and urea.

However, a bioadsorber that represents spherical carbohydrate particles is particularly suitable. These spherical carbohydrate particles are produced by suspending a fibrous or powdered carbohydrate in an aqueous urea solution, whereby

if necessary, low or high molecular weight fillers are added to the suspension. The water is then evaporated with stirring and increasing the temperature to 100 - 200 ⁰ C, preferably at a temperature of 130° - 160 ⁰ C, if necessary by applying a vacuum. The resulting spherical particles in pearl form are stable in aqueous solutions and organic solvents. They are cooled and cleaned using methods known per se, e.g. with cold and/or hot water, bases, acids, cold water until the wash water has a neutral reaction. They are then dried at elevated temperatures in a circulating air stream or by solvent exchange with e.g. alcohol, acetone and drying at ambient temperature or only slightly elevated temperature or by using a vacuum and finally classified according to grain size. The materials produced in this way are selective adsorbent materials for iron and manganese. They can also be derivatized or modified for use according to the invention if necessary.

The removal of As with inorganic adsorbents is known, but the use of chemicals for precipitation or flocculation (potassium permanganate or iron(III) chloride) requires complex technologies and may result in large residual amounts of hazardous waste that are difficult to dispose of.

In a preferred embodiment of the present invention, granulated iron(III) hydroxide (GEH) is used as an inorganic adsorber as a fixed bed adsorber (e.g. Ferrosorb® Plus). GEH is characterized by the

selective removal of arsenic species (both As(III) and As(V) compounds) and it has a high loading capacity ([mg] range As/g dry substance). The only hazardous waste to be disposed of is the As-loaded inorganic adsorber. Since arsenic concentrations in the [^g] range occur in drinking and/or groundwater, while the binding capacity of the adsorber material is in the [mg] range As/g dry substance, a multiple of the bed volume of water can be processed before the capacity of the GEH adsorber is exhausted.

The present inventive device preferably comprises a chromatography column containing spherical carbohydrate particles for removing Fe and Mn and a further chromatography column containing granulated iron(III) hydroxide for removing As, the columns being connected in series.

A particularly preferred embodiment of a water treatment device according to the present invention is shown in Fig. 1, wherein the device has the following individual components:

Several (at least three) chromatography columns, whereby in column 1 a bioadsorber (preferably spherical

carbohydrate particles), column 2 contains an inorganic adsorber (preferably GEH) and column 3 contains activated carbon as exchange materials,

Pipe system with shut-off devices to vary the water flow

several pumps,

Flow meter on each column pH meter with corresponding electrode measuring containers Conductivity meter

Switch box

Assembly scaffolding.

Thanks to a flexible piping system, the device has several options for connecting the chromatography columns, depending on the respective decontamination task:

1. A maximum of all three chromatography columns can be connected in series.

2. Each chromatography column can be operated alone, i.e. separately from the other columns.

3. The water flow can be switched both downstream and upstream.

Depending on the decontamination task, the water can be purified in individual steps or in a combination of several adsorbent materials one after the other. In a special design of the device, the first chromatography column is connected from bottom to top and the other two columns are connected one after the other from top to bottom.

This device according to the invention meets the requirements of many waterworks and has the following advantages:

a) For technical implementation, other water supply facilities (pumps, pure water storage tanks) can generally be used without modification.

b) No complex control and regulation technology is required.

The invention will be explained in more detail using the following embodiment, without limiting it thereto.

Example

Drinking water to be purified was passed through a device comprising a bioadsorber in a first column, GEH in a second column and, if necessary, activated carbon in a third column, at a flow rate of 10 to 15 bed volumes/hour.

The original Fe content in the drinking water to be examined was 490 ^g/l (prescribed limit value 2 00 μg/l) and the Mn content was 150 /xg/l (prescribed limit value 5 0 Mg/l). The As concentration was approximately 15 to 4 0 μg/l (prescribed limit value 10 μg/l).

After passing through the bioadsorber, the Fe and Mn content was below the legally prescribed values. With the adsorber material GEH (using the commercial product FerroSorb® Plus) more than 40,000

Bed volumes of drinking water are purified below the legally prescribed limit of 10 μg/l.

Legend to Fig. 1

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Chromatography columns with adsorbent

pump

Flowmeter

Pipeline system

Shut-off device

Claims (6)

1. Device for decontamination of waters containing traces of arsenic (As), manganese (Mn) and iron (Fe), characterized in that it comprises at least two chromatography columns ( 1 , 2 ), one column containing a bioadsorber for removing iron and manganese and the other column containing an inorganic adsorber for removing arsenic. 2. Device according to claim 1, characterized in that it additionally comprises a column with activated carbon as adsorbent. 3. Device according to claim 1, characterized in that the column ( 1 ) through which the water to be decontaminated is first passed contains the bioadsorber and the downstream second column ( 2 ) contains the inorganic adsorber. 4. Device according to claim 1, characterized in that the bioadsorber represents spherical carbohydrate particles and is produced by suspending a fibrous or powdered carbohydrate in an aqueous urea solution, optionally adding low or high molecular weight fillers to the suspension, then evaporating the water while stirring and increasing the temperature to 100-200°C, preferably at a temperature of 1300-160°C, optionally applying a vacuum, and the resulting spherical particles are purified by methods known per se and optionally derivatized or modified. 5. Device according to claim 1, characterized in that the inorganic adsorption material for removing As is granulated iron (III) hydroxide (GEH). 6. Device according to claim 1, characterized in that it comprises three chromatography columns ( 1 , 2 , 3 ) which are connected in series in such a way that the water to be decontaminated flows through column 1 from bottom to top and through columns 2 and 3 from top to bottom, column 1 containing a bioadsorber, column 2 containing an inorganic adsorber and column 3 containing activated carbon.