DD291541A5 - DEVICE AND METHOD FOR CLEANING WASTE WATER - Google Patents

Abstract

The invention relates to a process for the purification of wastewater, which contains a combination of adsorption stage (s) and reverse osmosis. The essence of the invention is that the water is contacted with at least one adsorption bed, then the at least partially purified water in the adsorption bed is fed to at least one reverse osmosis and the concentrate leaving the reverse osmosis is contacted with at least one adsorption bed. The water emerging from the first adsorption bed purification is freed from NH 3, with coke, in particular hearth furnace coke from lignite, being used as the adsorbent. adsorption; Reverse osmosis; adsorption bed; adsorbent; Coke; furnace coke; Brown coal}

Description

) by means of natural and / or artificial aluminum silicates

(Zeolites) is removed.

6. Process according to claims 1 and 2, characterized in that the NH ₃

is removed by means of adsorbents.

7. Process according to claims 1-6, characterized in that the separated

is reacted with NO ₂ .

8. Process according to claims 1-7, characterized in that a mobile container is used as Adsorptionsmittelbehälter in which above the Behäkerbodens a water-permeable, sieve-like soil is located on which the adsorbent is arranged and by at least one drain between the floors, through which the water can be removed.

9. Process according to claims 1-8, characterized in that coke is used as the adsorption agent.

10. The method according to claims 1-9, characterized in that the adsorbent Herdofenkoks is used on lignite.

11. The method according to claims' Ί-10, characterized in that the arranged behind the reverse osmosis adsorption bed purified water is at least partially mixed with the occurring from the reverse osmosis purified water.

For this 1 page drawing

Field of application of the invention

The present invention relates to a process for purifying wastewater containing a combination of adsorption step (s) and reverse osmosis.

Characteristic of the known state of the art

The purification of polluted water for the preservation of the environment is one of the great challenges to modern industrial cane management. Numerous methods are known, which operate on very different principles.

By way of example, mention may be made of biological processes which serve, above all, to aerobically remove organic impurities and nitrogen-containing impurities by means of bacteria. From the very extensive patent literature only a few examples can be mentioned, such as DE-OS 3523844, EP-A-0202626, EP-A-0154915, DE-PS 2512815.

Examples of anaerobic processes include:

DE-OS 3307796, EP 0046901, EP0119430.

The reverse osmosis is used for the purification of wastewater (DE-OS 3543661, EP-A-O229414).

Also of importance in the purification of alumina are adsorptive processes. According to DE-PS 2418169 and DE-PS 2819572 Y-Al ₂ O _{3 is used} as the adsorbent. According to DE-OS 3335994 a filter cartridge system is used which contains a suitable adsorbent. According to DE-OS 3401867 an adsorber resin is used.

Coal materials are also used as adsorbents. Thus, DE-OS 3436453 discloses a two-stage process, wherein in a first stage powdered activated carbon is dispersed in the wastewater and then the solids are filtered off.

In a second stage, the prepurified water is sprayed into an activated carbon adsorption tower with simultaneous supply of air.

According to OE-OS 32 21451 activated carbon, preferably carbon black from gasification plants, pressed with a flocculant and a polymer to pellets, which are introduced into the wastewater with stirring.

EP-A-0134271 discloses a sewage treatment process in which wastewater is moved from bottom to top through a coal bed with the coal bed expanding by about 30%.

A particularly important task here is to clean at least to the extent that they can be further purified in conventional treatment plants in an economical way even heavily polluted wastewater. It is known that landfill leachate is already legally classified as wastewater from 1.1.1989 under the amended Wastewater Act. It is therefore to be expected with increasing requirements for the purification of such wastewater. The current methods used to purify leachate are biological treatment with chemical / physical aftertreatment and reverse osmosis (see, eg, "Wastewater Technology," 1-2, 1989 pages 34-38).

Biological wastewater treatment processes have long been used in municipal and industrial plants.

A recent development compared to the shallow reservoirs are the biological wastewater treatment plants, in which tower-type tanks are placed in vertical tower-type tanks. Known processes are the Bayer tower biology and the bio-high-temperature reactor developed by Hoechst.

A disadvantage of the known biological treatment plants is that they are not on site, where certain wastewater, such. B.

Incurred landfill leachate, can be used, but the wastewater must be transported to the plant, wobai possibly large transport routes must be taken into account.

By contrast, reverse osmosis systems can be used as compact, mobile systems. The known disadvantage of reverse osmosis, however, is that it is a concentration method, i. E. H. Although the majority of the wastewater can be separated off from wastewater as pure water, there remains a concentrate containing the impurities, the disposal of which frequently represents a considerable problem. If it can not be returned to a landfill, it must be evaporated or incinerated (see Chem.-Ing.-Techn. 59 (1987) No. 3, pp. 187-196, especially p. 193, left column).

Object of the invention

The aim of the invention is to produce a cost-effective wastewater treatment without at the same time difficult to dispose of contaminants concentrates.

Explanation of the essence of the invention

The invention has for its object to develop an improved process that offers the possibility in both mobile and fixed installations the expert, the most frequent and environmentally harmful wastewater contaminants, namely by the COD value certain organic impurities, also ammonium compounds and Finally, to remove adsorbable organic halogen compounds (AOX) from the wastewater. The Applicant's investigations have led to the certainly unobvious result that the above-mentioned disadvantages of the prior art can be overcome in a hitherto unequaled manner by the inherent combination of adsorption and reverse osmosis, characterized in that the water is mixed with at least one adsorption bed in Contact is brought that the partially purified water in the adsorption is fed to at least one reverse osmosis, which is brought from the reverse osmosis leaving concentrate with at least one adsorption bed in contact. In the figure, the project according to the invention is shown by way of example.

According to the invention, wastewater containing organic impurities, optionally ammonium compounds and adsorbable chlorine-containing compounds, is first contacted with an adsorbent. A typical wastewater containing such impurities is landfill leachate.

An advantageous adsorption device is a container in which above the Behalterbodens a water-permeable, sieve-like soil is located, is arranged on the adsorbent material, wherein water can be removed by at least one drain between the bottoms.

Basically, the container may have any design, so be cylindrical and round, square, rectangular, trapezoidal or consist of composite Raumformsn such. B. expand trapezoidal in the upper part, but below square or rectangular.

Said device and the enumerated spatial forms are to be regarded as exemplary, but not as limiting. The device according to the invention may consist of different materials as they are customary in container construction, ie steel, cast iron, stainless steel, plastics, reinforced concrete, composite materials and the like.

However, it may also be a simpler device filled with an adsorbent through which the wastewater flows from top to bottom or is printed from bottom to top and leaves at the top without the need for special sieve-like devices. The special construction of the container depends u. a. on the type of adsorbent and also on its grain size. If the grain size is large, it may be possible to dispense with a sieve bottom. For example, a sieve just before the drain can suffice.

In principle, all known Ad sorption systems or devices can be used in the combination of method steps according to the invention.

In the method according to the invention, any adsorbent material can be used, a preferred material being cokes, since these are much more economical than, for example, activated carbon.

In the case of the use of coke, the Applicant has found that although any adsorbent can be used, lignite-based coke is a preferred material.

These may be cokes produced by various processes, such as high temperature, low temperature or hearth furnace coke. The latter has proven to be particularly suitable.

Particularly favorable results are obtained when the biscuit is subjected to a pretreatment by which the coke is degassed. This can be done by evacuating the coke and then filling with water or by filling with water in the first step and then evacuating. Other advantageous methods are steaming, followed by filling with water, which may be hot or cold, or sucking in the coke with a water jet pump, evacuating and mixing with water.

The purified in the adsorber in particular by lowering the cargo of organic impurities water-wherein in the adsorbent, other impurities can be recorded, such. B. heavy metals, can now in the presence of ammonium compounds by treatment with a base, especially with caustic soda, but also with Ca (OH) ₂ or mixtures thereof or other alkalis or mixtures of NH _{3 are} freed. The expelled NH ₃ can be used, but it is preferably in a treatment stage with NOj ", which may be present as free acid and / or salt, for example according to the equations:

HNO ₂ + NH ₃ - * N ₂ + 2H ₂ O

NH ₄ Cl + NaNO ₂ -> N ₂ + NaCl + H ₂ O

converted into elemental nitrogen. The further treatment of the NH ₃ , however, also depends on other available facilities. For example, it can be supplied to a biological wastewater treatment plant in which nitrification and denitrification result in biological conversion into elemental nitrogen. The separation of the NH ₃ , which is in aqueous solution in equilibrium with ammonium hydroxide

NH ₃ + H ₂ O ^ NH ₄ ⁺ OH "

or in the presence of acid with an ammonium salt NH ₃ + HX ^ NH ₄ ⁺ X ~

can also be separated by other known or yet to be developed methods for NH ₃ removal, such as by means of natural and / or artificial aluminum silicates, the latter being generally zeolites. If, for example, the alkali metal salts of such aluminum silicates are used, z. B. Na ⁺ or K ⁺ to NH ₄ ¹ * exchanged, the latter being bound to the aluminum silicate.

Examples of suitable aluminum silicates are: potassium zeolite F sodium zeolite X clinoptilolite A clinoptilolite B chabazite sodium zeolite A sodium zeolite Y potassium zeolite X potassium zeolite Y phillipsite eriomite (see US Pat. No. 3,723,308)

Also zeolites on Kohlenaschebasis, in particular Steinkohlenaschebasis z. B. on power plant ashes are used according to the invention.

Other ion exchangers z. B. on an organic-synthetic basis can be used.

Furthermore, all adsorbents suitable for NH ₃ adsorption can be used, such as adsorbents on SiO ₂ or Al ₂ O ₃ -BaSiS or finely divided coals, in particular lignite.

The materials mentioned are to be considered as exemplary, but not limiting.

The removal of the separated NH ₁ can also be carried out by treating the materials directly with an aqueous solution of NO ₂ "without previously removing the NH ₃ such as by stripping.

The aluminum silicates or zeolites, ion exchangers and adsorbents can be regenerated by conventional methods. Further possible reactions of the NH ₃ are, for example, catalytic combustion

4NH ₃ + 6O ₂ ^ 2N ₂ 4 6H ₂ O

Oxidation with H ₂ O ₂

CO ₂ 2 NH ₃ + 3 H ₂ O ₂ > N ₂ + 6 H ₃ O

or introducing into sulfuric acid

2 NH ₃ + H ₂ SO ₄ -> (NH ₄ I ₂ SO ₄ (used as fertilizer)

The liberated from NH ₃ wastewater now enters a Umkeiirosmose plant. All suitable reverse osmosis methods of the prior art or their further developments are applicable here.

For the combination of process steps according to the invention, all method steps of the prior art, as well as technical developments, but especially those in which a permeate can be obtained, which is at least to the extent of impurities that it meets the requirements for direct discharge into water equivalent. Preference is given to projects with which a particularly pure permeate can be obtained.

The resulting in the reverse osmosis concentrate is now r brought into contact with an adsorbent. For this stage, the already explained in connection with the first Adsoprtionsstufe.

The purified wastewater obtained from the second adsorption stage can now be returned to the first adsorption stage, alternatively it can be fed to a sewage treatment plant or preferably completely or partially mixed with the permeate of the reverse osmosis plant and introduced into public waters is achieved by el ^ s inventive method that the mixture complies with the legal requirements of direct introduction.

In principle, the concentrate emerging from the reverse osmosis can also be fed directly to the first adsorption stage. According to the invention, the steps described can also be connected several times in succession or in parallel.

The crucial inventive effect, which is based on the inventive combination of adsorption and reverse osmosis, the complete workup, including highly contaminated wastewater, the purity that they can be safely supplied to public waters without a concentrate of impurities remains.

The loaded adsorbents can be fed to a modem-equipped combustion, regenerated or even landfilled, since the adsorbent emit the impurities only to a very limited extent.

embodiments

The invention will be explained in more detail with reference to the figure and the data obtained.

Via (1), wastewater enters the adsoi ptive purification stage (2). If the wastewater is substantially free of ammonium compounds, it enters via (3) a reverse osmosis system (4). The purified waste water (permeate) exits at (5) and can be fed (via a receiving water) to public waters (15). The concentrate passes through (6) in the adsorber (7). The water leaving (7) can either be mixed with the permeate via (8) or it returns to the feed (1). Alternatively, it can be fed via (9) to a sewage treatment plant. The concentrate can also be directly after (10) after

(I) to be driven.

In the presence of ammonium compounds in (11) by adding a base, in particular NaOH and additional stripping z. B. expelled with steam NH ₃ . NH ₃ passes through (12) to (13), where the NH _{3 is} converted to elemental nitrogen (14) by the addition of HNO ₂ , or it passes via (16) to a biological nitrification-z-denitrification unit.

II1) may also contain a filling, such as natural or artificial aluminum silicates or zeolites, other ion exchangers or adsorbents to which NH _{3 is} adsorbed or held. The reaction with HNO ₂ or a nitrite can also be carried out directly in (11), but also as described in (13).

In principle, treatment with NOi is also possible in (2). Furthermore, depending on the wastewater, stage (7) can also be dispensed with and the concentrate from (4) can be recycled via (10) to (1) or (2).

example

In (1), 10m ³ / h of wastewater having a COD of 1500, ammonium nitrogen of 750 mg / l and AOX of 2.5 mg / l enter (2). The water leaving (2) has a COD of 500, an ammonium nitrogen value of 750 mg / l and AOX of 0.25 mg / l. The wastewater now passes to (11) where NH ₃ is expelled by the addition of NaOH.

• The water leaving (11) and flowing in reverse osmosis (4) has a COD of 500, an ammonium nitrogen value of 10 mg / l and an AOX value of 0.25 mg / l.

The permeate (6 m ³ ) leaving (4) still contains organic impurities according to a COD value of 15, an ammonium nitrogen value of 5 mg / l and an AOX value of 0.03 mg / l.

The concentrate (4m ³ ) has a COD value of 1230, an AOX betting of 1.2 mg / L and a NH ₄ -WeH of 17.

The water exiting from adsorber (7) (4m ³ ) has a COD value of 450, an NH ₄ ⁺ value of 17 mg / l and an AOX value of 0.12 mg / l.

Mixing the (7) leaving water (8) with the permeate (4) exiting permeate (5), we obtain a water (10m ³ ), which has a COD value of 150, NH ₄ ⁺ nitrogen of 10 mg / l and AOX of 0.07 mg / l.

The process according to the invention can accordingly be achieved with the use of only one respective purification stage (2), (4) and (7), a purification which makes it possible to easily introduce even heavily contaminated water into bodies of water.

Depending on the requirements, according to the invention it is also possible to use a plurality of these stages, connected in parallel or in series.

Claims (5)

A process for the removal of impurities from water, characterized in that the water is contacted with at least one adsorption bed, the at least partially purified water in the adsorption bed is fed to at least one reverse osmosis, the recirculating osmosis concentrate contacts at least one adsorption bed is brought. 2. The method according to claim 1, characterized in that the emerging from the first Adsorptionsbettreinigung water is freed from NH ₃ . 3. Process according to claims 1 and 2, characterized in that NH ₃ is removed by the addition of alkalis and subsequent stripping. 4. Process according to claims 1-3, characterized in that NaOH and / or Ca (OH) _{2 is} used as the alkali. 5. Process according to claims 1 and 2, characterized in that the NH ₃