CH630323A5 - Process and apparatus for treating utility water - Google Patents

Description

The present invention relates to a process for the treatment of industrial water with partial softening by aeration in conjunction with biological oxidation of oxidizable substances contained in the water in a column, which has a plurality of aeration stages arranged one above the other and a plurality of residence and / or reaction chambers

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has, and on an apparatus for performing the method.

Numerous methods and devices for aerating and / or deacidifying water for water treatment have already been proposed. For example, series connection of ventilation floors in a container and the so-called cross-flow ventilation are known for this purpose.

In AT-PS 187 863 devices are disclosed which contain either several series-connected aeration stages or at least between so-called baffles between several ceramic filter plates, which are conducive to the thorough aeration of the water in order to form CO 2. As is well known, C02 is highly soluble in water and will therefore hardly leave the water voluntarily, only through thorough gassing or vacuum formation.

Another step-shaped device structure is known from DE-OS 2 358 215.

Finally, AT-PS 187 863 shows that lime deposits can be achieved by intensive aeration of carbonate-hard water. Partial softening of brewing water is possible through lime deposits. This known method together with devices is only intended and suitable for consumer-owned small systems, such as those found in breweries. A targeted water softening, for example for a central water supply, is by no means feasible using this known method. As is well known, a chemical reaction sequence takes place in water softening according to the following formula:

Ca (HC03) 2 = CaC03 j + H20

In the method with device known from AT-PS 187 863, this reaction proceeds far too slowly and with far too little scope for the normal water throughput of an efficient aeration device. In practice, this means: with increasing water throughput, the lime scale that can be obtained decreases.

The object of the present invention is to demonstrate a method with a device suitable for carrying it out, with which a water treatment which meets all contemporary requirements for water quality is possible, for which purpose apart from ventilation and deacidification in particular the softening or partial softening while maintaining any desired degree of hardness and, if appropriate biological oxidation and nitrification are also included, and all of this regardless of possibly large fluctuations in the water flow volume per unit of time.

The method according to the invention which is suitable for achieving this object is defined in patent claim 1.

Certain processes can be accelerated, for example, by the water being supersaturated by aeration (expulsion of C02) at CaC03 in each case and the streams introduced into the reaction chambers being mixed with crystal seeds for faster equilibrium.

The dwell and / or reaction chambers can be connected in series or in parallel as required. In this way, different measures of different duration can take place simultaneously. The reaction time is expediently determined by controlling the flow time of the water through the relevant reaction chamber.

According to the method according to the invention, the water is first appropriately converted to a limescale-saturated state by the intensive aeration for the purpose of decarbonization and then fed to the reaction chambers in its unstable state, where it

hei is added to the Kaikabscheidung, which in turn releases carbonic acid. The processes are then carried out again and repeated until the desired softening is achieved. The quay separation is expediently accelerated by measures such as the creation of contacts. In particular, crystallization nuclei can be added.

For the purpose of the oxidation of organic substances or ammonium ions, different adsorbents or adsorbents of different partial selectivity or porous substances to which microorganisms can adhere and develop can be added to the residence or reaction chambers. Pressure losses can be minimized by means of a multi-stage floating bed arrangement. The adsorbents can be removed continuously and replaced with newly added adsorbents, so that a uniform product quality is guaranteed. If the same adsorbent is used in several stages, this can also be conveyed to the next higher stage and can thus be conducted in counterflow to the water.

In the case of intensive ventilation, the removal of volatile organic compounds is strongly promoted at the same time.

To improve the adsorption and biodegradation, different pH values can be set in the individual dwell or reaction stages by adding acid or alkali. Poorly degradable organic substances can possibly be converted into a more easily attackable form beforehand by adding stronger oxidizing agents. Here, catalysts and catalytically active materials can also be an advantage.

The device for carrying out the method according to the invention with a plurality of ventilation stages lying one above the other and through which water flows in one direction is defined in patent claim 12. It is advantageous if the aeration stages are connected to the dwell or reaction chambers via the connecting lines and are spatially arranged such that the flow takes place in a free gradient. This results in a space-saving design and pumping operations can be saved.

By means of the described device, a complete adjustment to the different treatment requirements, which are predetermined by the quality of the water, is made possible, whereby it can still be completed by flocculation processes.

One embodiment of the device described is equipped with sieve trays through which air generated in a blower can be directed from bottom to top,

the sieve trays are expediently arranged one above the other so that water on the sieve trays runs transversely to the air flow, falls from the ventilation stage to the ventilation stage and thus runs in a zigzag pattern through the entire device.

Unwanted gases (excess C02 and H2S) as well as volatile organic compounds (odorants) are removed immediately through intensive ventilation. Partial decarburization is achieved by multiple intensive aeration and the buffering of the water is reduced. At the same time, iron and manganese are precipitated. Strong alkalization with alkali or anion exchangers in the OH form naturally precipitates magnesium as a hydroxide, which has excellent flocculating properties. When using ion exchangers, additional anions (e.g. chloride) are removed. The use of different adsorbents with less than 5

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various properties can maximize the adsorptive removal of organic substances. The multiple intensive aeration promotes the biodegradation of organic substances and at the same time enables the nitrification of higher amounts of ammonium.

The invention will be explained below with reference to the drawings. The drawings show:

Figure 1 shows a device which is particularly suitable for decarbonization, in a schematic representation.

2 shows a diagram illustrating the decreasing lime content in the various stages:

3 shows a schematic illustration of the side view of an embodiment of a device which is preferably suitable for oxidation; and

Fig. 4 shows a device according to Fig. 3 in perspective.

In general, the device according to the invention consists of individual ventilation stages in a multi-stage reaction tower with packing elements, e.g. Ra-ski rings, or larger ventilation elements, at the upper end of which air can enter, which is released at the lower end of the ventilation level. There are retention and / or reaction chambers between the aeration stages, into which the water passes after exiting an aeration stage and before entering a new aeration stage.

A special embodiment consists of the fact that the water to be treated flows in a ventilation column before the first aeration stage into a third and then into the further odd-numbered aeration stage with intermediate retention and / or reaction chambers, and that the water then flows through even-numbered aeration stages, i.e. the second , fourth, etc. with interposed dwell and / or reaction chambers and that the odd and even ventilation stages are run either in parallel or - after a single pumping - in succession.

In the embodiment of the device according to FIG. 1, the raw water to be softened is fed from the raw water line 1 to an aeration tower 2 and reaches the first aeration stage, which is designated B I, via a distribution floor 3. In this case, air is sucked in through lateral ventilation contactors, not shown in detail, which forms a large, constantly changing boundary layer in the ventilation element 4 with the water and brings about a gas exchange. After passing through each ventilation element 4, the used air is released to the opposite side and the oxygen-rich water, which is depleted in carbon dioxide, is discharged into a separating reactor 7 via a drain line 6. Specifically, after passing through the first aeration stage B I, the water reaches the separation reactor A I, where the calcium carbonate is removed from the supersaturated solution and carbon dioxide is released again.

The water freed from the supersaturation is returned from the separation reactor 7 via return lines 8 in the ventilation tower to the renewed discharge of carbon dioxide. The water passes from the separation reactor A I into the aeration stage B III and then subsequently through the reactors A III, A V, A VII through the subsequently odd-numbered aeration stages B V, B VII and B IX. The even-numbered stages B II with the reactor A II, B IV with the reactor AIV etc. can either be subsequently charged with the same water with the aid of a pump 9, the slides 10 and 11 remaining closed. It is also possible to operate the system in such a way that the even-numbered ventilation levels B II, B IV etc. are acted on in parallel via the raw water supply line 1. This results in a noticeably lower decarbonization effect, but double the throughput. For this purpose, the pump 9 is switched off and the slide 12 is closed, while the slide 10 and 11 are opened. This water, which flows through the groups of aeration stages with reactors operated in parallel, reaches a collecting tank 13 and is discharged there via the pure water line 14.

The deposition materials accumulating in the individual reactors AI, A II etc. are discharged through the sludge lines after opening the assigned slide and

if necessary, subjected to a sludge treatment. In this way it is possible, depending on the circumstances, to let the water to be decarbonized flow through the required number of aeration stages with reactors and thus to set the desired degree of hardness of the water.

The free CO 2 (in mg / 1) is plotted against the carbonate hardness (in mmol / 1) in a diagram in FIG. 2.

The water to be decarbonized is normally in a state represented by the equilibrium curve 20. Aeration removes carbon dioxide from a starting point 21, and the water reaches an unstable state, which is represented by point 22, at an assumed, easy-to-reach output efficiency of tj = 40% per stage. The water is returned to a new equilibrium state by quay separation with simultaneous formation of equimolar amounts of CO 2, which is designated by 23. The water is again in a state described by the equilibrium curve, but with a lower lime content. This process is repeated several times through the individual ventilation stages until the desired final state 24 is reached.

Decarbonization with this method cannot lead to very low hardness. However, these are also undesirable for the task of drinking water supply, since hygienic concerns prevent the water from being softened too much. For this partial decarbonization, it is possible to do without chemical additives and to minimize the waste product to the amount of lime that is actually eliminated from the water during the decarbonization process.

The embodiment of the device shown in FIG. 3 is characterized by sieve trays 31 which are arranged one above the other and through which the air generated in a blower is directed from bottom to top. It is envisaged that the water on the sieve trays runs transversely to the air flow and then flows through retention and / or reaction chambers before it is led into the next sieve tray with a downstream retention and / or reaction chamber and thus flows through the entire system in a zigzag fashion. Both separation and settling processes as well as adsorption and flocculation processes can take place in the retention and / or reaction chambers; in the latter cases, the solids are expediently kept in a fluidized bed.

In particular, the device shown in FIG. 3 is constructed from similar elements, each of which comprises a square porous ventilation plate 31, usually a perforated plate, and a subsequent dwell and / or reaction chamber with conical walls 32. If necessary, two such chambers can also be installed one behind the other.

Several of these elements - depending on the required processing capacity 4 to 12 - are arranged one above the other in such a way that the ventilation plates lie exactly one above the other horizontally, while the attached retention and / or reaction chambers move from stage to stage

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are each offset by 90 °. The ventilation plates are sealed in such a way that a multi-stage closed column 34 is formed. The ventilation tower thus formed is sealed on the sides of the water inlet and outlet by water locks so that no air can escape laterally.

The (outer) retention and / or reaction chamber contains an overflow edge 35 on the side. Here, a small channel 36 is attached, which supplies the water to the perforated plate to the step below.

Above the uppermost aeration plate there is a bell with a vent 37. The water flows horizontally over the aeration plates, while a large excess of air is blown in from below through a distribution chamber 38 by means of a compressor, which flows through the porous plates and exits the vent 37 at the top .

Due to the cross-flow ventilation, an intensive gas exchange takes place on each plate with the formation of a foam layer, whereby Oa is absorbed and S02 is released. The water passes through a foam brake and then enters the retention and / or reaction chamber 32 - and from there, if necessary, into the reaction space 33 - where the reactions take place, possibly with metering additives. The reaction products formed are discharged laterally.

The following processes can take place in the multi-stage reactor:

In the case of harder water, the upper stages, possibly with the addition of crystallization nuclei, such as fine sand,

after the COz discharge a lime separation and thus a partial decarbonization takes place. After passing through the first stage reactor, the water is fed to the aeration plate of the stage below. This means that the C02 discharge and the subsequent lime precipitation can be repeated as often as required.

In the case of softer water or after partial decarbonization, the stages below can also be used for flocculation exchange or adsorption processes as well as for biological oxidation. For this purpose, flocculants, flocculants, activated carbons of various degrees of activation and other adsorbents, as well as other sub-3 porous structures, to which microorganisms adhere and can develop, are added to the feed troughs of the aeration plates or to the retention and / or reaction chambers themselves. By adding acids or alkalis or by adding cation and anion exchangers in H + or OH_ form, the environmental conditions of the water can be changed and optimally designed for these 10 processes. In the latter case, there is a simultaneous reduction in cations or anions (calcium or chloride ions). Stronger oxidizing agents, such as KMn04, H202 and ozone, can convert poorly degradable organic substances into a biodegradable form 15.

The operation in the fluidized bed with flowing water avoids high resistances and allows higher throughputs with better use of the added chemicals. A carryover of small residual amounts of 20 reaction products into the subsequent stages is generally not critical. For better utilization, it may even be advantageous to carry on certain portions of adsorbents, flakes and other directly into the subsequent stages, while the main amount 2s of the technical auxiliaries and reaction products are immediately or periodically removed from the individual stages. Using pumps of low power, it is also possible to add the adsorbable or biologically active substances against the water flow to the overlying reaction stage and thus achieve a countercurrent effect in such a way that the unpolluted adsorbent is initially offered to the largely purified water in the last stage and with increasing stress meets more preloaded water.

The entire preparation process runs on a free slope without intermediate pumps. Then only one filtration step is required. Since both metering and draining can take place continuously or in small steps, a constant product quality is achieved.

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Claims (21)

630323 1. Process for the preparation of process water with partial softening by aeration in conjunction with biological oxidation of oxidizable substances contained in the water in a column which has a plurality of aeration stages arranged one above the other and a plurality of retention and / or reaction chambers, characterized in that the water is in each case in one Aeration stage is ventilated and after each aeration is introduced into a separate retention and / or reaction chamber, and that the water separated from the precipitation products is then treated in the same manner in the subsequent similar stages and the precipitation or reaction products are removed continuously or periodically from the retention area - And / or reaction chambers are withdrawn. 2. The method according to claim 1, characterized in that the water is supersaturated by aeration of CaC03 in each stage and the streams introduced into the dwell and / or reaction chambers are mixed with crystal seeds for faster equilibrium. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that the water is intensively aerated in several stages and then dwell and / or reaction chambers are fed, in which biological oxidation of ammonium ions and organic substances takes place in the 02-saturated water. 4. The method according to claim 1, characterized in that agents are added to the water in the retention and / or reaction chambers, which enter into chemical and / or physical interactions with the substances contained in the water. 5. The method according to claim 4, characterized in that different adsorbents or adsorbents of different partial selectivity or porous substances are added to the residence and / or reaction chambers, to which microorganisms adhere and can develop, the adsorbents or the porous substances preferably in the upward flow to be kept in the floating bed. 6. The method according to claim 5, characterized in that different pH values are set in the individual retention and / or reaction chambers. 7. The method according to claim 5 or 6, characterized in that an adsorbent is counteracted to achieve a countercurrent effect on the watercourse. 8. The method according to any one of claims 4 to 7, characterized in that flocculants, flocculants, acids, alkalis or oxidizing agents are added to the residence and / or reaction chambers. 9. The method according to claim 5 or 8, characterized in that milieu changes are made by adding ion exchangers in H + - or in OH ~ form, which simultaneously causes a reduction in the cation or anion concentrations. 10. The method according to any one of claims 4 to 9, characterized in that a partial or complete derivation of reaction products or of solid technical auxiliaries is carried out periodically or continuously directly in lower levels. 11. The method according to any one of claims 4 to 10, characterized in that a promotion of the reaction products or of technical auxiliaries of a stage takes place periodically or continuously in higher stages. 12. The device for carrying out the method according to claim 1, having a plurality of aeration stages lying one above the other and through which water can flow in one direction, characterized in that aeration stages (BI to B VIII) via drain lines (6) with separately arranged retention and / or reaction chambers ( AI to A VIII) are connected, which are connected via return lines (8) to the next ventilation stage. 13. The apparatus according to claim 12, characterized in that the ventilation stages (BI to B VIII) via the lines (6, 8) in such a way with the dwell and / or reaction chambers (AI to A VIII) and spatially arranged so that the flow can take place in a free gradient. 14. The device according to claim 12 or 13, characterized in that the individual ventilation stages (4) arranged in a ventilation tower (2) and with filler-like elements, e.g. Raschig rings, but also coarser ventilation elements. 15. The apparatus according to claim 14, characterized in that in the aeration tower (2) to be treated water from a first aeration stage (BI) via the associated dwell and / or reaction chamber (AI) in a third aeration stage (B III) and from there in the next but one, i.e. initially through all odd-numbered ventilation levels (BI, B III, BV ...) and the associated dwell and / or reaction chambers (AI, A III, A V ...), and then the water through a pump ( 9) through the even-numbered ventilation stages (B II, B IV, B VI ...) with the associated dwell and / or reaction chambers (A II, AIV ...). 16. The apparatus according to claim 15, characterized by slide (11, 12, 10), the bridging of the pump (9) and a parallel operation between the odd and even ventilation stages (B) allow. 17. The apparatus according to claim 15 or 16, characterized in that all retention and / or reaction chambers (A I to A VIII) are provided with valves (v) which enable a sludge emptying via common sludge lines (15). 18. The apparatus according to claim 12, characterized by sieve trays (31) through which air generated in a blower can be passed from bottom to top, the sieve trays (31) being arranged one above the other, so that water on the sieve trays transversely to the air flow from the ventilation stage falls to the ventilation level and can thus flow zigzag through the entire device. 19. The apparatus according to claim 18, characterized in that after each ventilation stage, a simple or divided dwell and / or reaction chamber (32) is arranged with parallel or conical walls, which is particularly suitable for the formation of fluidized beds. 20. The apparatus according spoke 19, characterized in that an overflow edge (35) with a laterally attached discharge channel (36) leading to the next ventilation stage is arranged on the last part of the dwell and / or reaction chamber. 21. The device according spoke 19 or 20, characterized in that metering devices are attached to the individual discharge channels (36) or directly on the reaction basin (32) in order to dose different substances and to achieve processing sequences.