DE2943870A1 - Sewage clarification - in two flock(s) precipitation stages by injecting calcium salt and iron salt in aeration up draught - Google Patents

Abstract

A process for the phosphate precipitation and for the final clarification of sewage in basins or ponds includes a biological treatment by aeration, followed by two separate flocculation stages for a sedimentation of the sludge. In each subsequent stage, air or oxygen injection produces a circulatory flow. In the first stage, a calcium salt is added and in the second an iron salt, preferably by a metered admixture to the updraught produced by the aeration. Outside the mixing zone, the mixture passed through an anti-turbulence zone. This creates favourable conditions for the sedimentation and yields an easily processed sewage sludge. The large flocks make the precipitation more efficient.

Description

Method and device for treating waste water, in particular for

Phosphate precipitation and for post-purification of waste water in basins} or "Ponds" or "Ponds" The invention relates to a method and an apparatus for the treatment of wastewater, especially for phosphate precipitation and for the post-purification of Wastewater in basins or ponds after previous, esp. By entry of air or Oxygen biological treatment of the wastewater, in which two different Treatment agents, in particular an iron salt and a calcium salt as precipitants in successive separate treatment stages mixed with the wastewater and the resulting flakes formed sludge is separated by sedimentation.

It is known that wastewaters consistently contain phosphates, which are not degraded during the biological treatment of the wastewater. This in solution located phosphates, which partly from industrial wastewater, partly from Household wastewater or wastewater from agriculture are on average with mixed wastewater 15 to 25 mg per liter. If treated wastewater, for example from sewage treatment plants, into stagnant or slowly flowing waters ; ollen, the phosphate content must not exceed 1 mg according to the prescribed values per liter, as the phosphates in the sewage cause algae to form favor and lead to eutrophication, which in turn leads to an increased need for oxygen connected is.

to reduce the phosphate content of pre-treated wastewater, the process mentioned in the introduction has become known, with the lime in the form CaO or Ca (OH) 2 as well as iron sulfate in the form FeS04 or Fe2 (S04) 3 are used became. Instead of iron sulphate, there is also aluminum sulphate as a precipitating agent that has a similar effect used, but this leads to less favorable results in the subsequent sedimentation led.

The phosphate precipitation by means of lime and iron sulfate was both before tested during the biological treatment of wastewater as well as during this treatment, however, it was found that this results in disadvantages, which are essentially consist in the fact that redissolution phenomena occur after a precipitation a complete biological treatment of the wastewater can be avoided. The previous biological treatment does not have to go down to the last possible one Degree of purification must be carried out, since with the treatment of the wastewater for phosphate precipitation at the same time also a post-purification of the wastewater in the sense of a biological one Treatment is achieved because by mixing the precipitant with the wastewater is generally associated with an increased introduction of oxygen. One has namely at the known method for this mixing gyroscope or the like. used, which is also used in connection with biological treatment methods Can apply.

One is always in the previously known method mentioned at the beginning proceeded in such a way that the two precipitating agents mentioned are placed one after the other in separate tanks admitted. The iron sulfate was added in the first stage and the addition of the lime in the second stage, i.e. in the second basin. Elier through a flocculation of phosphate in the form of was obtained in the first basin Iron phosphate, which has the advantage of very good sedimentation and therefore added to the first treatment stage as being particularly suitable for coarse precipitation became. In the second treatment stage, the residual precipitation then took place by means of the Lime, while at the same time the previously carried out shift due to the addition of lime the pH of the wastewater was balanced again in the acidic range. Of the sewage sludge obtained by phosphate precipitation in the known process must prepared for further use in agriculture, especially with alkalis as mainly alkaline fertilizers in agriculture are needed to avoid over-acidification of the soil.

The object of the present invention is to provide a method of the introductory mentioned type so that while maintaining the favorable sedimentation properties a sewage sludge that can be processed immediately is obtained at the same time Increase the effectiveness of the felling process combined with a Formation of relatively large flakes. In addition, a particularly simple, effective Apparatus for the treatment of wastewater are created.

What is mentioned in the introduction is used to solve the above problem The method according to the invention in that the wastewater in each of the two successive Treatment stages set in a circulating flow by the introduction of air or oxygen and in the first treatment stage with a calcium salt and in the second treatment stage with an iron salt, preferably during the metered introduction of these precipitants Into the buoyancy zone created by the air or the oxygen, both intensely is mixed and passed outside the mixing zone in a calm flow. Of the Lime can - especially in smaller plants - in the form of milk of lime made from hydrated lime can be added to larger systems as quicklime. As iron salts are particularly suitable FeSO4, FeClSO4 and FeCl3.

In the new process, in contrast to what is known in the first Treatment stage mixes the wastewater with the lime, creating most of the precipitated phosphates in the form of calcium phosphate. By air or Oxygen entry is on the one hand an intensive mixing of the entered precipitant reached with the wastewater, but without being in this mixing zone mechanical forces occur which prevent flake formation. It was also noticed, that due to the entry of air or oxygen The buoyancy zone generated is the one that has already been formed, but by the circulating flow Several times by the buoyancy zone demanded flakes on the size of the itself newly forming flakes are broken up, however, in the subsequent calming down Unite the flow again to form relatively large flakes, as is the case with the oneself in the mixing zone forming new, relatively small flakes is the case.

The calcium phosphate flakes produced in the first treatment stage can, depending on the formation of the circulating flow, partly already in this first Discontinue the treatment stage, or they are transferred to the second treatment stage, in which the iron salt is added, also in this treatment stage the same ratios as they can be achieved with regard to the formation of flakes described above. Those that form in the second stage of treatment Flakes are specific due to their proportion of the iron phosphate that is formed heavier than the calcium phosphate flakes, so that made up of calcium phosphate and iron phosphate existing flakes have particularly favorable sedimentation properties. Included the proportion of iron phosphate is proportional to the proportion of calcium phosphate low, since the phosphate precipitation is essentially due to the addition of lime was achieved.

The sewage sludge obtained by the new process can easily and used as fertilizer in agriculture without additional processing will.

With the new process, air or oxygen is introduced at the same time a biological post-treatment of the wastewater and thus a biological post-treatment achieved, which has a corresponding effect on the quality of the wastewater.

The preferred addition of the precipitant in dosed form to the The upwelling zone created by the air or the oxygen is immediately after the entry of the precipitant achieved and promoted the formation of flakes, so that it it is advantageous to introduce the precipitant in this buoyancy zone.

It is particularly useful if the lime or the iron salt together with air or water as a means of transport in the respective mixing and entry zone of the wastewater in the circulating flow is transferred. This can a sensitive dosage an even distribution of the precipitant in the entry zone be made so that the precipitant in a correspondingly fine distribution with comes into contact with the wastewater and flakes form very briefly will. When air is used as a means of transport, the buoyancy flow in the Mixing zone increased or favored. At the same time, air or water is used as a means of transport made sure that deposits of the precipitant largely when fed to the wastewater be avoided. The choice of the means of transport depends on the type of precipitant, especially also according to whether the precipitant is in liquid or solid form in the wastewater is fed.

Due to the fact that in the new process there is no spraying of the water, for example by vortex or the like., To generate a circulating flow, are for the Procedure does not necessarily require two basins or ponds, which in the usual one Way for the continuous treatment of the waste water by means of an overflow connection pipe are flowed through one after the other by the wastewater, but in a particularly advantageous one Embodiment of the method can the wastewater within a single basin or pond through an air or oxygen input in two separate circulating currents, namely one the inlet and one the outlet of the water to or from the basin or The circulating flow tangential to the pond is offset and the lime flows into that tangent to the inflow as well as the iron salt are entered into the circulating flow tangential to the drain.

The creation of two separate, oppositely directed circulating currents inside a pond or basin is used for the biological cleaning of Wastewater is known per se, but these are in connection with phosphate precipitation Circulating currents have not yet been exploited.

For the treatment of wastewater with two different treatment agents, especially for phosphate precipitation according to the new process, one is particularly suitable device according to the invention which has no mechanically driven parts, but exclusively from resting systems arranged in the basins or ponds Accordingly, the new device is based on a with a Inlet and a drain provided pond or basin, esp. Simultanteich, with about arranged in the middle between the and drain, preferably of two parallel at a distance arranged pipes existing across the pond or the corner device for the entry of compressed air or oxygen in small bubbles to create two parallel buoyancy zones or currents, whereby to divert the buoyancy currents into opposing surfaces and circulating currents a deflection device preferably floating at the level of the water surface is provided. This device is developed in such a way that in the inlet side Circulating flow a distributor device for the one treatment agent, in particular that Calcium salt and a distributor device for in the outlet-side circulating flow the other treatment agent, in particular iron salt, are provided, which are connected via connecting lines are each connected to a metering device.

According to the explanations given above, this in itself becomes a biological treatment of sewage known arrangement for generating two separate opposing directions Circulating currents within a pond or basin also with a distributor device equipped for the two treatment agents, which in turn are equipped with metering devices are connected to depending on the particular phosphate content of the wastewater the above-mentioned precipitants separate the two circulating flows in the manner described above to feed.

It when the distribution devices as Tubes formed with outlet openings and above the facilities for the Air or oxygen entry and are arranged to run parallel to them. Through this the entry is made Precipitants in the area of the buoyancy zone, Intensive mixing is achieved through the rising air or oxygen bubbles takes place.

Although it is possible the two run parallel to each other Buoyancy zones are sufficiently spaced apart from one another separate in order to mix the water flowing upwards in the upwelling zones To avoid it, it is advisable to keep between the parallel buoyancy currents and the associated distribution devices, a preferably flexible, film-like, with to provide the diverter connected partition. This allows the two Buoyancy zones can be provided extremely close to one another without the danger adverse mixing. The partition wall can extend to the bottom of the pool or pond extend and end at a distance below the water level or up to Water level and end at a distance from the pool or pond floor. To this In this way, either a partial overflow or underflow of the partition is made possible, according to the inflow to the pond or basin, an overflow of the already treated water from one part of the pond or basin to the other part to enable, with the described arrangement of the distribution device within the buoyancy flow it is ensured that practically no water comes out one part of the basin crosses over into the other without first using the precipitant to have been treated.

A particularly advantageous embodiment results when the devices for the entry of air or oxygen and the distribution facilities for the lime and iron sulfate in the lower section of a pond or basin dividing shaft are arranged, which of two spaced parallel, to just below the water level as well as just above the pool or pond floor and from there diverging or mutually intimately angled guide walls and limited from the partition wall into two parallel shafts for the separate buoyancy currents is divided. As a result of this training, two will be based on the mammoth pump principle working shafts are formed, which generate an intense circulating flow with separate mixing zones for the two located within the buoyancy zones Precipitant, experience has shown that there is very high turbulence in these mixing zones occurs, which greatly favors the mixing effect.

The distribution facilities can either be via connecting lines be connected to a feed pump, which sucks in water from a supply, or but it can be connected to the connection lines for the distribution facility Compressed air compressor can be provided to transport air or water in to transfer the connecting lines, with these connecting lines in both Cases with a lime or

Dosing pump connected to the iron sulphate tank connected on the pressure side is.

In the drawing, exemplary embodiments of the invention are shown schematically Representation reproduced.

1 shows a cross section through a preferred embodiment an apparatus for carrying out the new method, FIG. 2 in schematic form Representation of a longitudinal section through a clarifier with a device according to FIG Fig. 1 and the device for supplying the precipitant, Fig. 3 is a longitudinal section according to FIG. 2, but with a different device for supplying the precipitant.

In the device shown in Fig. 1 is basically one Pond or basin a foundation 1 is provided on which a total of 2 marked itself across the pond and this aeration device divided into two halves is arranged.

The ventilation device 2 consists of two spaced apart and guide walls 4 and 5 held on the foundation 1 via a supporting frame 3, which end below the water level 6 and just above that of the foundation 1 in the area the aeration device formed pond floor 7 oppositely angled sections 8 and 9, these sections being proportionate in the example shown are long trained. Instead of these sections 8 and 9, the guide walls 4 and 5 be divergent in the area just above the basin floor, so that they can end approximately at the end of the curves 8a or 9a. The longer training of the sections 8 and 9, however, have the advantage that there is a very intense current in the pond Water along the pond bc (1en is generated.

They extend parallel to the guide walls to a ventilation device associated ventilation pipes 10 and ll, which protrude above the water level 6 and from there to a compressed air source not shown in the drawing are led.

At the ends of the ventilation pipes 10 and 11 protruding into the pond arranged with air outlet openings provided manifold pipes 12 and 13, which extend like the baffles 4 and 5 through the entire pond. Instead of the mentioned Distribution pipes 12 and 13 can also have so-called ventilation candles at the ends of the lines 10 and 11 be arranged, which by using sufficiently porous material allow the exit of the finest bubbles. Should, however, bubbles with a larger cross-section are generated, the arrangement of the manifold pipes mentioned is recommended 12 and 13, where you have control over the choice of the air outlet openings, determine the bubble size.

The air bubbles emerging from the distribution pipes i2 and 13 get there in the shaft 14 delimited by the guide walls 4 and 5 and lead to one there Buoyancy flow based on the mammoth pump principle.

Above the guide walls 4 and 5 or the shaft 14 is a floating one held deflection device 15 is provided, which ensures that the in the shaft 14 generated buoyancy flow into one in the drawing to the right and left split surface flow is converted, as indicated by the arrows 16 is indicated. At the same time, the deflection device 15 creates a surge above the shaft 14 avoided.

To stabilize the framework 3, supports 17 are provided, as inclined struts in the foundation 1 and at the top of the scaffolding 3 are attached. The frame 3 also serves to accommodate a catwalk 18 with Geländtilolmen 19 and 20, which are also designed as air supply lines could be.

The buoyancy flow generated in the shaft 14, which is described in FIG Shape is converted into the surface flow 16, leads to an opposite direction Circulating flow in the two in FIG. 1 to the right and left of the ventilation device 2 reproduced pond halves, with the return flow of the water to the aeration device takes place along the pond floor 7, as indicated by the arrows 21. Included this bottom flow is in the area of the ventilation device 2 through the sections 8 and 9 of the guide walls 4 and 5 favored.

In the lower part of the shaft 14, which is supported by the guide walls 4 and 5 are formed, however, are at approximately the same height in the example shown at a distance, two distribution devices 22 and 23 are provided, in the example as distribution pipes with corresponding outlet holes for the addition of lime or iron sulfate are formed. If in the direction of arrow 24 the influx of wastewater to be treated takes place and in the direction of arrow 25 its discharge, so the distributor device 22 is provided for supplying the lime and accordingly also connected to a corresponding conveying and metering device, while the Distribution device 23 for supplying iron sulfate with a corresponding conveyor and metering device for this precipitant is in connection.

Through the distribution devices 22 and 23 are thus in the in the shaft 14 generated buoyant currents, which from the distribution pipes 12 and 13 are generated by the air exiting there, in addition those mentioned Precipitant entered, which with the buoyancy current under simultaneous intimate Mixing with the water in the shaft upwards and from there into reach the circulating flow described.

There is accordingly an intensive mixing of the in the shaft 14 Precipitant with the water, with only small flakes in this area the intense mechanical movement of water can form while in the surface flow 16 and the subsequent circulating flow flocs larger Form expansion, which also allow a correspondingly better sedimentation.

A mixture of the two different precipitating agents relocated Avoiding buoyancy currents in the shaft 14 with safety is in the middle of the shaft over the entire length of a partition 26 is provided in the shown example is designed as a flexible film-like wall, which extends to the foundation 1, but ends at a distance from the deflection device and, if necessary, can be attached to the deflection device or to the supporting frame 3.

There is an extensive separation of the two with different things Buoyancy currents offset by precipitation agents are also possible without a partition 26, however, the width of the shaft must be appropriately increased somewhat for this purpose to leave a kind of neutral zone between the two upwelling currents. The shaft extension however leads to a reduction in the mixing effect in the two buoyancy currents, so that the arrangement of a partition wall 26 is preferable.

In the embodiment of the device described in the in Fig. 1 left half of the pond practically an exclusive precipitation of the in the wastewater existing phosphate in the form of calcium phosphate, while in Fig. 1 right part of the basin flakes arise, which are made of calcium phosphate and iron sulfate exist.

Some of the calcium phosphate flakes will be in the left part of the Settle in the pelvis and can be discharged from there in a known manner while in the right part of the pelvis the mentioned Mixed phosphates are formed, some of which can also be withdrawn from this basin after the sedimentation process or together with the flowing water in a downstream sedimentation basin reach.

By leaving a partition-free section below the The deflection device 15 flows over the partition 2 () to the extent that it is soft the inflow of sewage in the direction of arrow 24 to that on the left in the figure Pelvic part takes place, so that a proportion corresponding to this influx into the right Part of the pelvis arrives and from there in the manner described after Circulating flow is discharged.

In a similar way, a flow under the partition 26 can also be provided be, in which the partition wall 26 is arranged directly on the [Jmlenkeinrichtung and then does not extend to the pelvic floor 7 or the foundation 1. With this arrangement there is an underflow of the partition wall 26 to the extent that in which the wastewater flows to the left in Fig. 1 part of the pond or basin. When the flow under the partition wall 26 is also shown in the left part of FIG. 1 Pond or basin in the right part of the water, which is already with the added lime is mixed and thus contains calcium phosphate flakes.

From the arrangements of FIGS. Ii and 3 it can be seen how the feed of the precipitant to those shown in these figures Ponds or basin 26 takes place. In the arrangement according to FIG. 2, they are designed as tubes Distribution devices 22, which can be seen in FIG. 1, via connecting lines 27 or 28 connected to a feed pump 30 which is connected to it, ter suction line 31 connected to a water supply, for example to a secondary clarification pond or well is. From a precipitant container 32 is a metering pump 33, which on the pressure side is connected to the connecting line 28, the precipitant in a metered amount entered in the connecting line so that this with that of the feed pump 30 pumped water mixed is fed to the distributor device 22. the The dosage described in connection with the distribution device takes place in the same way Way also for the registered by the distributor device 23 in the wastewater other precipitants.

In the arrangement of FIG. 3, in which the same parts as they are also shown in Fig., are provided with the same suffix, the precipitant is not transported with water, but with the help of compressed air. For this purpose, instead of the metering pump 30, a compressor 34 is provided which is connected to the connecting lines s. Here is how in the arrangement 2, a precipitant container 32 with a metering pump 33 is provided which is connected on the pressure side to the connecting line 28. In this version the precipitant is fed in in the dry state, with compressed air and a fine atomization of the precipitant is achieved by the dosing pump.

Depending on the type of precipitant, either it is added with mixing with water, as shown in Fig. 2, or in powder form, as it is 3 shows.

Example procedure: two-stage post-precipitation point of use: last Simultaneous pond level precipitant: 1st level calcium, preferably for small systems as Ca (OH) 2, delivered in 50 kg sacks, 2nd stage iron, preferably for small systems as Fe Cl SO4, delivered in 50 l canisters. Addition point: line aerator; calcium in the outflow to the inlet side, iron in the outflow to the outlet side equipment : Mixing and dosing tank for calcium with automatic agitator, dosing pump, dissolving water pump; Mixing dosing tank for iron, dosing pump, lines to the addition point in the protective tube Advantages: a) place of use - only low biochemical activity = no redissolution; good pre-buffering of quantity and phosphate load = no complicated control b) Two-component precipitation-pH changes for Ca (alkaline) and Fe (acidic) cancel each other out against each other; overall lower precipitant costs, since Ca is cheap; better sludge quality and better plant availability of the ingredients (Ca is required by the soil, Fe and Al not); better softening of the water, lower residual turbidity; higher Insensitivity to changes in the composition of the waste water, considerably less Salination of the water, since less 804 and less Cl; better nitrogen elimination; more effective against toxic influences, e.g.

with heavy metals; easy to use Results : the P content of the discharge is below 1 mg / l; Algae development in the fining ponds is severely restricted (fish keeping!); Process becomes clearer.

Kasseburg P - Elimination 1. Basics: Population 65o E spec. Waste water volume 150 1 / Ud daily waste water volume 97.5 m3 / d spec. P-amount 3 g / E.d daily P load 1.95 kg P / d corresponding to (theoretically) 20 mg / l measured values at least 13.7 mg / l max. 17.3 mg / l 2. Precipitant: 2.1 Ca (OH) 2 Addition amount based on experience 100 kg / d With # y = 0.4, this corresponds to 24.3 l / d dilution ratio 1: 5 daily amount of milk of lime 121.5 l / d container content looo 1 content is sufficient for 8 days 2.2 Fe Cl SO4 added amount experience has shown that loo g / m3, with # = 1.0, corresponds to 100 ml / m3 of daily amount of felling agent 9.75 l / d container content loo 1 grind is sufficient for 10 days

Claims (10)

Claims 0 method for phosphate precipitation and post-purification of wastewater in basins or ponds, esp. simultaneous ponds, after previous, esp. biological treatment of the wastewater through the introduction of air or oxygen, in which an iron salt and a calcium salt each act as a precipitant in successive separate treatment stages are mixed with the wastewater and thereby sludge formed from flakes is separated by sedimentation, thereby g e k Note that the wastewater in each of the two consecutive Treatment stages set in a circulating flow by the introduction of air or oxygen and in the first treatment stage with the calcium salt and in the second treatment stage with the iron salt, preferably during the metered introduction of these precipitants Into the buoyancy zone created by the air or the oxygen, both intensely is mixed and passed outside the mixing zone in a calm flow. 2. The method according to claim 1, characterized in that g e k e n n z e i c h -n e t that the two treatment agents are each preferably combined in liquid form with air or water as a means of transport in the respective mixing and entry zone of the wastewater in the circulating flow is transferred. 3. The method according to any one of claims 1 or 2, characterized g e -k e n It does not indicate that the sewage within a basin or pond is carried out by a Air or oxygen entry into two separate circulating flows, namely one den Inlet and one that affects the outlet of the water to or from the basin or pond Circulating flow, offset and the calcium salt in the tangent to the inlet as well the iron salt is introduced into the circulating flow tangential to the drain. 4. Device for treating waste water or the like, especially for phosphate precipitation according to the method according to any one of claims 1 to 3, in which in one with one Inflow and a drain provided pond or basin about in the middle between the inlet and outlet are preferably made up of two parallel and spaced apart tubes existing facility running across the pond or basin for the Entry of compressed air or oxygen in small bubbles is arranged for generation two parallel buoyancy zones or currents, whereby to divert the buoyancy currents in opposing surface and circulating currents, one preferably at the level of the water surface floating deflection device is provided, thereby g e k e n n z e i c h n e t that in the inlet-side circulating flow and in the outlet-side circulating flow a distribution device (22 or 23) is provided in each case, which via connecting lines (27 or 28) each with a metering device (33) for different treatment agents, especially for a calcium salt and for an iron salt. 5. Apparatus according to claim 4, characterized in that g e k e n n z e i c h -n e t that the distributor devices (22, 23) are designed as tubes with outlet openings and above the devices (12, 13) for the introduction of air or oxygen and are arranged running parallel to these. 6. Apparatus according to claim 4 or 5, characterized in that g e k e n n -z e i c h n e t that between the parallel buoyancy currents and the associated distribution devices (12,13) a preferably flexible, film-like, with the deflection device (15) connected partition (26) is provided. 7. Apparatus according to claim 6, characterized in that g e k e n n z e i c h -n e t that the partition (26) extends to the basin or pond bottom (7 or 1) and ends at a distance below the water level (6) or up to the water level and ends at a distance from the pool or pond floor. 8. Device according to one of claims 4 to 7, characterized g e -k e n n z e i h n e t that the device (12,13) for the entry of the air or des Oxygen and the distribution devices (22, 23) for the two treatment agents arranged in the lower section of a shaft dividing the pond or the basin are, which of two at a distance running parallel to just below the water level (6) as well as close to the basin or pond floor (7 or 1) and diverging there or baffles angled in opposite directions (4,5) limited and from the partition wall (26) into two parallel shafts for the separate buoyancy currents is divided. 9. Device according to one of claims 4 to 8, characterized g e -k e n n z e i c h n e t that each distribution device (22 or 23) via the connecting line (27, 28) is connected to a feed pump (30) which supplies water from a supply sucks, and that one with a calcium salt on each of the connecting lines or iron salt container (32) connected metering pump (30) connected on the pressure side is. 10. Device according to one of claims 4 to 8, characterized g e -k e n n z e i c h n e t that each distribution device (22 or 23) via the connecting lines (27,28) is connected to a compressed air compressor (34), and that to the connecting lines a metering pump (30) connected to a calcium salt or iron salt container (32) is connected on the pressure side.