DE1642399A1 - Process for wastewater treatment with removal of phosphorus - Google Patents

Description

The invention relates to a combined chemical and biological treatment method for reducing the Nutrient content of organic waste material such as sewage. A fundamental problem in analyzing electricity pollution consists in the exact "prediction of the effects of domestic and industrial water outflows when the Waters. In the past, the greatest emphasis has been on the effects of organic waste on oxygen reaerven the current laid The oxygen criterion It is often valuable in the interpretation of the biological oxygen demand, but it can be because of a weaent borrowed share of the verruh pollution potentiala of house and

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Not satisfying industrial waste. In recent times one has in addition to the biological oxygen demand of the weakening excessive biological enrichment and the resulting growth profile of algae in the receiving waters. Excessive algae growth becomes a growing concern as it increases Area number because of the aesthetic destruction of surface waters, because algae foams discolor the water and when they decompose they release putrid smells. In addition, since the algae clog the cleaning filter ^ the Time factor reduced in Miterduran run. Also can serious secondary pollution results from the oxygen demand associated with final decomposition of the organic material built up by the algae "

It has now been found that ordinary household sewage is particularly With its phosphorus content it is a rich source of nutrients used by algae to sustain their growth are needed. As a result, phosphorus removal offers a practical and effective way to control algae growth in natural waters,

So far, the removal of phosphorus from incoming wastewater has primarily taken place by means of a chemical third treatment system with predominantly uneconomically massive doses of a chemical precipitant for phosphates, such as Oa: iGlueioxya _s alum or iron salsa.

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ORIGINAL

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The invention avoids the disadvantages of the known methods through a complementary chemical and biological process, which to a considerable extent both the soluble orthophosphate

compounds as well as suspended organic phosphates from organic waste material in a first treatment stage

belittles.

Basically, the invention provides for chemical dosing of the incoming organic waste material with sufficient lime in a clarifier and / or flocculator to coagulate and precipitate the phosphorus portion that can be removed most effectively by chemical treatment and the remaining portion for intferation through biological growth . The resulting sludge with the insoluble calcium phosphate is fed back through a small re-aerator or mixer to the clarifier or flocculation tank in order to ensure full utilization of the lime and to maximize the intended phosphorus removal. After a relatively short residence time, approximately 75 to 90 # of the suspended solids are equivalent to 60 to 70 % of the

make up the biological oxygen demand, precipitated in the clarifier or loosening device, and the clarified overflow is

directed to the biological treatment station At this point the process becomes an activated sludge system, i.e. there is oxygen through the floodplain into a main ventilator blown to the carbon-hydrogen, iSulfur and nitrogen compounds from their ethical set-up to be transformed into a more strongly oxidized stage «, Di © Osjdation

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to remove the remaining biological oxygen demand takes place by means of microorganisms that. in turn from these reactions energy for the synthesis of new cellulose pro to pls, snias absorb. These biological cells in particular it is the metabolically <Ien remaining phosphorus content of the Consume the outlet »by removing it from the solution, to generate and maintain the cell growth in the. That Ratio of nutrient removal, i.e. phosphorus precipitation, is generally a puncture of cell tissue synthesis, and as long as there is sufficient phosphorus in the solution, in order to maintain the growth of cells, the metabolic Phosphorus removal unafehäji ^ i g from the phosphorus concentration progress.

The aerated product is then transferred to a second clarification basin so that the newly formed sludge settles and the clarified discharge of reduced phosphorus content can then be drained into the receiving water. About 90 $ of the clarifier sludge is returned to the main aerator in order to increase the biological activity of the sludge to a large extent, while the remaining 10 fo are returned to the chemical treatment plant through the aerator or the mixing station. Partly äea Xi-s-l'-l ^ ufgyi shemeo % wa lüwa ^ f ^ r vflrehindsrt ·

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Experimental results from an operation of the process have shown that between 80 and 90 io of the urapane phorophore contents have been removed from the final effluent. Despite this greatly reduced phosphorus concentration, further analytical investigations have shown that the nitrogen is present in the effluent in the form of ammonium ions and acts as a catalyst in order to maintain continuous algae growth, albeit to a lesser extent.

The ultimate solution to the problem thus depends on the total removal of all sources of support for the algae. To this The purpose of the invention is also to increase the pH of the solution to a level sufficient to remove ammonium ions to split off their chemical compounds and then to strip out the dissociated ammonium ions as ammonia gas with air. The cost of the extra lime to raise the pH in the chemical treatment station to a value where the AramoniUE-ions dissociate from their chemical compounds, are more than offset, as practically, all of the phosphorus and nitrogen has been removed from the effluent effluent.

Another feature of the invention is regeneration the relatively expensive chemical precipitation agent from the Waste products. The process products are the final outlet, which is discharged into the receiving waters, and a mixture of organic sludge and lime waste sludge, which mainly ie according to the composition of the incoming Raw sewage is present in the form of calcium carbonate.

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The invention therefore increases the economy of the urea removal process in that the lime required for the process from the Sewage sludge extracted as a by-product. In particular the invention proposes to burn the organic sewage sludge and to continuously increase its lime content calcine and the resulting lime τοη dar inert ash to separate.

It should be noted that the sewage sludge is disposed of must and therefore the added benefit of obtaining that most expensive raw material from the process and elimination of an undesirable by-product in the same plant, the capital outlay greatly reduce for the system. In the process of the application, the increased pH also softens the Lye in the chemical treatment station the water that precipitates even more potassium carbonate, so that it is only extract more lime from the overall system than was originally introduced.

Accordingly, the invention thus primarily provides a method to reduce the phosphorus content of organic waste material to a predetermined value by removing the organic waste material mixed with a predetermined amount of a chemical precipitant for phosphorus, the treated waste material subject to an initial deposition by at least

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to let some of the phosphorus settle, the Outflow from the first deposition in a first ventilation zone "aerated to prevent phosphorus-consuming cell growth and the ventilated drain of a second deposition undergoes to remove the phosphorus-containing biological sludge and a final drain of predetermined To gain phosphorus content.

According to a further feature of the invention, the nutritional content of organic waste material is reduced to a predetermined value by removing the raw waste material mixed with a phosphorous coating agent that raises the pH value sufficiently to remove ammonium ions from their chemical compounds split off, this waste material is subjected to a first deposition to remove at least part of the phosphorus content to separate, the discharge from the first sedimentation is transferred to a second zone and the dissociated by increasing the pH Ammonium ions discharged as ammonia gas, the outlet from the first zone in a third zone for generation Phosphorus-consuming cell growth ventilates and the ventilated process of deposition of phosphorus-containing biological Undergoes common lamb and produces an end drain of the predetermined nutrient content.

In a third relationship, the invention provides a method for Removal of lime from sisaei 'mixture of organic waste material and KalkschlaiaiR before., at dam the mixture in

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a heat reactor with the formation of calcium oxide and Ash is thermally oxidized, the calcium oxide and at least part of the ash in the reaction gases pulled out and discharged from the reaction vessel, the solid particles are separated from the reaction gases, the solid particles are quenched with water and the ash is separated from the quenched calcium oxide.

For a clearer "understanding of the invention and its results." useful embodiments are described below,

Pig. 1 is a schematic representation of a flow sheet according to the invention with nutrient removal and lime extraction,

Pig, Fig. 2 schematically shows a modification of the method of the invention.

According to fig. 1, untreated organic waste or wastewater is introduced into a clarification-Plockungsajstem 10, which is shown schematically. Here the material is treated with a chemical precipitation agent for phosphorus, d, h <; in the present example mixed with lime.

According to the invention, sufficient chemical precipitating agent for phosphorus is added to eliminate those parts of the phosphorus which must be effectively removed by chemical treatment.

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ORIGINAL

precipitate and coagulate, with the remaining part remaining to be removed by biological action. The preferred Embodiment where complete nutrient removal is to be carried out, the pH of the liquid is raised to the range of 10 to 11, i.e. high enough to split ammonium ions from their chemical compounds.

The increased pH range, the optimum of which is 10.3 to 10.5, has a twofold effectί

1. It increases the amount of precipitated solids with removal a large amount of phosphorus from the solution.

2. The water is softened and depending on the hardness of the water and the exact operating pH, there will be some Calcium salts from the water with precipitated.

Lime has the additional advantage of being a flocculant and therefore sludge formation by not containing phosphorus Solids in the organic waste material · increases, thus making it considerably more biological Oxygen demand is eliminated from the system.

The resulting sludge, i.e. the solid product from the clarification-flocculation station 10 is either duroh line 12 in a

or small aeration or mixing basin 14 / through line 16 to

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an indicker 18 and the regeneration relay 20, as will be described in more detail. Empirical studies by the applicant have shown that a circuit of the retained sludge through a small aeration or mixing basin increases the operational efficiency of the chemical treatment stage by about 40 tfo maximum lime utilization returned. The clarified overflow from station 10 then goes through line 23 to a nitrogen stripping tower 24 for removal of the ammonia gas _β

The stripping tower 24 is assumed to be air-powered, although some conventional nitrogen stripping device is also used can be used. Air from a source not shown is introduced at the bottom of the tower to pass through the descending one Ascend overflow and convert the ammonia ions into ammonia gas. The gases escape at the head of the Turmea, and the stripped liquid is by conduction 25 transferred to the main aeration tank 26 for biological treatment and removal of the remaining phosphorus.

As a result of the chemical removal of $ 70 to $ 90 of the suspended solids with $ 60 to $ 70 of the biological oxygen requirement in the clarification * flocculation station, this aeration basin can be made about $ 50 smaller than it would otherwise be necessary for the production of the air required

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The effort required can be reduced accordingly, resulting in considerable savings in terms of investment and operating costs means. At this point the system becomes an active sludge process, i.e. carbon, hydrogen, sulfur and nitrogen compounds in overflow are caused by microorganisms oxidized from its reduced level to a fully oxidized level, the microorganisms or Cells absorb energy from the oxidation reactions for the systhesis of new cell protoplasm. This growth existing Cells and the generation of new cells, in turn, metabolically consume the remaining phosphorus content of the solution, whereby the Extent of Mhratoff removal, i.e. phosphorus precipitation in the is generally a function of cell tissue synthesis. As above mentioned, the algae continue their development regardless of the phosphorus concentration, provided, of course, that there is enough phosphorus in the solution to maintain cell growth.

After the phosphorus concentration is reduced to the predetermined value and the biological oxygen demand is eliminated has been, the aeration product is transferred through line 28 to the clarifier 30. A major part of the sludge from it About $ 90 settling basin is connected through line 32 to the aeration basin 26 sent back to the aeration tank with biological loaded with active sludge. The remaining $ 10 of the mud are transferred through line 34 to the chemical treatment stage, to remove biological oxygen demand

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to increase further. It has been found in accordance with the invention that a clarifier with rapid sludge removal is most beneficial for this stage of the system it is v / eil it maintains the greatest biological activity of the sludge and thus the amount of necessary Lime lowers.

It is known in the art that this can result in a wastewater treatment plant flowing volume fluctuates strongly during the daily span of 24 levels. In similar yfeise fluctuate within During this period of time also the PhosphorgeMt and the alkalinity of the

Inflow. Take effect at certain times on any operating day So the Iluss and / or the phosphorus concentration in it, the Attempt to precipitate the phosphorus from the solution. This has been taken into account by the invention by a Control system was developed to further increase the economic efficiency of the process.

A phosphate analyzer 29 is located downstream in the feed line switched on to record the flow of incoming waste material. As long as the phosphorus concentration in the raw material measured in mg / l is above the predetermined value, works the system as it is designed, with removal of all phosphorus from the liquid, a pH meter 31 within the line 23 between the clarification flocculation basin 10 and the Nitrogen stripping tower 24 records and controls the pH of the overflow by controlling the quay supply to the system.

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If the pH falls below the desired range, press the measuring device a valve 33, and the clarifying flocculation station 10 additional lime is added. On the other hand, if the pH should rise, for example because of the phosphorus concentration

decreases or the alkalinity of the feed increases, then the pH-I.Iesser throttle the lime supply by reducing the opening in valve 33 accordingly. However, the phosphorus concentration should fall below the predetermined value then the phosphate analyzer will overflow the pH meter and the lime introduction shut down completely in the system. So although the working parameters of the process have been established, iat the process is flexible enough to adjust to constantly fluctuating conditions and phosphate concentrations, which can appear during a working group,

As indicated above, a portion of the sludge from the clarifying flocculation station 10 is continuously removed from the phosphate extraction aayatem to the regenerator 20. The sludge, which prevents the build-up of solids in the phosphate extraction system,

is received in thickener 18 and either in a turkey or a centrifuge 35 thickened before going through line

'Introduced into the heat reactor 38, e.g., a vortex layer The overflow from the thickener 18 can either

thrown or returned to the process through line 39 will. Bar sludge in line 38 consists of a mixture of organic waste and veal porridge, the 3 · after the Composition of the inflowing Rohabwaasera mainly is in the form of calcium phosphate and potassium carbonate,

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ORIGINAL

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Oxygen is preferably fed to the Yfärmereaktor in the form of air in countercurrent to the Sch.lammisoh.ung in order to Burn organic waste material to ash and the calcium carbonate component to calcium oxide and carbon dioxide to calcine. The heat required for these reactions comes directly from the oxidation of the organic Waste material delivered.

In the first embodiment of the invention for lime recovery shown in FIG. 1, the lime, together with part of the ash, is discharged from the reaction vessel through the exhaust gases and transferred into a gas cyclone 40. The gases are then freed from the solid particles, which flow off to a slag basin 42. A scrubber 44 can be used to complete the solids gas separation process a. Two modifications are possible at this point. Either the calcium oxide can be slurried into a milk of lime or the calcium oxide can be diluted with additional water to form a calcium hydroxide solution. The Asoh.eteiloh.en can easily be separated from a calcium hydroxide solution either by clarification, settling or cyclone treatment. This process is indicated by the separation station 46. On the other hand, when using a milk of lime pulp, the particle sizes overlap ?! between the ashes and the potassium oxide calcium hydrocarbons, s: a £ a certain beard must be added and n% w * ä9T stwaa As one 1a the phosphorus extraction system must be returned "as is shown here,

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or some lime must be discarded and replaced by additional lime in the system, for example via line 48, in order to make up the difference. Depending on the method chosen, the ash is discharged as waste through line 50 and the lime is transferred through line 52 to line 40 and thus sent back to the phosphorus extraction system. This lime ^is intimately mixed with the inflowing sludge in the aerator or mixer 14 and then fed together with the incoming raw material to the clarifying flocculation station 10 for the purpose of chemical removal of the phosphorus.

In the second embodiment of the lime recovery system According to FIG. 2, the extracted portions are of the invention of rust and ash from the heat reactor 38 directly a Yenturi-type glass washer 54. By

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Line 56 introduced water / ripen the solid in countercurrent Particles from the gases and forms a calcium oxide sludge. At this point, the milk milk slurry obtained can either be diluted to a calcium hydroxide solution, or the ash particles can be separated from the sludge in the suspended state will. In any case, the sludge from the hass washer is passed through line 58 to a dilution and separation station, e.g. a dilution tank and a cyclone or a separation station, e.g. a cyclone, both of which are designated by 60 to remove the ash. Then the resulting lime slurry is passed through lines 52 and 40 as in the Pail above transferred to the phosphate extraction system.

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It should be noted that in certain galleries the implementation of the invention until shortly before a complete urine removal may be preferred. In this case it has been shown that the pH of the sewage is only on one area needs to be raised between 8 and 9. As stated above, when setting the procedure on this pH range 80 to 90 $ of the original phosphorus content removed from the final process.

It should also be noted that the process does not require regeneration the chemical liquid agent can be carried out. In

Smaller systems, where the investment costs for the recovery system are not justified, will be the Sludge consisting of a mixture of organic waste material and lime sludge, primarily calcium phosphate, as Waste discharged and discarded.

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Claims (11)

Claims 1. Process for reducing the phosphorus content of organic waste material by adding chemical precipitants, characterized in that a predetermined Amount of a chemical precipitant for phosphorus added to the waste material in such an amount that the phosphorus component is most effective by chemical treatment is removed, is precipitated, and one then consumes the remaining liquid in the presence of phosphorus aerated biological means and an indflow of a predetermined phosphorus content is generated. 2. The method according to claim 1, characterized in that the organic waste material with the chemical 3? Precipitating agent until the pH value is increased to a range between 8 and 9. 3. The method according to Anapruch 1 or 2, characterized in that part of the chemically precipitated soil is routed to the incoming organic waste material » 4 G dead man! ·! according to an aspiiiohe's measure 5? feta ^ ek. gekeEn » 2SQiCvBOt, claß a Tsii äan pliospl ^ Räöltigoa teeiogisahss chemical precipitation remains, while another part of the phosphorus-containing biological sludge initially ventilated and then returned to the incoming organic waste material. 5. The method according to claim. 1, characterized in that the organic waste material with the chemical phosphorus precipitant Up to a sufficiently high pH it is added to ammonium ions from their chemical Dissociate connections. 6. The method according to claim 5j, characterized in that the pH is raised to a range between 10 and 11 and the dissociated ammonium ions as Ammonia gas are discharged 7. The method according to claim 5 or 6, characterized in that practically all of the nutrients for algae growth removed from the waste material. 8. The method according to claim 1 or 5> characterized in that that the incoming organic waste HEfcerial analyzed to determine its phosphorus concentration and the supply of chemical oils for Phosphorus to the organic waste material is so upright lengthways about 5 _{s as the} phosphorus concentration is above a value * 109819/1413 BAD o _{Rra) NAL} 9. The method according to any one of claims 1 to 8, characterized in that that as a chemical! precipitating agent, lime we use 10. The method according to any one of claims 1, 5 or 9 »thereby characterized that part of the phpsphorhaltigen Heat treated sludge to regenerate the chemical precipitant for phosphorus. 11. Yerfahren according to claim 9 and 10, characterized in that the sludge is organic waste material and lime sludge contains. 12e method according to claim 10 and 11, characterized in that that the resulting in the thermal treatment solid substances are slurried with water and the mixture obtained is returned to the chemical pelling stage will.' 109819 / U18 Blank page