FI119148B - Apparatus and its use for precipitation of phosphorus from wastewater - Google Patents

Description

119148

FIELD OF THE INVENTION The present invention relates to an apparatus for precipitating phosphorus from waste water, which can be connected to a small purification plant.

The invention also relates to the use of the above-mentioned apparatus for precipitating phosphorus from waste water in small-scale treatment plants, preferably in continuous small-scale treatment plants.

Background of the Invention

In the last 15 years, more attention has been paid to the environmental impact of sparsely populated wastewater. Indeed, the Government Decree (542/2003) lays down minimum requirements for waste water treatment. For most properties, the existing treatment system does not meet the stricter cleaning requirements. There are a number of different site-specific wastewater treatment systems on the market, ranging from • 20 simple soil treatments to biochemical purification * * * '* * * hm.

• The Government of the Council Regulation (542/2003) on the treatment of household water in non-sewer networks sets limit values for waste water. chicken for the amounts of organic matter, total nitrogen, and total phosphorus discharged into the environment. For most treatment methods, it has been found in practical • • inta studies that it is most challenging to achieve the required purification efficiency for total phosphorus. • Reduction of the phosphorus load of diffuse population is important because of the release of phosphorus into Finnish waters. About 8% of the 30 loads come from diffuse and holiday settlements, especially in inland waters, which is the so-called minimum nutrient that regulates • • ·· · • 119148 2 production of phosphorus. abundant algae and cyanobacterium inflorescences, which may have serious repercussions on the toxins secreted by the algae, and depletion of biomass consumes oxygen, which can lead to the loss of oxygen to fish.

In site-specific wastewater treatment systems, phosphorus removal can be enhanced by adsorption masses and various precipitation chemicals. Biological-chemical equipment purifiers generally use an aluminum or iron-based coagulant. The precipitating chemical binds the phosphorus contained in the waste water to compounds which can be separated from the water by settling. The use of the correct amount of chemicals is crucial for the efficiency of the precipitation. At too low a dose, the chemical will not react with all the phosphate ions and thus some of the 15 phosphorus in the waste water will end up in the water. Excessive overdose may lower the pH of the wastewater, as aluminum and iron based precipitation chemicals are highly acidic. Too low a pH reduces the efficiency of the precipitation. Effective mixing of the precipitating chemical and the effluent is a prerequisite for successful precipitation. Mixing allows the total dose of • · | 20 and no unnecessary overdose is required. coagulants

The effect of Mt1 · on the waste water is to form microblocks which can join together to form ever larger flocs. Increase the size of the blocks to make it easier to separate them from the water by settling. This is attempted: ·· .1 ··, in an arrangement where the mixing is followed by a stirring step. During the mixing phase, the water velocity gradient, or G, is smaller than in the mixing phase. The most common implementation is to keep the wastewater in a slow rotation, which * · · “1. In large plants, actively rotating blades are actively achieved.

···. 1. Flocks in water should not be subjected to excessive forces so that they do not · · · 1 • · 1.

•! 30 2 t 3 4 5 • · 119148 3

Biological-chemical equipment treatment plants can be divided into batch and continuous treatment plants on a operational basis. In a batch treatment plant, the treatment process steps are carried out in the same pool. The process always treats the same amount of waste water, so that the same amount of phosphorus chemical can be dispensed into each batch. This is easy for pumping arrangements, as the dosing pump runs at the same time in the desired process step. In batch refiners, the precipitating chemical is usually dosed during the aeration phase, whereby the turbulence caused by the aeration effectively mixes the chemical with the entire aqueous mass.

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In continuous treatment plants, the amount of water displaced by the water entering the system is gravitationally transferred from one basin to another. In such a system, the technical implementation of dosing of the precipitating chemical is more challenging because the amount of water transferred from one reservoir to another may vary from time to time.

15 There are products on the market where dosing is organized using a timer. The dosing pump, controlled by a timer clock, pumps a certain amount of chemical at desired intervals, for example once an hour. In such an arrangement, the amount of chemical input is not dependent on the amount of water entering the system, but the chemical is consumed unnecessarily, for example, during holidays. Consumption of the coagulant chemical »»: 20 causes additional costs for the property owner. Käsitettä-

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A low dose of water may lead to overdose or overdose. situations. When the amount of water entering the system is higher than expected, • · • · 1: The amount of chemical to be fed is sufficient to treat the entire amount of water. Overdosing • · lmt [m] may, in addition to the extra cost, cause the problems of excessive pH drop · '1 · ** 25. It is also challenging to have a sufficiently effective mix. . organization of business. In commercially available systems, the chemical is • • · dispensed into a tube where the water to be treated flows. In such an arrangement, the mixing conditions of the water and the chemical are in no way affected.

* ·! The conditions are also not optimal for flock collision and • 1 * ·; · 1 30 joining.

«·· ···· m 4,119,148

Finnish Registered Utility Model No. 7006 discloses a waste water treatment plant for phosphorus removal, which includes a phosphorus treatment unit with a process tank, a phosphorus dopant chemical tank, a dosing tank for chemical dispensing, a mixed water and chemical collection tube that leads the mixing from the center of the plate to the process tank below. In the process tank, the water to be purified from the phosphorus is collected as an example, apparently after soil treatment, first in a pump well, from where it is pumped into the process tank for phosphorus removal treatment, after which the treated water is drained from the process tank.

In the Fl utility model 7006, a predetermined amount of chemical is metered into a trough from a chemical tank prior to pumping a certain amount of 15 water batches from a pump well. The water is led through the gutter, whereby the water is sucked in by the ejector suction and empties the chemical out of the gutter. After the trough, a mixing plate is provided, which is provided with flow-reversing partitions to ensure mixing.

It is an object of our present invention to provide an apparatus and method which, on the other hand, permits the correct and necessary use of a quantity of precipitating chemicals, thereby claiming inert precipitation of unreacted phosphorus. • · • ·· * ... reducing the effect of too low a pH on precipitation efficiency; and • a • a “* 25 on the other hand also a sufficiently effective mixing of water and chemical.

• a • a a a a a a. * ··. To achieve this, the apparatus according to the invention is characterized by a. *. that the apparatus includes a pumping vessel, a drainage pump for emptying the pumping vessel, a chemical reservoir, a chemical dosing pump for the chemical aa '** 30 for dispensing the chemical tank into the effluent to be discharged from the pumping vessel, tank, the dosing pump is arranged to introduce a coagulant chemical into the effluent stream to discharge the effluent pump during or almost the entire operating cycle of the drain pump.

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In a preferred embodiment of the apparatus according to the invention, it further comprises a stirring chamber, the shape of which forces the flow of the coagulant containing wastewater through it to rotate slowly in order to enhance the formation of flocculations caused by the coagulant.

The slow-rotating movement of the water-chemical mixture is thus intended to enhance the formation of the flocculation caused by the precipitating chemical before the mixture is introduced into a precipitation tank, i.e. a settling tank where the formed phosphorus binding precipitate is to separate from water and settle. The shape of the embarrassment can be any shape, either making the water containing the sa-15 purchase chemical into a slow rotating motion, which can be either uniformly slow throughout the embarrassing phase or progressively slower towards the end. Thus, the shape of the agitation chamber may be any shape which forces the wastewater containing the coagulant chemical to pass therethrough into a slow rotating movement such as, for example, a substantially circular shape. Example ·: 20 rocks of substantially circular shape are, for example, substantially cylindrical or cylindrical, substantially spherical or hemispherical, · · ·; · :: substantially conical or truncated cone shape. Other Substantially • · • ♦ ·: The circular shapes have a three-dimensional, essentially spiral shape. Whatever the shape, * * ** ... **, the main thing is that the wastewater containing the coagulant chemical is led into a slow rotating movement so that at least one wall surface of the agitation space, along which the miscible water-chemical mixture flows slowly • φ ·. ···. Wheels, have a substantially circular or curved shape.

In a particularly preferred embodiment, the stirring chamber is substantially a cylindrical stirring vessel. In this case, it is also advantageous that the ... T waste water flow from the pumping vessel and the amount of precipitation fluid supplied to it • · 119148 6 are arranged to be fed to or near the upper end of the stirring vessel; the bottom outlet.

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In another preferred embodiment, the baffle space or vessel has an outlet which is at or above the bottom of the baffle vessel. Advantageously, the outlet of the confusion space or vessel may be provided with an outlet having an extension below the outlet. Preferably, the outlet connection for the baffle space or vessel extends below the water level in the settling tank.

In another preferred embodiment, the outlet has a structure that allows air to enter the outlet and prevents the formation of a uniform water column and suction at the outlet.

Advantageously, the apparatus according to the invention may be located after biological treatment of waste water. Biological pretreatment may be a biological process based on activated sludge process, soil remediation or biological filtration.

• · • ♦: The system pump system is preferably configured to operate with a · · float switch that switches the drain pump on and off • · • · ** with a predetermined maximum of the wastewater level in the pumping vessel. 25, and a power control relay connected between the drain pump and the dosing pump, which again switches on the dosing pump when the drain pump * * t *:!: * Needs to be turned on and off when the drain pump does not power. In principle, the pumps and pump system may be any pump or pump system known to one of ordinary skill in the art.

• · · 30 «··· ···· • · 119148 7

In a preferred embodiment, the entire apparatus can be installed in one and the same small purifier settling tank, or i.e., a settling tank.

In connection with the use of the apparatus according to the invention, a method can be applied for precipitating phosphorus of wastewater from a wastewater in a small treatment plant, wherein the wastewater to be treated or, i.e., in a settling tank such that at least one precipitating chemical is metered by a metering pump to discharge the wastewater stream throughout or nearly the entire run of the drain pump.

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In this method, the effluent containing the coagulant chemical can be subjected to a stirring step to enhance the formation of flocculations by the coagulant chemical.

• · • · · | The precipitating chemical may be any precipitating chemical known to a person skilled in the art for the removal of phosphorus in waste * / water, e.g.

• · * · l y aluminum or iron based coagulant. The coagulant chemical is dosed as · · · II *: preferably as an aqueous solution.

The apparatus according to the invention is suitable for use in any small purifier, in particular in continuous operation having at least one precipitate. or several interconnected precipitation tanks.

• · ··· • · * # · y. ' The device to be protected achieves the following advantages over modern technology: • «* ·“ 30 «a« ·· • · 119148 8

In a continuous wastewater treatment process, phosphorus precipitation can be accomplished by dispensing the precipitating chemical only when water enters the system.

The control of the chemical pump run based on the drain pump run 5 allows the chemical dose to be kept constant with respect to the amount of water to be treated.

Dosing the chemical into the water flow from the pumping vessel evenly throughout the pumping cycle ensures a steady chemical concentration and good mixing of the chemical and water in the water leading into the mixing vessel.

The precipitation conditions remain the same regardless of the amount of water. The mixing step in the apparatus-related mixing vessel promotes the growth of flocculations formed by the precipitating chemical and thus improves the settling properties of the resulting slurry. The good sedimentation properties of the slurry facilitate its separation from the treated water and thus reduce the amount of phosphorus-containing precipitate escaping into the environment with the water leaving the system.

Conducting water leaving the mixing vessel below the surface of the settling tank prevents the sludge formed by precipitation from being transported by the water leaving the tank.

In the following, the apparatus will be described in more detail by way of example with reference to the accompanying figure 1, which illustrates an embodiment of the apparatus in a longitudinal cross section. However, the example below should not be construed as limiting the following claims.

• · ♦ · * • ♦ • • · · · · · · •? • · · ··· · # ·· • · · · ··· ·· * • * 119148 9

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Figure 1 shows an apparatus for treating waste water, which may be located, for example, in a precipitation tank or, i.e., a settling tank 12, located downstream of a continuous biological treatment unit for treating wastewater in one property, also called a septic tank.

The water enters gravity into the settling tank 12 through a conduit 13 leading thereto, with the incoming water being first directed and collected in the settling vessel 12 into a pumping vessel 1 located at its upper end when the water level reaches a sufficiently high maximum level in the pumping vessel 1. pun 2 automatically. The float switch 3 also stops pumping when the water level in the pumping vessel 1 has dropped to a desired level, i.e. a predetermined minimum level. The volume of the pumping vessel 1 is preferably> 20 I. The volume influences the rpm of the drainage pump.

The operating time of the drain pump 2 depends entirely on the amount of water entering the pumping vessel 1. If there is constant flow of water so that the water in the pumping vessel is not • «· ·; 20 1 cannot reach the desired minimum level, so that the drain pump / pu 2 is also continuously running. The drain pump 2 pumps water to the mixing vessel 4, also located inside the settling tank 12. Alternatively, both the pumping vessel * and the mixing vessel 4 may be located outside the settling tank 12, but preferably, and in accordance with this example, they form an assembly within the settling tank 12. at the upper end.

• · · • • • · · · · * ···

When the drain pump 2 is running, the dosing pump 5 pumps out a chemical tank inside the drain tank 12 from a chemical vessel inside or outside the hopper 12 into a mixing vessel 4. The drain pump 2 * · also stops the dosing pump . The drain pump 2 and the lifting pump 5 • 119148 are connected to each other by means of a power relay (not shown). Through the relay, the drain pump 2 is continuously energized. The float switch of the drain pump 2 controls the operation of the pump 2 by starting and stopping the pump 2 according to the water level of the pumping vessel 1. The current-5 monitoring relay operates so that whenever the drain pump 2 runs, it also supplies power to the dosing pump 5. Thus, the relay acts as a "sniff" when the drain pump draws power.

The precipitating chemical (aqueous solution) is conducted through a hose 14 near the point where the pipe 7 from the drain pump 2 ends. The tube 7 terminates horizontally at the upper end of the mixing vessel 4 having a substantially cylindrical shape such that water is introduced into contact with the shell wall of the mixing vessel 4 substantially parallel thereto. Due to the substantially cylindrical shape of the mixing vessel 4, the water entering the vessel 15 is thus subjected to a rotary movement, whereby the water preferably preferably rotates along or near the cylindrical vertical wall towards the bottom of the vessel from which it flows or rises. Thanks to this rotation, the water to be treated and the coagulant chemical are effectively mixed. When the drain pump 2 stops, the supply of water · ·: 20 to the mixing vessel 4 stops, and the speed of rotation of the water in the mixing vessel 4 slows down. This promotes the merging of flocks into larger floats • * ·· * ·. The water leaves the mixing vessel 4 in the middle of the bottom of the vessel

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• * ·: from outlet 8, which is at or above the level of its surroundings, i.e. at the same level or above the bottom surrounding the opening. This prevents • · ** “'25 outlets 8 from being completely submerged. The air space remaining in the outlet 8 prevents suction during water removal. In this case, the water retention in the mixing vessel 4 is considerably longer than in the case where the outlet 8 is completely below the surface of the water. A longer residence time promotes the effect of the coagulant

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* ·: ** In 30 mixing vessels 4, a plurality of flocs formed in water, which facilitates the flocculation of the flocs in the settling tank 12. The minimum volume of the settling tank • · 119148 11 is preferably about 151. Finally, the bottom is flat or at least some area around the opening. This prevents water from being packed into the outlet.

5 From the outlet 8 of the mixing vessel 4, water is discharged through the chamber 9 or an extension to the discharge pipe 10. The discharge pipe 10 leads to the water conduit 11. The end of the discharge pipe 10 is substantially above the water level of the settling vessel 12. The air space between the end of the discharge pipe 10 and the water surface of the settling tank 12 prevents the formation of a suction effect which quickly drains the mixing vessel 4. The discharge pipe 10 and the conduit 11 are positioned relative to each other such that any water coming from the discharge conduit 10 enters the conduit 11.

Thus, the upper end of the conduit 11 is also above the water level. The assembly of the discharge conduit 10 and the conduit conduit 11 is called the discharge conduit 15.

Through the conduit 11, the water treated with the precipitating chemical is discharged substantially below the water surface of the settling tank 12, i.e. substantially below the mouth of the drainage pipe 15 leading out of the drained water 12. This is important in a gravity-driven system because the amount of water discharged from the tank is equal to the amount of water entering. It is essential for a good cleaning ♦ ·! 'Y result that the phosphorus-containing precipitate is not • • * ·: drained by the water leaving the tank. When the water entering the tank is · · * ·· '... substantially below the water surface, adventitious surface water is already discharged from the top of the tank 12. A heavier precipitate than water settles on the bottom of the tank. The said prolongation of the water retention time in the stirring vessel 4 also reduces the • · ·. ···. 12 inputs to the tank. Of course, the tank ·· «* will naturally decrease as well. The discharge flow decreases the velocity of the outgoing water. Low speed • · · * · · further reduces the risk of precipitation.

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Claims (12)

1. Apparatus connected to small-scale treatment plant for precipitating phosphorus from waste water, characterized in that the apparatus comprises a pump vessel 5 (1), a discharge pump (2) for emptying the pump vessel, a chemical container (6), a chemical dosing pump (5) for dosing. of chemical from the chemical container (6) to the waste water removed from the pump vessel (1), wherein the separation of formed chemical precipitate from the water leaving the sewage plant is arranged to be effected in the sedimentation pump (12) of the small-scale treatment plant (12). 5) is arranged to supply a precipitating chemical to the waste water stream removed by the discharge pump (2) during the entire or almost the entire operating time of the discharge pump (2). 2. Apparatus according to claim 1, characterized in that the apparatus 15 further comprises a mixing space (4), the shape of which forces the precipitating chemical-containing wastewater to be passed through it into a slowly rotating movement, to effect the formation of the precipitating chemicals. welcoming flocks. • ·; 20 3. Apparatus according to claim 2, characterized in that the mixing space is a substantially cylindrical mixing vessel (4). 4. Apparatus according to claim 2 or 3, characterized in that the waste water flow coming from the pump vessel (1) and the amount of precipitate:: ** · 25 chemicals to be fed into said stream are arranged to be fed into the upper end of or in the vicinity of the mixing chamber or vessel (4). Apparatus according to any one of claims 2-4, characterized in that • 9 / "/ mixing space or vessel (4) has an outlet opening (8), which is at the same level or higher than the bottom of the mixing compartment or vessel (4) · ••• S • · 119148 Apparatus according to any one of claims 2-5, characterized in that an outlet pipe (10 and 11) which is connected to the outlet opening (8) of the mixing space or vessel (4) is connected to the outlet opening (8). . 5 7. Apparatus according to claim 6, characterized in that the outlet pipes (10 and 11) of the mixing space or vessel (4) extend below the water surface of the settling tank (12). 8. Apparatus according to claim 6 or 7, characterized in that the outlet pipe (10 and 11) has a structure which allows the passage of air into the outlet pipe and prevents the formation of a uniform water column and suction in the outlet pipe (10 and 11). Apparatus according to any one of claims 1-8, characterized in that it is placed after biological treatment of the waste water. Apparatus according to any one of claims 1-9, characterized in that it has a level switch (3) which switches on and off the discharge pump (2), a · · · · ·: 20 and a current monitoring relay connected between the discharge pump (2) and the dosage pump (5), which relays on its side switches on the metering pump (5) where J ♦ * · “The discharge pump receives Power and the discharge pump does not receive Power. • · · ♦ · · * · ♦ · «· * · * ♦ · 11. Apparatus according to any of the above claims, characterized in that the apparatus is fully installable in one and the same small scale .v. wastewater sedimentation tank (12). • · · • · ···. ·. Use of the apparatus according to any of the above claims for the precipitation of phosphorus from wastewater in small-scale wastewater treatment plants, preferably in * · 30 continuous small-scale wastewater treatment plants. • M · * ·· ···· • «