JPH04110004A - Plant for separating and filtering precipitated suspended and settled coagulation produced thereafter - Google Patents

Abstract

PURPOSE: To make the operation of a water-treating plant easier by carrying out a back-wash of a filter installed on the top of a sedimenting tank by opening an opening connecting with a back-wash tank by a float, and by positioning a sludge valve at a height at which the total volume of filtered substances remains in a sedimenting section. CONSTITUTION: Water to be treated is transported by a pump (6) through a flow-in pipe (5), where a measured amount of additives necessary for treating the water are added, to enter a sedimenting tank (4) along its tangential line. Agglomerated substances are held at a filter (1) positioned on the top of the sedimenting tank (4). The water passed through the filter (1) pushes up a float (15) to close an opening (16), flows into a back-wash tank (14) through a by-pass (17) and then is controlled and discharged by a flow-out valve (20). Back-wash starts in cases, a treating volume is too small, etc. By opening sludge valve (11), the float (15) opens the opening (16), generating a flow rate to the water in the back-washing tank (14) enough to agitate and clean the filter (1). The sludge valve (11) is installed at a height with which a volume of a sedimenting section (4) corresponding to the total volume of the substances on the filter (1) is left.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a plant for precipitating suspended solids from water.

[Problem to be Solved by the Invention] Industrial wastewater, waste leachate from landfills, biologically treated wastewater, and water that flows without being absorbed into the ground contain contaminants that must be separated from the water. These contaminants either bind to the cloudy components or are dissolved in the water. In the former case, the contaminants are destabilized by introducing suitable additives such as ferric (I[[) salts or aluminum salts. In the latter case, destabilization must be preceded by precipitation, for example with carbonates or sulfides, or adsorption with activated carbon. The destabilization results in the formation of particles, which aggregate to form a coagulum, in a suitable reaction tube such as a stirred tank or Norinder stirrer.
Or it can grow into a mass and separate in a conduit with turbulent flow. These can be separated by sedimentation, flotation, or filtration.

With respect to sedimentation and flotation, fine lumps remain in the water and must be removed by a subsequent filtration step. If filtration is used to remove aggregates, backwashing may optionally be used.
The filter can become clogged prematurely before a sufficient amount of filtrate is obtained for g). Therefore, the purpose is
The filtration was to be combined with one of two other steps so that the filtration was the final processing step.

Although the advantages of combining two processing stages are clear and have been discussed in detail in publications, many plants found in practice consist simply of a sedimentation stage or a flotation stage. i.e. the filtration step is missing. The reason for this is that the filtration stage is considered too complex, too expensive, and too prone to failure.

[Prior Art] In water treatment terminology, the term "filtration" refers to deep filtration in a filtration tank using particulate material.
filtration) is filled with gravel, pumice or anthracite, the direction of flow being from top to bottom. During backwashing, water is directed through the filter in a reverse direction from the bottom to the top so that the particulate matter is fluidized and heavily agitated. Dust that has settled on the granular material is washed off particularly well in this way.

In other construction arrangements, filtration is from bottom to top, which is the same direction as backwashing. In this case, the heavy dust particles together with the untreated water reach the bottom of the filter layer and initially remain there, so they have to be washed through the filter layer. Other arrangements use particulate foam materials that are lighter than water. In this embodiment, upward filtration is advantageously combined with a downward backwash step. To prevent foam material from leaving the plant, the top and bottom of the filter area are closed by a sieve.

Backwashing is a multi-step process, especially in the case of upward backwashing, such as with sand filters. The water stored in the upper part of the filter must first be drained out, the filter bed must be dismantled by introducing air, and in order to be able to obtain the required high backwash rate, a special A pump is used,
Must be switched on. The backwash water must be drained and the filter must be refilled before restarting the filtration process. After all, a large number of measurements have to be taken and a large number of control processes have to be adopted and attached. When backwashing a filter filled with granular foam material downwards, disassembling the filter with air is unnecessary, which reduces the cost of the backwashing process by half.

Nevertheless, the biggest feature is the powerful pump required for the backwashing process.

A plant for sedimentation separation and filtration of water using a flotation plant with plate separators is described below. This is described in German Patent No. 3540508. The flow direction of the water to be treated is from the bottom to the top. Some of the filter material in the flotation plant is withdrawn discontinuously from the lower filtration zone,
The outside is cleaned with a cleaning liquid in the backwash tank, after which the filter material is reintroduced to the top of the filter material bed.

The disadvantages of this plant are that the backwashing process is carried out outside the plant, that the backwashing process uses fresh water but is carried out using special cleaning fluids, and that only a portion of the total filter material is backwashed. It's in the tank where it's being washed.

There is also a risk that if the pump breaks or the flow direction changes, the filter material will fall downwards and escape uncontrollably through the outflow pipe.

Reopening a plant blocked in this way requires a lengthy operation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plant for the precipitation of suspended solids from water which, with minimal modifications to its construction, has an improved effectiveness.

An advantage of the present invention is that it is a highly effective plant that is easy to operate, so that the plant can be used with the introduction of reactants such as carbonates, sulfides, or activated carbon, which eliminates pollutants. Combined with a cloudy organization;
Subsequently, it should be suitable for use in treating turbid water or in treating water in general.

In particular, the backwashing process is simplified and cannot be performed without the high backwash rates necessary to simultaneously filter effectively.

In a preferred embodiment of the invention, upward filtration is used with a filter having particulate filter material in the form of a foam and filled with water and large enough to allow the contents to pour into the filter. A backwash tank with an opening is located above the filter. Since emptying occurs only during backwashing, the opening is closed by a float and the filtrate, for example filtered process water, is fed to the outlet through a bypass. Advantageously, the filtrate flows to the outlet through a backwash tank which is thus automatically kept full. The volume of the backwash tank determines the length of the backwash process.

Other disadvantages are eliminated by no longer requiring a sieve at the bottom of the filter. Such a sieve destroys the incoming aggregates, so that it cannot filter well. A sieve blocked with filter material impedes the backwash water flow by increasing the pressure, which , leading to the second and other requiring a backwash pump. Instead of placing the settling tank in front of or on top of the filter, according to the invention it is located at the bottom of the filter as part of the unit of the plant, so that the sieve is unnecessary and the settling tank is All filter material can be retained during the backwash step. Particulate filter material (foam)
In order to prevent the filter material from flowing out through the sludge outflow pipe in the floor of the settling separation tank, the sludge outflow pipe was directed upwards and its free outflow was configured such that the filter material remained in the settling separation tank. .

The backwashing step of the device according to the invention can be carried out using one valve, viz.
Controlled and regulated by opening the sludge valve in the sludge outflow pipe of the settling tank below the filter. The filter is washed with treated water at a sufficient rate without closing the inlet pipe.

As soon as the backwash tank is empty, the backwash process ends and the sludge valve in the sludge outlet pipe in the bed of the settling tank is closed again. The filtration process starts automatically after this short interruption.

The filtration process can be further improved by using the advantageous feature that raw water flows through a large filter surface area. Meanwhile, the backwash water from the opening should be evenly distributed in the filter area between the backwash tank and the filter. For this reason, the filter cross-section of a preferred filter according to the invention is smaller in the outflow region than in the inflow region.

The inflow into the backwash tank is controlled by a float valve to compensate for the filter resistance, which is small after the backwash process and constantly increases during filtration. It is thus possible to use conventional pumps and no control of the inflow of incoming raw water is necessary.

The results obtained in such a plant are shown in the following table for the removal of heavy metals from flue gas cleaning water: Heavy metal concentrations before and after treatment are shown (chlorine content 36g/4).

Cd Hg Ni Pb
Inflow to the Zn plant 1 tag/(2 Filtrate 0.001 rag/(1 0,140,650 0,0010,20,0010,01) Reduction of heavy metals caused by flue gas cleaning in an aqueous environment In order to determine the possible benefits, model calculations using the residual concentrations obtained using the plant according to the invention show that values such as the table below can be obtained in an industrialized country such as West Germany. .

It is understood that in terms of environmental protection, effective flocculation, sedimentation separation and filtration processes for flue gas wash water from waste incinerators are much more important than when used in flue gas wash water from coal-fired power plants. It will be. However, the analogy is that even in the latter case, 200 kg of mercury and 180 kg of mercury per year
It can prevent 0 kg of cadmium from entering the environment.

Moreover, apart from the efficiency of the plant, its reliability of operation, simplicity of construction and ease of operation are practically unacceptable, especially if water treatment is not the main operating purpose of the user. Of course, the most important thing about this is:

The memorial service states that heavy metals are completely precipitated from the flue gas wash water and
and environmental benefits in West Germany when filtered.

Cd Hg Ni Pd
Zn coal-fired power plant 1.8 0.2 18 0.9
Garbage incinerator from 1990 to 877 7.5 600 120 1140
2220 [Example] This plant, shown in Figure 1, is used to precipitate suspended solids emanating from water, such as above-ground wastewater, industrial wastewater, biological treatment wastewater, and leachate from landfill waste. It has a pump 6 for transporting the water through the plant. The inlet pipe 5 incorporates a first metering station 7 for introducing flocculant into the pipe. Other dosing stations/conn are for introducing polyelectrolytes as flocculants, at least one other dosing station is for introducing polyelectrolytes as flocculants, such as sulfides, carbonates or activated carbons. The mixing device 8, which is for introducing the reactants, destabilizes the flocculant after it has been added. The pipe 5 connecting to the mixing device 8 has a diameter such that the water flow velocity produces turbulence and forms a flocculation reaction pipe length 9 such that flocculation within the pipe occurs.

The subsequent plant for separating the flocculates by settling and filtration is filled with granular material 23 and is located at the top of the settling tank 4 of the plant, the water flow direction being from the bottom to the top. has a filter l.

A backwash tank 14 is filled with filtered water and is attached to the top of filter I and is separated from filter I by sieve L3. A settling tank 4 located below the filter 1 forms a structural unit with the filter. The outflow of the filtrate can be controlled by an outflow valve 20.

The float 15 closes an opening 16 with a cross section extending between the filter 1 and the backwash tank 14 in the upper position due to buoyancy, and the float 15 closes the opening 16 with a cross section extending between the filter 1 and the backwash tank 14 during the backwash process when the flow direction is reversed. Water flows from the backwash tank I4 to the filter l with a large flow rate that increases the efficiency of the washing process.
allow it to flow. The upper part of the float 15, which tapers conically upwards, lies in contact with the corresponding sealing surface of the opening 16 when in the upward position due to buoyancy.

When the opening 16 is closed by the float 15, the bypass 1
7 directs the filtrate surrounding flows 1-15, ie, treated and filtered water, into a backwash tank.

The flow into the backwash tank 14 is closed by a float valve 18 regulated by a second float 19 to keep the water level of the filtrate in the backwash tank 14 constant.

The filter 1 has a smaller cross-sectional area in the region of the outlet 2 than in the region of the inlet 3. The top radius of the filter in the outlet region 2 is equal to or larger than half the diameter of the filter in the inlet region 3. The height of the filter l is greater than 40 cm, preferably l~2II! It is. Filter 1 allows untreated water to pass through the cross-sectional area of filter 1 through 2-1
It is dimensioned to flow at a flow rate of 5 m3/(m2h), which corresponds to a surface load of 2 to 15+*/h. This filter has a direct ff of 10.5 to 1 m.
Shoulder Styrofoam 2
3 is filled. Sieve l3 is styroform sphere 2
3 is attached to the top of filter 1 to hold it.

The volume of the settling tank 4 located below the filter 1 is dimensioned to hold all the granular filter material 23. The sludge outflow pipe lO with the sludge valve 11 in the filter bed has a small fluid volume corresponding to a mixture of water and granular filter material 23 equal to the total volume of the granular filter material 23 when the sludge valve 11 is opened. Both are oriented upward against gravity so that they remain in the sedimentation separation tank 4. The water level 22 in the dash-dotted line in the drawing is directed upwards.
;corresponds to the height of the sludge outflow pipe lO.

The storage tank 12 located on the side of the sedimentation separation tank 4 is
It is configured to such an extent that it retains the entire volume of backwash water. A sieve at the lower end of the settling tank 4 in the direction of the sludge outlet pipe 10 is no longer necessary.

During operation of the plant, untreated water is transported through the inlet pipe 5 by a pump 6. The additives required for the treatment are metered into the pipe 5 and mixed with the untreated water in a compressed state in a pipe or other suitable means. Ferric chloride is dosed into the raw water stream to destabilize suspended matter.

After about 30 seconds, a polyamide solution is added as a flocculant. This process of forming flocs from turbid substances in water is called in-pipe flocculation and is well described in the technical literature. After a further reaction time of about 120 seconds in the pipe section 9 with turbulent flow, an agglomerate is formed and the raw water stream consists of destabilized turbid substances or precipitated contaminants which can be introduced into the plant according to the invention. The raw water with fully formed aggregates enters the settling tank 4 tangentially.

The flow velocity is between 2 and 15 m, which corresponds to an upward movement of water of 2 to 15 m/h, in relation to the cross-sectional area of the separating and settling section 4.
3/(+z2h). - A low surface load is uneconomical and a higher surface load is not advantageous since not enough agglomerates settle out. The height of the settling tank 4 can be chosen freely and does not affect the results. It is suggested that the height be the same as the diameter.

Thus, knowing the flow rate of the incoming raw water and the available intermediate storage volume, the size of the plant can be determined.

The flocculate is filtered through filter 1 located above the sedimentation separation tank.
, so that complete sedimentation of the flocculates in the sedimentation tank 4 is unnecessary. Firstly, the filter 1 has the same cross-sectional area as the settling tank 4. This is filled with styrofoam spheres 23 of a suitable diameter, in particular d-0.5-1.5 mm. The height of the filter can be determined by the actual spatial height and desired filtration time, such that a larger volume filter may retain more turbid material than a flatter configured filter. It is therefore recommended that the height of the filter not be less than 40 cm. From an operating point of view, a filter height of between 1 and 2 mm is advantageous.

The top diameter of the filter at 2 should not be larger than half the filter diameter at 3. In this way, (area 3)≦4·(area 2). The upward velocity of the water at 3 is mathematically equal to the velocity in the settling section 4, i.e. 2 to 15111/hr, and at 2 is at most 4 times lower than the velocity in the settling section 4.
twice as large, i.e. 8-60 m/hr.

A larger flow through the filter leads to the destruction of the agglomerates, leading to poor results.

The water pushes up the float 15 and closes the opening 16 located at its upper part. Water passes through bypass 17 to backwash tank 1
◇Volume velocity (voFui)
e rate) is discharged from the backwash tank 1 by the outflow valve 20.
It is adjusted by the outlet of 4. The float valve 18 is connected to the backwash trough 1 to such an extent that only the volume to be processed within a certain period of time, regulated by the outflow valve 20, passes through the entire plant.
The outflow amount of bypass 17 to 4 is throttled and adjusted.

If the throughput is too small (blockage) or the water is cloudy (filter breakthrough), backwashing of the plant begins. The sludge valve 11 of the sludge outflow pipe 10 opens. 70-) 15 sinks and the opening 16 opens, which creates a strong downward flow of water sufficient to agitate and clean the filter 1. The styrofoam sphere 23 sinks into the settling tank 4, but at such a height that the free outflow of the slo-noji outflow pipe IO remains such that a volume of the settling section 4 corresponding to the total volume of the styrofoam sphere 23 remains. Once in position, this Styrofoam ball cannot leave. When the strong downward water flow ends, the backwashing process ends. The sludge valve 11 in the sludge outflow pipe 10 is closed. When the untreated water stream fills the plant and fills the Styrofoam 23 again up to the top area of the filter 1, the plant automatically resumes the treatment, ie settling of the suspension from the untreated water.

It will be appreciated that various modifications, changes and adaptations to the above description of the invention may be made, but the same are encompassed within the meaning and scope of equivalents of the appended claims. It is intended that

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of a plant according to the invention. -11+1 Procedural Amendment Date: November 1990 τυ

Claims (1)

[Claims] 1. a. a pump for transporting turbid water through the plant; b. a first metering device for introducing a flocculant into the pipe; c. a second metering device for introducing the flocculant; d. a mixing device for destabilizing the turbid material after the introduction of the flocculant; e. turbulence (in-pipe flocculation) in the throughput of water a pipe connected to the mixing device, with a diameter such that it can produce f, a filter located in the upper part of the settling separation tank of the plant and filled with granular filter material, the direction of flow being from bottom to top; g. a backwashing tank for settling suspended solids from water such as surface runoff, industrial wastewater, biological treatment wastewater, and landfill waste leachate, and for sedimentation separation of the flocculate subsequently formed; and in a plant for filtration, consisting of the above-mentioned settling separation tank, the above-mentioned filter and the above-mentioned backwashing tank, for settling the formed flocculates, the following parts have the following characteristics: h. for the filtered water; said backwash tank is present on top of said filter; i. the float closes the opening connecting the filter and said backwash tank with a widening transverse section in the raised position due to buoyancy, the flow direction being from top to bottom; , opening the opening to allow the filter to be backwashed at high flow rates to improve the effectiveness of the backwashing process; j. when the opening is closed, the bypass is closed; directing the treated water past the float and into the backwash tank; k. the volume of the settling tank is large enough to hold all of the particulate filter material; and l. The sludge outflow pipe in the floor of the settling separation tank and the sludge valve in this sludge outflow pipe are such that when the sludge valve in the sludge outflow pipe is opened, the mixture of water and the above granular filter material is The plant is directed against gravity to such an extent that a volume of fluid equal to the total volume remains in the settling tank. 2. The plant of claim 1, wherein the bypass outlet is closed by a float valve controlled by a second float to maintain a constant level of filtered water in the backwash tank. 3. The plant of claim 1, wherein the diameter of the filter in the outflow region is smaller than the diameter of the filter in the inflow region. 4. The plant of claim 3, wherein the diameter of the filter in the outflow region is equal to or greater than half the diameter of the filter in the inflow region. 5. Plant according to claim 4, wherein the height of the filter is greater than 40 cm, in particular between 1 and 2 m. 6. The above filter has a surface load of 2 in the sedimentation separation tank.
~15 m^3/m^2 (h), so that the water correspondingly flows upwardly at a speed of about 2 to 15 m/h. Plants listed. 7. The above filter preferably has a diameter of 0.5 to 1.5 mm.
is filled with Styrofoam spheres with a diameter of
Plant according to claim 1. 8. Plant according to claim 1, characterized in that the settling tank forms a structural unit with the filter. 9. Claim 1, wherein only one sieve is located at the top of the filter.
Plants listed. 10. The plant of claim 1 having a storage tank located on the side of the settling tank capable of holding the entire backwash volume. 11. Plant according to claim 1, having at least a third metering device for introducing reactants such as 11. sulfides, carbonates or activated carbon.