JPH07222997A - Method and apparatus for treating water purifying sludge - Google Patents

Abstract

PURPOSE:To obtain sludge useful as an agricultural soil amendment material by decreasing Mn in sludge produced by supplying water, which is supernatant of a reduction-concentration apparatus and a reconcentration apparatus or a part of the separated water from a dewatering apparatus and is removed of manganese, to a displacement apparatus as dilution water. CONSTITUTION:In a reduction-concentration apparatus A, sludge (a) to be treated is adjusted of its pH to an acid range, separated into solid and liquid by natural sedimentation, and manganese in water purifying sludge is transferred into water. In a displacement apparatus B, the separated sludge (b) is diluted with dilution water to transfer residual manganese into water. In a reconcentration apparatus 7, the diluted sludge C is again concentrated; the reconcentrated sludge (d) is dewatered by a dewatering apparatus 8. In this process, the supernatant of the reduction-concentration apparatus A and the reconcentration apparatus 7 or at least a part of the separated water from the dewatering apparatus 8 is led to a manganese removing apparatus C, and the treatment water is supplied to the displacement apparatus B as dilution water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to treatment of sludge generated from water purification equipment, industrial water equipment and the like, and more particularly to a method for obtaining dehydrated sludge suitable for resource utilization.

In a water purification facility using river water as a water source and a water purification facility using industrial water as raw water, a typical process of conventional water treatment is a landing well 1 as shown in FIG. It is a treatment process with pond 3 and filtration pond 4.
A typical process of advanced water purification treatment is a treatment process in which a biological treatment facility 2, a coagulation sedimentation basin 3, a filtration basin 4, and an activated carbon filtration basin 5 are arranged as shown in FIG.

For example, in this advanced water treatment process, raw water 20 taken from a water source such as a river and stored in the landing well 1 is
First, biological treatment is performed in the biological treatment facility 2 by catalytic oxidation, and the biologically treated water 21 precipitates SS by solid-liquid separation in the coagulation sedimentation tank 3, and SS that did not sufficiently precipitate here is filtered in the filtration tank 4 and the activated carbon filtration tank 5. It is filtered off to obtain treated water. The sediment in the coagulation sedimentation basin 3 is the drainage basin 10, the SS filtered by the filtration basin 4 and the activated carbon filtration basin 5 is the drainage basin 11, and the separated and separated supernatant liquids are returned to the well via the return pipe. The sludge that has been returned to No. 1 is further subjected to the steps of the concentration tank 7 and the dehydration facility 8 to be recovered as a dehydrated cake, and the supernatant water and the filtrate thereof are returned to the landing well 1 via the return pipe.

The dehydrated cake recovered from the above-mentioned water purification process is dried in the drying equipment 9, and the obtained sludge cake is utilized as a soil for soil, cultivating soil, horticultural soil and the like for resource utilization in agriculture. When using the sludge cake for agriculture, etc., usually physical and chemical analyzes are conducted to determine whether the sludge cake is suitable for agricultural soil. Regarding the examination of physical properties when using it as a soil conditioner, there are some characteristics depending on the characteristics of river turbidity, but most of them depend on the treatment method such as dehydration method, crushing method and drying method. large. The study of the chemical properties, the analysis result whether applied to agricultural soil, what plants In addition to being used to apply whether the judgment of inorganic nitrogen (NH ₃ -N, NO ₃ -
If the amount of N) is large, adjust the amount of nitrogen added, and if the absorption coefficient of phosphoric acid is large, apply the necessary adjustments such as increasing the amount of phosphoric acid and then applying it to agricultural soil. Has been done. However, regarding the replaceable Mn and the water-soluble Mn, even if these analysis results are obtained, there is no effective method for responding to the results, and it is possible to mix them with soil or sludge cake with a very small amount of replaceable Mn and water-soluble Mn. , These Mn are diluted (Mn weight ratio is reduced) and used.

Generally, in rivers, Mn contained in suspended matter
And water-soluble Mn dissolved in water is present. Even if the amount of Mn per unit volume present in purified water taken from rivers or water used in industrial water equipment is very small, Mn is contained in sludge generated from the purified water or industrial water purification equipment. Exists in a concentrated state, and Mn is in a reduced state, so that a large amount of water-soluble Mn ²⁺ exists. As a result of water purification treatment of raw water such as river water and industrial water, among the Mn existing in sludge generated, it is easily eluted into water and the replaceable Mn that is ionized and solubilized by reducing state or pH change. The water-soluble Mn that is absorbed is easily absorbed by the roots of the plant, and causes harmful effects on the plant. Plants depend on their species, M
It is classified into those weak to n deficiency and weak to excess Mn, but as described above, there are many Mn in sludge,
In particular, since a large amount of water-soluble Mn ²⁺ is present, sludge generated by treating raw water such as river water or industrial water is Mn-excessive for many plants, especially replaceable Mn and water-soluble Mn. Cause an excess of.

[0006]

DISCLOSURE OF THE INVENTION The present invention is based on M in sludge generated as a result of purification treatment of raw water such as river water and industrial water.
It is an object of the present invention to reduce n, particularly the substituting Mn and the water-soluble Mn, and obtain a sludge effective as an agricultural soil improving material.

[0007]

The above-mentioned object of the present invention can be achieved by the following method for treating purified water sludge. That is,
(1) pH adjustment of the sludge to be treated, solid-liquid separation by natural settling, solid-liquid separation, transfer of manganese in the purified water sludge into water, and diluting the separated sludge with diluting water and remaining A step of displacing manganese into water, a reconcentration step of reconcentrating the diluted sludge, and a dehydration step of dehydrating the reconcentrated sludge, or a method for treating purified sludge, or preferably , (2)
At least a part of the supernatant water of the reduction concentration step and / or the separated water of the reconcentration step and / or the separated water of the dehydration step is introduced into the manganese removal treatment step and used as dilution water. This is achieved by the method for treating purified water sludge described in 1). As used herein, the terms of concentration and reconcentration relating to steps and devices indicate the kinetics of the suspension, not the adjustment of the amount of Mn.

When the pH of the sludge to be treated is around 5 to 6, it is economical and efficient to control the replaceable Mn value and the water-soluble Mn value in the sludge. In terms of the oxidation-reduction potential, the potential change required for reduction does not become so large even at pH 6 or lower because of the phase change characteristics of Mn shown in FIG. Also, Japanese soil has a high pH of 5-6. Therefore, soil materials with a pH of around 5 to 6 have little chemical change. It should be noted that the elution of Mn into water may take about half a day, so the length of the reduction and concentration step is determined in consideration of the SS sedimentation rate and the like.

The diluting water supplied to the replacing step may be river water such as raw water, purified water or city water, but the supernatant water of the reducing step and / or the supernatant water of the concentrating step and / or At least a part of the water separated in the dehydration step,
And the water can be reused because it is manganese-removed water,
Especially effective. Further, when supplying the dilution water to the replacement step, it is preferable to supply the dilution water after adjusting the pH. In the manganese removal treatment step, it is preferable to first perform biological treatment, then inject an oxidant, and further perform contact filtration. Alternatively, in the manganese removal treatment step, it is also possible to first perform biological treatment, then inject an oxidizing agent, and further perform coagulation sedimentation and contact filtration. The dehydrated cake in the dehydration step is preferably applied to soil improvement after crushing and storing it to a particle size distribution diameter of 10 mm or less, and the particle size distribution preferably has a regular curve. It is preferable to mix it in a ratio of about 10 to 15% when it is used for a wide range of plants and the like.

Further, the object of the present invention can be achieved by the following apparatus for treating purified water sludge. That is, (3) a reducing and concentrating device that is provided with at least a pH adjusting means that naturally separates purified water sludge, a replacement device that dilutes and cleans sludge discharged from the reducing and concentrating device with dilution water, and discharge from the replacing device. Apparatus for treating purified water, comprising a re-concentrating device for re-concentrating the sludge to be re-concentrated and a dehydrating device for dehydrating the sludge discharged from the re-concentrating device, or, preferably, (4) the reduction A manganese removal device for introducing at least a part of the supernatant water of the concentration step, and / or the separated water of the reconcentration step, and / or the separated water of the dehydration step to remove manganese to obtain diluted water is provided. It is a sludge treatment device characterized by the above (3).

The reduction / concentration apparatus of the present invention elutes Mn from all sludges produced in the water purification process to remove solid matter (S
An ordinary settling tank, which separates from S) and allows a certain residence time, is preferably used. The sedimentation tank may be a natural sedimentation type or a coagulation sedimentation type, and an auxiliary device such as an inclined slope may be provided. However, to elute Mn into the aqueous phase, sludge was adjusted to pH 6
In the following, it is preferable that the conditions are pH 5 to pH 6,
It is necessary to attach a pH adjusting means such as a pH sensor, an acid agent injection device, and an injection control device to the reduction concentration device. The reduction / concentration device of the present invention can be operated batchwise or continuously. The displacement device of the present invention elutes the remaining Mn into the aqueous phase with 1 to 10 times the sludge volume of the dilution water. Therefore, a pH adjusting means and a stirring means are preferably attached. The dilution water is resource-saving if the separated liquid generated in each step of the present invention is used. The separated liquid is treated with a manganese removing device such as a manganese sand bath or a device group corresponding to the treatment of the above-mentioned manganese removing process, but it is preferable to further adjust the pH before supplying. Known solid-liquid separators such as a precipitation separator, a centrifugal separator, a membrane separator can be applied to the reconcentrator of the present invention.

Next, in order to understand the present invention, the behavior of Mn during the purification process will be described with reference to FIG. Here, a case will be exemplified in which the purification treatment sludge in the purification treatment in which pre-chlorination and medium-chlorination are not performed is treated by the treatment method of the present invention. However, the method of the present invention does not, of course, prevent the combined use of chlorine injection, and is not limited by the following description.

In FIG. 1, the Mn flowing into the treatment system of the present invention from the raw water 20 in the landing well 1 is the original suspension obtained by the biological treatment apparatus 2 and the water-soluble Mn (Mn ²⁺ ) is biologically oxidized. As a result, it becomes a suspension, part of which sediments, and flows into the reduction / concentrator A as waste sludge. Next, in the coagulation sedimentation tank 3, Mn
Precipitates as a suspension and accumulates at the bottom of the pond, but is in a reducing state at the bottom of the pond, and flows into the reduction / concentration device A in a state where it easily changes to Mn ²⁺ or in a changed state. In the filtration basin 4, the Mn of the suspended matter that has flowed out flows out as filtration basin cleaning wastewater, and flows out to the reduction / concentration device A. After passing through the ozone treatment device, the suspended carbon Mn and the water-soluble Mn are both contained in the activated carbon filtration basin 5.
Mn that has been oxidized into valence Mn is captured as tetravalent suspension Mn by the reducing action of the activated carbon and flows out to the reduction concentrator A as cleaning wastewater.

In the reducing and concentrating device A, the sludge M, suspended matter, and washing wastewater are sufficiently retained so that the suspended solid M
n is Mn ^2+, and these are used as the supernatant water of the reducing and concentrating device and sent to the manganese removing facility C. In the reducing and concentrating device A, MnO ₂ (tetravalent M
The n) suspension is efficiently transferred to Mn ²⁺ water-soluble Mn. This is because the value at which the potential difference between the redox potential of MnO _{2 and} the redox potential of water under a reduced state can be economically large is pH 5 to 6, and sulfuric acid, hydrochloric acid, etc. are injected as a pH adjuster to carry out reduction concentration. The pH is adjusted when the apparatus A is introduced.

In the substitution device B, the sludge drawn out from the reduction concentration device A (reduction concentration device extraction sludge b) is mixed with dilution water. The amount of dilution water may be determined from the dilution ratio that gives the final target Mn concentration, which is determined by back-calculating the value of the replaceable Mn suitable for the plant species. It is usually 2 to 10 times.

(Function) The state of Mn present in water is roughly divided into insoluble Mn and soluble Mn.
^Corresponds to Mn ²⁺ in the reduced state.

Mn absorbed by plants is water-soluble Mn (Mn
²⁺ ), it is difficult to be a reliable index even if the amount of water-soluble Mn present is measured in the sludge treatment process. The reason is,
This is because the water-soluble Mn greatly changes depending on conditions such as the redox state and pH. Actually, it is considered that most of the quantified water-soluble Mn is the one in which the substituting Mn is converted into the water-soluble Mn due to the change in environment. Therefore, the replaceability Mn
The amount is an index of manganese that may be absorbed by plants, and is often used when measuring the amount of Mn in a sample to determine its suitability as a soil conditioner. By the way, the substitutable Mn is Mn extracted with 1N-ammonium acetate. The main point of the present invention is
This is to remove the replaceable Mn from the sludge by converting the replaceable Mn into water-soluble Mn by changing the state.

Charlot will now be described for the following description.
From the oxidation-reduction state diagram of manganese, iron and oxygen prepared by the above, only the oxidation-reduction state of manganese and oxygen is taken out and shown for easy understanding in FIG. As shown in FIG.
When H is low, Mn becomes Mn ²⁺ , that is, in a soluble state even in a relatively high redox potential region.
Therefore, in the present invention, the sludge to be treated is placed at a pH of 6 or less from the curve of FIG. 2, and Mn ²⁺ is transferred from the solid phase of the sludge to the liquid phase, that is, the supernatant water, for a sufficient time. By this operation, the sludge is concentrated while removing Mn from the sludge.
(Reduction and concentration process)

Further, by diluting the concentrated sludge, the residual Mn ²⁺ is transferred into the diluent. (Substitution step) At this time, it is clear from the above reason that the pH is preferably set to 6 or less. The diluted sludge is subjected to solid-liquid separation again, and sludge containing less Mn can be obtained. (Re-concentration step) Since the amount of Mn in the sludge is adjusted in the replacement step before, it is not necessary to retain it for a long time in the re-concentration step. As described above, the essence of the present invention is to create an environment in which Mn is easily eluted and to dilute and wash sludge.

Acids such as sulfuric acid, hydrochloric acid, nitric acid or organic acids can be used as the pH adjusting agent. The sludge subjected to the treatment of the present invention is suitable as a soil conditioner as described above, but the Mn in the sludge also changes during storage before application. This is not preferable for quality control. Therefore, when the dewatered cake is stored for several days or longer, the cake is crushed to a certain size, but if the crushing is too fine at this time, the porosity decreases due to compaction and the reduction state occurs, and Mn is It becomes easy to be returned. Therefore, the particle size at the time of crushing is preferably 1 to 10 mm. In addition, 1m
Even if a pulverized product having a particle size of m or less is produced, the amount thereof is preferably 30% or less by weight. Further, the dehydrated cake is dried to be commercialized as a soil improving agent. This drying process not only reduces the water content but also suppresses the generation of weed species and bacteria. However, when the temperature is too high, the elution of Mn due to thermal decomposition occurs, so when dry,
It is preferable that the temperature is 95 ° C. If steam sterilization (product temperature 100 ° C) is performed, Mn becomes excessive, which may damage plants.

[0021]

EXAMPLES The evaluation of the treatment results by the sludge treatment process of the present invention will be described below based on the results of both the substitution Mn value and the water-soluble Mn value. The results are shown in Table 1.

[0022]

[Table 1]

The process will be described below with reference to FIG. The sludge is sent to the reduction tank A via the biological treatment device 2, the coagulation sedimentation basin 3, the filtration basin 4, the ozone treatment device 6, and the activated carbon filtration basin 5. Therefore, the reduction concentration device A
A flowing into the is a mixture of sludge and washing waste water. Depending on the situation of the sludge and the cleaning drainage a at that time, it goes through each device shown by the arrow.

The mixture stays in the reducing and concentrating tank A for 24 hours while undergoing pH adjustment, and is separated into the reducing and concentrating tank drawn sludge b and the reducing and concentrating tank supernatant water g. The pH of the reduced concentration tank drawn-out sludge b and the reduction concentration tank supernatant water g decreased from 6.7 to 5.9 by adjustment, and the state of Mn was easily solubilized. This is clear from the numerical values in Table 1, a
The substituting Mn of 37.6 mg / liter in Example 2 was mostly converted to water-soluble Mn (Mn ²⁺ ) in b and g. Further, the solid matter concentration is concentrated about 5 times. Water-soluble Mn is 10.1 mg in this concentrated sludge (reducing concentration tank extraction sludge b).
Per liter, 40.6 mg / liter is contained in g of the supernatant water of the reducing concentration tank.

The above-mentioned reduction concentration tank supernatant water g is sent to the manganese removal equipment C, and as a part of the manganese removal treated water h, the reduction concentration tank draw-out sludge b is sent as it is to the replacement tank B, where b is h.
Is used to dilute the manganese in the sludge into water, and the manganese in the sludge is further eluted in water. Here, since the Mn value in the manganese-removed water h that is dilution water is below the measurement limit, as shown in Table 1, each Mn value in the displacement tank outflow sludge c is one tenth of b. . The diluted substitution tank outflow sludge c is concentrated again in the reconcentrator 7. That is, in the process of being transferred from the reduction concentration tank A through the substitution tank B to the reconcentration device 7,
The sludge will be washed. As the reconcentrator 7, for example, a tubular low pressure filtration device (pressurization pressure 2
kg / cm ² ) or the like can be preferably used.

As shown in Table 1, the Mn value contained in the sludge d extracted from the re-concentrator is about 14% in the replaceable Mn value and 6% in the water-soluble Mn value in the sludge and the cleaning waste water a at the beginning of the treatment. Decrease. The dynamics of Mn in the dehydration equipment 8 are as shown in Table 2. Here, the dehydration equipment was treated using a short-time filter cloth traveling type chemical-free dehydrator.

[0027]

[Table 2]

As can be seen from Table 2, dehydrated sludge cake i
The substituting Mn value of is 36.5 mg / kg of cake and the water-soluble Mn value of is 1 mg / kg of cake. From this value, it is understood that the sludge treatment of the present invention can provide a sludge cake which can be a good soil improver.

For comparison, the sludge produced by the conventional treatment method shown as sludge from the sludge basin 10 and the sludge basin 11 in FIGS. 3 and 4 (in the step of FIG. 1, sludge mixture a
3), and the sludge treatment process of the present invention shown in FIG.
The results of both the substitution Mn value and the water-soluble Mn value of the dehydrated sludge cake obtained by sludge treatment by the conventional sludge treatment step shown in Fig. 4 and dehydration in the dehydration facility 8 using a pressure dehydrator Is shown in Table 3.

[0030]

[Table 3]

From the results shown in Table 3, the dehydrated sludge cake treated by the sludge treatment step of the present invention shown in FIG. 1 has both the substitution Mn value and the water-soluble Mn value of the dehydrated sludge cake treated by the conventional sludge treatment step. Remarkably small, it can be seen that the purpose of the treatment has been achieved.

[0032]

INDUSTRIAL APPLICABILITY According to the present invention, sludge can be supplied as fertilizer without causing Mn damage. Further, since the Mn content can be freely adjusted, it can be supplied as a soil improving material for over-Mn soil and the like. In order to understand that the sludge cake obtained by treating the purified water sludge treatment apparatus of the present invention according to the treatment method of the present invention is excellent as a soil conditioner, an example of Mn disorders of plants will be outlined. Examples of Mn disorders in plants include (1) "abnormal deciduous leaves" that cause brown spots on the leaf blades of Unshiu mandarin oranges, resulting in a sharp decrease in yield, and (2) rash-like irregularities on the bark of apple branch trunks. , "Progressive skin disease" that caused a significant decrease in revenue and eventually died,
(3) It has been reported that "green spot disease" or the like in which large avatar-like green spots remain on the pericarp of the fruit of the oyster at the harvest stage, resulting in a marked decrease in commercial value. “Abnormal leaf fall” in (1) above and Mn of soil
Table 4 shows the results of the investigation of the content state.

[0033]

[Table 4]

In Table 4, water-soluble M in the abnormal deciduous garden
The n value is 2.8 to 6.0 mg / cake kg, the replaceable Mn value is 17.7 to 60.0 mg / cake kg, while the water-soluble Mn value is 0.6 to 1.3 mg / cake in Kenzenen. k
g, the substitutable Mn value is 6.0 to 27.3 mg / cake kg
Has become. Apparently it is a disease caused by Mn excess disorder. In the leaf analysis, 23 in the abnormal deciduous garden
5.3 to 262.4 mg / kg of leaf, while in healthy garden 4
The difference is 8.2 to 75.2 mg / kg of leaf. These results were reported to be very similar to the analytical data for manganese overabsorption in apples. The dry sludge cake for soil conditioner obtained by the sludge treatment of the purified water-treated sludge of the present invention has a sufficiently low Mn concentration, can be fertilized freely, and can be used for modifying excess Mn soil.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of an embodiment of sludge treatment of the present invention.

FIG. 2 is a diagram showing morphological changes of manganese according to redox potential and pH.

FIG. 3 is a flowchart showing a typical example of an embodiment of conventional sludge treatment.

FIG. 4 is a flow chart showing another typical example of the embodiment of the conventional sludge treatment.

[Explanation of symbols]

 1 Landing well 2 Biological treatment equipment 3 Sedimentation basin 4 Filtration basin 5 Activated carbon filtration basin 6 Ozone treatment equipment 7 Reconcentration equipment 8 Dehydration equipment 9 Drying equipment 10 Waste mud basin 11 Drainage basin 20 Raw water 21 Biotreatment water A Reduction reduction equipment B Substitution Equipment C Manganese removal equipment D Washing drainage tank E Dewatering equipment a Drainage and washing drainage b Reducing concentration tank drawing sludge c Substitution tank outflow sludge d Reconcentration equipment drawing sludge e Reconcentration equipment supernatant liquid f Dewatering filtrate g Reduction concentration tank Supernatant h Manganese-removed water i Dehydrated sludge cake

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shinichiro Egawa 1-6-27 Konan, Minato-ku, Tokyo Ebara In Filco Co., Ltd. (72) Yosuke Takashima 1-6-27 Konan, Minato-ku, Tokyo Ebara Within Infilco Corporation

Claims (4)

[Claims] 1. A sludge to be treated is adjusted to an acidic pH, and solid-liquid separation is carried out by natural sedimentation to transfer manganese in the purified water sludge into water, and a sludge separated is diluted with diluting water. The method for treating purified water sludge comprises a substitution step of migrating remaining residual manganese into water, a reconcentration step of reconcentrating the diluted sludge, and a dehydration step of dehydrating the reconcentrated sludge. 2. The supernatant water of the reduction and concentration step and / or the separated water of the reconcentration step and / or at least a part of the separated water of the dehydration step is introduced into a manganese removal treatment step and used as dilution water. The method for treating purified water sludge according to claim 1, which is characterized in that. 3. A reducing / concentrating device for spontaneously settling and separating purified water sludge, at least a pH adjusting means, a replacement device for diluting and washing sludge discharged from the reducing / concentrating device with dilution water, and discharging from the replacement device. A sludge treatment device for purified water, comprising a re-concentrator for re-concentrating the sludge to be regenerated and a dehydrator for dehydrating the sludge discharged from the re-concentrator. 4. Removal of at least a part of the supernatant water of the reduction concentration step and / or the separated water of the reconcentration step and / or the separated water of the dehydration step to remove manganese to obtain diluted water. The sludge treatment device for purified water according to claim 3, further comprising a manganese device.