JP4405286B2 - Fishery processing wastewater scum treatment method - Google Patents

Description

  The present invention relates to a method for treating drainage scum generated in fishery processing to remove solids therein and purifying it so that it can be discharged into sewage or rivers.

  Seafood processing includes, for example, surimi production, paste product production, seasonal production, fish meal, fish carp production, canned food production, frozen marine product production, frozen marine food production, etc.For sewage discharged from these production facilities, Since general discharge regulations of the Water Pollution Control Law apply, in many cases, it cannot be discharged as it is.

  And when processing the waste_water | drain produced by this fisheries processing, a scum will generate | occur | produce as a waste, and when performing a biological process, excess sludge will generate | occur | produce as a waste material. The pollutants present in these wastes vary depending on the processing industry and product, but are mainly carbohydrates such as polysaccharides, nitrogen-containing compounds such as proteins, fats and oils, and the like.

  Recently, a number of fishery processing establishments have been consolidated in various places to construct a fishery processing complex, and a joint wastewater treatment facility has been set up in the area, resulting in a large amount of wastewater and sludge. Efficiently performing this process is being taken up as an important issue.

  Until now, as a processing method of fishery processing wastewater, first, after removing scales and fish pieces with a screen, the floating oil is removed in an oil separation tank, and in wastewater with high pollution, flocculation treatment and microbial treatment are performed. Direct microbial treatment has been carried out with low drainage.

  And for the separation of water-soluble protein, a method of separating using the property that it coagulates and insolubilizes at an isoelectric point and a method of treatment with an iron salt or an aluminum salt having an action of aggregation by charge neutralization are used. Synthetic polymer flocculants are used to facilitate separation of fine flocs generated by this treatment from water. Further, the pressure flotation separation method is widely used for solid-liquid separation of flocs thus aggregated (see Non-Patent Document 1).

  And so far, as a method of agglomerating and removing solids from wastewater from such aquatic processing, ferric chloride, polyferric chloride or aluminum sulfate as a flocculant, activated carbon, zeolite or A method using a powdery treatment agent comprising fly ash and a polymeric surfactant (see Patent Document 1), or a method of adding a water-absorbing material to wastewater containing scum and mixing it to gel the wastewater (Patent Document) 2), and as a method of separating and recovering oil and fat from these wastewaters, a method of separating and recovering oil and fats in wastewater in an organic solvent is proposed (see Patent Document 3). .

  However, the conventional marine processing wastewater scum treatment method has no particular problem in treating scum discharged from a single treatment plant with a relatively constant composition. However, wastewater from a number of different establishments handled When processing wastewater scum whose composition changes with the seasons and demand changes, such as equipment that collects and jointly processes the aggregate, the aggregates cannot be dewatered by the screw press, and this can be improved. In each case, the combination of flocculants and coagulant aids suitable for the composition, the amount of use must be determined in advance by preliminary experiments, but such preliminary experiments are complicated and time consuming, It is practically impossible to implement, and most of the fishery processing complex wastewater treatment plants are closed.

JP-A-9-10508 (Claims and others) JP 2000-154378 A (Claims and others) JP 2003-290604 A (Claims and others) Waste disposal / recycling technology handbook editorial edition, “Waste disposal / recycling technology handbook”, published by Construction Industry Research Council, Inc., November 25, 1993, p. 407 left column lines 9-32

  The present invention can form a dewaterable floss by appropriately modifying the processing conditions depending on the situation even when the type and composition of the scum in the wastewater to be treated is not constant, such as an integrated drainage facility of a fishery processing complex. It is made for the purpose of providing a drainage scum treatment method.

  The present inventor has conducted various studies on a method for producing scum aggregates from fishery processed wastewater scum, and separating and removing solids from the scum to produce purified water below a reference value that can be discharged into sewage and rivers. As a result, activated sludge was formed by adding activated regenerated cellulose to the drainage scum after the oil was removed, and then a synthetic polymer flocculant was added to agglomerate to form a dewaterable floss. Thus, it was found that the water could be easily purified to the extent that it would not be contaminated even if it was discharged, and the present invention was made based on this finding.

That is, the present invention
(A) Process of removing oil from fishery processed wastewater scum,
(B) adding and mixing activated pulp fine fibers to the drainage scum from which oil has been removed;
(C) adding a synthetic polymer flocculant to the above mixture and mixing to form a hydrated cake; and (d) dehydrating the hydrated cake and recovering the solid residue.
Activated pulp fine fiber beats wood chemical pulp excluding impurities in a swollen state and fibrillates to add mechanical energy to cut the fiber and mechanochemically activated fine fiber A fishery processing wastewater scum treatment method is provided.

  In the method of the present invention, it is difficult to form a dewaterable floss so far, and it is possible to purify the fishery processing drainage scum, which could not be purified to the extent that it can be discharged, to a water quality that can be discharged. . Such drainage scum includes a single processing plant, such as a surimi manufacturing plant, a paste product manufacturing plant, a seasonal product manufacturing plant, a fish meal fish bowl manufacturing plant, a canned food manufacturing plant, a frozen seafood manufacturing plant, a frozen seafood manufacturing plant, etc. The wastewater scum derived from a wide variety of factory wastewater in the wastewater processing facility of the fishery processing complex is included as well as the wastewater discharged from the factory.

Since the above-mentioned factory waste water scum usually contains 0.5 to 3% by mass of oil, the method of the present invention first needs to remove the oil from the drainage scum in the step (a).
The removal of the oil can be performed using an oil separator, or can be performed using a method using a flotation, such as a foam method and a pressure levitation method.

  The foam method is roughly divided into a foam contact type and a foam precipitation type. The former is a method in which foam is introduced into an emulsion containing oil to apply adhesion by collision and wetting between oil droplets and foam, and the latter is in a supersaturated state. In this method, gas deposition, foam formation, and adhesion are applied to the surface of oil droplets in an emulsion in which gas is dissolved.

  On the other hand, the pressure flotation method is a method in which air is injected into water at a pressure of 300 to 500 kPa to form air-dissolved water, and the pressure is returned to normal pressure and mixed with an emulsion containing oil. The amount of dissolved air is about 30%.

  The removal of oil in the method of the present invention is performed by adding the foaming agent to the predetermined aquatic processing drainage scum and mixing the above-mentioned pressurized flotation method and introducing air through a perforated plate arranged below to form bubbles. It is advantageous to raise the oil by entraining it and to overflow the oil-containing foam from the top and remove it. As the foaming agent in this case, a surfactant having usually 6 to 10 carbon atoms and about 6 to 10 HLB, for example, sulfonate ester salts such as α-terpineol and 2-ethylhexanol are used. There is no particular limitation as long as it is an agent.

  In this way, the drainage scum from which the oil has been removed is sent to the subsequent step at a solid content of 0.5 to 5% by mass, preferably 1 to 3% by mass. At this time, if desired, it can be mixed with sludge generated in another processing facility for processing.

  In the method of the present invention, the activated regenerated pulp fine fiber is added to the drainage scum from which the oil has been removed in the above-described manner in the next step (b).

  This activated pulp fine fiber is made by pulverizing wood chemical pulp excluding impurities such as hemicellulose and lignin in a swollen state, and adding mechanical energy to the fibrillated fiber by grinding treatment, etc. It is a fine fiber that has been cut and mechanochemically activated, and has a feature that the action of aggregating suspended substances in water is remarkably enhanced.

  As a raw material for the activated pulp fine fiber, recycled fiber of waste paper can also be used. In this case, additives such as fillers, pigments, sizing agents, paper strength enhancers, anti-slime agents, etc. added during papermaking from waste paper immersed in water and defibrated into individual single fibers Used after removing printing ink.

  Activation of this raw material is performed by grinding in a dry state or stirring the liquid in which the fiber is suspended at high speed. In this way, activated pulp fine fibers having a length of 500 to 2000 μm, preferably 500 to 1000 μm, and a diameter of 1 to 40 μm, preferably about 10 to 30 μm are obtained.

  In the step (b), this activated pulp fine fiber is prepared into a suspension having a concentration of 0.1 to 20% by mass, preferably 0.3 to 0.5% by mass, and based on the solid content in the scum. After adding in the range of 1 to 15% by mass, preferably 5 to 10% by mass, it is sufficiently mixed. Thus, if it stirs for 4 to 10 hours at room temperature and a normal pressure, the scum in waste_water | drain will float as a foamy lump.

  Next, in the method of the present invention, in the step (c), the synthetic polymer flocculant is added to the above mixture and further stirred.

  Examples of the synthetic polymer flocculant include, for example, sodium polyacrylate as an anionic one, a copolymer of acrylamide and sodium acrylate as a weak anionic one, and a polyacrylamide hydrolyzate as a cationic one. It is preferable to use a Mannich reaction modified product of polyvinyl imidazoline, polyalkylamino acrylate or methacrylate, chitosan, or polyacrylamide, and polyacrylamide or polyethylene oxide as nonionic ones.

  In this case, if desired, an inorganic flocculant such as aluminum sulfate, polyaluminum chloride, sodium aluminate, ferric sulfate, ferrous sulfate, ferric chloride and the like can be used in combination.

These flocculants are added as an aqueous solution having a concentration of 0.05 to 1.0% by mass, preferably 0.1 to 0.5% by mass, to the drainage scum mixed with activated pulp fine fibers, and stirred. The amount of the synthetic polymer flocculant added at this time is in the range of 1 to 10% by mass based on the solid content in the drainage scum.
When this stirring is continued for 10 to 120 minutes, frogs are formed in the liquid, and the whole becomes a soft cake.

  After sufficiently stirring and forming a water-containing cake in this manner, the water-containing cake is dehydrated in the next step (d). This dehydration treatment is advantageously performed by, for example, a screw press dehydration method using a screw press dehydrator. In addition, a batch centrifugal filter, a continuous centrifugal filter, an automatic discharge centrifugal dehydrator, a screw discharge centrifugal dehydration, and the like. It can also be carried out by a centrifugal dehydration method using a machine, a vibration discharge type centrifugal dehydrator, a single-stage or multistage extrusion plate type centrifugal dehydrator, a screw discharge type centrifugal dehydrator, a belt press type dehydrator or the like. When a screw press dehydrator is used, for example, a rotational speed of 0.2 to 2.0 rpm, preferably 0.4 to 1.0 rpm is used.

  Further, in the case of a floss having a high water content and difficult to form a floc, it is preferable to remove 50 to 90% of water in advance using a drainer before the dehydration treatment.

  Finally, by recovering the dehydrated cake obtained by the dehydration treatment as described above, the water content is 98 to 99% by mass or higher, and the water content is 60 to 65% by mass, mainly from protein. A solid residue can be obtained.

Next, an example of an apparatus suitable for carrying out the method of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a flow sheet diagram of an example of an apparatus for treating fishery processing wastewater scum in accordance with the method of the present invention. In this figure, the raw fishery processing wastewater scum is first introduced into the separation tank 2 of the pressurized flotation machine 1, added with a foaming agent, supplied from the air compressor 3, and dispersed in the air diffuser 4. Mixed with. As a result of this treatment, the drainage scum foams, and the oil in the scum rises in the separation tank 2 along with the foam, and is defoamed and collected in the crushing tank 6 through the guide pipe 5.

  On the other hand, the drained scum stock solution from which oil has been removed is sent to a mixing tank 7 equipped with a stirrer 8, where it is mixed with a dispersion of activated pulp fine fibers supplied from a fiber activation tank 9 by a pump 10. After that, it is transferred to an agglomeration reaction tank 11 equipped with a stirrer 12.

  In the agglomeration reaction tank 11, the polymer aggregating agent aqueous solution supplied from the polymer aggregating agent storage tank 13 by the pump 14 is mixed. If stirring is continued in the agglomeration reaction tank 11, the sludge collected in a block shape gradually begins to aggregate in the mixing tank 7 at the previous stage and becomes a viscous floss, so that it passes through a draining device such as a net-type draining device 15. After draining, it is dehydrated by a screw press dehydrator 16 to recover the solid residue. The above draining device 15 can be omitted in some cases, and the viscous floss produced in the agglomeration reaction tank 11 can be directly fed to a screw press dehydrator for dehydration.

In this way, it is possible to dewater the fishery processing wastewater scum, which has been difficult to dehydrate to a solid residue of 80% by mass or less until the water content becomes 70% by mass or less. The BOD of the treated water by-produced at this time is 5000 ppm or less, and it is purified to a level that sufficiently satisfies the normal sewage drainage standard.
The solid residue having a low water content thus obtained is used as it is as a fertilizer or as a raw material for compost fertilizer.

  With conventional methods, fishery processed wastewater scum that could not be dewatered can be efficiently dewatered using a small amount of polymer flocculant, and solid residue that can be effectively used as compost fertilizer can be obtained. On top of that, the waste water can be purified until it can be discharged into sewage or rivers. This method can also be applied to the treatment of a mixture of sludge collected separately from the drainage scum and the sludge itself.

  Next, the best mode for carrying out the present invention will be described by way of examples. The water content, biochemical oxygen demand (hereinafter referred to as BOD) and suspended solids (hereinafter referred to as SS) in each example are numerical values measured by the following methods.

(1) Moisture content (%)
Measured by the method described in Chapter 4 Section 6 of the sewage test method.
(2) BOD (ppm)
Measured by the method defined in JIS 0102 21, 32.3.
(3) SS (ppm)
Measured by the method prescribed in Appendix 8 of the Environmental Agency Notification No. 59 in 1971.

Reference example 1
Drainage scum (solid content concentration 6.7% by mass) 500kg from the internal water treatment facility of Shiogama City Housing Complex Fisheries Processing Industry Co., Ltd. was charged into a pressurized levitation machine (internal volume 1000 liters, air pressure 250 kPa) and foamed As an agent, 500 g of sodium dodecylbenzenesulfonate was added, and the oil was removed by treating for 20 minutes while removing the generated foam.
The deoiled wastewater scum thus obtained was BOD 26000 ppm.

  Each 500 g of the deoiled wastewater scum thus obtained was fractionated into 5 beakers, and activated pulp fine fibers (manufactured by Reserver, trade name “Reserver Z”) based on the solid content. 5% by weight, 3.0% by weight, 4.5% by weight, 6.0% by weight, and 7.5% by weight are added as a water dispersion and stirred at 2200 rpm for 2 minutes. A flocculant (manufactured by Asada Chemical Co., Ltd., trade name “Paraloc 410K101”) was added as a 0.2 mass% aqueous solution, and the mixture was further stirred for 3 minutes to form a lump cake.

  Next, the treated wastewater containing the water-containing cake was dehydrated for 10 minutes with a hand squeezing machine having a pressure of 1200 kPa, and the water content of the residual cake was measured. The results are shown in Table 1.

  For reference, waste paper derived from toilet paper defibrated in water is blended in a proportion of 20% by mass based on the solid content, and the same polymer flocculant as above is added and dehydrated and only the polymer flocculant In the case of mixing 5% by mass based on the solid content, a residue cake was formed and the moisture content was measured. As a result, the former was 81.3% by mass and the latter was 78.5% by mass.

Reference example 2
Table 2 shows the results of measuring the moisture content of the residue cake obtained by performing the same treatment as in Reference Example 1 for the drainage scum derived from the same source as in Reference Example 1 and having a solid content concentration of 2.9% by mass.

In the apparatus shown in FIG. 1, a pressurized flotation machine (separation tank internal volume 1.5 m ³ ), a mixing tank (internal volume 2.0 m ³ , stirring speed 2000 rpm), a screw press dehydrator (manufactured by Shin Meiwa Co., Ltd., product) The symbol “SSP-1000”, volume 1.89 m ³ ) was connected in series with a pipe, and the fishery processing wastewater scum (BOD 75000 mg / liter) discharged from the water treatment facility in Shiogama City Complex Fishery Processing Industry Cooperative was treated.

That is, 500 g of 2-ethylhexanol sulfonic acid sodium salt as a foaming agent was added to 1000 liters of this drainage scum, and air was injected at a pressure of 350 kPa at a rate of 10 liters / minute for 10 minutes to float and separate the oil. After that, it is transferred to a mixing tank, where activated pulp fine fibers are added at a rate of 7.5% by mass based on the solid content in the drainage scum,
The mixture was stirred and mixed at a stirring speed of 2400 rpm for 10 minutes. At this time, the activated pulp fine fibers used were activated in advance in a fiber activation tank and prepared into an aqueous dispersion having a concentration of 0.6%.
By mixing with the activated pulp fine fiber, a soft agglomerate is formed on the surface of the drainage scum.

  Subsequently, the mixture thus obtained was transferred to an agglomeration reaction tank, and a 0.8% aqueous solution of a polymer flocculant (manufactured by Hymo Co., Ltd., liquid cationic polymer flocculant, product name “Riselfoc RB-03”) was added. It added in the ratio of 6 mass% (solid content conversion 7.5 mass%) with respect to the waste_water | drain scum, and stirred for 3 minutes with the stirring speed of 2000 rpm. By this treatment, a soft cake containing water was formed in the drainage scum. As this agglomeration reaction tank, a reaction tank having four blades having a length of 500 mm stacked in three stages in a bottomed cylindrical container having a diameter of 950 mm and a height of 1500 mm was used.

Next, this water-containing cake was subjected to a screw press dehydration treatment under conditions of a pressure of 500 kPa and 0.8 rpm.
In this way, a solid residue having a water content of 59.8% and treated water having a BOD of 2500 ppm were obtained. This treated water satisfies the sewage discharge standard and can be discharged into the sewage as it is.

  After removing the oil from the scallop protease treatment solution (solid concentration 16.8% by mass, BOD 12000 ppm) in the same manner as in Example 1, the pH was adjusted to 3 with 1 M sulfuric acid, based on the solid content in the solution. Then, dehydration treatment was performed in the same manner as in Example 1 using 17.9% by mass of activated pulp fine fibers and 3% by mass of the polymer flocculant. As a result, a solid residue having a water content of 53.6% and treated water having a BOD of 3500 ppm were obtained.

  It is useful as a method for treating various types of fishery processing wastewater and purifying it to a standard that can be drained into sewage and rivers.

The flow sheet figure of one example of the apparatus suitable for performing this invention method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure levitation machine 7 Mixing tank 9 Fiber activation tank 10,14 Pump 11 Coagulation reaction tank 15 Net-type draining device 16 Screw press dehydrator M Motor

Claims (6)

(A) Process of removing oil from fishery processed wastewater scum,
(B) adding and mixing activated pulp fine fibers to the drainage scum from which oil has been removed;
(C) a synthetic polymer flocculant to the above mixture was added and mixed step to form a wet cake, and (d) above wet cake dehydrated by, viewed contains recovering the solid residue,
Activated pulp fine fiber beats wood chemical pulp excluding impurities in a swollen state and fibrillates to add mechanical energy to cut the fiber and mechanochemically activated fine fiber processed marine waste water scum process wherein the at. The method according to claim 1 , wherein the addition amount of the activated pulp fine fiber in the step (b) is selected in the range of 1.5 to 10.3 % by mass based on the solid content in the scum.   The method according to claim 1 or 2, wherein the oil in the step (a) is separated by flotation.   The method according to claim 3, wherein the flotation is a foam method or a pressure levitation method. The method according to any one of claims 1 to 4 , wherein the dehydration treatment in step (d) is performed by screw press dehydration. 6. The method according to claim 5 , wherein the screw press dehydration in the step (d) is carried out after draining 50 to 90% of the water previously contained.

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