JPH0431760B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention rationally treats organic sewage such as human waste water, sewage, wastewater from landfills, and various industrial wastewater using a new concept and structure, and always stably and highly The present invention relates to a method for obtaining purified treated water. [Conventional technology] The newest method for treating organic wastewater such as human waste is as follows: human waste → non-dilution biological nitrification and denitrification → ultrafiltration → Fe ³⁺ addition flocculation treatment → ultrafiltration → activated carbon adsorption → This is a process called treated water and is called membrane separation method. This membrane separation method has the extremely important advantage that solid-liquid separation of activated sludge and coagulated flocs is always perfect and maintenance is easy.
It is very much in the spotlight. [Problems to be Solved by the Invention] However, even with such a new membrane separation method, the following serious problems remain unsolved, and there is a strong need for the development of an even better treatment process. That is, remaining in biological nitrification and denitrification treated water.
A large amount of FeCl ₃ injection rate (2000 to 3000 mg/) is required to coagulate and remove COD, chromaticity, and PO ₄ ^3- , which inevitably leads to the use of difficult-to-dehydrate substances mainly composed of Fe(OH) ₃ and FePO ₄ . The amount of flocculated sludge generated increases. As a result, equipment costs and operating costs for the sludge treatment process increase. Since two steps of solid-liquid separation using an ultrafiltration membrane are required, equipment costs and running costs for solid-liquid separation are high. For example, the running cost of the ultrafiltration membrane separation process, including the two stages, is extremely high at 500 to 600 yen per kiloliter of human waste, which significantly increases the cost burden on the user. The purpose of the present invention is to completely solve these serious drawbacks of the membrane separation method, and specifically, to significantly reduce the amount of flocculated sludge generated and streamline the sludge treatment and disposal process. To apply an ultrafiltration membrane only to solid-liquid separation of activated sludge, making it unnecessary to install an ultrafiltration membrane for solid-liquid separation of flocculated sludge. In other words, the equipment cost and running cost of the ultrafiltration membrane process should be halved compared to conventional methods. Conventional membrane separation methods remove phosphoric acid from human waste.
Although FePO ₄ had to be disposed of as sludge and could not be used effectively, a method should be established to recover the phosphoric acid content in a form that can be easily used effectively as fertilizer. These are the issues to be solved. [Means for Solving the Problems] The present invention involves adding and mixing a magnesium-based alkaline agent and a polymer flocculant to organic wastewater, followed by solid-liquid separation, and subjecting the resulting separated liquid to biological nitrification and denitrification treatment. A Fe ³⁺ -based or Al ³⁺ -based flocculant is added to the microbial slurry that is processed in the process and flows out of the process or from the process to cause flocculation, the flocculated slurry is separated by a membrane, and the separated concentrated slurry is This method of treating organic wastewater is characterized in that a part of the wastewater is returned to the biological nitrification and denitrification process, and the remaining part is mixed with the organic wastewater. [Function] The function of the present invention will be described in detail below with reference to the drawings showing one embodiment of the present invention. Surplus concentrated slurry 2, which will be described later, is added to the carried human waste 1.
After adding and mixing, a magnesium-based alkaline agent 3 (preferably using Mg(OH) ₂ ) is added, and a polymer flocculant 4 (preferably a cationic polymer) is added and mixed to form a floc. The flocs are separated by a wedge wire screen 5 (preferably a rotary screen with an opening of about 0.5 mm). The properties of the floc produced by adding and mixing excess concentrated slurry 2, magnesium-based alkaline agent 3, and polymer 4 to human waste 1 are as follows:
Crystalline formed by the reaction of PO ₄ ^3- and NH ₄ ⁺ with Mg ²⁺
The NH ₄ MgPO ₄ particles, the fibers in the human waste 1, and the SS are integrated into a product with high strength and good dewatering properties.The screen-separated sludge 6 separated by the wedge wire screen 5 is Mechanical dehydrators such as U-Press dehydrator and belt press dehydrator 7
Dehydrated cake with low moisture effectively by
65% or less is obtained). This dehydrated cake 8 has a low moisture content, is easy to handle, and has a high phosphoric acid content, so it can be effectively used as fertilizer. On the other hand, with wedge wire screen 5, SS, SS
The screen separated liquid 9 from which most of the BOD and PO ₄ ^3- have been removed (approximately 80 to 90%) is subjected to an undiluted biological nitrification and denitrification treatment process 10 (known batch type, nitrification liquid circulation type). ) to perform nitrification and denitrification treatment, and remove the nitrogen components in the screen separation liquid.
Biologically removes BOD components etc. In this process, a small amount of PO ₄ ^3- remaining in the screen separation liquid 9 is also taken up by the activated sludge and removed. Next, activated sludge slurry 11 flowing out from biological nitrification and denitrification treatment process 10 contains Fe ³⁺ or Al ³⁺
System flocculant 12 (FeCl ₃ or polyferric sulfate,
Alum, PAC is preferably used) to aggregate the non-biodegradable COD components and colloidal particle components contained in the activated sludge slurry 11.
Complete solid-liquid separation is carried out by feeding the membrane module 13 equipped with an ultrafiltration membrane, precision membrane, etc. (preferably a tubular or flat membrane type ultrafiltration module with a molecular weight cut-off of about 40,000 to 100,000). Then, it is separated into completely clear membrane permeated water 14 with zero SS and concentrated slurry 15. Most of the concentrated slurry 15 separated by the membrane module 13 is recycled to the biological nitrification and denitrification treatment step 10, but the remaining surplus concentrated slurry 2 is mixed with human waste 1 as described above. death,
It is made to aggregate with SS etc. in human urine. As described in the above embodiments, the gist of the technical idea of the present invention is (a) adding a magnesium-based alkaline agent and a polymer to a mixed liquid of organic wastewater and membrane-separated surplus concentrated slurry; Agglomerated floc and NH ₄ MgPO ₄
Point of solid-liquid separation of particles (b) After undergoing biological nitrification and denitrification treatment of the liquid whose PO ₄ ^3- concentration and SS have been significantly reduced through such pretreatment, Fe ³⁺ or Al ³⁺ The concept can be summarized as a combination of two technologies: flocculation treatment using a system flocculant and membrane separation. [Example] Human waste brought to the Shiga Prefecture Group I sanitary plant,
The surplus of concentrated activated sludge separated by a tubular type membrane module equipped with an ultrafiltration membrane (described later) is mixed, 1000 mg/Mg(OH) ₂ is added, stirred for 2 to 3 minutes, and then EVAGROWTH is used as a cationic polymer. C104G [Ebara Infilco Co., Ltd. product name] from 200
When 250mg was added, huge flocs were rapidly formed. Thereafter, when the mixture was fed to a rotating wedge wire screen with an opening of 0.5 mm, the flocs were easily separated, and a screen-separated liquid having the water quality shown in Table 1 was obtained.

[Table] This screen separated liquid was treated without dilution using a known nitrification liquid circulation type biological nitrification and denitrification treatment process. The operating conditions at this time were set as shown in Table-2.

[Table] Next, 1600 mg/FeCl ₃ was added to the activated sludge slurry flowing out from the reaeration tank at the final stage of this biological nitrification and denitrification treatment process, and the pH was adjusted to 5.0 with NaOH.
After adjusting the temperature to ~5.2 and stirring for 2 minutes, the mixture was supplied at a flow rate of 1.5 m/sec to a tubular module equipped with an ultrafiltration membrane made of polyolefin with a nominal molecular weight cutoff of 100,000, and cross-flow filtration was performed.
As a result, the permeation flow rate (Flux) of the ultrafiltration membrane is 1.4
m ³ /m ² - membrane area/day, and the quality of the membrane permeate water is:
As shown in Table 3, the results were extremely good.

[Table] On the other hand, most of the concentrated activated sludge separated by this membrane separation was recycled to the biological nitrification and denitrification treatment process, and the remaining surplus was mixed with the human waste to be treated. In addition, the separated sludge discharged from the above-mentioned rotating wedge wire screen installed at the front stage of the biological nitrification and denitrification treatment process was collected with a diameter of 300 mmφ and a length of 1.5 m.
When it was dehydrated using a screw press dehydrator, it was dehydrated very effectively and a cake with a moisture content of 63 to 65% was obtained. [Effects of the invention] Most of the PO ^43- in organic wastewater is removed in advance.
After removing it as NH ₄ MgPO ₄ , PO ₄ ^3- is further incorporated into activated sludge and removed in the biological nitrification and denitrification treatment process, so the Fe ³⁺ flocculant added afterwards becomes PO ₄ ^3- It is not consumed for the removal of COD, chromaticity, etc. As a result, the required amount of Fe ³⁺ flocculants such as FeCl ₃ is reduced to about 2/3 compared to the conventional membrane separation method mentioned above, and the amount of sludge generated is also reduced, making it easier to treat and dispose of sludge. Processes can be streamlined. After biological nitrification and denitrification treatment of organic wastewater to which a magnesium-based alkaline agent has been added
As a result of adding a Fe ³⁺ type or Al ³⁺ type flocculant to perform the flocculation treatment, the amount of alkaline agent used in the flocculation process can be significantly reduced. That is, the magnesium-based alkaline agent performs two functions: removing PO ₄ ^3- and acting as a PH regulator for the coagulation process. The membrane separation process is only one step, and the running cost and initial cost of the membrane separation process are halved compared to conventional membrane separation methods. PO ₄ ^3- and organic matter in organic wastewater are
Since it is recovered as a low-moisture organic sludge dewatered cake containing a high concentration of NH ₄ MgPO ₄ , phosphorus,
Organic matter can be used as a resource for fertilizers, etc., an important effect that cannot be obtained with conventional membrane separation methods.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the present invention. 1... Human waste, 2... Excess concentrated slurry, 3... Magnesium-based alkaline agent, 4... Polymer, 5... Wedge wire screen, 6... Screen separated sludge, 7...
Mechanical dehydrator, 8... Dehydrated cake, 9... Screen separated liquid, 10... Biological nitrification and denitrification treatment process, 11
...Activated sludge slurry, 12...Fe ³⁺ type or Al ³⁺ type flocculant, 13... Membrane module, 14... Membrane permeated water, 1
5... Concentrated slurry.

Claims (1)

[Claims] 1 After adding and mixing a magnesium-based alkaline agent and a polymer flocculant to organic wastewater, solid-liquid separation is performed, and the resulting separated liquid is treated in a biological nitrification and denitrification treatment process, and the process is carried out within or during the process. A Fe ³⁺ -based or Al ³⁺ -based flocculant is added to the microbial slurry flowing out to cause flocculation, the flocculated slurry is membrane-separated, and a part of the separated concentrated slurry is passed through the biological nitrification and denitrification treatment step. 1. A method for treating organic wastewater, which comprises returning the wastewater to a wastewater source and mixing the remainder with the organic wastewater.