JPH0433519B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an apparatus for rationally treating human waste water such as human waste and septic tank sludge using a novel conceptual configuration and stably obtaining highly purified treated water at all times. . [Prior Art] The most advanced conventional equipment for treating human wastewater is to send the human wastewater together with the gray water to a biological nitrification and denitrification tank, and from there the activated sludge slurry is passed through an ultrafiltration (UF) device. The activated sludge from there is returned to the biological nitrification and denitrification tank, and the separated water from there is subjected to Fe ³⁺ addition flocculation treatment, and the liquid is further sent to an ultrafiltration device. The separated water is subjected to activated carbon adsorption treatment to obtain highly treated treated water, and this is called the UF membrane separation method. This UF membrane separation system has the advantage of being easy to maintain and manage, as the solid-liquid separation of activated sludge and Fe ³⁺ flocs is always perfect and there is no need to worry about the sedimentation of SS. Because of this, it has been attracting a lot of attention recently. [Problems to be Solved by the Invention] However, even this latest UF membrane separation method has the following serious drawbacks, and the development of an even better method is desired. (a) COD contained in activated sludge permeated water through UF membrane,
In order to remove PO ₄ ^3- and chromaticity, an Fe-based flocculant must be added and the produced flocs must be removed by a second UF membrane separator. As a result, two-stage
A UF membrane separation device is required, which significantly increases equipment and operating costs. (b) The activated sludge in the biological nitrification and denitrification tank is diluted because gray water such as sludge dewatering filtrate and floor washing sewage flows into the biological nitrification and denitrification tank and is treated together with human waste water. As the MLSS concentration decreases and the liquid temperature decreases, the nitrification and denitrification reaction rate slows down. As mentioned above, while the latest UF membrane separation method has ensured improved fiber control, the operating and equipment costs are significantly higher than previous methods (for example, the low dilution two-stage activated sludge method). Moreover, it has the serious drawback of decreasing the MLSS of the biological nitrification and denitrification tank and decreasing the nitrification and denitrification rate due to the drop in water temperature, so it cannot be called an ideal treatment device. The purpose of the present invention is to provide a device that completely solves the drawbacks of the conventional UF membrane separation method, and specifically, (1) eliminates the need for two-stage application of the UF membrane separation device; 1
Achieving advanced treatment of human waste with UF membrane separation equipment,
Significantly reduces equipment and operating costs. (2) Preventing the nitrification and denitrification reaction rate from decreasing due to the inflow of gray water. The object of the present invention is to provide a processing device that achieves these two problems and eliminates the drawbacks of the conventional UF membrane separation system. [Means for Solving the Problems] The present invention provides a biological nitrification and denitrification tank into which organic wastewater flows, and a biological nitrification and denitrification tank that is followed by a biological nitrification and denitrification tank in which organic wastewater is introduced. A biological treatment tank is installed to allow activated sludge slurry and gray water to flow into it.
Further, a circulation tank is provided into which the activated sludge slurry from the biological treatment tank flows, and a UF or MF membrane separation device into which the activated sludge slurry from the circulation tank flows is provided, and an intermediate between the biological treatment tank and the UF or MF membrane separation device is provided. is equipped with a chemical injection device for injecting an inorganic flocculant into the activated sludge slurry, a flow path for sending most of the flocculated concentrated slurry separated by the UF or MF membrane separation device to the circulation tank, and a remaining portion of the flocculated concentrated slurry. This organic sewage treatment apparatus is characterized in that it is provided with a flow path for returning the sludge to the biological nitrification and denitrification tank as return sludge. One embodiment of the present invention will be described with reference to FIG. The human waste 1 from which the carried human waste has been removed is supplied to a non-dilution type biological nitrification and denitrification tank 2, and air 5 is sucked from an ejector 4 by a circulation pump 3 having aeration and stirring functions for the slurry in the tank. At the same time, the nitrification and denitrification reaction is carried out. This nitrification and denitrification tank 2
is the main biological reaction tank in the apparatus of the present invention. In the nitrification and denitrification tank 2, more than 95% of the BOD and nitrogen components in the human waste are removed, and in the activated sludge slurry 6 flowing out from the nitrification and denitrification tank 2, trace amounts of BOD and
Contains only nitrogen concentration. The nitrification and denitrification tank may be of any type as long as it can perform biological nitrification and denitrification treatment, and may be either a batch type or a continuous type, and the continuous type may be of any known type. Next, the activated sludge slurry 6 flowing out from the nitrification and denitrification tank 2 is sent to the biological treatment tank 8 provided next to the nitrification and denitrification tank 2, and the dewatered filtrate discharged from the sludge dewatering process is also sent to this biological treatment tank 8. , let gray water 7 such as car wash sewage and floor washing sewage flow in,
Using the activated sludge of the activated sludge slurry 6,
Pollutant components in gray water 7 are removed biologically. The activated sludge slurry 9 flowing out from the biological treatment tank 8 is guided to the circulation tank 10 and
An inorganic flocculant 11 such as a system, and an alkaline agent 1 for adjusting the pH of the activated sludge slurry to 4 to 5.5 when the pH of the activated sludge slurry becomes too acidic due to the addition of the inorganic flocculant.
2 is added, flocculation treatment is performed in an acidic region, and the flocculated slurry 13 is supplied by a pump to the module of an ultrafiltration (UF) membrane separator 14 at a high flow rate to obtain completely clear UF membrane permeated water 15 with SS zero. and agglomerated concentrated slurry 16 blocked by a UF membrane. As the inorganic flocculant, Fe-based flocculants such as FeCl ₃ are preferred. Most of the flocculation and concentration slurry 16 is circulated to the circulation tank 10, and a portion 17 is used to maintain the activated sludge concentration in the biological nitrification and denitrification tank 2 to a predetermined value (usually 10,000 to 15,000).
mg/degree is adopted. ) will be returned for maintenance. The amount of the flocculated concentrated slurry circulated to the circulation tank 10 is effectively 20 to 70 times, preferably 30 to 40 times, the amount of the flocculated concentrated slurry (return sludge) 17 sent to the nitrification and denitrification tank 2. Note that 18 is surplus sludge, which is supplied to a dehydrator (not shown). In addition, since the pH of the flocculated concentrated slurry 17 is acidic at 4 to 5.5, depending on the water quality of the human waste, especially the magnitude of the M alkalinity, if the flocculated concentrated slurry 17 is continued to be returned to the nitrification and denitrification tank 2, the nitrification and denitrification tank within 2
It is theoretically possible that the pH will decrease and the nitrification and denitrification reaction will be inhibited, so as a safety measure, add alkali to either the inflowing human waste 1, the nitrification and denitrification tank 2, or the flocculated concentrated slurry (return sludge) 17. It is preferable to provide a device for injecting the agent. In the illustrated example, an alkali agent injection device 20 is provided in the return sludge flow path. Therefore, completely clear UF membrane permeated water from the UF membrane separation equipment, that is, highly treated human waste water15
can be discharged as is, but if necessary, COD and chromaticity may be further removed using an activated carbon adsorption tower 19. In addition, the excess sludge 17 is dehydrated using a filter press,
When a dehydrator with a case filtration function is used, such as a filter with a filter cloth as a filter element, cake filtration is performed because the inorganic flocculant is contained in the excess sludge, and the dehydrated separated water becomes clear. This separated water does not need to be subjected to biological treatment, so there is no need to send it as gray water to the biological treatment tank 8 for biological treatment. The power required for this can be significantly reduced. An MF membrane separation device using an MF membrane can be used instead of the UF membrane separation device. To summarize the technical ideas in the configuration of the present invention as described above, (1) gray water is not allowed to flow into the nitrification and denitrification tank, (2) a biological treatment tank is provided following the nitrification and denitrification tank,
(3) A circulation tank is installed following the biological treatment tank and flocculation treatment is performed using an inorganic coagulant; (4) Gray water is supplied to the biological treatment tank for biological treatment; A part of the circulated flocculated concentrated slurry is separated and supplied to the nitrification and denitrification tank, which is organically combined. [Function] In the present invention, gray water is not allowed to flow into the nitrification-denitrification tank 2, thereby preventing a decrease in the activated sludge concentration and water temperature in the nitrification-denitrification tank 2. The biological treatment tank 8 has an extremely important function, and by receiving gray water into it, it produces the action in the nitrification and denitrification tank described above, and also causes the activated sludge slurry 6 flowing out from the nitrification and denitrification tank 2 to Trace amount of residual nitrogen component (usually 40mg/or less)
In addition to further removing pollutants from gray water, it also biologically removes pollutants from gray water. Further, since an inorganic flocculant is added to the activated sludge slurry 9 flowing out from the biological treatment tank 8 in the circulation tank 10, and the flocculated concentrated slurry is added thereto by circulation, separation by the UF membrane separation device becomes easy. [Example] The following conditions were set for the processing apparatus shown in FIG. (1) Nitrification and denitrification tank MLSS = 12,000 to 13,000 mg/ Days of human waste retention: 10 days Stirring and aeration method: Pump circulation and suction with air ejector (2) Biological treatment tank MLSS = 9,000 to 9,500 mg/ Number of days of residence: 1 day Gray wastewater inflow Amount 0.5Q (The amount of human waste treated is Qm ³ /day) (3) Circulation tank capacity 0.05Q PH automatic control device installed FeCl ₃ , NaOH chemical injection point installed Coagulation PH 4 to 5 Controlled circulation volume of coagulated concentrated slurry 20Q (4) UF membrane separation device Model: Tubular type, cross-flow filtration method UF material: Polyacrylonitrile molecular weight cutoff
50000 (nominal value) Liquid flow rate in module 2.5m/sec Permeation flow rate 1.2m ³ /m ² / membrane / day UF membrane separation slurry Solids concentration 20Kg / m ³ Return flow rate of UF membrane separation slurry to nitrification and denitrification tank 0.6 ~0.7Qm ³ /day Under the above design and operating conditions, the treated human waste with the water quality shown in the table below was treated.

【table】

[Table] Activated sludge slurry flowing out from the nitrification and denitrification tank and the amount of water 0.5Q (BOD400~500mg/, T-N50~100
mg/) of gray water (various washed sewage and sludge dewatering filtrate) is flowed into a biological treatment tank and subjected to biological treatment through repeated anaerobic and aerobic treatment. Add 2000 to 2500 mg of FeCl ₃ and 500 mg of NaOH to the sludge slurry.
~600mg/was added, subjected to agglomeration treatment under conditions of PH4 to 5, and then supplied to a UF membrane separator. As a result,
The quality of the water permeated through the UF membrane was extremely purified as shown below.

〔Effect of the invention〕

The present invention has the following effects. (1) SS, BOD,
COD, chromaticity, and PO ₄ ^3- are well removed, resulting in extremely clear highly treated water. Therefore, it is not necessary to use two stages of UF membrane separation equipment, and only one stage is sufficient. (2) Since gray water does not flow into the biological nitrification and denitrification tank, there is no dilution of the activated sludge MLSS concentration in the tank, and there is no drop in water temperature, so the nitrification and denitrification reaction does not decrease and biological treatment goes smoothly. It will be held in (3) Instead of circulating most of the UF membrane-separated slurry to the nitrification and denitrification tank as in the past, most of the flocculated and concentrated slurry separated by the UF membrane separation device is placed subsequently in the biological treatment tank. Since the slurry is circulated through the nitrification and denitrification tank and only a portion is circulated to the nitrification and denitrification tank, there is no possibility of a drop in the pH of the liquid in the nitrification and denitrification tank due to the inflow of coagulated and concentrated slurry with a low pH. . Therefore, the nitrification and denitrification reaction does not deteriorate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a processing apparatus of the present invention. 1... Human waste, 2... Biological nitrification denitrification tank, 7... Gray water, 8... Biological treatment tank, 10... Circulation tank, 11
...Inorganic flocculant, 14...UF membrane separation device.

Claims (1)

[Claims] 1. A biological nitrification and denitrification tank into which organic sewage flows, and a biological treatment tank which follows the biological nitrification and denitrification tank into which activated sludge slurry and gray water from the biological nitrification and denitrification tank flow. Furthermore, a circulation tank is provided into which the activated sludge slurry from the biological treatment tank flows, and a UF or MF membrane separation device is installed into which the activated sludge slurry flows from the circulation tank, and the biological treatment tank and the UF or MF membrane are separated. A chemical injection device for injecting an inorganic flocculant into the activated sludge slurry is provided in the middle of the device, and a flow path for sending most of the flocculated concentrated slurry separated by the UF or MF membrane separation device to the circulation tank and a flow path for feeding the flocculated concentrated slurry An apparatus for treating organic wastewater, comprising: a flow path for returning the remaining portion to the biological nitrification and denitrification tank as return sludge.