JPH0310397B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention uses a novel concept and structure to rationally treat human waste water such as human waste and septic tank sludge, and to produce highly purified treated water. The present invention provides a method for stably obtaining . Furthermore, the present invention provides a novel method that can very rationally treat sludge and gray water generated during the treatment of human waste water. [Prior Art] The most advanced conventional method for treating human waste water has the system configuration shown in Figure 2, in which an ultrafiltration membrane (UF membrane) is used in ultrafiltration. It is called UF membrane separation method.
This UF membrane separation method always completely separates activated sludge and flocculated flocs, and there is no need to worry about the sedimentation of SS (activated sludge, etc.), making it easy to maintain and manage. It is attracting a lot of attention as a human waste disposal method. [Problem to be solved by the invention] However, as a result of the technical evaluation of the latest UF membrane separation method described above by the present inventor by setting various evaluation items, the following serious drawbacks were found. It has become clear that this method cannot be called an ideal human waste disposal method for users. That is, (1) Ultrafiltration (UF) separation of activated sludge FeCl ₃ was added to the permeate water in order to remove non-biodegradable COD, PO ₄ ^3- and chromaticity contained in the permeate water. The agglomerated flocs formed by
Must be removed using a UF membrane separator. As a result, a two-step UF membrane separation process is required.
The operating and equipment costs of the UF membrane separation process are extremely high. (2) Because gray water such as sludge dewatering filtrate and on-site washing sewage is treated by flowing into the biological nitrification and denitrification process along with human waste, the activated sludge MLSS concentration in the biological nitrification and denitrification tank is low. It is diluted by gray water and the MLSS concentration decreases. Moreover, the water temperature in the biological nitrification and denitrification tank decreases due to the inflow of gray water, resulting in a decrease in the nitrification and denitrification reaction. (3) The running cost is high because the dewatering method for excess activated sludge and flocculated sludge requires a large amount of dewatering aids such as cationic polymers. As mentioned above, the UF membrane separation method, which was previously recognized as the most advanced human waste treatment method, has easier maintenance and management, but the initial cost and running cost are lower than previous treatment methods (for example, low dilution two-stage). This method is significantly more expensive than the activated sludge method (activated sludge method), and cannot be called an ideal method at all. The purpose of the present invention is to accurately eliminate the serious drawbacks of the above-mentioned UF membrane separation method, and specifically, (a) eliminate the need for two stages of UF membrane separation process, and perform only one stage of UF separation; Achieving advanced treatment of human waste in the process,
Significantly reduces equipment and operating costs for the UF separation process. (b) Accurately prevent the reaction rate of the biological nitrification and denitrification process from decreasing due to the inflow of gray water. (c) Significantly streamline the sludge dewatering process and reduce the amount of dewatering aid required. It also reduces the moisture content of the dehydrated cake. This provides a method for solving the problems in sections (a) to (c). [Means for Solving the Problems] The present invention treats night soil wastewater from which human waste has been removed in a first biological nitrification and denitrification step, and removes the activated sludge slurry flowing out from the step, the human waste and the solid liquid described below. The gray water such as the filtrate obtained by dewatering the mixture of flocculated activated sludge from the separation process is treated in a second biological nitrification and denitrification process, and the active sludge flowing out from the second biological nitrification and denitrification process is Adding an inorganic flocculant to the sludge slurry, further mixing the flocculated activated sludge circulated from the solid-liquid separation process described below, and separating this mixture in a solid-liquid separation process using an ultra- or microfiltration membrane under acidic conditions, Most of the flocculated activated sludge separated in the solid-liquid separation step is circulated to be introduced into the activated sludge slurry to which an inorganic flocculant has been added before the solid-liquid separation step, and a portion of the remainder is This is a method for treating night soil wastewater, which is characterized in that it is returned to the biological nitrification and denitrification process in step 1, and the remaining residue is mixed with the sludge and led to the sludge dewatering process. One of the features of the present invention is that before dewatering excess flocculated activated sludge that has been flocculated in advance with an inorganic flocculant, it is mixed with sludge and then a commonly used dewatering aid is added to it. It is to be. This method has the great effect of lowering the water content of the sludge dewatering cake obtained by the dewatering and reducing the amount of the dewatering aid added. As the inorganic flocculant used in the present invention, iron-based flocculants such as FeCl ₃ are most preferable. Aluminum-based flocculants can also be used, but are less effective than iron-based flocculants. [Function] The function of the present invention will be explained with reference to FIG. 1 showing one embodiment of the present invention. The human waste 1 carried into the human waste treatment plant is supplied to a human waste separator 2 such as a fine mesh screen or centrifugal separator to remove coarse solids such as paper and hair (these are called "human waste"). is removed and separated into human waste 3 and removed human waste 4. The residue 3 is sent from the solid-liquid separation process described below.
Excess activated sludge flocculated by inorganic flocculant 5
(This is referred to as "agglomerated surplus sludge") is sufficiently mixed in the mixing tank 6 (which also serves as a storage tank for the flocculated surplus sludge 5), then a dewatering aid 7 such as a cationic or nonionic polymer flocculant is added. and sludge dewatering machine 8
and is separated into a low-moisture dewatered cake 9 with a water content of 60 to 66% and a sludge dewatered filtrate 10. The most suitable sludge dehydrator 8 is a screw press, which does not require filter cloth washing water. The removed human waste 4 is supplied from the storage tank 11 to a non-dilution biological nitrification and denitrification treatment tank 12 (hereinafter referred to as the "main biological reaction tank"), and is treated with nitrifying bacteria, denitrifying bacteria, etc. that are present in high concentration in the tank. BOD, by microorganisms of
More than 90% of COD and nitrogen components are removed.
A portion 13 of the flocculated activated sludge from the solid-liquid separation process described later is circulated to the main biological reaction tank 12. The type of biological nitrification and denitrification reaction in the main biological reaction tank 12 may be any of the known types, such as the known nitrification liquid circulation type, intermittent aeration type, and combined type of intermittent input of human waste and DO control in the tank. type can be applied. Figure 1 Intermittent input of human waste (usually 2 to 3 times)
(once per hour) and DO control combination type. In this way, the first biological nitrification and denitrification step is performed. The gray water mainly consisting of the activated sludge slurry 14 and the sludge dewatering filtrate 10 flowing out from the main biological reaction tank 12 is transferred to the biological nitrification and denitrification tank 15 in order to perform the second biological nitrification and denitrification process. (hereinafter referred to as "byproduct reaction tank"), the N components, BOD components, and sludge components in the gray water that remain in the activated sludge slurry 14 are removed biologically to a high degree. The byproduct reaction tank 15 shown in FIG. 1 is preferably of a type in which nitrification and denitrification proceed through intermittent aeration, but it is not limited thereto. In addition, by-product reaction tank 15
The volume of is smaller than the volume of the main biological reaction tank 12,
It is usually about 1/4. After that, FeCl ₃ 17 and NaOH 18 are added to the activated sludge slurry 16 flowing out from the by-product reaction tank 15.
PH4 to 5.5 in coagulation mixing tank/circulation tank 19
flocculate under acidic conditions. At this time, most of the flocculated activated sludge 23 from the solid-liquid separation process described later is circulated to the circulation tank 19 and used as seed crystals for the flocculation reaction. The activated sludge slurry coagulated in the circulation tank 19 is
Through the pump and the UF membrane separator 20, SS,
It is separated into membrane-permeable water 21, in which COD, PO ₄ ^3- , and chromaticity have been highly removed and whose pH is acidic, and flocculated activated sludge 22 . A UF membrane having a molecular weight cut-off of 50,000 or more is suitable. In addition, the separation device 20 has UF
Microfiltration (MF) membranes may be used instead of membranes.
The obtained membrane permeated water 21 is highly purified and is highly treated human waste water. Coagulated activated sludge 2 obtained by UF membrane separation device 20
Most of the activated sludge 22 is circulated to the circulation tank 19, and the proportion thereof is usually 80% or more of the flocculated activated sludge 22. On the other hand, a part of the flocculated activated sludge 22 is supplied to the main biological reaction tank 12 as return sludge 13, and the other part is sent to the mixing tank 6 as flocculated surplus sludge 5.
Mixed with residue 3. Note that it is effective to add an alkali such as NaOH to the returned sludge 13 to improve microbial activity. [Example] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto. Example 10 Kl of human waste/
Processed the day. (1) Night soil removal device Rotary wedge wire screen with opening of 0.5 mm (drum type) (2) Main biological reaction tank Non-diluted nitrification liquid circulation type MLSS: 12,000 to 14,000 mg/Natural waste retention period: 9 days Nitration liquid circulation amount : ^30m3 /day Water depth: 10m (3) By-product reaction tank Nitrification liquid circulation type MLSS: 7000-8000mg/Natural urine retention period: 1.5 days (4) Coagulation mixing tank and circulation tank _FeCl3 supply amount for human waste: 2500- 2800mg/ PH adjustment: Automatic control to PH4-5.5 with NaOH: PH electrode installation for automatic control (electrode automatic cleaning type) Coagulation activity from UF membrane separation device Sludge circulation flow rate: 400m ³ /day Tank capacity: 500 (5) UF membrane separator tubular cross-flow filtration type Pipe flow velocity: 2m/sec UF membrane nominal molecular weight cutoff: 50000 UF membrane material: Polyolefin Permeation flux: 1.7m ³ /m ² / membrane / day (6) Sludge / Dehydration equipment for sludge mixture Screw press type dehydrator Screw rotation speed: 1.5 rpm (7) Dehydration aid Cationic polymer (Evagrowth C104G) Polymer injection rate: 0.5 to 0.5 to sludge/sludge mixture
0.6% to SS As a result of continuous operation for three months under the above conditions, the excellent treatment results shown in the table below were obtained.

〔Effect of the invention〕

According to the present invention, the following effects are achieved. (1) With only one step of UF membrane separation process, advanced treatment of human waste can be achieved. (2) By not allowing gray water to flow into the first biological nitrification and denitrification process, the reaction rate of the biological nitrification and denitrification reaction in this process does not decrease and can be maintained at a high rate. (3) By coagulating excess sludge and mixing residue,
It facilitates the dewatering of flocculated excess sludge, thereby reducing the amount of dewatering aid required and yielding a dewatered cake with low moisture content.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of an apparatus for carrying out one embodiment of the present invention, and FIG. 2 shows a flow sheet of the most advanced conventional human waste wastewater treatment method. Codes in the figure: 1... Human waste, 2... Human waste separator, 3
... night soil, 4 ... removed human waste, 5 ... flocculated excess sludge, 8 ... sludge dehydrator, 12 ... main biological reaction tank,
15... Byproduct reaction tank, 16... Activated sludge slurry, 17... Inorganic flocculant, 19... Coagulation mixing tank/circulation tank, 20... UF membrane separation device, 21... Membrane permeate liquid, 22... Coagulated activated sludge.

Claims (1)

[Claims] 1 The night soil wastewater from which the human waste has been removed is treated in the first biological nitrification and denitrification process, and the activated sludge slurry flowing out from this process and the mixture of the human waste and the flocculated activated sludge from the solid-liquid separation process described below are treated. Gray water such as dehydrated filtrate is treated in a second biological nitrification and denitrification process, an inorganic flocculant is added to the activated sludge slurry flowing out from the second biological nitrification and denitrification process, and further solid-liquid as described below is added. The flocculated activated sludge circulated from the separation process is mixed, this mixture is separated in a solid-liquid separation process using an ultra- or microfiltration membrane under acidic conditions, and the size of the flocculated activated sludge separated in the solid-liquid separation process is A portion is circulated to be introduced into the activated sludge slurry to which an inorganic flocculant is added before the solid-liquid separation step, and a portion of the remaining portion is returned to the first biological nitrification and denitrification step; A method for treating night soil wastewater, which comprises mixing the remainder with the sludge and introducing the mixture to a sludge dewatering step.