JPH02172596A - Treatment of organic sewage - Google Patents

Abstract

PURPOSE:To suppress the foaming in a biological nitrifying and denitrifying process by supplying a part of powdery activated carbon coexisting flocculated sludge separated by adding a flocculant to membrane transmitted water to the biological nitrifying and denitrifying process. CONSTITUTION:Residue removed excretion 1 is nitrified and denitrified in a non-dilution biological nitrifying and denitrifying process 2 and BOD is also removed simultaneously to form an activated sludge slurry 3 which is, in turn, subjected to membrane separation in a solid-liquid separation process 4 to be separated into conc. activated sludge 5 and membrane transmitted water 6 while the greater part of the conc. activated sludge 5 is returned to the process 2 and a part 8 thereof is sent to a sludge dehydration process 9. The membrane transmitted water 6 is supplied to a mixing tank and an iron or aluminum type flocculant 10 is added to said transmitted water 6 and, further, powdery activated carbon 12 is added thereto to perform mixing in a contact tank 13 and a powdery activated carbon coexisting flocculated slurry is separated under an acidic pH condition in a solid-liquid separation process 4 and a part of said slurry remains in the contact tank 13 to be supplied to the process 2 to obtain highly treated water 16. By this method, foaming is not almost generated in the biological nitrifying and denitrifying process and a defoaming agent can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for treating human waste, septic tank sludge, wastewater sewage from landfills, and other organic sewage containing a large amount of nitrogen components, including biological nitrification and denitrification treatment. When processing through the processing process,
The present invention relates to a method for treating organic wastewater that can suppress foaming in a biological nitrification and denitrification treatment process and stably obtain extremely highly purified treated water.

[Conventional technology]

Nitrogen, phosphorus, BOD, COD, chromaticity, etc. of sewage, etc.
The most typical conventional treatment method for treating organic wastewater containing a large amount of SS is the process shown in FIG. 2, which is actually widely used.

This process is called a "high-load denitrification process."

However, in this process, foaming is intense in the non-nitrification-denitrification process, so it is impossible to perform biological nitrification-denitrification treatment without adding a large amount of antifoaming agent. Also,
Since a precipitation method is used for solid-liquid separation after the treatment, SS carryover is likely to occur. Furthermore, an activated carbon adsorption tower is required for the final treatment, and an activated carbon regeneration furnace is therefore essential, which has the major drawbacks of complicated maintenance and a high equipment ratio.

Therefore, very recently, a solid-liquid separation method using ultrafiltration membranes (UP membranes) or microfiltration membranes (MF membranes) has been developed, and a method of treating organic wastewater using this method has been adopted at several actual facilities. It looks like this.

The method for treating organic wastewater using this membrane separation method is as follows.
It is called ``UF membrane separation phosphorus adsorption process'', and the process is the same as shown in Figure 3, and there is no precipitation step at all.
It has the characteristic that it is much easier to maintain and manage than before.

However, even in this UP membrane separation phosphorus adsorption process, a large amount of antifoaming agent is required in the non-dilution biological nitrification and denitrification treatment process, the antifoaming cost is high, and an activated carbon adsorption tower and activated carbon regeneration furnace are required. This process is similar to the high-load denitrification process described above, and no improvements have been made in these aspects.

Moreover, in this process, in the case of non-dilution treatment of human waste, the PO4''- concentration of purified water flowing from the activated carbon adsorption tower to the PO4'-adsorption removal process is 600 to 800 tpq/
Since the PO43 adsorption and removal process is extremely high, even if an adsorbent with a considerably large PO43 adsorption capacity, such as a zirconium oxide adsorbent, is used in the PO adsorption removal process, regeneration must be performed extremely frequently, such as once every few days. However, there was a serious drawback in that not only the maintenance and management became extremely complicated, but also the disposal of recycled waste liquid was required.

[Problem to be solved by the invention]

The object of the present invention is to fundamentally solve the drawbacks of the prior art, and specifically, the following points are the object of the invention.

(11) To develop and establish a non-foaming biological treatment method that eliminates or greatly reduces the need to add antifoaming agents to the biological nitrification and denitrification treatment process. To reduce drug costs to zero or to a minimum.

(2) Eliminating the need for the conventionally used activated carbon adsorption tower and activated carbon regeneration furnace. This not only reduces construction costs and equipment costs, but also simplifies processes and facilitates maintenance.

(3) To eliminate the need for the process of adsorption and removal of P □, 3- ions, which not only reduces running costs but also eliminates the need for the process of disposing of adsorbent regeneration waste liquid.

[Means to solve the problem]

The present invention subjects organic wastewater to biological nitrification and denitrification treatment, and then membrane-separates the activated sludge slurry from the biological nitrification and denitrification treatment process using an ultrafiltration membrane or a precision filtration membrane. At least a part of the obtained concentrated activated sludge is returned to the biological nitrification and denitrification treatment process, and after adding an iron or aluminum-based flocculant to the membrane permeated water obtained by the membrane separation, powdered activated carbon is added. While adding and mixing, solid-liquid separation is performed while maintaining the pH under acidic conditions to obtain clear treated water, at least a portion of the separated flocculated sludge coexisting with powdered activated carbon is subjected to the biological nitrification and denitrification treatment step. A method for treating organic wastewater characterized by supplying organic wastewater.

Hereinafter, the present invention will be described in detail with reference to FIG. 1, which shows a schematic diagram of an apparatus for carrying out the present invention.

The removed human waste 1 is passed through a non-dilution biological nitrification and denitrification treatment step 2 to be nitrified and denitrified, and BOD is also removed at the same time. As the nitrification and denitrification untreated process 2, any known method may be applied, such as a nitrification liquid circulation type, a step flow type, a single type, or an aerobic denitrification type.

The activated sludge slurry 3 flowing out from the biological denitrification untreated process 2 is subjected to a solid-liquid separation process (
In membrane separation step) 4, the sludge is separated into concentrated activated sludge 5 and membrane permeated water 6. Most part 7 of the concentrated activated sludge 5 is returned to the nitrification-denitrification untreated process 2 as return sludge, and a part 8 is led to the sludge dewatering process 9 as a portion corresponding to surplus sludge.

Membrane permeate water 6 has non-biodegradable 00D, chromaticity, PO43-
Since ions and a small amount of organic nitrogen remain, an iron or aluminum flocculant such as ferric chloride, ferric polysulfate, sulfuric acid clay, or polyaluminum chloride is added to mixing tank 1.
1 to the membrane permeated water 6 to form agglomerated flocs under acidic conditions of pH 4 to 5.5, and then powdered activated carbon 12
After adding OO
D, chromaticity 5PO4''-s Obtain extremely clear highly treated water 16 in which organic nitrogen and 88 are highly removed.The amount of iron or aluminum flocculant added is usually 1500 to 3000w.
/I, and the amount of powdered activated carbon added in the above treatment is usually 100 to 800 η/J! , preferably 150 to 500 .mu./2. Further, it is usually sufficient for the mixing time in the contact tank 13 to be 30 to 90 minutes, and the contact tank 13 may be, for example, one using air agitation as shown in the figure or one using mechanical agitation.

Further, in the solid-liquid separation step 14, any of precipitation, filtration, membrane separation, etc. may be adopted, and in the case of Fig. 1, a microfiltration membrane (
MF membrane) was used.

On the other hand, a part 15 of the powdered activated carbon coagulated sludge that has been completely captured and separated in the solid-liquid separation process 14 is returned to the contact tank 13 or membrane permeated water 6, and the other part 15' is the biological nitrification and denitrification treatment process 2. is supplied to In addition, depending on the case, the entire amount of the powdered activated carbon-coexisting flocculated sludge separated in the solid-liquid separation step may be supplied to the biological nitrification and denitrification treatment step 2.

In this way, when the powdered activated carbon-coexisting flocculated sludge was supplied to the biological nitrification and denitrification treatment step 2, there was no or almost no intense foaming in the treatment step 2, and there was no need to add an antifoaming agent or It was found that it was reduced to a large extent. In the above-mentioned conventional process, silicone or alcohol-based defoaming agents are often used as defoaming agents, and the cost of using them is 9 to
The cost used to be very large at 150 yen, but the present invention eliminates this cost at all.

In addition, part 15 of the powdered activated carbon coexisting flocculated sludge was transferred to the mixing tank 1.
1 (the process corresponds to the aggregation treatment process) or contact tank 13
It has also been found that the required amount of flocculant 10 and fresh powdered activated carbon 12 is reduced when added to membrane permeate water 6 in front of the membrane permeate water 6.

In addition, when applying an ultrafiltration membrane or a precision filtration membrane to the solid-liquid separation step 14, when powdered activated carbon coexists, the membrane permeation flux (
It was observed that FAux) was improved by 15-20% and the degree of membrane contamination was also reduced.

In FIG. 1, 17 is a dehydration aid such as a polymer flocculant, 18 is a sludge dewatering cake, 19 is a dewatered filtrate, and 20 is air.

The amount of the powdered activated carbon-coexisting flocculated sludge 15' sent from the solid-liquid separation step 14 to the biological nitrification and denitrification treatment step 2, and furthermore the amount of powdered activated carbon sent to the treatment step 2, is determined by the contact tank 1.
Powdered activated carbon 12 newly added to membrane permeated water 6 before step 3
It is determined by the amount of flocculated sludge 15' and the ratio of flocculated sludge 15 with powdered activated carbon that is added to the membrane permeated water 6 before the mixing tank 11 or the like.

Regarding the amount of the powdered activated carbon coagulated sludge 15' sent to the biological nitrification and denitrification treatment process 2, the amount returned to the nitrification and denitrification bed treatment process 2 is set to V1%, and the amount returned to the flocculation treatment process is set to v2. When, (1) assumes that the amount of sludge generated by the flocculation treatment is aKp・88/E3゜, the amount of powdered activated carbon added is bKg・88/day, and the concentration of the flocculated sludge with powdered activated carbon that is separated in the solid-liquid separation process is If OA Kq@557m5, set the value to OA. On the other hand, V2 can be set to any value. Therefore, (VV/V1) can be varied from about 0.5 to 100, and normally (VJVI) is about 50 to 60.
It is best to set it to a certain degree.

In addition, the amount of powdered activated carbon-coexisting flocculated sludge 15' to be sent to the biological nitrification and denitrification treatment process 2 relative to human waste is, for example, 90.2 to 2.7 to 1 kl of human waste. It can be done to a certain extent.

The powdered activated carbon used in the present invention can be used as it is commercially available, and its particle size has an average particle size of 1.
00 mesh or less is preferable.

[Effect]

In the present invention, when at least a portion of the powdered activated carbon coagulated sludge separated in the subsequent solid-liquid separation step is supplied to the biological nitrification and denitrification treatment step, the foaming phenomenon is significantly suppressed or almost no longer occurs in the same treatment step. . As for the mechanism that causes such an effect, it is unclear what kind of joint effect the powdered activated carbon and flocculating sludge produced by the flocculant are responsible for, but in any case, the addition of the activated carbon causes the above-mentioned effect. occurs noticeably.

In the present invention, the above effects are produced by adding powdered activated carbon or the like to the above-mentioned locations and supplying at least a portion of the resulting powdered activated carbon-coexisting flocculated sludge to the nitrification-denitrification untreated process. , from the viewpoint that powdered activated carbon may be useful in preventing foaming, if fresh powdered activated carbon is added after the flocculant addition step as in the present invention, for example, it is possible to add fresh powdered activated carbon to a biological nitrification-denitrification bed. When added to a treatment step, a high concentration of soluble COD and chromaticity components (COD after agglomeration treatment) of the liquid in the treatment step.

chromaticity)) and powdered activated carbon will come into contact with these CODs.

Because the chromatic component is a high molecular weight component that is difficult to be adsorbed by activated carbon, the COD and chromaticity of the effluent water are 4 to 5 times higher than those of the effluent water of the present invention, when evaluated as a total process. lead to extremely unreasonable results.

Therefore, the method of adding fresh powdered activated carbon to the biological nitrification-denitrification bed treatment process results in an overall water quality improvement that is extremely inferior to that of the present invention.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

However, the present invention is not limited to this example.

EXAMPLE Human waste was treated using an apparatus embodying the present invention as shown in the schematic diagram of FIG.

A non-dilution type biological nitrification-denitrification treatment was performed on the desalted human waste having the water quality shown in Table 1 in the biological nitrification-denitrification bed treatment step 2 while circulating it through the powdered activated carbon-coexisting flocculated sludge 15' described later. . The operating conditions for this process are shown in Table 2. In addition, the added powdered activated carbon coexistence flocculated sludge 15' has a concentration of powdered activated carbon of 200 to 500 with respect to the removed human waste.
7IIP/J! It was designed so that

In this treatment, almost no foaming was observed in this treatment step 2 even without adding an antifoaming agent, and smooth operation was possible.

Table 1 with blank space below: Removal of human waste water quality The permeation flux of the ultrafiltration membrane is 1.9 to 2. Qm3
/m2・day.

Next, when the activated sludge slurry 3 flowing out from the biological nitrification and denitrification bed treatment process 2 was ultrafiltered using a tubular type ultrafiltration membrane (nominal molecular weight cutoff: 100,000), the water quality as shown in Table 3 was obtained. Membrane permeate water was obtained.

Next, ferric chloride was added to the membrane-separated water having the water quality shown in Table 3 above at a concentration of 2500η/cm, and after agglomeration treatment under weakly acidic conditions of pH 4 to 50, powdered activated carbon (KD 500LP-
Ebara Infilco Co., Ltd. products) from 200 to 500 ■/
After adding the powder to a concentration of 2 and air stirring in the contact tank 13 for 60 minutes, the powdered activated carbon co-agglomerated slurry was separated using an ultrafiltration membrane (molecular weight cut off: 100,000). In this solid-liquid separation step 14, extremely clear highly treated water having the water quality shown in Table 4 was obtained.

Note that the permeation flux of the UF membrane in this solid-liquid separation step 14 was 2.5 to 2.62 m37 m2·day.

On the other hand, for comparison, the above-mentioned powdered activated carbon coexisting flocculated sludge 15
If the operation is performed without circulating the nitrification and denitrification process 2 to the biological nitrification and denitrification treatment step 2, the silicone antifoaming agent is constantly added at
If 01Ni/X is not added, foaming will be intense.

It was impossible to drive. In addition, the quality of the ultrafiltration membrane permeate water obtained in membrane separation step 4 is as shown in Table 5.
The quality of the membrane-permeated water obtained by the present invention shown in the table also deteriorated. In addition, the permeation flux of the UP membrane at that time is 1,
66-1, 74 m "7 m" 6 days, and the present invention also decreased.

In addition, when the powdered activated carbon 12 was not added in front of the contact tank 13 and only 2,500 η/bu of ferric chloride was added and membrane separation was performed using the same ultrafiltration membrane, silicone antifoaming agent was constantly added at 200 η/h. If ~300 .mu./2 was not added, foaming would be severe and operation would be impossible. Further, the permeation flux (Flux) of this membrane was 2*O~2-2 mVm''a day and -1, which was also a small value in the present invention.

〔Effect of the invention〕

The present invention has the following effects based on its configuration.

(1) Foaming hardly occurs during the biological nitrification and denitrification treatment process, and the need for antifoaming agents, which were required in large quantities in conventional processes, becomes unnecessary or can be greatly reduced. As a result, running costs are significantly reduced, and since there is no need to add an antifoaming agent, which is an OOD-producing substance, the OOD of the treated water is reduced. In addition, the efficiency of biological nitrification and denitrification reactions is improved and treatment can be performed in a concentrated manner.

(2) activated carbon adsorption tower, activated carbon regeneration furnace, PO-1 adsorption tower,
Since a PO43-adsorbent regeneration device is not required, the treatment process is significantly simplified, construction costs are greatly reduced, and maintenance and management are also facilitated.

(3) The permeation flux in the membrane separation process of activated sludge slurry is improved, and the quality of the water permeated through the membrane is improved.

(4) When a part of the coagulated sludge with powdered activated carbon is added to the membrane permeated water before or after addition of the flocculant, the required amounts of the flocculant and new powdered activated carbon can be reduced.

(5) When an ultrafiltration membrane or a microfiltration membrane is used in the solid-liquid separation step after adding a flocculant to membrane-permeated water, the permeation flux of the membrane is improved.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of an apparatus for carrying out the present invention, and FIG.
The figure shows a flow sheet for a high-load denitrification process, which is the most typical conventional organic wastewater treatment method, and Figure 3 shows a flow sheet for a UP membrane separation phosphorus adsorption process. 1... Removal human waste, 2... Biological nitrification and denitrification treatment process, 3... Activated sludge slurry 4... Membrane separation process,
5... Concentrated activated sludge, 6... Membrane permeated water, 10...
Flocculant, 11... Mixing tank, 12... Powdered activated carbon, 1
3... Contact tank, 14... Solid-liquid separation step, 15.15
'... Powdered activated carbon coexistence flocculated sludge, 16... Treated water

Claims (1)

[Claims] After biological nitrification and denitrification treatment of organic wastewater, the activated sludge slurry from the biological nitrification and denitrification treatment process is subjected to membrane separation using an ultrafiltration membrane or a microfiltration membrane, and the concentrated product obtained by the membrane separation is At least a part of the activated sludge is returned to the biological nitrification and denitrification treatment step, and an iron or aluminum-based flocculant is added to the membrane permeated water obtained by the membrane separation, and then powdered activated carbon is added and mixed. , performing solid-liquid separation while maintaining the pH under acidic conditions to obtain clarified treated water, while supplying at least a portion of the separated flocculated sludge coexisting with powdered activated carbon to the biological nitrification and denitrification treatment step. Characteristic organic wastewater treatment method.