JPH1066997A - Treating device for high concentration chlorine-containing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and efficiently perform a nitrification/denitrification treatment by providing a nitrification/denitrification device for a high concentration chlorine- containing waste water, a desalting device for desalting a part of the treated water and a means for returning a part of the treated water to the nitrification/denitrification device to prevent the nitrification hindrance due to the salts. SOLUTION: A flowing-in refuse exudation liquid is once stored in an adjusting tank, pumped-up into a calcium removing equipment, where ferric chloride, a high molecular flocculant or the like is poured therein, is adjusted to pH10 and the formed calcium carbonate is sedimented and removed. A desalted water is mixed therewith to be diluted, a BOD or COD component is removed in the nitrification/denitrification equipment and phosphoric acid, sodium hydroxide, methanol or the like is poured. Next, the residual COD or chromaticity component is removed in a flocculation separation equipment, SS is removed in a sand filtration equipment, the COD or chromaticity component is highly removed in an activate carbon adsorption equipment, desalting is executed in a desalting equipment, a part is returned to the nitrification/ denitrification equipment and the residual is disinfected with chlorine in a disinfection equipment and discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for treating wastewater containing high-concentration salts, and more particularly, to a high-concentration salt such as landfill wastewater (hereinafter referred to as "waste leachate") flowing out of a landfill for waste incineration ash. The present invention relates to an apparatus for efficiently denitrifying wastewater by avoiding biological inhibition by salts.

[0002]

2. Description of the Related Art FIG. 3 shows a typical example of a conventional refuse leachate treatment apparatus. That is, in the related art, the leachate is generally treated in the following procedure.

[0003] (1) The incoming leachate is temporarily stored in a regulating tank. (2) Pump up the liquid in the adjustment tank, inject sodium carbonate, ferric chloride, polymer flocculant (polymer), etc. in the calcium removal equipment, adjust the pH to about 10,
The generated calcium carbonate is precipitated and removed. (3) Various types of nitrification denitrification equipment such as activated sludge floating method, contact aeration method, and rotating disk method, remove BOD and COD components and nitrogen. In this nitrification denitrification treatment step, phosphoric acid as nutrients, caustic soda for pH adjustment, methanol as a nutrient source for denitrification, and the like are injected. (4) Coagulation and separation equipment that injects ferric chloride and a polymer to remove COD and chromaticity components that cannot be removed by the nitrification denitrification treatment in the preceding stage. (5) Remove the SS using a sand filtration facility. (6) Activated carbon treatment with activated carbon adsorption equipment to achieve even higher CO
D and chromaticity components are removed. (7) After disinfecting chlorine by adding sodium hypochlorite at the disinfection facility, release it.

[0004] By the way, recent leachate leachate tends to have a high salt concentration depending on the number of years elapsed after landfilling and the amount of rainfall, and in some cases, the salt concentration exceeds 30,000 mg / L and exceeds the seawater concentration level. Is gone.

Japanese Patent Application Laid-Open No. Hei 5-277492 discloses a processing apparatus as shown in FIG. 3 in order to avoid corrosion of pipes and equipment and a biological system caused by leachate having a high salt concentration. It has been proposed that a desalination treatment facility for removing chloride ions by electrodialysis treatment is provided downstream of the activated carbon adsorption facility to reduce the chloride ion concentration in the leachate. In the method described in JP-A-5-277492, calcium removal, nitrification and denitrification, coagulation separation, sand removal, Desalination equipment is provided after the series of processing steps such as filtration and activated carbon adsorption.

[0006]

When a leachate having a high salt concentration is subjected to nitrification denitrification treatment, nitrification is inhibited by salts, and the nitrification does not proceed smoothly, or a very low nitrification activity is obtained. In many cases, high-quality treated water cannot be obtained.

[0007] That is, nitrifying bacteria are present in natural water and soil, and a nitrification denitrification treatment apparatus is established by accumulating and culturing such nitrifying bacteria. Generally, nitrifying bacteria are inhibited from growing when the salt concentration is high, but nitrifying bacteria growing in seawater are halophiles. Therefore, a nitrification denitrification treatment apparatus capable of treating with such a concentration of salts as seawater by accumulating and culturing such nitrifying bacteria has been put to practical use. However, since salt concentrations higher than seawater hardly exist in nature, even nitrifying bacteria acclimated in seawater are inhibited from growing under high salt conditions exceeding seawater, and do not exhibit sufficient nitrification activity.

In the case of nitrifying and denitrifying wastewater containing high concentration of salt, if clear water can be easily obtained as dilution water, the raw water is diluted until its salt concentration becomes substantially equal to that of seawater, thereby stabilizing the water. It is possible to maintain reduced nitrification activity. However, in general, it is not always easy to obtain dilution water, and simply adding dilution water is not preferable because it increases the amount of final treated water.

In the method described in JP-A-5-277492, although a desalination treatment step is provided, the desalination treatment step includes a series of steps including nitrification and denitrification in order to stabilize the treatment. Therefore, the problem of nitrification inhibition cannot be solved because the liquid having a high salt concentration flows into the nitrification denitrification step.

[0010] For these reasons, avoiding the inhibition of nitrification by high-concentration salts has become an important issue in the nitrification and denitrification treatment of leachate in the future.

The present invention has been made in view of the above-mentioned conventional circumstances, and is an apparatus for stably and efficiently nitrifying and denitrifying wastewater having a high salt concentration such as leachate leachate while avoiding inhibition of nitrification by salts. The purpose is to provide.

[0012]

SUMMARY OF THE INVENTION An apparatus for treating wastewater containing high-concentration salts according to the present invention comprises a nitrification-denitrification apparatus for biologically nitrifying and denitrifying wastewater containing high-concentration salts; A desalination treatment device for desalinating at least a part of the treated water, and means for returning at least a part of the treated water of the desalination treatment device to the nitrification denitrification treatment device are provided. .

In the present invention, all or a part of the nitrification denitrified water is desalted, and the raw water is diluted with all or a part of the demineralized water to lower the salt concentration of the raw water. As described above, since the desalinated water is used as the dilution water, stable and efficient nitrification denitrification can be performed without introducing fresh water from outside the system, and without increasing the final treated water amount.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for treating wastewater containing high-concentration salts according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of an apparatus for treating wastewater containing high-concentration salts according to the present invention.

The apparatus for treating wastewater containing high-concentration salts shown in FIG.
A desalination treatment facility is provided downstream of the activated carbon adsorption facility to desalinate the activated carbon adsorption treatment water, return part of the desalination water to the nitrification denitrification treatment facility, and send the remainder to the disinfection facility. However, unlike the conventional device shown in FIG. 3, the other components have the same configuration.

That is, in the treatment apparatus for wastewater containing high-concentration salts shown in FIG. 1, the treatment of leachate is performed in the following procedure.

The incoming leachate is temporarily stored in the adjustment tank. Pump up the liquid in the adjustment tank and inject sodium carbonate, ferric chloride, polymer flocculant (polymer), etc. in the calcium removal equipment, adjust the pH to about 10, and precipitate and remove the generated calcium carbonate I do. The calcium-removed treated water is mixed with diluted demineralized water at the subsequent stage, and the diluted liquid is diluted with various types of nitrification denitrification treatment equipment such as activated sludge floating method, contact aeration method, and rotating disk method. COD components and nitrogen are removed. In this nitrification denitrification treatment step, phosphoric acid as nutrients, caustic soda for pH adjustment, methanol as a nutrient source for denitrification, and the like are injected. This is a coagulation / separation treatment facility that injects ferric chloride and a polymer, and removes COD and chromaticity components that cannot be removed by the nitrification denitrification treatment at the preceding stage. SS is removed by sand filtration equipment. Activated carbon treatment with activated carbon adsorption equipment for even higher COD
And chromaticity components are removed. The activated carbon treated water is desalted in a desalination facility. Part of the demineralized water is returned as dilution water to the introduction side of the nitrification denitrification facility, and the rest is disinfected by adding sodium hypochlorite to disinfect the chlorine and then discharged.

In the present invention, the desalination treatment apparatus includes:
An electrodialyzer or a reverse osmosis membrane separation device can be used.

According to the present invention, the raw water is diluted with this demineralized water to a salt concentration that does not cause nitrification inhibition, and the nitrification denitrification treatment is carried out. There are no particular restrictions on the installation location, the amount of desalinated water, the rate of desalination, the dilution ratio of raw water, and the like.

Therefore, the present invention is not limited to the configuration shown in FIG.

That is, in FIG. 1, the desalination treatment equipment is installed after the activated carbon adsorption equipment, and a part of the desalination water is mixed and diluted with the inflow water of the nitrification denitrification treatment equipment. There is no particular limitation on the installation location of the processing equipment, and another location may be used. However, in general, from the viewpoint of preventing membrane contamination of a reverse osmosis membrane of a reverse osmosis membrane separation device as a desalination treatment device or an ion exchange membrane of an electrodialyzer, a coagulation separation treatment device,
It is preferable to provide it after the sand filtration equipment and the activated carbon adsorption equipment. Further, the dilution with the demineralized water may be performed in an adjusting tank, a piping from the adjusting tank to the calcium removing equipment, or a calcium removing equipment.

Further, only a part of the nitrified denitrified water (the activated carbon treated water in FIG. 1) is subjected to a desalination treatment (in this case, the size of the desalination treatment equipment can be reduced), or the desalination water can be reduced. The whole amount may be used as dilution water.

It is also possible to use any small-sized desalination treatment apparatus and obtain desalted water so as to obtain a desired dilution ratio by adjusting the operation time.

When the treatment apparatus of the present invention is applied to the treatment of dust leachate with the configuration as shown in FIG. 1, the salt concentration varies depending on the salt concentration of the dust leachate to be treated. By adding 30 to 200% of the demineralized water to about 1/20 to 1/10 of the raw water, the water flowing into the nitrification denitrification treatment apparatus has a salt concentration that does not inhibit nitrification, generally, seawater. Lower salt concentration, eg, C
l: 10,000 to 15,000 mg / L, conductivity: 2
It is preferable to dilute so as to be about 5 to 40 ms / cm.

[0026]

The present invention will be described more specifically with reference to the following examples.

Example 1 After the landfill was completed, nitrate denitrification treatment of a leachate having a salt concentration higher than that of seawater, which had flowed out of a landfill site mainly composed of incinerated ash, which had passed about two years ago, was performed. Table 1 shows the water quality of this leachate leachate.

As shown in FIG. 2, the nitrification denitrification treatment apparatus used comprises a nitrification tank 1 to which caustic soda for pH adjustment is added, a denitrification tank 2 to which methanol as a nutrient is added, and a precipitation tank 3. The waste leachate is subjected to nitrification treatment in the nitrification tank 1, the nitrification treatment liquid is subjected to denitrification treatment in the denitrification tank 2, the denitrification treatment liquid is solid-liquid separated in the precipitation tank 3, and the separated sludge is returned to the nitrification tank 1. Then, the supernatant is extracted as treated water. In this apparatus, the activated sludge in the apparatus for nitrifying and denitrifying human waste by dilution with seawater was used as seed sludge.

The specifications and processing conditions of each part of the nitrification denitrification treatment apparatus are as follows.

Raw water inflow: 1.0 m ³ / day Nitrification tank capacity: 500 L Nitrification tank pH: 7.5 Denitrification tank capacity: 500 L Denitrification tank methanol addition amount: 300 g / day Sedimentation tank capacity: 250 L Sludge return amount: 1.2 m ³ / day When this leachate leachate was directly treated with a nitrification denitrification treatment apparatus without dilution, 0.01 kg-N / kg-
It showed only a very low nitrification activity of MLSS / day, and the nitrogen removal rate was only 24%. This condition did not change even after the acclimatization period of about 2 months, and the nitrification activity did not increase. Table 1 shows the quality of the treated water at this time.

Therefore, a reverse osmosis membrane separator having the following specifications is provided as a desalination treatment device at the subsequent stage of the nitrification denitrification treatment device, and the nitrification denitrification treatment water from the nitrification denitrification treatment device is supplied to the desalination treatment device (reverse osmosis membrane). Separation device) to reduce the salt concentration to 1/10
Part of the demineralized water reduced to
The operation was continued under the same conditions except that a liquid (dilute leachate) diluted by mixing at a ratio of 0% and having a reduced salt concentration was injected into the nitrification denitrification treatment apparatus. Therefore, the remaining demineralized water was taken out of the system as treated water for this apparatus.

Reverse Osmosis Membrane Separator Specifications Reverse osmosis membrane type: Cellulose acetate membrane (membrane with 90% desalting rate) As a result, nitrification activity gradually increased, and was reduced to 0.0 in about one month.
It recovered to 5 kg-N / kg-MLSS-day. Table 2 shows the qualities of the leachate, deionized water, diluted leachate, and nitrification-denitrified water at this time.

[0033]

[Table 1]

[0034]

[Table 2]

By comparing Tables 1 and 2, according to the apparatus of the present invention, high-concentration salt-containing wastewater is diluted with demineralized water without introducing dilution water from outside the system to efficiently perform nitrification and denitrification. It can be seen that the processing can be performed.

In the above embodiment, the nitrification denitrification-treated water was directly subjected to the desalination treatment. However, as shown in FIG.
If there is a treatment step such as coagulation separation treatment or activated carbon treatment after the nitrification denitrification treatment, desalination treatment of the treated water in these steps may have higher desalination efficiency, in this case, The desalination treatment device is preferably provided at a stage subsequent to these treatment facilities. That is, as described above, the present invention is mainly directed to avoiding nitrification inhibition by high-concentration salts by diluting high-concentration salt-containing wastewater of raw water with desalination treatment water. There are no particular restrictions on where the equipment is installed.

[0037]

As described above in detail, according to the treatment apparatus for wastewater containing high concentration of salt of the present invention, wastewater having high concentration of salt such as leachate can be stably and efficiently removed by avoiding biological inhibition by salt. Can be subjected to a nitrification denitrification treatment.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a treatment apparatus for wastewater containing high-concentration salts according to the present invention.

FIG. 2 is a system diagram of a nitrification denitrification treatment apparatus used in an experimental example.

FIG. 3 is a system diagram showing a conventional example.

[Explanation of symbols]

 1 Nitrification tank 2 Denitrification tank 3 Sedimentation tank

Claims (1)

[Claims] 1. A nitrification denitrification apparatus for biologically nitrifying and denitrifying wastewater containing high-concentration salts, a desalination apparatus for desalinating at least a part of the treatment water of the nitrification denitrification apparatus, Means for returning at least a part of the treated water of the desalination treatment apparatus to the nitrification denitrification treatment apparatus.