JPS5911359B2 - Biophysical and chemical treatment methods for wastewater - Google Patents

Description

[Detailed Description of the Invention] Conventionally, wastewater containing pollutants such as soluble and insoluble organic substances has been treated by various biological treatment methods including activated sludge method. becomes too large.

b) Weak against shock loads.

C) Contamination with toxic substances makes treatment difficult.

d) Difficult to dispose of surplus sludge.

e) The treatment effect is poor at low water temperatures.

f) There is a limit to the quality of treated water that can be obtained.

There were drawbacks such as.

This invention uses incineration ash obtained by incinerating sludge separated or generated during the process under conditions such that a part of it becomes activated carbon, and uses a countercurrent two-stage adsorption method similar to the known countercurrent adsorption method using powdered charcoal. This method attempts to achieve high-rate activated sludge treatment by adsorbing pollutants and at the same time providing an aeration tank in the first stage to mix and contact activated carbon-containing incineration ash through aeration. It is.

That is, the method of this invention streamlines the sewage treatment process by efficiently combining biological treatment, activated carbon adsorption, coagulation sedimentation, and sludge disposal by incineration, and improves the quality of treated water, treatment cost, and amount of waste generated. , advantages not available with conventional methods can be obtained.

Next, the processing method of the present invention will be explained according to embodiments shown in the accompanying drawings.

FIG. 1 shows a process flow chart explaining the present invention.

Raw sewage 1 is introduced into an aeration tank 5 after removing earth and sand and coarse sedimentary solids in a settling tank 2.

At the inlet of this aeration tank 50, slurry 3 containing activated carbon-containing incineration ash discharged from the second-stage sedimentation tank 11 is added to
In order to maintain the mixed water suspended solids amount (MLSS,) in the aeration tank 5 at a concentration of 400 mti/t or more, the sedimentation tank 7 in the first stage is pumped as necessary. Partially circulate the discharged slurry 4, and relatively
It reduces the OD load and helps maintain the treatment effect when microbial activity decreases, such as in winter.

In this case, the value of the MLSS in the aeration tank 5 can temporarily reduce the amount of surplus incinerated ash 13 generated in the activated carbonization device 9, which concentrates and incinerates the slurry 4 discharged from the first-stage settling tank 1. By adding the stored surplus incineration ash to the aeration tank 5, the required value can be increased.

The sewage that has flowed into the aeration tank 5 is purified while being in contact with the discharged slurry 4 containing activated carbon-containing incinerated ash and the activated sludge generated in the tank 5 for about 1 to 2 hours while being aerated from the air supply device 6. The liquid then flows into the first stage sedimentation tank 7.

In this first stage sedimentation tank T, floating solids are separated by sedimentation due to the settling properties of activated carbon-containing incineration ash and the flocculating ability of activated sludge found in normal biological treatment, and soluble organic matter is It is converted into microorganisms by microorganisms in the activated sludge that use it as a nutrient source, and is separated as activated sludge, or adsorbed and separated into activated carbon-containing incineration ash by the adsorption power of activated carbon in the incineration ash.

In this way, 80 to 90% of the organic carbon in the raw sewage 1 is fixed in the discharged slurry 4 by the outlet of the first-stage settling tank 7.

The slurry discharged from the first stage sedimentation tank 7 contains incinerated ash with good concentration of 50 parts or more, so it is easily concentrated to a solid concentration of 20 parts or more, and the oxygen concentration in the furnace is reduced to 0.2 parts or less. The slurry is incinerated in a controlled activated carbonization device (calciner) 9 to activate carbonize the organic carbon in the slurry and convert the inorganic solids into harmless anhydrous substances.

As shown in FIG. 3, this incinerated ash 8 also has the ability to adsorb organic matter, so it can be effectively used as an adsorbent.

Therefore, more than half of the incinerated ash 8 is added to the inlet of the contact tank 100, mixed and contacted with the outflow water of the first stage settling tank 7, and after adsorbing the remaining pollutants mainly consisting of soluble organic matter, In the second stage sedimentation tank 11, a polymer flocculant (such as sodium alginate) is supplementarily added by the flocculant injection device 14 shown in FIG. The treated water is separated by sedimentation.
Take it out as 2.

Note that FIG. 3 above is a chart using urban sewage as a sample water, and shows the COD adsorption capacity of activated carbon-containing incineration ash.

The separated slurry in the second stage sedimentation tank 11 has adsorption capacity as an adsorbent, so after being concentrated in this tank 11, it is returned to the inlet of the aeration tank 50 and recycled.

In addition, as the incinerated ash from the activated carbonization device 9 is recycled, the unnatural ash content increases, so as shown in Figure 1, the excess incinerated ash 13 should be disposed of. , as shown in Fig. 2, the activated carbon-containing incineration ash is separated into a heavy fraction mainly consisting of ash and a light fraction containing a large amount of activated carbon, and the heavy fraction containing a large amount of inorganic ash is discarded by means such as a fluid separator 15. Adjust by method.

By rationally combining biological treatment and physicochemical treatment, this invention maintains stable treatment effects and achieves high water quality comparable to tertiary treatment found in conventional sewage treatment in a relatively small-scale facility. can get.

In other words, the facility according to the method of this invention is one in which a mixing tank for the adsorption process, a sedimentation tank, and an activated carbonization device (incinerator 9) are added to the high-rate activated sludge method, which requires the smallest facility among conventional biological treatment. This is similar to the well-known fact that adding incineration ash containing activated carbon to the first stage of high-rate activated sludge treatment dramatically increases the treatment effect when powdered activated carbon is added to standard activated sludge. By using the incineration ash containing activated carbon as an adsorbent and sedimentation agent, the treatment effect of the conventional high-rate activated sludge method is significantly improved. By using a spray type fluidized incinerator, for example, it is possible to obtain the same treatment effect as that of a spray incinerator, which previously required two types of furnaces, one for incinerating excess sludge and one for regenerating activated carbon. By controlling the combustion conditions so that the organic carbon in the slurry is activated carbonized or regenerated,
The unique feature of this method is that it streamlines the process and reduces the amount of waste generated to a fraction of conventional methods.

According to the method of this invention, most of the soluble or dispersible organic matter that enters the treatment equipment is converted into solid form by biological treatment, rather than simply converting contaminated organic matter into living organisms as in the conventional method using biological treatment. In addition to converting the total amount of organic matter that flows into the incineration process into activated carbon, sludge treatment is also performed, which greatly reduces secondary pollution and energy loss associated with water treatment.

An example of the results of a comparative experiment between the method of the present invention and a conventional method regarding urban sewage is shown below.

(Note) 1) Activated carbon cannot adsorb colloidal.

2) Because soluble organic matter is destroyed during carbonization,
This is turned into a bacterial cell and a colloidal is taken.

3) Aeration should be carried out to the extent that self-extinguishment does not occur.

4) Activated sludge tanks using activated carbon can be made smaller.

[Brief explanation of drawings]

In the accompanying drawings, Fig. 1 is a process diagram of an embodiment of the method of the present invention, Fig. 2 is a diagram showing an example of a flocculant injection device, and Fig. 3 is a diagram showing the COD adsorption capacity of activated carbon-containing incineration ash. It is a line diagram. In the figure, 1... raw sewage, 2...
・Sand settling tank, 3...Mud drain, 4...Discharge mud drain, 5...Aeration tank, 6...Air supply device, 1... ...First stage sedimentation tank, 8...
...Incineration ash, 9...Activated carbonization device (incinerator)
, 10... Contact tank, 11... Second stage sedimentation tank, 12... Treated water, 13... Surplus incinerated ash, 14... ...Flocculant injection device, 15...
...It is a fluid separator.

Claims (1)

[Claims] 1 In a sewage treatment system consisting of an aeration tank, a first-stage sedimentation tank, a contact tank, and a second-stage sedimentation tank, a portion of the discharged sludge containing activated sludge from the first-stage sedimentation tank is added to the sewage that has undergone sedimentation treatment. After mixing the activated carbon-containing incineration ash and sewage in the aeration tank while adding a part of the slurry containing the activated carbon-containing incineration ash from the second-stage settling tank to obtain the required sludge concentration, The incinerated ash is introduced into a stage sedimentation tank, and the sedimentation promoting properties of the incinerated ash and the flocculating ability of the activated sludge are used to improve the efficiency of sedimentation and separation of suspended solids, and most of the settled sludge is activated carbonized in a kiln. It is added to the treated water in the first stage sedimentation tank, brought into contact with the treated water in the contact tank, adsorbs the soluble organic matter remaining in the treated water, is separated by sedimentation in the second stage sedimentation tank together with the incinerated ash, and is then brought into contact with the raw wastewater. A biophysical and chemical treatment method for sludge characterized by a series of treatment steps that combine various operations of sludge disposal through the cyclical use of calcined activated carbon.