JPH0419919B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for rationally treating human waste. In particular, by adding magnesium compounds, surplus activated sludge, flocculating sludge, and polymer flocculants in the solid-liquid separation process before biological treatment,
The present invention relates to a method for greatly improving a coagulation separation treatment step located in a tertiary treatment step.

[Conventional technology]

Conventionally, human waste is separated from coarse suspended matter and subjected to biological treatment such as activated sludge treatment, and then is further treated with phosphorus, COD,
In order to further remove chromatic or colloidal SS, it is flocculated and separated before being discharged, but since this coagulation and separation process also aims to remove phosphorus, an extremely large amount of flocculant is injected, and the running In addition to the disadvantage of high cost, a large amount of flocculated sludge that is difficult to concentrate and dewater is generated, making it difficult to process and process sludge.
The problem was that the disposal process was technically and cost-intensive.

[Problem that the invention seeks to solve]

The present invention significantly reduces the amount of inorganic flocculant required to be injected after the biological treatment process, thereby significantly reducing the amount of flocculated sludge generated, thereby maintaining the quality of treated water and treating human waste. It is a rational process.

[Means for solving problems]

The present invention provides a method for treating human waste comprising the steps of solid-liquid separation of human waste, treating the separated water with activated sludge treatment, and adding an inorganic flocculant to the resulting treated water to coagulate and separate suspended matter. After adding surplus activated sludge, coagulated sludge, and polymer flocculant, the sludge is introduced into a solid-liquid separator and separated into separated water and concentrated sludge, and the separated water is introduced into an activated sludge treatment device and subjected to activated sludge treatment to form activated sludge. A method for treating human waste that is characterized by adding an inorganic flocculant after separation to coagulate and separate suspended matter. By adding a magnesium compound and a polymer flocculant to the flocculated sludge generated in the sludge and flocculation separation process, phosphorus is removed in the solid-liquid separation process, thus reducing the amount of flocculant added in the flocculation process. It is something that can be encouraged.

As the magnesium compound used in the present invention, magnesium compounds such as Mg(OH) ₂ , MgO, MgCl ₂ and MgSO ₄ can be used. The amount of magnesium compound added is Mg/P=0.5.
It may be added in an amount within a molar ratio of ~2.5.
If Mg/P is added at a molar ratio of 0.5 or less, the desired effect cannot be achieved, and even if Mg/P is added at a molar ratio of 2.5 or more, not only is it not possible to achieve a better effect, but it is also economically undesirable. do not have.

In addition, surplus activated sludge and coagulated sludge are treated with human waste 1
Although it is sufficient to add sludge at a ratio of 5 kg to 8 kg to Kl, it is preferable to add the entire amount of generated surplus activated sludge and flocculated sludge. By doing so, the amount of surplus activated sludge and flocculated sludge to be processed can be reduced or even omitted.

As the polymer flocculant, any polymer commonly used in wastewater treatment may be used, but it is preferable to use cationic polymers with high cationic strength, such as polyethyleneimine, chitosan, polyvinylimidazoline, etc. The amount of the cationic polymer flocculant added is preferably in the range of 0.5 to 2.0%, particularly 0.7 to 2.0%, based on SS in human urine.
It is preferable to add it in an amount within the range of 1.5%.

In addition, inorganic flocculants used when coagulating and separating overflow water after activated sludge treatment include:
Any of those used in wastewater treatment technology, such as iron chloride, iron sulfate, aluminum chloride, and aluminum sulfate, may be used. The amount of these inorganic flocculants added to activated sludge treated water is per 1Kl of night soil to be treated.
Amounts within the range of 0.5 to 2 Kg, preferably 1 to 1.2 Kg may be used.

Hereinafter, the method of the present invention will be explained in more detail based on the drawings.

Mixed sludge 5 consisting of magnesium compound ₂ such as Mg(OH) 2 and surplus activated sludge 3 and flocculated sludge 4 is added to human waste 1, and after stirring and mixing thoroughly, polymer flocculant 6 is injected to form flocs. Then, this floc is separated in a solid-liquid separator 7 (rotating or inclined screen is most suitable) to obtain separated water 8 and concentrated sludge 9.

In this process, the following remarkable phenomenon occurs.

That is, when Mg ²⁺ ions are added to human waste, the NH ₄ ⁺ ions and PO ₄ ^3- ions that are present in high concentrations in the human waste undergo the reaction Mg ²⁺ +NH ₄ ⁺ +PO ₄ ^3- →NH ₄ MgPO ₄ ↓ According to the formula, a dense, microcrystalline magnesium ammonium phosphate precipitate is produced.

Since this NH ₄ MgPO ₄ precipitate is extremely fine, there is a serious technical problem in that solid-liquid separation is very difficult, but the present invention has solved this problem rationally as follows. That is, mixed sludge 5 was added to human waste containing fine SS of NH ₄ MgPO ₄ ,
Furthermore, by adding polymer flocculant 6, fine
NH ₄ MgPO ₄ crystals are adsorbed or encapsulated in the flocs of mixed sludge, allowing for easy and rapid solid-liquid separation.

Moreover, what should be noted is that the thickened sludge 9 coexists with paper fibers, which are contained in large amounts in human waste, and contains dense NH ₄ MgPO ₄ crystals, making it difficult to dewater. It has been confirmed that the water can be easily dehydrated to a low moisture content (50 to 55%) in a dehydration process (for example, a screw press type dehydrator is suitable). Furthermore, the low-moisture dehydrated cake 11 is rich in fertilizing ingredients.
Since it contains a large amount of NH ₄ MgPO ₄ , it can be used as is or after composting as a useful fertilizer with high fertilizer value, eliminating the need for wasteful landfill disposal.

Solid-liquid separation liquid (at this stage, 80% of the phosphoric acid in human urine is removed)
In addition, more than 90% of colloidal SS BOD has been removed) by biological treatment12 using the activated sludge method.
Then, an inorganic flocculant 14 is added to the overflow water of the activated sludge settling tank 13, and coagulation and sedimentation 15 is carried out as a coagulation separation treatment process.

16 is flocculation and sedimentation treated water, and 4 is flocculation sludge.

In the conventional process (biological treatment → coagulation sedimentation), the required injection rate of the inorganic flocculant 14 is per 1 Kl of human waste,
Surprisingly, in the present invention, coagulation and sedimentation treated water having the same water quality as the conventional process can be obtained by adding 1 to 1.2 _{kg of FeCl 3 per} 1 Kl of human waste.

As a result, the running cost required for adding flocculant is reduced to about one-third, and the amount of coagulated sludge generated is also reduced to about one-third, making it possible to significantly streamline the sludge treatment and disposal process.

Furthermore, in the present invention, the flocculated sludge 4 is not simply transported as it is to the dewatering process, but is utilized effectively. In other words, since the flocculated sludge 4 still has some remaining ability to adsorb phosphoric acid and colloidal SS, the flocculated sludge 4
This is to recycle human waste into human waste 1 and use it for purifying human waste.

Excess activated sludge and flocculated sludge may be added separately to human waste.

Example 1 BOD10000 delivered to Kanagawa Otsu City human waste treatment plant
~13000mg/, SS13000~15000mg/,
Add 1000 mg/Mg(OH) ₂ to PO ₄ 900-1200 mg/, COD 3800-4500 mg/human waste, and
Total amount of mixed sludge consisting of surplus activated sludge generated from the biological treatment process of human waste and flocculated sludge discharged from the coagulation-sedimentation process (per 1 Kl of treated human waste, 4 to 4.5
Kgd.s.) and stirred thoroughly (stirring time: 2 hours), 1.5% polydimethylaminomethacrylate (DAM)-based cationic polymer was added based on the solid content of the dry sludge, and after stirring for 2 minutes,
A large grain floc with a grain size of 5 to 10 mm was formed. This could be quickly separated into solid and liquid using a 60 degree inclined wedge wire screen with an opening of 0.6 mm. The solids concentration of the thickened sludge separated by the screen is
3.5~4.0%, SS of screen separated water is 500
It was ~700mg/.

The screen thickened sludge could be dehydrated as it was in a screw press dehydrator, and the moisture content of the dehydrated cake was extremely low at 50 to 55%.

On the other hand, a mixed liquid of the screen separated water 8 and the separated water 18 of the screw press dehydrator 10 (solubility
BOD2500~3000mg/, soluble phosphoric acid 90~130
mg/) using the undiluted activated sludge method (MLSS8000mg/
, residence time 6 hours, DO level 0.5-1.2 mg/)
As a result of treatment, the BOD of treated water was 30 to 60 mg/,
Biologically treated water containing COD 350-460 mg/, SS 40-80 mg/, and soluble phosphoric acid 5-12 mg/was obtained.

Next, 1000 mg/FeCl ₃ was added to this biologically treated water, and as a result of coagulation and precipitation treatment at pH 4.5, the quality of the treated water was SS10-20 mg/, phosphoric acid 0.01 mg/,
Treated water with a COD of 55 to 67 mg/ and a BOD of 2 to 4 mg/was obtained.

As a comparative example, after treating the filtered human urine with activated sludge under the same conditions as in the example of the present invention, FeCl ₃ was added to the biologically treated water without using the process of the present invention.
The treated water treated with coagulation and precipitation by adding 3,500 mg of SS contains 10 to 25 mg of SS, 0.02 to 0.5 mg of phosphoric acid,
COD 73-86 mg/, BOD 10-18 mg/,
Despite adding 3.5 times as much FeCl ₃ as in the present invention, the quality of the treated water was inferior to that in the present invention.

[Effects of the invention] The injection rate of inorganic flocculant in the coagulation separation process in human waste treatment can be significantly reduced compared to conventional processes, and running costs can therefore be reduced.
In addition, since the amount of coagulated sludge generated can be significantly reduced, the sludge treatment and disposal process can be streamlined.

Since a dehydrated cake rich in C, N, Mg, and P components and low in moisture can be produced, it can be effectively used as a high-value fertilizer.

Produced by adding Mg to human waste
Although NH ₄ MgPO ₄ is dense but extremely fine, there was a major problem in that solid-liquid separation was extremely difficult.
By utilizing co-aggregation with NH ₄ MgPO ₄ or adsorption envelopment phenomenon, fine crystals of NH ₄ MgPO ₄ can be easily formed and solid-liquid separated from urine.

The flocculated separation sludge can be used as a preliminary purification agent for human waste.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the processing steps of the present invention. 1... Night soil supply pipe, 2... Magnesium compound supply pipe, 3... Excess activated sludge return pipe, 4... Coagulated sludge transfer pipe, 6... Polymer flocculant supply pipe,
7... Solid-liquid separator, 10... Dehydrator, 11... Dehydrated cake, 12... Activated sludge treatment tank, 13... Sedimentation tank, 14... Inorganic flocculant supply pipe, 15... Coagulation sedimentation tank.

Claims (1)

[Claims] 1. In a method for treating human waste, which consists of a step of separating solid-liquid human waste and treating the separated water with activated sludge, adding an inorganic flocculant to the resulting treated water to flocculate and separate suspended matter, the human waste contains magnesium compounds, excess activity, etc. After adding sludge, coagulated sludge, and polymer flocculant, it is led to a solid-liquid separator and separated into separated water and concentrated sludge, and the separated water is led to an activated sludge treatment equipment and subjected to activated sludge treatment, and the activated sludge is separated. A method for treating human waste characterized by adding an inorganic flocculant to flocculate and separate suspended matter.