JPS61129097A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To reduce the Cl<->-concn. in sludge, by washing sludge with various waters such as filter cloth washing water prior to burning discharged sludge. CONSTITUTION:Waste water 1 is treated in a waste water treatment apparatus 2 to be separated into treated water 3 and excessive sludge 4. Excessive sludge 4 is washed by machinery washing waste water in a washing tank 5 and the washed sludge 6 is conc. in a sludge concn. tank 7 to be separated into sludge washing waste water 16 and conc. sludge 18. Conc. sludge 18 is dehydrated by a sludge dehydrator 9 to obtain dehydrated sludge 10. The sludge dehydrator 9 is washed with machinery washing waste water 14 and washing waste water 15 is used in washing the excessive sludge 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for treating sludge discharged from wastewater treatment, and particularly to a method for treating sludge that reduces the Ct concentration in the sludge.

(Prior Art) Sludge discharged from wastewater treatment equipment is often incinerated in an incinerator to render it harmless. On the other hand, wastewater such as night soil contains chlorine ions (aZ-), so the sludge discharged also has Cl-
00 da/l). When this OZ-containing sludge is incinerated, HOj is generated in the incinerator and is released into the atmosphere as exhaust gas.

The Air Pollution Control Law stipulates that the concentration of HOj discharged from such incineration facilities must be below 450 ppm, and the following methods have been used to maintain this value.

(1) H generated by mixing lime into sludge before incineration
A method of removing Oj by reaction absorption with lime (see Figure 3) (2) A method of spraying lime into sludge incineration exhaust gas and reacting and absorbing HOj and removing it (see Figure 4) (3) A method of converting exhaust gas into alkali (see Figure 4) For example, wash with Maxi solution etc.
(See Figure 5) (4) Dilute the raw wastewater to remove the o contained in the discharged sludge.
A method of incinerating after reducing the r-concentration (see Figure 6) (5) A method of incinerating after washing the sludge and reducing the O2- concentration (see Figure 7) In Figures 3 to 7 above, 1 is wastewater, 2 is wastewater treatment equipment, 3 is treated water, 4 is surplus sludge, 5 is sludge thickening equipment,
6 is thickened sludge, 7 is lime, 8 is sludge dehydrator, 9 is dehydrated sludge, 10 is sludge incinerator, 11 is incineration waste gas, 12 is ash recovery equipment, 13 is exhaust gas, 14 is Alka IJI, 15 is gas Cleaning equipment, 16 gas cleaning waste liquid, 17 dilution water, 1
8 is sludge washing water, j? ij: washing tank; 20 is washing waste liquid;

Of the above, (1), (2), and (3) require chemicals such as lime and NaOH;
2) For K, equipment was required to recover scattered lime, and for (3), treatment of cleaning waste liquid was required. Also (4)
(Even with 5JK, large amounts of dilution water and washing water are required, which is also a cause of strain on wastewater treatment equipment.

(Problems to be Solved by the Invention) The present invention solves the problem of Cl-
The present invention aims to provide a method of reducing the concentration, particularly focusing on the above (5), and a method of saving water for washing sludge.

(Means for Solving the Problems) That is, the present invention uses equipment cleaning wastewater such as furnace cloth cleaning water generated during sludge dewatering operation and miscellaneous wastewater used in treatment equipment before incinerating sludge discharged from wastewater treatment. This is a sludge treatment method characterized by washing the sludge with water or the like to reduce the Ol- concentration in the sludge.

Usually, sludge discharged from wastewater treatment equipment is incinerated after its moisture content is reduced in a dewatering process. A centrifugal separator, belt press, filter press, etc. are used in this dehydration process. These dehydrators necessarily require equipment washing water such as cloth washing water, and water with a low O/- concentration, such as well water or industrial water, is used as this washing water. Conventionally, this wash water was transferred to a wastewater treatment process, treated, and then discharged.

The present invention reuses this water with low ar- concentration as sludge washing water before transferring it to the wastewater treatment process, reduces the Cl- concentration contained in the sludge, and reduces the Fi-concentration discharged from the sludge incinerator.
It is characterized by reducing CJl 9 degrees.

Conventionally, the present invention was directly sent to the wastewater treatment process and wasted (!/- In order to reuse water with a low concentration, H
(3/i It is an economical sludge treatment method that does not require chemicals or new washing water to reduce degrees.

The present invention is an improved aCt reduction method of method (5) (FIG. 7). The present invention will now be explained in detail by comparing FIG. 2, which shows the apparatus of the method of FIG. 7 in detail, including equipment washing water, with FIG. 1, which shows an embodiment of the method of the present invention. Describe.

1 and 2, 1 is wastewater, 2 is wastewater treatment equipment, 3 is treated water, 4 is excess sludge, 5 is a washing tank, 6 is washed sludge, 7 is a sludge thickening tank, 8 is thickened sludge, 9 is a sludge dehydrator,
10 is dehydrated sludge, 11 is a sludge incinerator, 12 is exhaust gas,
13 is sludge washing water, 14 is equipment washing water, 15 is equipment washing wastewater, and 16 is sludge washing wastewater.

In FIG. 1, wastewater 1 is treated in a wastewater treatment device 2,
Separated into treated water 3 and surplus sludge 4.

Excess sludge 4 is sent to the cleaning tank 5 as equipment cleaning wastewater 15, which will be described later.
The sludge is washed and the Ol- content contained in the sludge is reduced. The washed sludge 6 is concentrated in the sludge thickening tank 7 and becomes sludge washing wastewater 16! It is separated into reduced sludge 8. The sludge cleaning wastewater 16 is sent to the wastewater treatment device 2 for treatment, and the concentrated sludge 8 is dehydrated by the sludge dehydrator 9 to become dehydrated sludge 10. Sludge dehydrator 9
is washed with equipment washing water 14, but the equipment washing waste water 1
5 is reused as sludge washing water 13 as mentioned above,
It is sent to the cleaning tank 5. Dehydrated sludge 10 is transferred to sludge incinerator 11
The waste gas 12 is incinerated and the exhaust gas 12 is discharged.

Equipment cleaning water is usually well water or industrial water with a low O2 concentration, and the Ct concentration in the equipment cleaning wastewater is also low. Conventionally, this equipment washing wastewater was sent as is to a wastewater treatment facility, but in the present invention, this equipment washing wastewater is sent to a washing tank for reuse as sludge washing water. Since the Cl- concentration in equipment washing wastewater is low, aZ- in the excess sludge is washed and diluted, and the Cl- concentration in the excess sludge decreases. Therefore, even if the sludge is incinerated after being concentrated and dehydrated, the hot concentration in the exhaust gas is reduced.

In contrast, the method shown in FIG. 2 uses separate cleaning water at two locations: sludge cleaning water 13 and equipment cleaning water 14. On the other hand, in the trap of the present invention, since equipment washing water is reused as sludge washing water, the amount of washing water (usually well water or industrial water) can be reduced to about 4 times. Additionally, these cleaning wastewaters were conventionally sent to wastewater treatment facilities for treatment;
The amount of these washing wastewaters can be as much as 2 to 3 times the amount of raw wastewater, and if the amount of washing wastewaters can be reduced to about 1/2, it is also possible to reduce the capacity of wastewater treatment equipment.

[Brief explanation of the drawing]

Fig. 1 shows the flow of one embodiment of the present invention, and Fig. s2~
FIG. 7 shows the flow of a conventional method for reducing the Ol concentration in sludge. Sub-Agent 1) Meifu Agent Ryo Hagiwara - Figure 6 Figure 7

Claims (1)

[Claims] Before incinerating the sludge discharged during wastewater treatment, the sludge is washed with equipment cleaning wastewater such as filter cloth washing water generated during sludge dehydration, gray water used in treatment equipment, etc. to remove Cl^ in the sludge. - A sludge treatment method characterized by reducing the concentration.