JPH02255586A - Fermentative treatment of sludge - Google Patents

Abstract

PURPOSE:To prevent the agglomeration of fermented material and to ferment sludge with high efficiency by charging a mixture of the dehydrated cake of excess sludge generated from the activated-sludge treatment of night soil and the composed return compost into a biological fermenter as raw sludge. CONSTITUTION:The excess sludge is dehydrated to about 70% water content in a dehydrated cake hopper 5, and the dehydrated cake is charged 4 into the biological fermenter 1 and disintegrated. Meanwhile, the compost which has been fermented, dried, composed and dehydrated to about 40% water content in the fermenter 1 is discharged 6 and disintegrated into agglomerates. A part of the disintegrated compost is supplied to a raw material supply passage 4 through a bypass 9 as return compost and mixed with the disintegrated and dehydrated cake, and the mixture is charged into the fermenter 1 as raw sludge. At this time, the weight ratio of the return compost to be supplied to the dehydrated cake is controlled to >=5. Air is then blown into the raw sludge staying in the fermenter 1 by a blower 3, and the raw sludge is fermented, dried and composed.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for fermentation treatment of sludge.

Conventional technology The conventional fermentation treatment method involves dewatering excess sludge produced when human waste is treated with activated sludge using a dehydrator, crushing the dehydrated cake and feeding it into a sludge fermentation tank. was fermented and dried.

Then, into the sludge fermentation tank, the already fermented and dried dung post and the crushed dehydrated cake are mixed in equal amounts and put into the fermentation tank, and the mixture is left in the fermentation tank for about 10 to 20 days, during which time air is removed from the sludge. It was fermented and dried biologically by blowing into it. In addition, in order to carry out fermentation efficiently, various measures have been taken, such as forming the inside of the fermenter in multiple stages and providing a stirring device in the fermenter.

Problems to be Solved by the Invention However, in the above-mentioned configuration, in order to increase the contact efficiency between the fermented material, sludge, and air, the fermented material was forcibly moved (switched) using a stirring device. There was a problem in which the product was partially kneaded and hardened.

The present invention solves the above-mentioned problems, and aims to provide a sludge fermentation treatment method that can prevent fermented products from forming agglomerates and ferment fermented products with high efficiency.

Means for Solving the Problems In order to solve the above problems, the present invention dehydrates excess sludge generated in activated sludge treatment of human waste to form a dehydrated cake,
In a fermentation treatment method in which this dehydrated cake is put into a biological fermenter as raw material sludge and the raw material sludge is fermented in the biological fermenter, the compost that has already been fermented and composted is taken out from the biological fermenter, A portion of the removed compost is mixed with the dehydrated cake at a ratio of at least 5 times by weight as returned compost, and the dehydrated cake mixed with the returned compost is fed into the biological fermentation tank as raw material sludge. be.

Effect With the above-described configuration, as the amount of returned compost increases, the moisture content of the raw material sludge decreases, the fermentation rate of the dehydrated cake contained in the raw material sludge improves, and the drying of the dehydrated cake progresses rapidly. In addition, by mixing the returned compost with the dehydrated cake at a ratio of at least 5 times by weight to form raw material sludge, the fermentation of the dehydrated cake fed into the biological fermentation tank is completed in about one day. The biological fermenter can be fed daily with dehydrated cake.

EXAMPLE An example of the present invention will be described below based on the drawings. 1st
In the figure, raw material sludge 2 is accumulated on the floor inside a biological fermenter 1, and a blower 3 for supplying air to the raw material sludge 2 is installed in communication with the lower part of the biological fermenter 1. It is being A raw material supply channel 4 is opened at the top of the biological fermenter 1, and a dehydrated cake hopper 5 is connected to the base end of the raw material supply channel 4. This dewatering cake hopper 5 is for dewatering excess sludge produced when human waste is treated with activated sludge. Further, a compost discharge passage 6 is provided to open at the bottom of the biological fermenter 1, and the compost discharge passage 6 is connected to a dry cake hopper 8 with a crusher 7 interposed therebetween. moreover,
Compost discharge path 6 and raw material supply path 4 on the downstream side of the crusher 7
are in communication via a bypass path 9. Moreover, a conveyor device is provided inside the raw material supply path 4, the dung post discharge path 6, and the bypass path 9.

Hereinafter, the effects of the above configuration will be explained.

Excess sludge is dehydrated to a moisture content of 70% in cake hopper 5.
The dehydrated cake is taken out to the raw material supply path 4 and fed toward the biological fermenter 2. At this time, the dehydrated cake is crushed by the screw blades of the conveyor device in the raw material supply path 4. On the other hand, biological fermenter 1
moisture content 40 which has already been fermented, dried and composted in
% of the compost is taken out from the biological fermenter 1 through the compost discharge path 6, and the lumped compost is crushed by the crusher 7. Then, a part of the crushed compost is supplied as return compost to the raw material supply route 4 through the bypass route 9, and the raw material sludge formed by mixing the returned compost and the dehydrated cake is sent from the raw material supply route 4 to the raw material supply route 4. Pour into fermenter 1. At this time, the amount of returned compost supplied to the dehydrated cake should be at least 5 times or more by weight. This ensures that the water content of the raw material sludge is within 5% of the water content of the returned compost. In addition, the water content X of the raw material sludge is calculated by the following formula.

X= (mt w+m2W)/(W+nW) However, W
: weight of dehydrated cake, n: magnification, ml: moisture content of dehydrated cake, m2: moisture content of returned compost.

Then, air is blown into the raw material sludge staying in the biological fermenter 1 using a blower 3 to ferment and ferment the raw material sludge.
Dry and compost. Further, the composted compost is sent to the dry cake hopper 8 through the compost discharge path 6, and a portion is supplied to the raw material supply path 4 as the above-mentioned return compost.

In the above drying and fermentation process, as the amount of returned compost increases, the moisture content of the raw material sludge decreases, the fermentation speed of the dehydrated cake contained in the raw material sludge improves, and the drying of the dehydrated cake increases. Proceed quickly.

Then, by mixing the returned compost with the dehydrated cake at a ratio of at least 5 times by weight to form raw material sludge, the fermentation of the dehydrated cake fed into the biological fermenter 1 is completed in about one day. However, the biological fermenter can be fed with dehydrated cake daily. Figure 2 shows the fermentation process conducted by changing the mixing ratio of returned compost and dehydrated cake.
A comparison of the drying process is shown, where A shows the case where the amount of returned compost is 5 times, B shows the case where the amount is 3 times, and C shows the case where the amount is the same. As is clear from FIG. 2, the higher the water content of the raw material sludge, the slower the temperature rise and the longer the high temperature duration. In addition, the drying of the fun post progresses,
If the temperature is not lowered, the conveyor equipment or crusher will become clogged, resulting in an overload on the conveying capacity. Normally, the temperature of compost that can be transported is about +15°C from room temperature.

Therefore, when the ratio of returned compost is 5 times, it is almost 1
Fermentation is completed within a day, and raw material sludge can be added every day. On the other hand, when the ratio of returned compost decreases, the high temperature duration becomes longer, so the feeding interval of raw material sludge becomes longer, and as a result, a biological fermenter 1 with a larger capacity is required. For example, when comparing case A and case B, in order to process the same amount of dehydrated cake in the same period, fermentation will take 2 to 3 days in case B, so compared to case A, it will take 2 to 3 days.
Requires ~3 times the fermenter volume.

Effects of the Invention As described above, according to the present invention, the returned compost is mixed with the dewatered cake at a ratio of at least 5 times by weight to form raw material sludge, which is then charged into the biological fermenter. Fermentation of the dehydrated cake can be accelerated and fermentation can be completed in approximately one day, and the dehydrated cake can be charged to the biological fermenter every day.

Furthermore, since fermentation proceeds quickly, a stirring device is not required, and it is possible to prevent the compost from clumping together due to stirring.

[Brief explanation of drawings]

FIG. 1 is an overall diagram showing an embodiment of the present invention, and FIG. 2 is a comparison diagram of the fermentation process of raw material sludge with different return sludge ratios. 1... Biological fermenter, 2... Raw material sludge, 4...
Raw material supply path, 5... Dehydration cake hopper, 6... Compost discharge path, 9... Bypass.

Claims (1)

[Claims] 1. Dehydrate excess sludge generated in activated sludge treatment of human waste to form a dehydrated cake, feed this dehydrated cake as raw material sludge into a biological fermenter, and ferment the raw material sludge in the biological fermenter. In the fermentation treatment method, the compost that has already been fermented and composted is removed from the biological fermenter, and a part of the removed compost is mixed into the dewatered cake at a ratio of at least 5 times by weight as return compost, and the return compost is A sludge fermentation treatment method characterized by charging a mixed dehydrated cake as raw material sludge into a biological fermentation tank.