JPH0378160B2 - - Google Patents

Description

Detailed Description of the Invention "Industrial Application Field" This invention relates to a solar drying process for waste sludge, in which sludge generated in construction foundation work and various industries and existing bottom sludge are treated by solar drying. It is about the method.

``Conventional technology'' As is well known, methods for treating waste sludge include (a)
Solidification treatment, (B) Solid-liquid separation treatment using agents such as flocculants, (C) Mechanical dehydration treatment such as pressure dehydration, vacuum dehydration, centrifugal dehydration, (D) (B) or (B) and ( There is a combination treatment with (c) and (e) sun drying treatment.

"Problems to be Solved by the Invention" The conventional treatment methods described above each have the following problems, and it is desired to establish a more effective treatment method.

That is, in method (a), the amount of solidifying material is large, resulting in high cost. Since the strength after solidification increases, there is no volume reduction of sludge. The solidified material becomes alkaline (PH = 12.5 to 13.0), which affects the biological environment after disposal. There are problems such as.

Furthermore, methods (b), (c), and (d) require chemicals, mechanical equipment, etc., and are therefore costly. There are problems such as.

In the solar drying method (e), if rainwater gets mixed in during solar drying, it may return to a sludge-like state. Even if the surface dries, the inside hardly dries, resulting in poor processing efficiency. There are problems such as.

This invention was made in view of the above circumstances,
The purpose of this project is to provide a method that can effectively dry waste sludge without the need for chemicals or mechanical equipment that increase costs. It was designed so that

``Means for Solving the Problems'' The method for solar drying waste sludge according to the present invention applies to waste sludge generated from construction sites, etc.
After adding 5wt% of solidifying agent such as cement and stirring, immediately transfer to a solar drying place and dry in the sun.
This is a solar drying treatment method for hardening waste sludge. In the solar drying area, gravel is spread and the periphery of the gravel is raised to form a depression, and the interior of the depression is divided into an initial drying area, a secondary drying area, and a secondary drying area by two rows of removable partition walls. It is separated into three tertiary drying areas. Then, in the initial drying area, the sludge after stirring is solidified and cured and dehydrated, and this sludge is pushed to the secondary drying area so that the bottom part of the sludge is exposed to the top, and in the secondary drying area, The sludge is further dried in the sun, and the sludge is extruded to the tertiary drying area so that the bottom part of the sludge is exposed to the top, and is dried and solidified in the tertiary drying area.

"Effect" The above method was obtained as a result of various experimental studies, and although it differs depending on the properties of the sludge, when 2 to 5 wt% of solidifying agent is mixed into the sludge, the sludge does not solidify and its fluidity increases. This was done based on the knowledge that people lose their sexuality. This loss of fluidity appears 30 to 60 minutes after addition of the solidifying agent and stirring, so it is fully possible to transfer the sludge to the solar drying facility while it remains fluid. Since sludge that has lost its fluidity does not flow and spread, the required area of the solar drying field for the amount of sludge is smaller than before. In addition, since sludge has a weak support structure due to the solidification material, the porosity after drying is large, and internal moisture can easily move to the surface. Also, due to the support structure, cracks are likely to occur as drying progresses. Therefore, the area in contact with outside air tends to increase, and the drying efficiency is very high. Depending on the sludge depth and weather, drying can be completed in 4 to 8 weeks under average weather conditions and sludge thickness is approximately 30 cm. Although sludge mixed with a solidification agent exhibits high alkalinity, the increase in surface area due to the occurrence of cracks causes a neutralization reaction with acidic substances such as carbon dioxide gas in the atmosphere, and the pH gradually decreases. Furthermore, since the mixing of rainwater further promotes neutralization, the adverse effects of high alkalinity are extremely alleviated.

As described above, according to the present invention, sludge can be efficiently dried by simply mixing a small amount of solidifying agent into sludge and transferring this sludge to a solar drying facility, which makes it possible to efficiently process waste sludge. can be carried out at low cost and with high efficiency.

In addition, the sludge stirred after adding the solidifying agent is transferred to the initial drying area. At this time, a depression is formed in the solar drying area, and the fluidity of the sludge is lost by the solidifying agent immediately after being transferred to the initial drying area, so that more sludge can be accommodated. In addition, sludge is
Since the sludge is sent sequentially from the initial drying area to the secondary drying area and then to the tertiary drying area, the initial drying area can be used continuously for the initial drying of the next sludge after the initial drying is completed.
In addition, when pushing the sludge from the initial drying area to the secondary drying area and the tertiary drying area using a bulldozer, etc., the sludge is pushed out so that the lower part of the sludge is at the top.
It can speed up the drying of sludge.

Hereinafter, this invention will be explained in more detail with reference to Examples.

"Example" This example is an example in which industrial sludge is actually treated. In this actual treatment method, a solar drying field as shown in FIGS. 1 and 2 is used. As shown in the figure, this solar drying area is made up of gravel 1 spread over it so that it drains well, and the surrounding area is raised to form a depression. The drying area is divided into an initial drying area 3, a secondary drying area 4, and a tertiary drying area 5 each consisting of 6 blocks (in the figure). In addition, permeated water such as sludge separated water and rainwater that has passed through the gravel 1 is configured to flow into a water storage tank 7 through a side gutter 6. 8, the supernatant liquid is sent to the water storage tank 7, and the settled sludge is flowed into the mixer tank 10 by the pump 9, and in the mixer tank 10,
A solidifying agent with a concentration determined according to the properties of the sludge is added and mixed, and the sludge is transferred to the initial drying area 3. Here, the sludge is left for 7 to 10 days to undergo solidification, curing, and dewatering. When the initial drying period is completed, the partition wall 2 is removed and the sludge is transferred to the secondary drying area 4 using a bulldozer B or the like with the bottom portion exposed to the top. Here, it is left to stand for about 7 days to further progress the drying in the sun. When this secondary drying is completed, the material is transferred to the tertiary drying place 5 using a bulldozer B or the like as described above. Here, it is further dried in the sun for 7 to 14 days to completely dry and solidify it. During this time, moisture such as water separated from the sludge and rainwater flows into the gutter 6 through the gravel 1 and is directed to the water storage tank 7. The sludge that has been sufficiently dried in this manner is taken out of the drying area by a bulldozer B or the like and transported for disposal or reuse. On the other hand, the permeated water that has flowed into the water storage tank 7 is checked for water quality through PH and SS, and if it is below the standard value, it is discharged or reused, and if it does not meet the standard value, it is subjected to treatment such as neutralization and filtration. The water is treated to bring it below the standard value and then released or reused.

In addition, when we check the properties of the sludge brought in, if it can be treated as residual soil or if it has no fluidity and has good dewatering properties, it can be processed without adding a solidifying agent.
Each is processed as follows. First, if the waste soil can be handled, its moisture content, strength, etc. are checked, and when the moisture content is sufficiently low, or when it has become low, it is taken out and disposed of or reused. Those with no fluidity and good dehydration properties are directly transferred to a solar drying facility, subjected to the above-mentioned solar drying treatment, and then disposed of.

According to the above embodiment, a large amount of waste sludge can be continuously disposed of and reused, the seepage water generated at the same time can be disposed of and reused, the area of the treatment plant is smaller than before, and special treatment is possible. No equipment required,
Bottom cost processing becomes possible.

Next, an example will be described in which a solidifying agent is added to sludge and the sludge is dried in the sun.

(Example) As shown in "Table 1", six types of test sludge were prepared, and the change over time in solar drying of each was measured.
Nos. 1, 2, and 3 are constructed to cover various types of sludge generated from construction sites. In addition, Nos. 4 and 5 are the above Nos. 1 and 2 mixed with 4wt% of ordinary Portland cement, respectively.
No. 6 is the sludge of No. 2 that has been coagulated.
Nos. 1, 2, and 3 are sludges for solar drying made by the conventional method, Nos. 4 and 5 are sludges for sun drying made by the method of the present invention, and No. 6 is sludges made by the solid-liquid separation method using chemicals, which is costly. Sludge (comparative example).

Each of these sludge samples was subjected to only evaporative drying from the surface, and the processing conditions as described below were observed.

() Since each sample sludge was left in natural weather conditions, measurements were taken on the roof of a building in a location unaffected by sunlight, wind direction, etc.

() The number of days for sun drying was approximately two consecutive months, and the survey was conducted once a week on measurement days. Therefore, samples for the same sample were prepared for the number of measurements.

() The sample container was made of glass or plastic and was embedded in sand saturated with water to prevent evaporation due to radiant heat from the sides of the container.

() Temperature, humidity, solar radiation, rainfall, wind direction, and wind speed were measured during the measurement period as meteorological data.

() Evaluation of the sludge treatment status was performed in the following (a) to (c).

(a) Moisture content (weight change) and depth direction were also measured.

(b) Change in sludge level (distance the sludge level drops due to evaporation).

(c) Change in sludge pH (eluted pH).

When measured in this manner, the results shown in Table 2 were obtained.

During the implementation period (49 days), there were 11 rainy days. During the period, there were three consecutive weeks with 0 mm of rainfall. The 14th is a "sunny" or "clear" day.
There were 28 days with solar radiation above 8MJ/ ^m2 . Relative humidity naturally varied in relation to the rainy weather.
The daily average wind speed was 2 to 5 m/s, but no clear trend could be seen in correlation with other meteorological data. The outside temperature was from November to December when the test was carried out.
The temperature gradually decreased as the month progressed, but from a seasonal perspective, it was judged to be the typical temperature from autumn to winter. These weather data are from the Japan Meteorological Agency's past
There was no significant difference from the 30-year average data, and it was determined that the weather during the implementation period was not caused by abnormal weather.

Additionally, during the implementation period, there were four rainy days in the third week, with a total rainfall of 50.5 mm during this period. Therefore, the water content after 3 weeks is due to the influence of this rainwater, but the water content of sludge other than sample No. 1 has decreased to the same or lower than after 2 weeks. These sludges are considered to have very little penetration of rainwater into the sludge. That is,
It can be said that the water evaporated by sun drying does not absorb into sludge again, and the treatment effect is being shown. From the experimental results shown in Table 2, the following became clear.

(1) Due to solidification of sludge, no fluidity occurs even in the initial stage.

(2) Therefore, even when rainwater enters, it is clearly separated, and drainage is easy to remove.

(3) The efficiency of solar drying is improved by mixing 2 to 5 wt% of cement (the range varies depending on the type of sludge) to high moisture content sludge and bentonite slurry that have extremely poor settling properties. do.

(4) Due to the low solidification strength of cement, cracks are easily generated due to evaporation of water, and these cracks increase the surface area for evaporation, which further accelerates drying.

(5) As water evaporates, the volume of cement solidified sludge decreases significantly (30-50%).

(6) Cement solidified sludge initially exhibits high alkalinity (PH12.5-13), but its neutralization is promoted by contact with atmospheric carbon dioxide and rainwater;
It is easy to adjust the pH of drainage and seepage water.

(7) In addition, the neutralization of the eluted PH of the sludge is promoted, so the sludge after drying treatment can be used in a wide range of applications.

"Effects of the Invention" As explained above, according to the present invention, the following excellent effects can be achieved.

First, 2 to 5 wt% of a solidifying agent such as cement is added to the waste sludge, stirred, and then dried and hardened in the sun.As is clear from the results of the examples, a. Also, liquidity does not occur.

b For this reason, even when rainwater enters, it is clearly separated, and drainage is easy to remove.

C. The efficiency of solar drying is improved by mixing 2 to 5 wt% of cement into high water content sludge or bentonite slurry that has extremely poor settling properties.

d Due to the low solidification strength of cement, cracks are easily generated due to evaporation of water, and these cracks increase the surface area for evaporation, which further accelerates drying.

e As mentioned above, since the solidification strength of cement is low, dry sludge can be easily moved by pushing it with a bulldozer, etc.; The remaining sludge can be easily reused as earth and sand.

f The volume of cement solidified sludge decreases significantly (30-40) with the evaporation of water.

g. Cement solidified sludge initially exhibits high alkalinity (PH12.5-13), but its neutralization is promoted by contact with atmospheric carbon dioxide and rainwater;
It is easy to adjust the pH of drainage and seepage water.

h Also, since the neutralization of the eluted PH of the sludge is promoted, the uses of the sludge after drying treatment are widened.

Second, in the solar drying area, gravel is spread and the periphery of the gravel is raised to form a depression, and the interior of the depression is separated by two rows of removable partition walls, which provide an initial drying area and a secondary drying area. It consists of three separate drying areas: a drying area and a secondary drying area, and does not require any special treatment equipment, and therefore does not require a large investment in equipment. Furthermore, by forming a depression, more waste sludge can be accommodated.

Thirdly, in the treatment drying field, the sludge after stirring is solidified and cultivated and dehydrated, and this sludge is pushed to the secondary drying field so that the bottom part of the sludge comes out to the top. Then, the sludge is further dried in the sun, and the sludge is extruded into the tertiary drying area so that the bottom part of the sludge is exposed to the top, and the sludge is dried and solidified in the tertiary drying area, so that when the initial drying is completed, The initial drying area can be used continuously for the initial drying of the next sludge, and therefore, it is possible to handle a large amount of sludge.
When the sludge is transferred to the secondary drying area and the tertiary drying area, the bottom part of the sludge is pushed out to the top, thereby speeding up the solar drying of the sludge.

[Brief explanation of drawings]

FIGS. 1 and 2 are for explaining a second embodiment of the present invention, and are a plan view and a side sectional view of a solar drying place, respectively. 1... Gravel, 2... Partition wall, 3... Initial drying area, 4... Secondary drying area, 5... Tertiary drying area, 6...
...Gutter, 7...Water tank, 8...Sludge stock tank,
9...Pump, 10...Mixer tank.

【table】

【table】

【table】

【table】

Claims (1)

[Claims] 1. Waste sludge generated from construction sites, etc. 2.
After adding 5wt% of solidifying agent such as cement and stirring, immediately transfer to a solar drying place and dry in the sun.
The solar drying field is a solar drying method for hardening waste sludge, in which gravel is spread and the periphery of the spread gravel is raised to form a depression, and the interior of the depression is filled with two removable rows. Three drying areas, an initial drying area, a secondary drying area, and a tertiary drying area, are separated by partition walls.
In the initial drying field, the sludge after stirring is solidified and cured and dehydrated, and this sludge is pushed out to the secondary drying field so that the bottom part of the sludge is exposed to the top. The sludge is further dried in the sun in the secondary drying area, and the sludge is pushed out to the tertiary drying area so that the bottom part of the sludge is exposed to the top, and is dried and solidified in the tertiary drying area. A solar drying treatment method for waste sludge.