JPS6233599A - Treatment of sun-drying waste sludge - Google Patents

Abstract

PURPOSE:To efficiently dry waste sludge without necessitating chemicals resulting in an increase in the cost by adding a caking agent to waste sludge generated from a construction site, etc., agitating the sludge, immediately transferring the sludge to the sun-drying place and drying the sludge by the sun. CONSTITUTION:Waste sludge generated from a construction site, etc., is uniformly agitated to regulate the concn. to a specified value. The sludge is added with 2-5wt% caking material such as cement, agitate, then transferred to a sun-drying place and accumulated in specified depth. After the fluidity of the sludge is eliminated, the sludge is dried by the sun. For example, about 30cm-thick sludge can be dried in 4-8 weeks in average weather. Since sludge can be efficiently dried in this way, waste sludge can be treated at a low cost and with high efficiency.

Description

[Detailed Description of the Invention] "Industrial Field of Application J This invention relates to a solar drying method 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 something.

``Prior art'' As is well known, methods for treating waste sludge include (a) solidification treatment, (b) solid-liquid separation treatment using agents such as coagulants, and (
C) Mechanical dehydration treatment such as pressure dehydration, vacuum dehydration, centrifugal dehydration, etc.; (B) or a combination of (B) and (C); and (E) solar drying.

"Problems to be Solved by the Invention" The conventional processing methods described above have the following four problems:
It is desired to establish a more efficient 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 is alkaline (pH=7.5
~/, 3.0) It affects the biological environment after disposal. There are problems such as.

Furthermore, methods (b) and (c) require chemicals, mechanical equipment, etc., and are therefore expensive. 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, and aims to provide a method that can efficiently dry waste sludge without requiring chemicals or mechanical equipment that increase costs. The solar drying method has been improved to make it more efficient.

"Means for Solving the Problems" The method for solar drying treatment of waste sludge according to the present invention first includes:
The waste sludge is stirred uniformly to maintain a constant concentration, 2 to 5 wt% of solidifying agent such as cement is added to this sludge, stirred, and immediately (before the sludge loses its fluidity) dried in a solar drying field. In this method, the sludge is transferred to a tank so that the depth is uniform, and the sludge is dried in the sun to lose its fluidity.

"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 5 wt% of the solidifying agent is mixed with the sludge, the sludge does not solidify and its fluidity increases. This was done based on the knowledge that the This loss of fluidity occurs 30 to 10 minutes after addition of the solidifying agent and stirring, so it is fully possible to transfer the sludge to a solar drying facility while it remains fluid. Since sludge that has lost its fluidity does not flow and spread, the area required for a solar drying field relative to the amount of sludge is smaller than in the past. 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. It depends on the sludge depth and the weather, but if the sludge is about 30 cm thick and the weather is average, <z-
Drying can be completed in g weeks. The sludge mixed with a solidifying agent exhibits high alkalinity, but due to the increase in surface area due to the occurrence of cracks, acidic substances such as carbon dioxide gas in the atmosphere and neutralized ashes are formed, and the pH gradually decreases. Furthermore, since the mixing of rainwater promotes neutralization, the harmful 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. A low cost, high efficiency bus can be carried out.

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

"Example 1" As shown in "Table 1", six types of test sludge were prepared, and the change over time in solar drying of each was measured.

ml, 2.3 is configured to cover various types of sludge generated from construction sites. In addition, positive 4 and 5 are those mixed with the above-mentioned th 1 and 2 VCII wt ordinary Portland cement, respectively, and floor 6 is N1.
It is made by coagulating the sludge from step 2, l'! 11. 2
゜3 is sludge for solar drying using the conventional method! D, N14.
5 is sludge for solar drying according to the method of the present invention, and 6 is sludge obtained by solid-liquid separation using chemicals (comparative example), which is expensive.
It is.

Each of these sludge samples was subjected to evaporative drying only from the surface, and the treatment status was observed as follows.

Medium Since each sample sludge was left in natural weather conditions, it was set up on the roof of a building where it would not be affected by sunlight, wind direction, etc.

(II) The number of days for drying under the sun was continuous for approximately 1-2 months, and the measurement days for the survey were set on a per week basis. Therefore, samples for the same sample were prepared for the number of measurements.

GiD sample containers were made of glass or plastic and were embedded in sand saturated with water to prevent evaporation due to radiant heat from the sides of the container.

1ψ As meteorological data, m degrees, humidity, solar radiation, rainfall, wind direction, and wind speed were measured during the measurement period.

M The evaluation of the sludge treatment state was performed in the following (a) to (e).

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

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

(e) Change in sludge pH (elution pH).

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

During the implementation period (9 days), there were 77 days of rain. There were three consecutive weeks of rain during the period.

The number of "clear" and "clear" days was llI days, but the number of days with solar radiation of gMx/- or more was 2g days. Relative humidity naturally varied in relation to the rainy weather. The daily average wind speed was 1 to 2 m/s, but no clear trend could be seen in relation to other meteorological data. The outside temperature gradually decreased from July to July, when the experiment was conducted, but from a seasonal perspective, it was judged to be the typical temperature from autumn to winter. These weather data do not differ much from the Japan Meteorological Agency's average data over the past 30 years, and it has been determined that the weather during the implementation period was not due to abnormal weather.

Also, during the implementation period, there will be 9 days of rain in the third week, and during this period! f; 0. ! There was a total rainfall of r mm.

Therefore, the water content after 3 weeks is due to the influence of this rainwater, but the sludge water content of samples other than sample 1 has decreased to the same level or lower than after − week. It is thought that the penetration of rainwater into the sludge is extremely low. In other words, water evaporated by sun drying is
It can be said that the treatment effect is being shown without water being absorbed into sludge again.

This example, which resulted in the measurement results shown in Table 2, revealed the following effects of the method of the present invention.

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

(2) Therefore, the infiltration of rainwater, etc. 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 (a range of variation depending on the type of sludge) to high water content sludge or bentonite slurry that has extremely poor settling properties.

(4) Since the solidification strength of cement is low, cracks are easily generated due to evaporation of water, and these cracks increase the surface area for evaporation, thereby promoting drying.

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

(6) Cement solidified sludge is initially highly alkaline (
The pH of the water is 5 to 3), but neutralization is promoted by contact with carbon dioxide gas in the atmosphere and rainwater, making it easy to adjust the pH of wastewater and permeated water.

(7) In addition, neutralization of sludge elution pH is promoted,
Sludge after drying can be used in a wide range of applications.

"Example 2" This Example 2 is an example in which industrial sludge is actually treated. In this actual treatment method, a solar drying field of the type shown in FIGS. 1 and 1 is used. As shown in the figure, this solar drying field is made by spreading gravel 1 so that it drains well, and the surrounding area is raised to form a depression.
The inside is divided by a removable partition wall 2 into an initial drying area 3, a primary drying area 4, and a tertiary drying area 5, each consisting of a plurality of blocks (one block in the figure). The sludge separated water, rainwater, and other permeated water that has passed through is configured to flow into a water storage tank 7 through a side gutter 6. In this embodiment, the imported sludge is first transferred to the sludge stock tank 8.
The supernatant liquid is sent to the water storage tank 7iC, and the settled sludge is flowed into the HS mixer tank 10 by the pump 9. In a 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 an initial drying place. Here, the sludge is left for 71 to θ days to undergo solidification, curing, and dewatering. After the initial drying period is completed, the partition wall 2 is removed and the sludge is transferred to the primary 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 materials are transferred to the tertiary drying place 5 using a bulldozer or the like as described above. Here, it is further dried in the sun for 7 to 1 day 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 collected in the water storage tank 7. The sludge that has been sufficiently dried in this way is removed from the drying area using a bulldozer and isobarized, and then 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 such as pH 18S, 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 treatments such as neutralization and filtration. The water is treated to bring it below standard values and then released or reused.

In addition, when the properties of the sludge carried in are checked, sludge that can be treated as residual soil and sludge that has no fluidity and good dewatering properties can be treated without adding a solidifying agent, so they are treated as follows. First, if the remaining soil can be handled, its moisture content, strength, etc. are checked, and if or when the moisture content is sufficiently low, it is removed and disposed of or reused. and,
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,
Disposal of the seepage water that occurs at the same time, which can be reused
It can be reused, requires a smaller processing plant area than before, and requires no special processing equipment, making low-cost processing possible.

"Effects of the Invention" As explained above, according to the present invention, sludge can be dried very efficiently by simply mixing a very small amount of solidifying agent into sludge and transferring this sludge to a solar drying place. Therefore, waste sludge can be treated at low cost and in a short period of time.

[Brief explanation of the drawing]

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 place, 4...Second drying place, 5.
...Third drying area, 6...Gutter, 7...
...Water storage monk, 8...Sludge stocking monk, 9...
...Pump, 10...Misensuichi tank.

Claims (1)

[Claims] Solar drying of waste sludge, which is characterized by adding 2 to 5 wt% of a solidifying agent to waste sludge generated from construction sites, etc., stirring it, immediately transferring it to a solar drying place, and drying and hardening in the sun. Processing method.