JPS61220800A - Treatment of organic sludge - Google Patents

Abstract

PURPOSE:To produce inexpensive and excellent compost by adding iron sulfate, a porous inorg. additive and a high molecular flocculant to unwashed org. sludge, mixing, flocculating, dehydrating and composting the sludge. CONSTITUTION:Iron sulfate is added to unwashed org. sludge such as septic tank sludge, sewage crude sludge, digested sludge and crude night soil sludge and the sludge is mixed and flocculated. Moreover, a porous inorg. additive consisting essentially of 50-56% CaO, 20-30% SiO2, 7-10% Al2O3 and 4-10% SO3 and a high molecular flocculant are added and the sludge is mixed, flocculated, dehydrated and composted. Namely, the flocculating effect by the flocculant and dehydrating property of unwashed sludge are enhanced, the sludge can be efficiently dehydrated with inexpensive chemicals and a small-sized filter and excellent compost can be produced at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating organic sludge such as septic tank sludge, raw sewage sludge, digested sludge, and human waste sludge.

[Conventional technology]

Generally, organic sludge such as septic tank sludge is simply dumped or incinerated, but this has disadvantages such as secondary pollution and high costs. Therefore, various attempts have been made to use organic sludge as a raw material for compost, but when fermenting organic sludge to make compost, the moisture content of organic sludge must be kept below 70% to activate bacterial activity. An important issue was how to reduce the

Normally, in order to facilitate the dewatering process of organic sludge, there is a method of adding a flocculant before dewatering, but this requires a large amount of flocculant. After washing in two stages with diluted water, 15-20% of ferric chloride and 25% of calcium hydroxide were added to the solid weight.
~40 g, and 0.3% or more of a polymer flocculant, respectively, which not only requires a large amount of money for chemicals, but also has an insufficient dehydration rate, and increases the fermentation temperature due to the large amount of inorganic substances. However, fermentation took a long time. In addition, large pressurized filters with a filtration pressure of 2 to 3 Kf/crn2 are used for dewatering organic sludge, but the equipment is expensive and the operating cost is high, so the compost obtained is It was unsuitable for practical use.

[Problem that the invention seeks to solve]

In view of the current situation, the present invention has been developed to improve the coagulation effect and dewatering property using a coagulant without washing, to perform dewatering treatment efficiently with low chemical costs, and with an inexpensive small filter, and to produce inexpensive and good compost. The purpose of this invention is to provide a method for treating organic sludge that enables production.

[Means for solving problems]

In the present invention, iron sulfate is added to organic sludge such as septic tank sludge, raw sewage sludge, digested sludge, and human waste sludge without washing, mixed and flocculated, and further CaO 50-56%, 5i02
20-30%, At2o 7-10%
, a porous inorganic additive mainly composed of 4 to 10% SO, a polymer flocculant, and t are added, mixed to advance flocculation, dehydrated, and composted.

[Effect]

Since the present invention has the above configuration, organic sludge is treated with Cabbage in addition to iron sulfate and a polymer flocculant without washing.

By using porous inorganic additives mainly composed of At203 and SO3, agglomeration is promoted and dehydration is extremely good, and dehydration can be performed efficiently with low chemical costs and an inexpensive filter. The moisture content of the obtained dehydrated sludge is greatly reduced, and the organic matter content is high and it can be effectively used as a raw material for compost. Fermentation proceeds quickly without the need for complicated operations, making it an inexpensive and good product. Compost will be obtained.

〔Example〕

Hereinafter, the present invention will be explained in detail according to illustrated embodiments.

In the figure, 1 is the sludge to be treated, and this sludge 1 includes digested sludge, septic tank sludge, raw sewage sludge, activated sludge, raw human waste sludge, pig manure wastewater, raw cow dung wastewater, kitchen wastewater, food wastewater, etc. In particular, those free of harmful substances such as heavy metals are desirable. It is particularly suitable for sludge with high alkalinity.

The sludge 1 is stored in advance in the storage tank 2 in the form of only one type or a mixture of two or more types, and then is continuously supplied into the screen 4 by the liquid feed pump 3. The screen 74 is designed to remove coarse particles 5 having a diameter exceeding about 5111I+ in the sludge, and is preferably a movable (rotary) fine screen that removes moisture in the coarse particles by applying appropriate pressure, for example. In this way, the sludge 1 from which coarse substances have been removed and which can be easily subjected to subsequent coagulation and dewatering treatment is stored in the receiving tank 7 via the F liquid pipe 6.

Next, the sludge 1 is supplied in fixed amounts from the receiving tank 7 to the coagulation mixing tank 9 by the pump 8. The flocculation mixing tank 9 is divided into a first tank 9□ and a second tank 92. In the first tank 91, iron sulfate such as ferrous sulfate is added, and in the second tank 92, a porous inorganic additive is added. After addition, a polymeric flocculant is added. It is desirable that the iron sulfate added in the first tank 91 be 2 to 15% pure with respect to the solids in the sludge. The inorganic additive added in the second tank 92 is CaO 50-56%, 5i0
220~30%, At2057~10%, 5034~l
It is an inorganic substance whose main component is 0%. Furthermore, Mg01
It is desirable to contain ~5% of Fe2051~5%. Further, the polymer flocculant is preferably a cationic polymer, and examples thereof include aniline resin hydrochloride, polythiohydrochloride, polyethyleneimine, polyvinylpyridine copolymer salt, and polyacrylamide. It is desirable that the amount of the inorganic additive added is 5 to 40% based on the solids of the sludge, and the amount of the polymer flocculant is 0.05 to 0.35% based on the solids of the sludge.

The first tank 91 and the second tank 92 are equipped with a stirring device,
Here, the sludge is mixed with flocculants, etc., and the diameter of
A floc of about 411III is generated.

Next, the sludge in which flocs have grown is supplied to a dehydrator 11 using a pump 1o, where it is dehydrated. As the dehydrator, a pressurized belt press type dehydrator is preferable, but a vacuum filtration machine, a pressure filtration screw press, etc. can also be used.

As mentioned above, in addition to ferrous sulfate and a polymer flocculant, inorganic additives are especially used, which not only promotes floc growth but also significantly increases dewatering efficiency.・Dewatered sludge obtained through dewatering treatment Although it differs depending on the dehydrator, it has a high moisture content of 50 to 70%, and since it adsorbs and contains organic substances, it is effectively used as a raw material for compost.

The F liquid from the dehydrator 11 is carried out of the system through the F liquid pipe.
The dehydrated sludge obtained by the dehydrator 11 after being subjected to water treatment is stored in the dehydrated sludge storage tank 13 via the sludge feeding system 12.

Next, the dewatered sludge is introduced into a mixing tank 15 via a conveyor 14. For example, as shown in FIG. 3, the mixing tank 15 has a semicircular dome shape in cross section, the upper part of which is covered with a heat insulating material 17 such as a double film, and is connected to the next fermentation tank 16. Aged compost 19 is deposited on the concrete layer 18 of the mixing tank 15 to a thickness of about 20 to 40 ctn, and about 15 to 20 ctn of aged compost 19 is deposited on top of the aged compost 19.
Dehydrated sludge 2G is deposited with a thickness of α, partially mixed with the compost in the aging tank as needed. High-temperature actinomycetes 21 are administered onto the dehydrated sludge 20, and nutrients such as cow, pig, chicken, etc. feces are added as necessary to adjust the composition of the compost. The dehydrated sludge 20 is mixed by a blade 23 of a rotary machine that reciprocates along a rail 22 that is continuously arranged from the mixing tank 15 to the fermentation tank 16, and is sequentially transferred to the fermentation tank 16.

A hot air circulation duct 24 is buried in the aged compost 19 deposited from the mixing tank 15 to the fermentation tank 16, and is mainly used for heating the aged compost 19 in the fermenting tank 16. The dehydrated sludge 20 is moderately heated by warm air passing through the aging compost 19 from below, promoting the activity of actinomycetes and causing active fermentation. The effect of the aged compost 19 is to eliminate the drawback that uneven fermentation caused by uneven temperature and moisture content of the dehydrated sludge 20 cannot be sufficiently adjusted with a stirrer alone, and the fermentation is improved compared to when this aged compost is not used. The temperature increases rapidly by 5 to 7°C, and fermentation progresses rapidly. Fermentation temperature is 60-65
°C, in some cases rising to 75 °C. The hot air that passes through the dehydrated sludge 20 from below to above has the function of equalizing the temperature in the dehydrated sludge 20 to promote uniform fermentation, as well as promoting the evaporation of water in the sludge and removing generated gas. has.

As described above, the hot air containing evaporated moisture and generated gas is sucked into the fan 26 installed at the top of the mixing tank 15 through the upper exhaust duct 25, mixed with new air, and then sent downward through the pipe 27. A portion is discharged outward through the exhaust pipe 28, and a portion is supplied to the hot air circulation duct 24. It is desirable that the degree of exhaustion of hot air is adjusted at the branch point between the exhaust pipe 28 and the hot air circulation duct 24 to appropriately change the amount of water and gas contained in the hot air. Further, the temperature of the hot air is preferably around 35° C., and if necessary, it is heated by a heater placed at an appropriate location within the hot air circulation system.

In this way, the temperature of the compost on the exit side obtained from the fermentation tank 16 has decreased, and it is in the shape of 20 to 30 square holes, which is introduced into the crusher and mixer 29, where it is
It will be crushed in about 7 days.

After pulverization and mixing, the compost is put into the aging tank 30 shown in Figure 1 using a conveyor or 7 units, where the remaining unfermented content is completely fermented.
Although the fermentation tank 30 is stored at a height of ~3 m for about 11 to 15 days, there is no need to heat the aging tank 30 as in the conventional case. This is because the fermentation in the fermentation tank 16 proceeds better than before.

Below, Table 1 shows the flocculation effect and Table 2 shows the dewatering effect of specific examples in which each flocculant was added as shown below for each sludge having the following components. However, n-hex in Table 1 indicates the amount of n-hexane extract, and SS indicates the amount of solid matter. Further, the amounts added in Table 1 are expressed as weights based on the weight of solid matter, and in the case of 'Fe5011, they are expressed as amounts of 15% aqueous solution.

(Left below) Table 2 From these tables, the average Fe content for each of the above sludges
50. (15% aqueous solution) about 18% based on solid weight
The sludge was flocculated using approximately 25% additive and approximately 0.27% polymer flocculant, and the sludge with a sludge concentration of 1.5 to 3% before passing was passed through a belt filter to a net cake overrate of 15 to 25%.
It was found that dewatering at a rate of Kg.SS/m2.hr makes it possible to obtain dehydrated sludge with a cake thickness (thickness of the dehydrated sludge) of approximately 6 mm and a moisture content of approximately 55 to 69%.

In the above case, the case where the sludge does not contain heavy metals or harmful organic substances has been described according to Fig. 1. However, if the sludge contains heavy metals or harmful organic substances, it is necessary to It is desirable to perform coagulation and dehydration treatment as shown in Fig. 2 to remove harmful substances. That is, in the first coagulation mixing tank 31, first, acid and ferrous sulfate, ferric sulfate, etc. are added to the sludge. Add iron sulfate to pH'i
3-5 to elute heavy metals, then 2-3-5
Add the above-mentioned inorganic flocculant having a coarse tea diameter in an amount approximately 10 times the content of heavy metals and other harmful substances, mix (the pH will naturally rise to 6 to 8), transfer to the sedimentation tank 32, and add alkali. When the pH is raised to 9.6 to 10.5, heavy metals etc. are completely adsorbed by coarse additives (true specific gravity 2.6) and settle to the bottom, and are removed by the scraper into the sludge pipe 33. It is removed after

Next, the sludge from which harmful substances have been removed is transferred to the second coagulation mixing tank 34.
and the fine inorganic additives mentioned above are mixed therein. Note that the amount of additives to be added is set to be 8 to 30% in total (based on the solid components of the sludge). Furthermore, the sludge mixed with a cationic polymer flocculant and sufficiently flocculated is transferred to the dehydrator 11 by the pump 35, and thereafter undergoes the same treatment as shown in Fig. 1, which was previously considered impossible. The content of heavy metal scraps, etc. is also removed to a large extent, resulting in good compost. According to this method, a large amount of heavy metals, dioxane, etc., which were contained in the digested sludge and activated sludge of the human waste digester and sewage septic tank and could not be removed, are removed to the extent of about 80 to 99, so it is called resource reuse. There are huge benefits from your position.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, in addition to the polymer flocculant, a porous inorganic additive mainly composed of Cab, At20, and S05 is used in combination, which is necessary in the past. Coagulation progresses quickly and extensively without washing, resulting in extremely good dewatering properties.
Dewatering can be performed efficiently with low chemical costs and with an inexpensive filter, and the moisture content of the resulting dehydrated sludge is greatly reduced, making it suitable for use as it is as a raw material for compost. Fermentation progresses extremely quickly, and not only is it possible to obtain inexpensive compost, but the use of inorganic additives allows for the production of compost that is highly effective as a fertilizer, as it contains a large amount of organic matter necessary for compost. can play.

[Brief explanation of drawings]

The drawings show embodiments of the present invention; FIG. 1 is a schematic explanatory diagram of one example, FIG. 2 is a schematic explanatory diagram of main parts of another example,
FIG. 3 is a schematic cross-sectional view showing an example of a mixing tank and a fermentation tank. 1: Sludge 2: Storage tank 4 clean 7: Receiving tank 9: Coagulation mixing tank 11: Dehydrator 13: Dehydrated sludge storage tank 15: Mixing tank 16: Fermentation tank 29: Pulverizer/mixer 30: Aging tank 31: First coagulation mixing tank 32: Sedimentation tank
34: 2nd coagulation mixing tank Figure 1 Figure 2 Cause Figure 3 Procedure amendment July 8, 1985

Claims (1)

[Claims] Iron sulfate is added to and mixed with organic sludge such as septic tank sludge, raw sewage sludge, digested sludge, and human waste sludge without washing to cause flocculation, and furthermore, 50-56% of CaO and 20-20% of SiO_2 are added.
30%, Al_2O_3 7-10%, SO_3 4-
A method for treating organic sludge, which comprises adding and mixing 10% of a porous inorganic additive and a polymer flocculant as main components to advance flocculation, dewatering, and composting.