JPH035879B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to sedimentation separation of suspended components and removal of dissolved components in wastewater. [Prior Art] Conventionally, a sedimentation separation method has been widely used in which flocculants and other chemicals are added to wastewater to solidify dissolved components, and floating components are flocculated and separated by sedimentation.
In addition, a biological oxidation method in which microorganisms present in wastewater are allowed to adhere to and propagate on the floor, and dissolved components in the wastewater are decomposed and removed by the activity of these microorganisms, has also been widely used in recent years. [Problems to be Solved by the Invention] However, the conventional sedimentation separation method has the following problems. (1) Since the sedimentation rate of suspended components is slow, treatment takes a long time and treatment efficiency is poor. (2) Since the settled sludge is taken out in a swollen state containing a large amount of water and has poor dewatering properties, a large amount of sludge is discharged and its handling is poor. (3) Although it is possible to remove some dissolved components, it is insufficient, and in particular, it is almost impossible to remove ammonia, which has recently become a problem. (4) Since large amounts of flocculants and other chemicals are used,
Not only is it economically disadvantageous, but there is also the risk of secondary pollution caused by the chemicals used. Furthermore, although the biological oxidation method can remove dissolved components without the need for special chemicals, it has the following problems. (1) Floors and aeration are essential for the adhesion and propagation of microorganisms that naturally exist in wastewater, and cannot be used to purify polluted lakes and marshes. (2) Although it is possible to decompose and remove a considerable amount of dissolved components, not only does it take a long time to decompose and remove, but denitrification is still insufficient. [Means for Solving the Problems] To explain the measures taken in the present invention to solve the above problems, the present invention uses wastewater and compost obtained by aerobic fermentation treatment. The method is to bring them into contact with each other. The wastewater that can be treated with the present invention is water that is contaminated with a large amount of organic components, such as domestic wastewater,
Examples include organic industrial wastewater, human animal human waste, lake water, and aquaculture pond water. Compost obtained by aerobic fermentation may be of any kind as long as it is obtained through good fermentation conditions, but compost obtained by fermentation with alkaline side is particularly preferred. That is, if an aerobic fermentation treatment is performed after adding and mixing an alkaline substance such as slaked lime to the raw material so that the pH of the raw material is about 9 to 12, an extremely good fermentation state can be obtained, which is useful for the present invention. It is also thought that the number of microorganisms that cause the effect will increase. In addition, when sewage is brought into contact with calcium-rich compost obtained by fermenting raw materials to which slaked lime and the like are added, there is an advantage that the phosphorus component in the sewage is bound to calcium and becomes easier to remove. The raw material for the compost to be brought into contact with sewage in the present invention may be any material that can be subjected to aerobic fermentation, such as sewage sludge, food processing residue, agricultural waste, human waste, etc. In particular, if the settled sludge discharged when carrying out the method of the present invention is recycled as a raw material for compost, it is possible to eliminate the need to collect the raw material for compost from outside. The contact between compost and wastewater can be carried out, for example, as follows. A method of directly throwing compost into wastewater.
This is the simplest method. A method in which compost is mixed in an appropriate amount of water in advance, and the compost is dissolved into waste water. This makes it easier to ensure uniform contact between wastewater and compost. A method in which the above compost water dispersion is allowed to stand still and only the supernatant liquid is poured into wastewater. In this method, wastewater and compost come into contact indirectly through the supernatant liquid. For example, a method in which compost is hardened to an appropriate size using a water-absorbing material such as gypsum, and the compost is filled into a net, cloth bag, or perforated container, and then immersed in waste water. With this method, it is easy to obtain long-lasting effects. The amount of compost to be brought into contact with wastewater is usually 10 to 10 times the amount of wastewater to be purified when bringing the wastewater and compost into contact by the above method or the method described above.
Approximately 1000ppm, depending on the condition of the wastewater 10~
Even around 100ppm is sufficient. In addition, when the wastewater is accompanied by abnormalities such as bulking, 1000 to 7000 ppm
If the MLSS is 4000ppm, the amount of compost should be 4000ppm relative to the wastewater.
It is preferable to set it as approximately. If the amount of compost is too small, it will be difficult to obtain the benefits of the present invention. It is perfectly acceptable to bring compost in an amount exceeding the above-mentioned value into contact with wastewater, if the increase in consumption of compost is ignored. In particular, when compost and sewage are brought into contact by the above method and, the degree of contact between the two is lower than in the case of the above method and, so it is preferable to use more compost than in the case of the above method and. During the purification process according to the present invention, wastewater is
It is preferable to maintain the water temperature at 10°C or higher, especially between 20 and 30°C. If the water temperature drops too low, microbial activity slows down and treatment efficiency tends to drop. The wastewater that has come into contact with the compost can be left alone to take its own course. In particular, if the object to be purified is a lake or marsh, and if you want to directly pour compost into it and purify it all at once, you have to leave it alone, but it is preferable to aerate it if possible. The above aeration can be easily performed using an aeration tank. The amount of aeration may be about the standard amount established for the aeration tank. Furthermore, in aquaculture ponds and the like, aeration for supplying oxygen to cultured fish and shellfish can also serve as aeration for purification. In the present invention, it is preferable to add slaked lime, gypsum, and even activated silicic acids that are porous and have strong adsorption power together with the compost. These enable rapid removal of more dissolved components. Moreover, it can also be used in combination with a general flocculant. [Effect] The present inventor speculates that the major cause of recent pollution of lakes and rivers is not only eutrophication due to inflow of wastewater, but also annihilation of microorganisms due to large amounts of pesticides and insecticides sprayed. are doing. In other words, the ability to purify pollution originally exists in the natural world, and the basis of this ability is microorganisms, but today, the number of relatively weak microorganisms that perform this purifying action has decreased dramatically, and the ability to purify pollution has decreased dramatically. It is thought that the fundamental cause of pollution of lakes and rivers is that these substances are disappearing from the natural world. From the standpoint of the inventor, the reason why the currently used biological oxidation method cannot achieve sufficient denitrification is because there are microorganisms that perform denitrification in the water of the rivers and lakes that are the target of the treatment. This is thought to be due to the fact that its existence is becoming extremely rare. By the way, at first glance, it may seem that adding compost to wastewater contaminated with a large amount of organic components merely increases the amount of contaminated organic components.
However, there are a large number of extremely diverse types of microorganisms in compost, and their activities and their metabolic products, enzymes, promote the settling of suspended components in wastewater, syneresis from settled sludge, and the decomposition of remaining organic components. is thought to play a major role in Therefore, the addition of compost in the present invention acts as an artificial replenishment of microorganisms necessary for purification. As mentioned above, in the present invention, by adding compost, missing or diluted microorganisms are replenished and nature's original purifying ability is reproduced. Component removal, especially high denitrification effect, can be obtained without the addition of special chemicals. Further, since the density of the settled sludge is high and the water repellency is improved, the amount of sludge discharged can be reduced accordingly, and the handling of the sludge can be improved. [Example] Example 1 Activated sludge (SS =
1500ppm) was used as a sample, and a compost water dispersion was injected into it to examine the sedimentation properties of the sludge. The compost used was obtained by adding compost obtained through a similar fermentation process to sewage sludge to adjust the moisture content, and then adding slaked lime to adjust the pH to 12.The material was then subjected to an aerobic fermentation process. . The compost water dispersion was prepared by pulverizing compost using a mixer and adding it to water and stirring well. The above-mentioned compost aqueous dispersion was added to the sample so that the amount of compost to the sample was 1000 ppm, and after stirring briefly, the sample was left to stand immediately and the state of sedimentation was observed. The results are shown in Fig. 1. Example 2 The sedimentation state was observed in the same manner as in Example 1, except that a compost water dispersion was added to the sample so that the amount of compost to the sample was 2000 ppm. The results are shown in Figure 1. Comparative Example 1 The same sample used in Example 1 was briefly stirred without adding the compost water dispersion, and then left to stand directly to observe the sedimentation state. The results are shown in Figure 1. Example 3 A double concentrated solution (SS) of the activated sludge used in Example 1
= 3500ppm) was used as a sample, and compost contact water was injected into it to examine the sedimentation properties of the sludge. A diameter of 2-3 mm from the same compost as in Example 1.
The granular materials were sieved and packed into a container, and a double concentrated solution of the same activated sludge as the sample was passed through this to create compost contact water. Add 50ml of the above compost contact water to 450ml of the sample.
After stirring briefly, the mixture was allowed to stand immediately and the state of sedimentation was observed. The results are shown in Figure 2. Example 4 The state of sedimentation was observed in the same manner as in Example 3, except that 100 ml of compost contact water was added to 400 ml of the sample. The results are shown in Figure 2. Comparative Example 2 The same sample used in Example 3 was briefly stirred without adding compost contact water, and then left to stand immediately to observe the sedimentation state. The results are shown in Figure 2. Example 5 In the same sample as in Example 1, a 5 cm diameter vinyl chloride pipe filled with granular compost similar to that used in Example 3 and having both ends closed with a net was immersed, and while being aerated, Contact between sample and compost
Lasted for an hour. Thereafter, the vinyl chloride tube was taken out from the sample, briefly stirred, and then left to stand immediately to observe the state of sedimentation. The results are shown in Figure 3. Comparative Example 3 The state of sedimentation was observed in the same manner as in Example 5, except that the sample and the compost were not brought into contact. The results are shown in Figure 3. Example 6 Compost similar to that used in Example 1 was put into an aeration tank of a human waste treatment plant, and the dehydration of excess sludge and changes in the color of the water in the aeration tank due to the addition of compost were investigated. The aeration tank has a capacity of 1064m ³ and its operating status is as follows. MLSS: 4000ppm Load: 300ppm/day Returned sludge: ^360m3 /day Supply dilution water: ^560m3 /day The same compost as that used in Example 1 was used, and 40Kg/day (approximately 40ppm) was added to the returned sludge. /
It was supplied into the aeration tank and brought into contact with wastewater. Excess sludge taken out from the aeration tank was collected twice each on the 1st, 12th, 19th, 27th, and 31st days after the start of composting, and the sludge was dehydrated using a centrifuge. The moisture content was measured. The results are shown in Table 1. In addition, the aeration tank water had a deep brown color until the 19th day, but the water sampled after the 27th day turned light brown.

[Table] Example 7 Activated sludge from the aeration tank of the human waste treatment plant explained in Example 6 was collected every day from the first day of composting (day 0), and the sedimentation property (SV) of the activated sludge in 30 minutes was measured.
-30), pH, and transparency of the supernatant were measured. The results are shown in FIGS. 4, 5, and 6. Example 8 The aeration tank water of the human waste treatment plant explained in Example 6 was
Samples were collected for 5 consecutive days from the first day of composting (day 0), and the NH ₄ ⁺ concentration and NO ₃ ^- concentration were measured. The results are shown in FIG. Example 9 60 kg of compost similar to that used in Example 1 was put into a pond with an area of about 1200 m ² and an average depth of about 0.5 m. The transparency, NH ₄ ⁺ concentration, NO ₃ ^- concentration, and PH of the pond were measured before and one week after compost was added. The results are shown in Table 2.

[Table] Example 10 2.5 g of the same compost as used in Example 1 was added to ammonia water diluted with distilled water (ammonia concentration 200 ppm, PH 11.3) 1, and aeration was carried out at room temperature for 2 days. Ivy. When the ammonia concentration was then measured, it was 100 ppm and the pH was 8.2. [Effects of the Invention] According to the present invention, not only can wastewater treatment efficiency be greatly improved, but also lakes and marshes, which have been difficult to purify in the past, can be easily purified.

[Brief explanation of drawings]

Fig. 1 is a graph showing the settling properties of activated sludge measured in Examples 1 and 2 and Comparative Example 1, Fig. 2 is a graph showing the settling properties of activated sludge measured in Examples 3 and 4 and Comparative Example 2, Figure 3 is a graph showing the settling properties of activated sludge measured in Example 5 and Comparative Example 3, Figure 4 is a graph showing changes in SV-30 measured in Example 7, and Figure 5 is a graph showing the change in SV-30 measured in Example 7. FIG. 6 is a graph showing changes in the measured PH, FIG. 6 is a graph showing changes in transparency measured in Example 7, and FIG. 7 is a graph showing changes in ion concentration measured in Example 8.

Claims (1)

[Claims] 1. A method for purifying sewage, which comprises bringing sewage into contact with compost obtained through aerobic fermentation.