JPH03161096A - Treatment process for organic soil water - Google Patents

Abstract

PURPOSE:To treat raw sewage water efficiently by including the processes of the aerobic biological treatment, the biological nitrification treatment and the ammonium nitrite decomposition treatment, and separating the ammonium nitrile producing process and the ammonium nitrite decomposing process. CONSTITUTION:The process consists of three respective processes of the direct removal process I for removing impurities in organic soil water, the aerobic process II for decomposing BOD and producing ammonium nitrite and the inorganic denitrification process III for decomposing ammonium nitrite produce in the aerobic process and turning the same into nitrogen gas. The BOD removal process and the N removal process for the raw sewage water can be carried out efficiently by the process to recover treated water of high quality in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for treating organic wastewater, and particularly to a method for treating organic wastewater that can efficiently treat human waste wastewater.

[Prior art] Human waste sewage contains 3000 to 4000
Since it contains ppm of ammonia nitrogen, etc., it is necessary to efficiently remove this in the treatment of human waste wastewater. Conventionally, biological nitrification and denitrification methods have been widely used as nitrogen removal processes. Although this method has many advantages, (1) it requires a large amount of 02 for nitrification;

■ For denitrification, it is necessary to supply BOD as a hydrogen donor. Such a lack. There is a point. On the other hand, in order to reduce the consumption of 02, biological nitrification is performed in the nitrite form using immobilized nitrite bacteria, and the generated ammonium nitrite is decomposed into N2 gas using a catalyst using a catalyst. A method has been proposed (Japanese Patent Laid-Open No. 197196/1983). [Problems to be Solved by the Invention] However, even if human waste wastewater was actually treated using the method disclosed in JP-A-62-197196, ammonia nitrogen could not be removed. The reason for this is thought to be that the preparation of the catalyst in this method is extremely delicate and not reproducible. That is, decomposition of ammonium nitrite at high temperatures is known, and it is also known that platinum group elements have a catalytic effect on such decomposition, but catalytic decomposition of ammonium nitrite at room temperature is difficult. On the other hand, immobilized bacteria are killed by heat when heated. For this reason, in Japanese Patent Application Laid-open No. 62 (1982), ammonium nitrite biocontrol through biological nitrification and catalytic decomposition of ammonium nitrite are simultaneously carried out in the same oak.
In the method of No. 197196, it is not possible to set conditions suitable for both the production of nitrous acid and the decomposition of ammonium nitrite, and therefore no denitrification effect can be obtained. An object of the present invention is to solve the above-mentioned conventional problems and provide a method for treating organic wastewater that can efficiently treat human waste wastewater.

[Means for Solving the Problems] The method for treating organic wastewater of the present invention includes the steps of subjecting organic wastewater to aerobic biological treatment to oxidize and decompose BOD, and biologically nitrifying it to generate ammonium nitrite. and a step of decomposing the generated ammonium nitrite into nitrogen gas. That is, in order to eliminate the above-mentioned conventional problems, the method for treating organic wastewater of the present invention separates the ammonium nitrite production step and the ammonium ammonium ammonite decomposition step.

The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a system diagram showing one implementation method of the organic wastewater treatment method of the present invention.

As shown in the figure, the method of this example basically consists of a direct desorption step (2) to remove impurities from organic wastewater, and an aerobic biological treatment to oxidize and decompose BOD and generate ammonium nitrite. It consists of three steps: step +1 and inorganic denitrification step (2), in which anthonicum nitrite produced in the aerobic step is decomposed into nitrogen gas. That is, in the method of this embodiment, first, organic wastewater, for example, human waste wastewater (raw human waste, etc.) is introduced into the flocculating tank 1 through the pipe 11, a flocculant is added through the pipe 12, and the mixture is stirred by the agitator IA. After agglomerating the water, it is sent to the dehydrator 2 through the pipe 13 for dehydration treatment, thereby removing impurities such as SS fraction contained therein (direct dehydration step ①). Generally, raw human urine contains about 13,000 ppm of SS components, but in this direct removal process (2), more than 95% of SS and about 50% of BOD are removed. The wastewater from which substances have been removed is sent to the aerobic tank 3 through the pipe 14, where it is treated with aerobic organisms (
Aerobic process ■). In this aerobic step n, in the presence of BOD bacteria and nitrite bacteria under aerobic conditions where air is supplied from the pipe 15,
It biodegrades BOD and nitrifies NH4 to NO2 to generate NH4 NO2. By the way, when BOD decomposition and nitrification are performed in the same cypress as in the present invention, BOD decomposing bacteria and nitrifying bacteria (in the present invention, nitrite bacteria) cannot be treated separately in the normal floating method. The ratio of each bacteria is BOD, NH4 of the wastewater at the tank inlet.
+ concentration multiplied by the yield of each bacterium. In the case of human waste wastewater, the proportion of nitrifying bacteria in MLSS is only a few percent, making it impossible to obtain sufficient nitrification efficiency. As a method to improve this, it is possible to adopt the following methods (1) and (2).

■ A method in which suspended sludge (BOD bacteria) and immobilized nitrifying bacteria are operated in the same tank.This allows the suspended sludge and immobilized nitrifying bacteria to be operated under different set conditions, reducing the presence of nitrifying bacteria in the system. The ratio can be increased.In order to make it easier to separate the two, it is also effective to increase the difference in specific gravity by co-fixing an appropriate inorganic material when fixing. ■ As shown in Figure 1. Through the direct desorption process, SS components in human waste water are separately treated, and NH4◆/BOD in human waste is
Increase the ratio. This direct denitrification process is also effective in preventing inhibition of catalyst activity in the inorganic denitrification process. That is, SS in wastewater
A part of BOD is difficult to decompose, and its presence inhibits the catalytic activity of the inorganic denitrification process, but by removing SS components through a direct denitrification process, this inhibition of activity can be reduced. can do. In the present invention, it is preferable to simultaneously employ methods ① and ② above. In the aerobic process, B O D in wastewater
It is biodegraded biologically under aerobic conditions in the presence of m, and CO2 is generated in this process. This CO2 reacts with the ammonia component (NH4+) in the wastewater to form NH4 HCO3.

In the aerobic process, NH4+ is nitrified to NO2, but here, in the next inorganic denitrification process, NH*NO2-4 N2
+ 2 8 2 0 to perform denitrification denitrification, NH4
It is necessary to generate NO2. That is, 50% nitrification
Stop at 1 to obtain nitrified water with a concentration of NH4''/N02-'' of 1.

This point will be explained below.

Sewage contains various pH levels such as bicarbonate, carbonate, and phosphate.
There is a substance that has a binding force, that is, a buffer. As nitrification progresses and NO2- ions are released, the buffer is consumed. When all buffers are consumed, PH
decreases rapidly and nitrification stops. Therefore, NH in wastewater
4+ concentration and buffer concentration or alkalinity,
By adding acid or alkali to adjust this equivalent ratio, the buffer can be adjusted and the nitrification rate can be adjusted to a desired value. That is, when the ammonia concentration and alkalinity in wastewater are equivalent, half of the NH4+ in the wastewater is nitrified and converted to NH4 NO2 (NH4 7'N
Since no buffer 1- remains at the stage when O2 = 1) is generated, the pH decreases and nitrification stops, resulting in a nitrification rate of 50%.
becomes. Furthermore, when the ammonia concentration is higher than the alkalinity, the buffer is completely digested at a stage where the amount of nitrification is smaller, and when nitrification stops, NH4+ remains, and the nitrification rate is less than 50%. On the other hand, if the ammonia concentration is lower than the alkalinity, even when nitrification is half completed,
Since the buffer remains, the pH does not decrease, and nitrification progresses further, resulting in a nitrification rate of over 50%.

By the way, the biological nitrification reaction is expressed by the following basic equation.

NH4" +372 02 = NO2- +H2 0-}-2H" In the past, the pH was prevented from decreasing due to the generated H+.
Therefore, 100% nitrification is normally performed by controlling the %PH.

On the other hand, most of the N in wastewater is in the form of NH4-N, and the source of its generation is the decomposition of the amine groups of proteins. When BOD, which is common in sewage, decomposes, CO2 is produced, and NH4+ combines with this to form NH4+, and ants produce NH
4 8 C O 3.

The reaction formula when nitrifying NH4HCO3 without pH adjustment is as follows.

N H 4 H CO s + 3/4 0 2→1
/2NH4NO2+ 3/2 H 2 0 + C 0
2N H 4 N O When 2 is released, the N in the raw water
If all the H4HCO3 is consumed and no other buffer is present in the solution, the pH will drop and nitrification will stop. That is,
The reaction spontaneously stops in a state of NH 4 /N O 2-1.

In the present invention, if the amount of buffer in the inflow water to aerobic step II is equimolar to NH4+, N
Treated water with H 4 /N O 2 = 1 can be obtained.

However, the process of BOD oxidation is accompanied by the production of acids and alkalis, or the alkalinity is reduced by using an inorganic flocculant in the direct desorption process, and the equivalence relationship between NH4+ and alkalinity is shifted, resulting in NH4/N. If O2=1 or not, it is important to measure the NH4+ concentration and the amount of buffer in the solution, that is, the alkalinity, and adjust the equivalence ratio in advance. That is, N H 4 / N O 2 >
In case 1, a predetermined amount of alkali is added and N H 4
/ If N 0 2 < 1, add acid. In this way, by measuring the ammonia concentration and alkalinity, adding acid or alkali so that the equivalent ratio of both is 1, and performing nitrification using nitrifying bacteria, the nitrification rate can be reduced to 50%.
It is possible to obtain treated water with N H 4 / N O 2 = 1, and in this case, by performing nitrite-type nitrification and chemical decomposition of N H a N O 2 in stages, It is believed that efficient nitrification and denitrification can be performed.

The treated water from the aerobic process H is then passed through the pipe 16 to the heater 4.
The N}14 NO2 produced in the aerobic step I1 is decomposed and denitrified into N2 gas in a non-porous manner under heating. The treated water from the decomposition tower 5 is extracted from the piping 17, passed through the water-cooled pipe 6, and sent to the degassing tank 7, where the N2 gas is separated. 8 and then discharged outside the prefecture. In this way, ssF and other substances in human waste are removed by adding a flocculant to human waste wastewater (direct removal process), and soluble BOI)
The components are decomposed by aerobic treatment, and the nitrogen components are biologically nitrified by nitrifying bacteria to produce NH4NO2 (
aerobic process), by inorganically denitrifying the purified N H 4 N O 2 to N2 gas (inorganic denitrification process),
It is believed that efficient human waste treatment is possible. Although it is not necessarily necessary in the method of treating organic wastewater of the present invention, by providing a direct removal step to remove impurities such as SS in organic wastewater, it is possible to improve the aerobic step of the next step. It is possible to improve the reaction rate in the process, improve the processing efficiency of the post-process, and enable high-load processing. In addition, some of the SS BOD is decomposable by H'JI substances, and its presence inhibits the catalytic activity of the subsequent inorganic denitrification process. Removal of the SS component can reduce this activity inhibition. It is also effective for

[Function] In the method for treating organic wastewater of the present invention, in the aerobic step, oxidative decomposition of BOD and generation of NH4 NO2 are performed. By performing the oxidative decomposition of BOD and the generation of NH4 NO2 in the same tank in this way, it is possible to increase the efficiency of the nitrification reaction.

In the inorganic denitrification process, NH4 NO2 produced in the aerobic process
NH4NO2 is inorganically decomposed to remove N2 gas.
begins to decompose at around 70°C, and the decomposition rate increases as the temperature increases; at 200°C, the denitrification rate is 100 kg-N/N.
This improvement effect is even greater when the temperature is raised in the presence of a catalyst.Incidentally, in a column packed with a pt-alumina catalyst,
When the reaction is carried out at ℃, the denitrification rate is up to 3000k.
g-N/rn'·day or more is possible.

In the method of the present invention, the aerobic step in which NH4 NO2 is released and the inorganic denitrification step in which NH4 NO2 is decomposed and denitrified are carried out separately, so that suitable reaction conditions for each can be set independently. Therefore, the nitrification efficiency and denitrification efficiency are significantly increased. [Example] The present invention will be explained in more detail with reference to Examples below. Example 1 Human waste having the water quality shown in Table 1 was treated by the method shown in FIG. 1 at a load of 10,117 days.

In addition, in the direct desorption step I, cationic polymer 200 mg/i and polyferric sulfate 5 were used as flocculants.
00 mg/It was added. In addition, in the aerobic process
The treatment was carried out at 0 ppm with a residence time of 2 days, and solid-liquid separation was performed with UFg. Decomposition of inorganic denitrification process III! 55 was filled with 0.5% pt-aluminum as a catalyst, and the temperature was 200°C.
The treatment was carried out at a pressure of 30 kg/am'% and a residence time of 15 minutes.

Table 1 shows the quality of the waste water from each process.

From Table 1, it is clear that according to the method of the present invention, treated water of high quality can be obtained.

Table 1 [Effects of the Invention] As detailed above, according to the method for treating organic wastewater of the present invention, organic wastewater can be efficiently de-BOD and de-N treated, and can be used in high water trade. It is possible to recover treated water in a short time.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing one embodiment of the present invention.

Claims (1)

[Claims] (1) A process of aerobic biological treatment of organic wastewater to oxidize and decompose BOD and biological nitrification treatment to generate ammonium nitrite, and a process of decomposing the generated ammonium nitrite into nitrogen gas. A method for treating organic wastewater, characterized by comprising: