JPS5939395A - Treatment of ammonia nitrogen-contg. waste water - Google Patents

Abstract

PURPOSE:To enable to sufficiently exhibit the effect of a dual-phase anaerobic digestion process to be performed in succession, by adjusting a pH of waste water with an alkali agent and then removing the concentration of ammonia nitrogen in the waste water by air or the like. CONSTITUTION:In the dual-phase anaerobic digestion process for separating ammonia nitrogen-contg. waste water such as night soil or the excrementitious matter of cattle into acid and methane-forming phases and then reacting them, said waste water is adjusted to a pH above 11 with an alkali agent, stripped with air or steam until the concentration of ammonia nitrogen in the waste water comes below 2,000mg/l and then treated by said dual-phase anaerobic digestion process. Hence, the effect of the dual-phase anaerobic digestion is sufficiently exhibited, so that the capacity of a fermentation tank can be made small and that the amount of formed digestive gas is made large. Thus, the extention of said process to all kinds of organic waste water disposal is promoted, and the waste matter can be further effectively used as resources.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wastewater treatment method for treating organic wastewater containing a high concentration of ammonia nitrogen, such as human waste and livestock urine, by an anaerobic digestion method.

The general anaerobic digestion method found in conventional human waste, sewage sludge treatment, etc. requires less electricity than aerobic treatment methods, etc., and also uses methane-based digestion gas that can be effectively used as fuel etc. Despite the fact that it has characteristics such as the ability to obtain progress is delayed. This takes a long time to process (20 to 20 days for digestion).
This is due to drawbacks such as the required residence time of 30 days, which makes the scale of the 4Ia facility too large and increases construction costs, and the delay in establishing a rational design method based on engineering considerations. In response to this, there has been a growing momentum in recent years to review anaerobic digestion methods, and in order to improve the efficiency of the digestion reaction and shorten the residence time, high-rate tank digestion methods employ a fluidized bed type, packed four column type, or high temperature fermentation type fermenter. Various methods are being developed, such as anaerobic digestion and two-phase anaerobic digestion.

As is well known, in the anaerobic digestion reaction, high-molecular organic substances such as fats, carbohydrates, and proteins in organic wastewater pass through low-molecular organic substances such as higher fatty acids and saccharides, and then turn into volatile organic substances such as acetic acid and bucc acid. This is a two-stage reaction consisting of an acid generation phase in which an acid is generated and a methane generation phase in which volatile organic acids generated in the acid generation phase are converted into methane gas and carbon dioxide gas. The microorganisms involved in the acid-producing phase and the methanogenic phase are facultative in the former, and obligate in the latter.
Is is a methanogenic bacterium, and the optimal environmental conditions for growth are different.

Conventional digestion methods and high-rate tank digestion methods perform these two-stage reactions with different optimal environmental conditions in the same tank under the same environmental conditions, whereas the two-phase [gas digestion method] This method separates the two and performs the reaction under optimal conditions for each. According to the two-phase anaerobic digestion method, the retention time can be shortened to 10 culms for night soil and sewage sludge, and the amount of digestion gas generated can also be increased. 17 However, if 2000 mg/1 or more of ammonia nitrogen is present in the wastewater to be treated, it will have an inhibitory effect on the acid-generating phase and methane-generating phase, reducing the rate of decomposition of organic matter. The amount of digestive gas generated is also significantly reduced. In particular, it has a significant inhibitory effect on the methanogenic phase. Although the theoretical elucidation of this Cζ is delayed, it is presumed that the cause is that the concentration of NHn ions in the treated liquid reaches an upper limit, which adversely affects the activity of microorganisms, or that Pl+ increases.

Furthermore, ammonia nitrogen is not removed by approximately 71 degrees during pneumatic digestion. As mentioned above, in the two-phase anaerobic digestion method, each phase is separated.17 In order to carry out the reaction under optimal conditions, it is compared with the conventional digestion method.17 The buffering capacity of the liquid is also weak, and the separated methanogenic phase is caused by ammonia nitrogen. The present invention was made in consideration of these circumstances, and aims to remove ammonia nitrogen through simple pretreatment to make the two-phase anaerobic digestion method more effective. The purpose of the present invention is to provide a two-phase anaerobic digestion method in which organic wastewater containing ammonia nitrogen is subjected to reaction treatment by separating the production phase and the methanogenesis phase. , the wastewater was adjusted to pH 1 with an alkaline agent.
Ammoniacal nitrogen-containing wastewater, which is adjusted as above, and after stripping the wastewater to an assimoniacal nitrogen concentration of 2000 mg/e or less using air or steam, the wastewater is treated by the two-phase aerobic digestion method. This is the processing method. Hereinafter, the present invention will be described in detail based on the drawings showing embodiments thereof.

FIG. 1 shows a 70-sheet according to an embodiment of the present invention.

Organic wastewater A containing high concentration of ammonia nitrogen is
After introducing into the H adjustment tank (1) and injecting an alkaline agent B such as caustic soap or slaked lime to adjust the pH to 11 or more, it is introduced into the ammonia strip and soaping tank (2) and air C is blown into the wastewater Δ. Stripping ammonia etc. The stripping method may be steam boiler soaking using steam.

The stripped ammonia is removed from the cleaning device 'f1 (9).
It is removed by washing with an acid such as sulfuric acid.

Alternatively, instead of washing with ammonia, a method may be used in which the ammonia is catalytically combusted to convert it into Nll and then discharged.

Wastewater A whose asimonia nitrogen concentration has become 2000 mg/I or less is introduced into a neutralization tank (3), and after being neutralized to around 7 (7) with an acid such as 1M acid, it is transferred to an acid fermentation tank (
4) and brought into contact with facultative anaerobic bacteria to decompose the organic matter in the wastewater Δ into volatile organic acids such as acetic acid and pyrene acid.

In the acid fermenter (4), the digestion gas D circulated by the gas circulation blower (13) is stirred and mixed to enhance the contact effect with jη, and at the same time, the digestion gas (■) is mixed with the fuel
By blowing generated steam from the steam boiler (12), the liquid temperature is increased to 35 to 38°C. Note that the pounding may be performed by mechanical stirring, and the heating may be performed by indirect heating using a heat exchanger or the like. The residence time in the acid fermenter (4) is about 1 to 3 days.

Also, circle 1 in the acid fermenter is maintained at 5-6. The effluent A' from the acid fermenter (4) is introduced into the methane fermenter (5) and brought into contact with obligate anaerobic methanogens to remove the volatile organic acids in the effluent A'. is converted into methane gas and carbon dioxide gas. In the methane fermentation tank (5) (Yo, acidic fermentation tank (6)
Similarly to 4), the liquid temperature is maintained at 35 to 38° C. by Stino, gas stirring mixing is performed using the digestion gas D, and the pH is maintained at around 7. In addition, the fermenter conditions are yen (
, liquid temperature, anaerobic, etc. should be controlled more strictly than in the acid fermenter (4). Also, the residence time in the methane fermentation tank (5) is about 7 to 1
It is day 0.

Digestion gas D generated in the i++ fermenter (4) and methane fermenter (5) contains CI (460-70%, the remainder is CO,
.

Desulfurization equipment (10) that uses N2, etc., and removes H and S from microshells.
After desulfurization, the gas is stored in a gas boulder (11) and effectively used for fuel fuel 1, etc. The desorbed liquid A" flowing out from the methane fermentation tank (5) is separated into solid and liquid in a separation tank (6), then treated in a secondary treatment device (7) such as an activated sludge treatment device, and then released. A part of the sludge E separated in the separation tank (6) is circulated to the acid fermentation tank (4), and the remaining part (is dehydrated by a sludge treatment device (8) such as a dehydrator, and then sent to a composting device (not shown), etc.). Processed and effectively used as compost and 17) J
or incinerated.

As described above, the present invention uses a two-phase aerobic digestion method that is more efficient than the conventional anaerobic digestion method, and uses a simple method to remove ammonia nitrogen, which is an inhibitory substance that inhibits the digestive reaction. Since the effect of two-phase aerobic digestion can be fully demonstrated, the capacity of the fermenter can be reduced, and more digestive gas is generated, promoting the spread of organic wastewater treatment as a whole and further reducing waste. It is extremely useful industrially because it can be used effectively as a resource.

Table 1 below shows the data of an example of a pilot blunt in which pig manure was treated using the present invention and a comparison example of the conventional method.

Table-1

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of one embodiment of the present invention. (1) ; PHNINj)! 4'R(2); x
)! I-/Hi:zritM(3): Neutralization tank
(4); Acid fermentation tank (5); Methane fermentation tank (6);
Preparation tank (7); Secondary treatment device (8); Sludge treatment device (9); Cleaning device (10); Desulfurization device (11)
1, gas holder +12), steam boiler (1
3); Gas circulation blower A; Organic wastewater A'H effluent A#; De#ing liquid Bi-flukaline agent C; Air D; Digestion gas E; Sludge patent applicant Mitsubishi Kakoki Co., Ltd.

Claims (1)

[Claims] In a two-phase pneumatic digestion method in which organic wastewater containing ammonia nitrogen is subjected to reaction treatment by separating an acid-generating phase and a methanogenic phase, the wastewater is adjusted to P-O-1-H with an alkaline agent, Treatment of ammoniacal nitrogen-containing wastewater, characterized in that the ammoniacal nitrogen concentration in the wastewater is stripped to 2000 mg/l or less using air or steam, and then treated by the two-phase pneumatic digestion method. Method.